如何将顶视图折叠成较小尺寸的视图？
How to have a collapsing of top view into a smaller sized view?
这个问题之前被问的太笼统和不清楚 here，所以我把它变得更加具体，并提供了我尝试过的内容的完整解释和代码。
背景
我需要模仿 Google 日历在顶部有一个视图的方式，该视图可以动画和下推底部的视图，但它有额外的、不同的行为。我总结了我在 3 个特征上尝试做的事情：
- 按下工具栏上的按钮将始终有效，以切换 expanding/collapsing 顶视图，同时有一个箭头图标可以改变其旋转。这就像 Google 日历应用程序。
- 顶视图将始终捕捉，就像在 Google 日历应用程序上一样。
- 当顶视图被折叠时，只有在工具栏上按下才能展开它。这就像 Google 日历应用
- 当顶视图展开时，在底视图滚动将只允许折叠。如果您尝试向另一个方向滚动，什么也不会发生，甚至不会滚动到底部视图。这就像 Google 日历应用
- 折叠后，顶视图将替换为较小的视图。这意味着它总是需要一些 space，高于底部视图。这与 Google 日历应用程序不同，因为在日历应用程序中，顶部视图一旦折叠就会完全消失。
Google 日历应用的外观如下：
滚动底部视图也会慢慢隐藏顶部视图：
问题
使用我过去发现的各种解决方案，我只成功实现了所需行为的一部分：
在工具栏中有一些 UI 是通过在其中包含一些视图（包括箭头视图）来完成的。对于手动 expanding/collapsing，我在 AppBarLayout 视图上使用 setExpanded。对于箭头的旋转，我使用 AppBarLayout 调整大小的侦听器，在其上使用 addOnOffsetChangedListener。
通过将 snap 值添加到 CollapsingToolbarLayout 的 layout_scrollFlags 属性中，可以轻松完成捕捉。然而，为了让它真正运行良好，没有奇怪的问题（报告here), I used .
阻止滚动时影响顶视图可以通过使用我在 #2 () 中使用的相同代码来完成，方法是在此处调用 setExpandEnabled。
这在顶视图折叠时效果很好。
与#3 类似，但遗憾的是，由于它使用了 setNestedScrollingEnabled，它是双向的，因此仅当顶视图折叠时效果很好。当它展开时，它仍然允许底部视图向上滚动，这与日历应用程序相反。展开时，我需要它只允许折叠，不允许真正滚动。
以下是优点和缺点的演示：
- 我完全没有做到这一点。我已经尝试了很多我想到的解决方案，将视图放在带有各种标志的各个地方。
简而言之，我成功地完成了 1-3，但没有完成 4-5。
密码
这是当前代码（也可作为整个项目 here）：
ScrollingActivity.kt
class ScrollingActivity : AppCompatActivity(), AppBarTracking {
private var mNestedView: MyRecyclerView? = null
private var mAppBarOffset: Int = 0
private var mAppBarIdle = false
private var mAppBarMaxOffset: Int = 0
private var isExpanded: Boolean = false
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_scrolling)
val toolbar = findViewById<Toolbar>(R.id.toolbar)
setSupportActionBar(toolbar)
mNestedView = findViewById(R.id.nestedView)
app_bar.addOnOffsetChangedListener({ appBarLayout, verticalOffset ->
mAppBarOffset = verticalOffset
val totalScrollRange = appBarLayout.totalScrollRange
val progress = (-verticalOffset).toFloat() / totalScrollRange
arrowImageView.rotation = 180 + progress * 180
isExpanded = verticalOffset == 0;
mAppBarIdle = mAppBarOffset >= 0 || mAppBarOffset <= mAppBarMaxOffset
if (mAppBarIdle)
setExpandAndCollapseEnabled(isExpanded)
})
app_bar.post(Runnable { mAppBarMaxOffset = -app_bar.totalScrollRange })
mNestedView!!.setAppBarTracking(this)
mNestedView!!.layoutManager = LinearLayoutManager(this)
mNestedView!!.adapter = object : RecyclerView.Adapter<RecyclerView.ViewHolder>() {
override fun getItemCount(): Int = 100
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
return object : ViewHolder(LayoutInflater.from(parent.context).inflate(android.R.layout.simple_list_item_1, parent, false)) {}
}
override fun onBindViewHolder(holder: ViewHolder, position: Int) {
(holder.itemView.findViewById<View>(android.R.id.text1) as TextView).text = "item $position"
}
}
expandCollapseButton.setOnClickListener({ v ->
isExpanded = !isExpanded
app_bar.setExpanded(isExpanded, true)
})
}
private fun setExpandAndCollapseEnabled(enabled: Boolean) {
mNestedView!!.isNestedScrollingEnabled = enabled
}
override fun isAppBarExpanded(): Boolean = mAppBarOffset == 0
override fun isAppBarIdle(): Boolean = mAppBarIdle
}
MyRecyclerView.kt
/**A RecyclerView that allows temporary pausing of casuing its scroll to affect appBarLayout, based on */
class MyRecyclerView @JvmOverloads constructor(context: Context, attrs: AttributeSet? = null, defStyle: Int = 0) : RecyclerView(context, attrs, defStyle) {
private var mAppBarTracking: AppBarTracking? = null
private var mView: View? = null
private var mTopPos: Int = 0
private var mLayoutManager: LinearLayoutManager? = null
interface AppBarTracking {
fun isAppBarIdle(): Boolean
fun isAppBarExpanded(): Boolean
}
override fun dispatchNestedPreScroll(dx: Int, dy: Int, consumed: IntArray?, offsetInWindow: IntArray?,
type: Int): Boolean {
if (type == ViewCompat.TYPE_NON_TOUCH && mAppBarTracking!!.isAppBarIdle()
&& isNestedScrollingEnabled) {
if (dy > 0) {
if (mAppBarTracking!!.isAppBarExpanded()) {
consumed!![1] = dy
return true
}
} else {
mTopPos = mLayoutManager!!.findFirstVisibleItemPosition()
if (mTopPos == 0) {
mView = mLayoutManager!!.findViewByPosition(mTopPos)
if (-mView!!.top + dy <= 0) {
consumed!![1] = dy - mView!!.top
return true
}
}
}
}
val returnValue = super.dispatchNestedPreScroll(dx, dy, consumed, offsetInWindow, type)
if (offsetInWindow != null && !isNestedScrollingEnabled && offsetInWindow[1] != 0)
offsetInWindow[1] = 0
return returnValue
}
override fun setLayoutManager(layout: RecyclerView.LayoutManager) {
super.setLayoutManager(layout)
mLayoutManager = layoutManager as LinearLayoutManager
}
fun setAppBarTracking(appBarTracking: AppBarTracking) {
mAppBarTracking = appBarTracking
}
}
ScrollingCalendarBehavior.kt
class ScrollingCalendarBehavior(context: Context, attrs: AttributeSet) : AppBarLayout.Behavior(context, attrs) {
override fun onInterceptTouchEvent(parent: CoordinatorLayout?, child: AppBarLayout?, ev: MotionEvent): Boolean = false
}
activity_scrolling.xml
<android.support.design.widget.CoordinatorLayout
android:id="@+id/coordinatorLayout" xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent" android:layout_height="match_parent" tools:context=".ScrollingActivity">
<android.support.design.widget.AppBarLayout
android:id="@+id/app_bar" android:layout_width="match_parent" android:layout_height="wrap_content"
android:fitsSystemWindows="true" android:stateListAnimator="@null" android:theme="@style/AppTheme.AppBarOverlay"
app:expanded="false" app:layout_behavior="com.example.user.expandingtopviewtest.ScrollingCalendarBehavior"
tools:targetApi="lollipop">
<android.support.design.widget.CollapsingToolbarLayout
android:id="@+id/collapsingToolbarLayout" android:layout_width="match_parent"
android:layout_height="match_parent" android:fitsSystemWindows="true"
android:minHeight="?attr/actionBarSize" app:contentScrim="?attr/colorPrimary"
app:layout_scrollFlags="scroll|exitUntilCollapsed|snap" app:statusBarScrim="?attr/colorPrimaryDark">
<LinearLayout
android:layout_width="match_parent" android:layout_height="250dp"
android:layout_marginTop="?attr/actionBarSize" app:layout_collapseMode="parallax"
app:layout_collapseParallaxMultiplier="1.0">
<TextView
android:layout_width="match_parent" android:layout_height="match_parent" android:paddingLeft="10dp"
android:paddingRight="10dp" android:text="some large, expanded view"/>
</LinearLayout>
<android.support.v7.widget.Toolbar
android:id="@+id/toolbar" android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize" app:layout_collapseMode="pin"
app:popupTheme="@style/AppTheme.PopupOverlay">
<android.support.constraint.ConstraintLayout
android:id="@+id/expandCollapseButton" android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize" android:background="?android:selectableItemBackground"
android:clickable="true" android:focusable="true" android:orientation="vertical">
<TextView
android:id="@+id/titleTextView" android:layout_width="wrap_content"
android:layout_height="wrap_content" android:layout_marginBottom="8dp"
android:layout_marginLeft="8dp" android:layout_marginStart="8dp" android:ellipsize="end"
android:gravity="center" android:maxLines="1" android:text="title"
android:textAppearance="@style/TextAppearance.Widget.AppCompat.Toolbar.Title"
android:textColor="@android:color/white" app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintStart_toStartOf="parent"/>
<ImageView
android:id="@+id/arrowImageView" android:layout_width="wrap_content" android:layout_height="0dp"
android:layout_marginLeft="8dp" android:layout_marginStart="8dp"
app:layout_constraintBottom_toBottomOf="@+id/titleTextView"
app:layout_constraintStart_toEndOf="@+id/titleTextView"
app:layout_constraintTop_toTopOf="@+id/titleTextView"
app:srcCompat="@android:drawable/arrow_down_float"
tools:ignore="ContentDescription,RtlHardcoded"/>
</android.support.constraint.ConstraintLayout>
</android.support.v7.widget.Toolbar>
</android.support.design.widget.CollapsingToolbarLayout>
</android.support.design.widget.AppBarLayout>
<com.example.user.expandingtopviewtest.MyRecyclerView
android:id="@+id/nestedView" android:layout_width="match_parent" android:layout_height="match_parent"
app:layout_behavior="@string/appbar_scrolling_view_behavior" tools:context=".ScrollingActivity"/>
</android.support.design.widget.CoordinatorLayout>
问题
如何在展开顶部视图时阻止滚动，但在滚动时允许折叠？
如何使顶视图在折叠时被替换为较小的视图（并在展开时变回大视图），而不是完全消失？
更新
尽管我已经了解了我所询问的基本内容，但当前代码仍然存在 2 个问题（在 Github、here 上可用）：
- 小视图（您在折叠状态下看到的视图）具有内部视图，需要对其产生点击效果。在它们上面使用
android:background="?attr/selectableItemBackgroundBorderless" 并在展开时单击此区域时，单击是在小视图上完成的。我通过将小视图放在不同的工具栏上来处理它，但是点击效果根本没有显示出来。我已经写过关于这个 here 的文章，包括示例项目。
修复方法如下：
<android.support.design.widget.CoordinatorLayout
android:id="@+id/coordinatorLayout" xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent" android:layout_height="match_parent" tools:context=".MainActivity">
<android.support.design.widget.AppBarLayout
android:id="@+id/app_bar" android:layout_width="match_parent" android:layout_height="wrap_content"
android:fitsSystemWindows="true" android:stateListAnimator="@null" android:theme="@style/AppTheme.AppBarOverlay"
app:expanded="false" app:layout_behavior="com.example.expandedtopviewtestupdate.ScrollingCalendarBehavior"
tools:targetApi="lollipop">
<android.support.design.widget.CollapsingToolbarLayout
android:id="@+id/collapsingToolbarLayout" android:layout_width="match_parent"
android:layout_height="match_parent" android:clipChildren="false" android:clipToPadding="false"
android:fitsSystemWindows="true" app:contentScrim="?attr/colorPrimary"
app:layout_scrollFlags="scroll|exitUntilCollapsed|snap|enterAlways"
app:statusBarScrim="?attr/colorPrimaryDark">
<!--large view -->
<LinearLayout
android:id="@+id/largeView" android:layout_width="match_parent" android:layout_height="280dp"
android:layout_marginTop="?attr/actionBarSize" android:orientation="vertical"
app:layout_collapseMode="parallax" app:layout_collapseParallaxMultiplier="1.0">
<TextView
android:id="@+id/largeTextView" android:layout_width="match_parent"
android:layout_height="match_parent" android:layout_gravity="center"
android:background="?attr/selectableItemBackgroundBorderless" android:clickable="true"
android:focusable="true" android:focusableInTouchMode="false" android:gravity="center"
android:text="largeView" android:textSize="14dp" tools:background="?attr/colorPrimary"
tools:layout_gravity="top|center_horizontal" tools:layout_height="40dp" tools:layout_width="40dp"
tools:text="1"/>
</LinearLayout>
<!--top toolbar-->
<android.support.v7.widget.Toolbar
android:id="@+id/toolbar" android:layout_width="match_parent" android:layout_height="wrap_content"
android:layout_marginBottom="@dimen/small_view_height" app:contentInsetStart="0dp"
app:layout_collapseMode="pin" app:popupTheme="@style/AppTheme.PopupOverlay">
<android.support.constraint.ConstraintLayout
android:layout_width="match_parent" android:layout_height="wrap_content" android:clickable="true"
android:focusable="true">
<LinearLayout
android:id="@+id/expandCollapseButton" android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:background="?android:selectableItemBackground" android:gravity="center_vertical"
android:orientation="horizontal" app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent">
<TextView
android:id="@+id/titleTextView" android:layout_width="wrap_content"
android:layout_height="wrap_content" android:ellipsize="end" android:gravity="center"
android:maxLines="1" android:text="title"
android:textAppearance="@style/TextAppearance.Widget.AppCompat.Toolbar.Title"
android:textColor="@android:color/white"/>
<ImageView
android:id="@+id/arrowImageView" android:layout_width="wrap_content"
android:layout_height="wrap_content" android:layout_marginLeft="8dp"
android:layout_marginStart="8dp" app:srcCompat="@android:drawable/arrow_up_float"
tools:ignore="ContentDescription,RtlHardcoded"/>
</LinearLayout>
</android.support.constraint.ConstraintLayout>
</android.support.v7.widget.Toolbar>
<android.support.v7.widget.Toolbar
android:id="@+id/smallLayoutContainer" android:layout_width="match_parent"
android:layout_height="wrap_content" android:layout_marginTop="?attr/actionBarSize"
android:clipChildren="false" android:clipToPadding="false" app:contentInsetStart="0dp"
app:layout_collapseMode="pin">
<!--small view-->
<LinearLayout
android:id="@+id/smallLayout" android:layout_width="match_parent"
android:layout_height="@dimen/small_view_height" android:clipChildren="false"
android:clipToPadding="false" android:orientation="horizontal" tools:background="#ff330000"
tools:layout_height="@dimen/small_view_height">
<TextView
android:id="@+id/smallTextView" android:layout_width="match_parent"
android:layout_height="match_parent" android:layout_gravity="center"
android:background="?attr/selectableItemBackgroundBorderless" android:clickable="true"
android:focusable="true" android:focusableInTouchMode="false" android:gravity="center"
android:text="smallView" android:textSize="14dp" tools:background="?attr/colorPrimary"
tools:layout_gravity="top|center_horizontal" tools:layout_height="40dp"
tools:layout_width="40dp" tools:text="1"/>
</LinearLayout>
</android.support.v7.widget.Toolbar>
</android.support.design.widget.CollapsingToolbarLayout>
</android.support.design.widget.AppBarLayout>
<com.example.expandedtopviewtestupdate.MyRecyclerView
android:id="@+id/nestedView" android:layout_width="match_parent" android:layout_height="match_parent"
app:layout_behavior="@string/appbar_scrolling_view_behavior" tools:context=".ScrollingActivity"/>
</android.support.design.widget.CoordinatorLayout>
- Google 日历允许在工具栏本身上执行向下滚动手势，以触发显示月视图。我只成功地在那里添加了一个点击事件，但没有滚动。它是这样的：
注意：完整的更新项目可用 here。
How can I make the scrolling being blocked when the top view is expanded, yet allow to collapse while scrolling ?
问题 #1： 当应用栏未折叠时，RecyclerView 根本无法滚动。要解决此问题，请将 enterAlways 添加到 CollapsingToolbarLayout 的滚动标志，如下所示：
<android.support.design.widget.CollapsingToolbarLayout
android:id="@+id/collapsingToolbarLayout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:clipChildren="false"
android:clipToPadding="false"
android:fitsSystemWindows="true"
app:layout_scrollFlags="scroll|exitUntilCollapsed|snap|enterAlways"
app:statusBarScrim="?attr/colorPrimaryDark">
enterAlways 不会导致应用栏在关闭时打开，因为您正在抑制该功能，但可以正常工作。
问题 #2： 当应用栏完全展开时，不应允许 RecyclerView 向上滚动。这恰好是问题 #1 的不同问题。
[已更新] 要更正此问题，请修改 RecyclerView 的行为以在 RecyclerView 尝试向上滚动和应用栏时消耗滚动已完全展开或将在 scroll(dy) 被消耗后完全展开。 RecyclerView 可以向上滚动，但它永远不会看到该操作，因为它的行为 SlidingPanelBehavior 会消耗滚动。如果应用栏未完全展开但会在当前滚动条被消耗后展开，该行为会通过调用修改 dy 并在完全消耗滚动条之前调用 super 来强制应用栏完全展开。 （参见 SlidingPanelBehavior#onNestedPreScroll()）。 （在之前的回答中，修改了 appBar 行为。将行为更改放在 RecyclerView 上是更好的选择。）
问题 #3： 当嵌套滚动已处于所需状态时，将 RecyclerView 的嵌套滚动设置为 enable/disabled 会导致问题。为避免这些问题，只有在 ScrollingActivity:
中真正进行更改时才更改嵌套滚动的状态
private void setExpandAndCollapseEnabled(boolean enabled) {
if (mNestedView.isNestedScrollingEnabled() != enabled) {
mNestedView.setNestedScrollingEnabled(enabled);
}
}
这是测试应用程序在进行上述更改后的行为方式：
有上述变化的模块在post.
的末尾
How can I make the top view be replaced with a smaller one when collapsed (and back to large one when expanded), instead of completely disappear ?
[更新] 使较小的视图成为 CollapsingToolbarLayout 的直接子视图，因此它是 Toolbar 的兄弟视图。下面是这种方法的演示。较小视图的 collapseMode 设置为 pin。较小视图的边距以及工具栏的边距都进行了调整，因此较小的视图紧靠工具栏下方。由于 CollapsingToolbarLayout 是一个 FrameLayout，视图堆栈和 FrameLayout 的高度刚好成为最高子视图的高度。 这种结构可以避免insets需要调整的问题和点击效果缺失的问题。
最后一个问题仍然存在，向下拖动应用栏应该打开它，假设向下拖动较小的视图不应该打开应用栏。使用 AppBarLayout.Behavior 的 setDragCallback 允许应用栏在拖动时打开。由于较小的视图已合并到 appBar 中，因此将其向下拖动将打开 appbar。为防止这种情况，应用栏附加了一个名为 MyAppBarBehavior 的新行为。此行为与 MainActivity 中的代码结合可防止拖动较小的视图以打开应用栏，但允许拖动工具栏。
activity_main.xml
<android.support.design.widget.CoordinatorLayout
android:id="@+id/coordinatorLayout"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<android.support.design.widget.AppBarLayout
android:id="@+id/app_bar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:fitsSystemWindows="true"
android:stateListAnimator="@null"
android:theme="@style/AppTheme.AppBarOverlay"
app:expanded="false"
app:layout_behavior=".MyAppBarBehavior"
tools:targetApi="lollipop">
<android.support.design.widget.CollapsingToolbarLayout
android:id="@+id/collapsingToolbarLayout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:clipChildren="false"
android:clipToPadding="false"
android:fitsSystemWindows="true"
app:layout_scrollFlags="scroll|exitUntilCollapsed|snap|enterAlways"
app:statusBarScrim="?attr/colorPrimaryDark">
<!--large view -->
<LinearLayout
android:id="@+id/largeView"
android:layout_width="match_parent"
android:layout_height="280dp"
android:layout_marginTop="?attr/actionBarSize"
android:orientation="vertical"
app:layout_collapseMode="parallax"
app:layout_collapseParallaxMultiplier="1.0">
<TextView
android:id="@+id/largeTextView"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_gravity="center"
android:background="?attr/selectableItemBackgroundBorderless"
android:clickable="true"
android:focusable="true"
android:focusableInTouchMode="false"
android:gravity="center"
android:text="largeView"
android:textSize="14dp"
tools:background="?attr/colorPrimary"
tools:layout_gravity="top|center_horizontal"
tools:layout_height="40dp"
tools:layout_width="40dp"
tools:text="1" />
</LinearLayout>
<!--top toolbar-->
<android.support.v7.widget.Toolbar
android:id="@+id/toolbar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginBottom="@dimen/small_view_height"
app:contentInsetStart="0dp"
app:layout_collapseMode="pin"
app:popupTheme="@style/AppTheme.PopupOverlay">
<android.support.constraint.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:clickable="true"
android:focusable="true">
<LinearLayout
android:id="@+id/expandCollapseButton"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:background="?android:selectableItemBackground"
android:gravity="center_vertical"
android:orientation="horizontal"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent">
<TextView
android:id="@+id/titleTextView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:ellipsize="end"
android:gravity="center"
android:maxLines="1"
android:text="title"
android:textAppearance="@style/TextAppearance.Widget.AppCompat.Toolbar.Title"
android:textColor="@android:color/white" />
<ImageView
android:id="@+id/arrowImageView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="8dp"
android:layout_marginStart="8dp"
app:srcCompat="@android:drawable/arrow_up_float"
tools:ignore="ContentDescription,RtlHardcoded" />
</LinearLayout>
</android.support.constraint.ConstraintLayout>
</android.support.v7.widget.Toolbar>
<!--small view-->
<LinearLayout
android:id="@+id/smallLayout"
android:layout_width="match_parent"
android:layout_height="@dimen/small_view_height"
android:layout_marginTop="?attr/actionBarSize"
android:clipChildren="false"
android:clipToPadding="false"
android:orientation="horizontal"
app:layout_collapseMode="pin"
tools:background="#ff330000"
tools:layout_height="@dimen/small_view_height">
<TextView
android:id="@+id/smallTextView"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_gravity="center"
android:background="?attr/selectableItemBackgroundBorderless"
android:clickable="true"
android:focusable="true"
android:focusableInTouchMode="false"
android:gravity="center"
android:text="smallView"
android:textSize="14dp"
tools:background="?attr/colorPrimary"
tools:layout_gravity="top|center_horizontal"
tools:layout_height="40dp"
tools:layout_width="40dp"
tools:text="1" />
</LinearLayout>
</android.support.design.widget.CollapsingToolbarLayout>
</android.support.design.widget.AppBarLayout>
<com.example.expandedtopviewtestupdate.MyRecyclerView
android:id="@+id/nestedView"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_behavior="@string/appbar_scrolling_view_behavior"
tools:context=".SlidingPanelBehavior" />
</android.support.design.widget.CoordinatorLayout>
最后，在 addOnOffsetChangedListener 中添加以下代码以在应用栏扩展和收缩时在较小的视图中淡出 out/fade。一旦视图的 alpha 为零（不可见），将其可见性设置为 View.INVISIBLE，这样就无法单击它。一旦视图的 alpha 增加到零以上，通过将其可见性设置为 View.VISIBLE.
使其可见和可点击
mSmallLayout.setAlpha((float) -verticalOffset / totalScrollRange);
// If the small layout is not visible, make it officially invisible so
// it can't receive clicks.
if (alpha == 0) {
mSmallLayout.setVisibility(View.INVISIBLE);
} else if (mSmallLayout.getVisibility() == View.INVISIBLE) {
mSmallLayout.setVisibility(View.VISIBLE);
}
结果如下：
这是合并了上述所有更改的新模块。
MainActivity.java
public class MainActivity extends AppCompatActivity
implements MyRecyclerView.AppBarTracking {
private MyRecyclerView mNestedView;
private int mAppBarOffset = 0;
private boolean mAppBarIdle = true;
private int mAppBarMaxOffset = 0;
private AppBarLayout mAppBar;
private boolean mIsExpanded = false;
private ImageView mArrowImageView;
private LinearLayout mSmallLayout;
@Override
protected void onCreate(Bundle savedInstanceState) {
LinearLayout expandCollapse;
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = findViewById(R.id.toolbar);
expandCollapse = findViewById(R.id.expandCollapseButton);
mArrowImageView = findViewById(R.id.arrowImageView);
mNestedView = findViewById(R.id.nestedView);
mAppBar = findViewById(R.id.app_bar);
mSmallLayout = findViewById(R.id.smallLayout);
// Log when the small text view is clicked
findViewById(R.id.smallTextView).setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Log.d(TAG, "<<<<click small layout");
}
});
// Log when the big text view is clicked.
findViewById(R.id.largeTextView).setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Log.d(TAG, "<<<<click big view");
}
});
setSupportActionBar(toolbar);
ActionBar ab = getSupportActionBar();
if (ab != null) {
getSupportActionBar().setDisplayShowTitleEnabled(false);
}
mAppBar.post(new Runnable() {
@Override
public void run() {
mAppBarMaxOffset = -mAppBar.getTotalScrollRange();
CoordinatorLayout.LayoutParams lp =
(CoordinatorLayout.LayoutParams) mAppBar.getLayoutParams();
MyAppBarBehavior behavior = (MyAppBarBehavior) lp.getBehavior();
// Only allow drag-to-open if the drag touch is on the toolbar.
// Once open, all drags are allowed.
if (behavior != null) {
behavior.setCanOpenBottom(findViewById(R.id.toolbar).getHeight());
}
}
});
mNestedView.setAppBarTracking(this);
mNestedView.setLayoutManager(new LinearLayoutManager(this));
mNestedView.setAdapter(new RecyclerView.Adapter<RecyclerView.ViewHolder>() {
@Override
public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
return new ViewHolder(
LayoutInflater.from(parent.getContext())
.inflate(android.R.layout.simple_list_item_1, parent, false));
}
@SuppressLint("SetTextI18n")
@Override
public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
((TextView) holder.itemView.findViewById(android.R.id.text1))
.setText("Item " + position);
}
@Override
public int getItemCount() {
return 200;
}
class ViewHolder extends RecyclerView.ViewHolder {
public ViewHolder(View view) {
super(view);
}
}
});
mAppBar.addOnOffsetChangedListener(new AppBarLayout.OnOffsetChangedListener() {
@Override
public void onOffsetChanged(AppBarLayout appBarLayout, int verticalOffset) {
mAppBarOffset = verticalOffset;
int totalScrollRange = appBarLayout.getTotalScrollRange();
float progress = (float) (-verticalOffset) / (float) totalScrollRange;
mArrowImageView.setRotation(-progress * 180);
mIsExpanded = verticalOffset == 0;
mAppBarIdle = mAppBarOffset >= 0 || mAppBarOffset <= mAppBarMaxOffset;
float alpha = (float) -verticalOffset / totalScrollRange;
mSmallLayout.setAlpha(alpha);
// If the small layout is not visible, make it officially invisible so
// it can't receive clicks.
if (alpha == 0) {
mSmallLayout.setVisibility(View.INVISIBLE);
} else if (mSmallLayout.getVisibility() == View.INVISIBLE) {
mSmallLayout.setVisibility(View.VISIBLE);
}
}
});
expandCollapse.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
setExpandAndCollapseEnabled(true);
if (mIsExpanded) {
setExpandAndCollapseEnabled(false);
}
mIsExpanded = !mIsExpanded;
mNestedView.stopScroll();
mAppBar.setExpanded(mIsExpanded, true);
}
});
}
private void setExpandAndCollapseEnabled(boolean enabled) {
if (mNestedView.isNestedScrollingEnabled() != enabled) {
mNestedView.setNestedScrollingEnabled(enabled);
}
}
@Override
public boolean isAppBarExpanded() {
return mAppBarOffset == 0;
}
@Override
public boolean isAppBarIdle() {
return mAppBarIdle;
}
private static final String TAG = "MainActivity";
}
SlidingPanelBehavior.java
public class SlidingPanelBehavior extends AppBarLayout.ScrollingViewBehavior {
private AppBarLayout mAppBar;
public SlidingPanelBehavior() {
super();
}
public SlidingPanelBehavior(Context context, AttributeSet attrs) {
super(context, attrs);
}
@Override
public boolean layoutDependsOn(final CoordinatorLayout parent, View child, View dependency) {
if (mAppBar == null && dependency instanceof AppBarLayout) {
// Capture our appbar for later use.
mAppBar = (AppBarLayout) dependency;
}
return dependency instanceof AppBarLayout;
}
@Override
public boolean onInterceptTouchEvent(CoordinatorLayout parent, View child, MotionEvent event) {
int action = event.getAction();
if (event.getAction() != MotionEvent.ACTION_DOWN) { // Only want "down" events
return false;
}
if (getAppBarLayoutOffset(mAppBar) == -mAppBar.getTotalScrollRange()) {
// When appbar is collapsed, don't let it open through nested scrolling.
setNestedScrollingEnabledWithTest((NestedScrollingChild2) child, false);
} else {
// Appbar is partially to fully expanded. Set nested scrolling enabled to activate
// the methods within this behavior.
setNestedScrollingEnabledWithTest((NestedScrollingChild2) child, true);
}
return false;
}
@Override
public boolean onStartNestedScroll(@NonNull CoordinatorLayout coordinatorLayout, @NonNull View child,
@NonNull View directTargetChild, @NonNull View target,
int axes, int type) {
//noinspection RedundantCast
return ((NestedScrollingChild2) child).isNestedScrollingEnabled();
}
@Override
public void onNestedPreScroll(@NonNull CoordinatorLayout coordinatorLayout, @NonNull View child,
@NonNull View target, int dx, int dy, @NonNull int[] consumed,
int type) {
// How many pixels we must scroll to fully expand the appbar. This value is <= 0.
final int appBarOffset = getAppBarLayoutOffset(mAppBar);
// Check to see if this scroll will expand the appbar 100% or collapse it fully.
if (dy <= appBarOffset) {
// Scroll by the amount that will fully expand the appbar and dispose of the rest (dy).
super.onNestedPreScroll(coordinatorLayout, mAppBar, target, dx,
appBarOffset, consumed, type);
consumed[1] += dy;
} else if (dy >= (mAppBar.getTotalScrollRange() + appBarOffset)) {
// This scroll will collapse the appbar. Collapse it and dispose of the rest.
super.onNestedPreScroll(coordinatorLayout, mAppBar, target, dx,
mAppBar.getTotalScrollRange() + appBarOffset,
consumed, type);
consumed[1] += dy;
} else {
// This scroll will leave the appbar partially open. Just do normal stuff.
super.onNestedPreScroll(coordinatorLayout, child, target, dx, dy, consumed, type);
}
}
/**
* {@code onNestedPreFling()} is overriden to address a nested scrolling defect that was
* introduced in API 26. This method prevent the appbar from misbehaving when scrolled/flung.
* <p>
* Refer to <a href="https://issuetracker.google.com/issues/65448468" target="_blank">"Bug in design support library"</a>
*/
@Override
public boolean onNestedPreFling(@NonNull CoordinatorLayout coordinatorLayout,
@NonNull View child, @NonNull View target,
float velocityX, float velocityY) {
//noinspection RedundantCast
if (((NestedScrollingChild2) child).isNestedScrollingEnabled()) {
// Just stop the nested fling and let the appbar settle into place.
((NestedScrollingChild2) child).stopNestedScroll(ViewCompat.TYPE_NON_TOUCH);
return true;
}
return super.onNestedPreFling(coordinatorLayout, child, target, velocityX, velocityY);
}
private static int getAppBarLayoutOffset(AppBarLayout appBar) {
final CoordinatorLayout.Behavior behavior =
((CoordinatorLayout.LayoutParams) appBar.getLayoutParams()).getBehavior();
if (behavior instanceof AppBarLayout.Behavior) {
return ((AppBarLayout.Behavior) behavior).getTopAndBottomOffset();
}
return 0;
}
// Something goes amiss when the flag it set to its current value, so only call
// setNestedScrollingEnabled() if it will result in a change.
private void setNestedScrollingEnabledWithTest(NestedScrollingChild2 child, boolean enabled) {
if (child.isNestedScrollingEnabled() != enabled) {
child.setNestedScrollingEnabled(enabled);
}
}
@SuppressWarnings("unused")
private static final String TAG = "SlidingPanelBehavior";
}
MyRecyclerView.kt
/**A RecyclerView that allows temporary pausing of casuing its scroll to affect appBarLayout, based on */
class MyRecyclerView @JvmOverloads constructor(context: Context, attrs: AttributeSet? = null, defStyle: Int = 0) : RecyclerView(context, attrs, defStyle) {
private var mAppBarTracking: AppBarTracking? = null
private var mView: View? = null
private var mTopPos: Int = 0
private var mLayoutManager: LinearLayoutManager? = null
interface AppBarTracking {
fun isAppBarIdle(): Boolean
fun isAppBarExpanded(): Boolean
}
override fun dispatchNestedPreScroll(dx: Int, dy: Int, consumed: IntArray?, offsetInWindow: IntArray?, type: Int): Boolean {
if (type == ViewCompat.TYPE_NON_TOUCH && mAppBarTracking!!.isAppBarIdle()
&& isNestedScrollingEnabled) {
if (dy > 0) {
if (mAppBarTracking!!.isAppBarExpanded()) {
consumed!![1] = dy
return true
}
} else {
mTopPos = mLayoutManager!!.findFirstVisibleItemPosition()
if (mTopPos == 0) {
mView = mLayoutManager!!.findViewByPosition(mTopPos)
if (-mView!!.top + dy <= 0) {
consumed!![1] = dy - mView!!.top
return true
}
}
}
}
if (dy < 0 && type == ViewCompat.TYPE_TOUCH && mAppBarTracking!!.isAppBarExpanded()) {
consumed!![1] = dy
return true
}
val returnValue = super.dispatchNestedPreScroll(dx, dy, consumed, offsetInWindow, type)
if (offsetInWindow != null && !isNestedScrollingEnabled && offsetInWindow[1] != 0)
offsetInWindow[1] = 0
return returnValue
}
override fun setLayoutManager(layout: RecyclerView.LayoutManager) {
super.setLayoutManager(layout)
mLayoutManager = layoutManager as LinearLayoutManager
}
fun setAppBarTracking(appBarTracking: AppBarTracking) {
mAppBarTracking = appBarTracking
}
override fun fling(velocityX: Int, velocityY: Int): Boolean {
var velocityY = velocityY
if (!mAppBarTracking!!.isAppBarIdle()) {
val vc = ViewConfiguration.get(context)
velocityY = if (velocityY < 0) -vc.scaledMinimumFlingVelocity
else vc.scaledMinimumFlingVelocity
}
return super.fling(velocityX, velocityY)
}
}
MyAppBarBehavior.java
/**
* Attach this behavior to AppBarLayout to disable the bottom portion of a closed appBar
* so it cannot be touched to open the appBar. This behavior is helpful if there is some
* portion of the appBar that displays when the appBar is closed, but should not open the appBar
* when the appBar is closed.
*/
public class MyAppBarBehavior extends AppBarLayout.Behavior {
// Touch above this y-axis value can open the appBar.
private int mCanOpenBottom;
// Determines if the appBar can be dragged open or not via direct touch on the appBar.
private boolean mCanDrag = true;
@SuppressWarnings("unused")
public MyAppBarBehavior() {
init();
}
@SuppressWarnings("unused")
public MyAppBarBehavior(Context context, AttributeSet attrs) {
super(context, attrs);
init();
}
private void init() {
setDragCallback(new AppBarLayout.Behavior.DragCallback() {
@Override
public boolean canDrag(@NonNull AppBarLayout appBarLayout) {
return mCanDrag;
}
});
}
@Override
public boolean onInterceptTouchEvent(CoordinatorLayout parent,
AppBarLayout child,
MotionEvent event) {
if (event.getAction() == MotionEvent.ACTION_DOWN) {
// If appBar is closed. Only allow scrolling in defined area.
if (child.getTop() <= -child.getTotalScrollRange()) {
mCanDrag = event.getY() < mCanOpenBottom;
}
}
return super.onInterceptTouchEvent(parent, child, event);
}
public void setCanOpenBottom(int bottom) {
mCanOpenBottom = bottom;
}
}
这个问题之前被问的太笼统和不清楚 here，所以我把它变得更加具体，并提供了我尝试过的内容的完整解释和代码。
背景
我需要模仿 Google 日历在顶部有一个视图的方式，该视图可以动画和下推底部的视图，但它有额外的、不同的行为。我总结了我在 3 个特征上尝试做的事情：
- 按下工具栏上的按钮将始终有效，以切换 expanding/collapsing 顶视图，同时有一个箭头图标可以改变其旋转。这就像 Google 日历应用程序。
- 顶视图将始终捕捉，就像在 Google 日历应用程序上一样。
- 当顶视图被折叠时，只有在工具栏上按下才能展开它。这就像 Google 日历应用
- 当顶视图展开时，在底视图滚动将只允许折叠。如果您尝试向另一个方向滚动，什么也不会发生，甚至不会滚动到底部视图。这就像 Google 日历应用
- 折叠后，顶视图将替换为较小的视图。这意味着它总是需要一些 space，高于底部视图。这与 Google 日历应用程序不同，因为在日历应用程序中，顶部视图一旦折叠就会完全消失。
Google 日历应用的外观如下：
滚动底部视图也会慢慢隐藏顶部视图：
问题
使用我过去发现的各种解决方案，我只成功实现了所需行为的一部分：
在工具栏中有一些 UI 是通过在其中包含一些视图（包括箭头视图）来完成的。对于手动 expanding/collapsing，我在
AppBarLayout视图上使用setExpanded。对于箭头的旋转，我使用AppBarLayout调整大小的侦听器，在其上使用addOnOffsetChangedListener。通过将
snap值添加到CollapsingToolbarLayout的layout_scrollFlags属性中，可以轻松完成捕捉。然而，为了让它真正运行良好，没有奇怪的问题（报告here), I used阻止滚动时影响顶视图可以通过使用我在 #2 (
setExpandEnabled。 这在顶视图折叠时效果很好。与#3 类似，但遗憾的是，由于它使用了
setNestedScrollingEnabled，它是双向的，因此仅当顶视图折叠时效果很好。当它展开时，它仍然允许底部视图向上滚动，这与日历应用程序相反。展开时，我需要它只允许折叠，不允许真正滚动。
以下是优点和缺点的演示：
- 我完全没有做到这一点。我已经尝试了很多我想到的解决方案，将视图放在带有各种标志的各个地方。
简而言之，我成功地完成了 1-3，但没有完成 4-5。
密码
这是当前代码（也可作为整个项目 here）：
ScrollingActivity.kt
class ScrollingActivity : AppCompatActivity(), AppBarTracking {
private var mNestedView: MyRecyclerView? = null
private var mAppBarOffset: Int = 0
private var mAppBarIdle = false
private var mAppBarMaxOffset: Int = 0
private var isExpanded: Boolean = false
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_scrolling)
val toolbar = findViewById<Toolbar>(R.id.toolbar)
setSupportActionBar(toolbar)
mNestedView = findViewById(R.id.nestedView)
app_bar.addOnOffsetChangedListener({ appBarLayout, verticalOffset ->
mAppBarOffset = verticalOffset
val totalScrollRange = appBarLayout.totalScrollRange
val progress = (-verticalOffset).toFloat() / totalScrollRange
arrowImageView.rotation = 180 + progress * 180
isExpanded = verticalOffset == 0;
mAppBarIdle = mAppBarOffset >= 0 || mAppBarOffset <= mAppBarMaxOffset
if (mAppBarIdle)
setExpandAndCollapseEnabled(isExpanded)
})
app_bar.post(Runnable { mAppBarMaxOffset = -app_bar.totalScrollRange })
mNestedView!!.setAppBarTracking(this)
mNestedView!!.layoutManager = LinearLayoutManager(this)
mNestedView!!.adapter = object : RecyclerView.Adapter<RecyclerView.ViewHolder>() {
override fun getItemCount(): Int = 100
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
return object : ViewHolder(LayoutInflater.from(parent.context).inflate(android.R.layout.simple_list_item_1, parent, false)) {}
}
override fun onBindViewHolder(holder: ViewHolder, position: Int) {
(holder.itemView.findViewById<View>(android.R.id.text1) as TextView).text = "item $position"
}
}
expandCollapseButton.setOnClickListener({ v ->
isExpanded = !isExpanded
app_bar.setExpanded(isExpanded, true)
})
}
private fun setExpandAndCollapseEnabled(enabled: Boolean) {
mNestedView!!.isNestedScrollingEnabled = enabled
}
override fun isAppBarExpanded(): Boolean = mAppBarOffset == 0
override fun isAppBarIdle(): Boolean = mAppBarIdle
}
MyRecyclerView.kt
/**A RecyclerView that allows temporary pausing of casuing its scroll to affect appBarLayout, based on */
class MyRecyclerView @JvmOverloads constructor(context: Context, attrs: AttributeSet? = null, defStyle: Int = 0) : RecyclerView(context, attrs, defStyle) {
private var mAppBarTracking: AppBarTracking? = null
private var mView: View? = null
private var mTopPos: Int = 0
private var mLayoutManager: LinearLayoutManager? = null
interface AppBarTracking {
fun isAppBarIdle(): Boolean
fun isAppBarExpanded(): Boolean
}
override fun dispatchNestedPreScroll(dx: Int, dy: Int, consumed: IntArray?, offsetInWindow: IntArray?,
type: Int): Boolean {
if (type == ViewCompat.TYPE_NON_TOUCH && mAppBarTracking!!.isAppBarIdle()
&& isNestedScrollingEnabled) {
if (dy > 0) {
if (mAppBarTracking!!.isAppBarExpanded()) {
consumed!![1] = dy
return true
}
} else {
mTopPos = mLayoutManager!!.findFirstVisibleItemPosition()
if (mTopPos == 0) {
mView = mLayoutManager!!.findViewByPosition(mTopPos)
if (-mView!!.top + dy <= 0) {
consumed!![1] = dy - mView!!.top
return true
}
}
}
}
val returnValue = super.dispatchNestedPreScroll(dx, dy, consumed, offsetInWindow, type)
if (offsetInWindow != null && !isNestedScrollingEnabled && offsetInWindow[1] != 0)
offsetInWindow[1] = 0
return returnValue
}
override fun setLayoutManager(layout: RecyclerView.LayoutManager) {
super.setLayoutManager(layout)
mLayoutManager = layoutManager as LinearLayoutManager
}
fun setAppBarTracking(appBarTracking: AppBarTracking) {
mAppBarTracking = appBarTracking
}
}
ScrollingCalendarBehavior.kt
class ScrollingCalendarBehavior(context: Context, attrs: AttributeSet) : AppBarLayout.Behavior(context, attrs) {
override fun onInterceptTouchEvent(parent: CoordinatorLayout?, child: AppBarLayout?, ev: MotionEvent): Boolean = false
}
activity_scrolling.xml
<android.support.design.widget.CoordinatorLayout
android:id="@+id/coordinatorLayout" xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent" android:layout_height="match_parent" tools:context=".ScrollingActivity">
<android.support.design.widget.AppBarLayout
android:id="@+id/app_bar" android:layout_width="match_parent" android:layout_height="wrap_content"
android:fitsSystemWindows="true" android:stateListAnimator="@null" android:theme="@style/AppTheme.AppBarOverlay"
app:expanded="false" app:layout_behavior="com.example.user.expandingtopviewtest.ScrollingCalendarBehavior"
tools:targetApi="lollipop">
<android.support.design.widget.CollapsingToolbarLayout
android:id="@+id/collapsingToolbarLayout" android:layout_width="match_parent"
android:layout_height="match_parent" android:fitsSystemWindows="true"
android:minHeight="?attr/actionBarSize" app:contentScrim="?attr/colorPrimary"
app:layout_scrollFlags="scroll|exitUntilCollapsed|snap" app:statusBarScrim="?attr/colorPrimaryDark">
<LinearLayout
android:layout_width="match_parent" android:layout_height="250dp"
android:layout_marginTop="?attr/actionBarSize" app:layout_collapseMode="parallax"
app:layout_collapseParallaxMultiplier="1.0">
<TextView
android:layout_width="match_parent" android:layout_height="match_parent" android:paddingLeft="10dp"
android:paddingRight="10dp" android:text="some large, expanded view"/>
</LinearLayout>
<android.support.v7.widget.Toolbar
android:id="@+id/toolbar" android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize" app:layout_collapseMode="pin"
app:popupTheme="@style/AppTheme.PopupOverlay">
<android.support.constraint.ConstraintLayout
android:id="@+id/expandCollapseButton" android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize" android:background="?android:selectableItemBackground"
android:clickable="true" android:focusable="true" android:orientation="vertical">
<TextView
android:id="@+id/titleTextView" android:layout_width="wrap_content"
android:layout_height="wrap_content" android:layout_marginBottom="8dp"
android:layout_marginLeft="8dp" android:layout_marginStart="8dp" android:ellipsize="end"
android:gravity="center" android:maxLines="1" android:text="title"
android:textAppearance="@style/TextAppearance.Widget.AppCompat.Toolbar.Title"
android:textColor="@android:color/white" app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintStart_toStartOf="parent"/>
<ImageView
android:id="@+id/arrowImageView" android:layout_width="wrap_content" android:layout_height="0dp"
android:layout_marginLeft="8dp" android:layout_marginStart="8dp"
app:layout_constraintBottom_toBottomOf="@+id/titleTextView"
app:layout_constraintStart_toEndOf="@+id/titleTextView"
app:layout_constraintTop_toTopOf="@+id/titleTextView"
app:srcCompat="@android:drawable/arrow_down_float"
tools:ignore="ContentDescription,RtlHardcoded"/>
</android.support.constraint.ConstraintLayout>
</android.support.v7.widget.Toolbar>
</android.support.design.widget.CollapsingToolbarLayout>
</android.support.design.widget.AppBarLayout>
<com.example.user.expandingtopviewtest.MyRecyclerView
android:id="@+id/nestedView" android:layout_width="match_parent" android:layout_height="match_parent"
app:layout_behavior="@string/appbar_scrolling_view_behavior" tools:context=".ScrollingActivity"/>
</android.support.design.widget.CoordinatorLayout>
问题
如何在展开顶部视图时阻止滚动，但在滚动时允许折叠？
如何使顶视图在折叠时被替换为较小的视图（并在展开时变回大视图），而不是完全消失？
更新
尽管我已经了解了我所询问的基本内容，但当前代码仍然存在 2 个问题（在 Github、here 上可用）：
- 小视图（您在折叠状态下看到的视图）具有内部视图，需要对其产生点击效果。在它们上面使用
android:background="?attr/selectableItemBackgroundBorderless"并在展开时单击此区域时，单击是在小视图上完成的。我通过将小视图放在不同的工具栏上来处理它，但是点击效果根本没有显示出来。我已经写过关于这个 here 的文章，包括示例项目。
修复方法如下：
<android.support.design.widget.CoordinatorLayout
android:id="@+id/coordinatorLayout" xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent" android:layout_height="match_parent" tools:context=".MainActivity">
<android.support.design.widget.AppBarLayout
android:id="@+id/app_bar" android:layout_width="match_parent" android:layout_height="wrap_content"
android:fitsSystemWindows="true" android:stateListAnimator="@null" android:theme="@style/AppTheme.AppBarOverlay"
app:expanded="false" app:layout_behavior="com.example.expandedtopviewtestupdate.ScrollingCalendarBehavior"
tools:targetApi="lollipop">
<android.support.design.widget.CollapsingToolbarLayout
android:id="@+id/collapsingToolbarLayout" android:layout_width="match_parent"
android:layout_height="match_parent" android:clipChildren="false" android:clipToPadding="false"
android:fitsSystemWindows="true" app:contentScrim="?attr/colorPrimary"
app:layout_scrollFlags="scroll|exitUntilCollapsed|snap|enterAlways"
app:statusBarScrim="?attr/colorPrimaryDark">
<!--large view -->
<LinearLayout
android:id="@+id/largeView" android:layout_width="match_parent" android:layout_height="280dp"
android:layout_marginTop="?attr/actionBarSize" android:orientation="vertical"
app:layout_collapseMode="parallax" app:layout_collapseParallaxMultiplier="1.0">
<TextView
android:id="@+id/largeTextView" android:layout_width="match_parent"
android:layout_height="match_parent" android:layout_gravity="center"
android:background="?attr/selectableItemBackgroundBorderless" android:clickable="true"
android:focusable="true" android:focusableInTouchMode="false" android:gravity="center"
android:text="largeView" android:textSize="14dp" tools:background="?attr/colorPrimary"
tools:layout_gravity="top|center_horizontal" tools:layout_height="40dp" tools:layout_width="40dp"
tools:text="1"/>
</LinearLayout>
<!--top toolbar-->
<android.support.v7.widget.Toolbar
android:id="@+id/toolbar" android:layout_width="match_parent" android:layout_height="wrap_content"
android:layout_marginBottom="@dimen/small_view_height" app:contentInsetStart="0dp"
app:layout_collapseMode="pin" app:popupTheme="@style/AppTheme.PopupOverlay">
<android.support.constraint.ConstraintLayout
android:layout_width="match_parent" android:layout_height="wrap_content" android:clickable="true"
android:focusable="true">
<LinearLayout
android:id="@+id/expandCollapseButton" android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:background="?android:selectableItemBackground" android:gravity="center_vertical"
android:orientation="horizontal" app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent">
<TextView
android:id="@+id/titleTextView" android:layout_width="wrap_content"
android:layout_height="wrap_content" android:ellipsize="end" android:gravity="center"
android:maxLines="1" android:text="title"
android:textAppearance="@style/TextAppearance.Widget.AppCompat.Toolbar.Title"
android:textColor="@android:color/white"/>
<ImageView
android:id="@+id/arrowImageView" android:layout_width="wrap_content"
android:layout_height="wrap_content" android:layout_marginLeft="8dp"
android:layout_marginStart="8dp" app:srcCompat="@android:drawable/arrow_up_float"
tools:ignore="ContentDescription,RtlHardcoded"/>
</LinearLayout>
</android.support.constraint.ConstraintLayout>
</android.support.v7.widget.Toolbar>
<android.support.v7.widget.Toolbar
android:id="@+id/smallLayoutContainer" android:layout_width="match_parent"
android:layout_height="wrap_content" android:layout_marginTop="?attr/actionBarSize"
android:clipChildren="false" android:clipToPadding="false" app:contentInsetStart="0dp"
app:layout_collapseMode="pin">
<!--small view-->
<LinearLayout
android:id="@+id/smallLayout" android:layout_width="match_parent"
android:layout_height="@dimen/small_view_height" android:clipChildren="false"
android:clipToPadding="false" android:orientation="horizontal" tools:background="#ff330000"
tools:layout_height="@dimen/small_view_height">
<TextView
android:id="@+id/smallTextView" android:layout_width="match_parent"
android:layout_height="match_parent" android:layout_gravity="center"
android:background="?attr/selectableItemBackgroundBorderless" android:clickable="true"
android:focusable="true" android:focusableInTouchMode="false" android:gravity="center"
android:text="smallView" android:textSize="14dp" tools:background="?attr/colorPrimary"
tools:layout_gravity="top|center_horizontal" tools:layout_height="40dp"
tools:layout_width="40dp" tools:text="1"/>
</LinearLayout>
</android.support.v7.widget.Toolbar>
</android.support.design.widget.CollapsingToolbarLayout>
</android.support.design.widget.AppBarLayout>
<com.example.expandedtopviewtestupdate.MyRecyclerView
android:id="@+id/nestedView" android:layout_width="match_parent" android:layout_height="match_parent"
app:layout_behavior="@string/appbar_scrolling_view_behavior" tools:context=".ScrollingActivity"/>
</android.support.design.widget.CoordinatorLayout>
- Google 日历允许在工具栏本身上执行向下滚动手势，以触发显示月视图。我只成功地在那里添加了一个点击事件，但没有滚动。它是这样的：
注意：完整的更新项目可用 here。
How can I make the scrolling being blocked when the top view is expanded, yet allow to collapse while scrolling ?
问题 #1： 当应用栏未折叠时，RecyclerView 根本无法滚动。要解决此问题，请将 enterAlways 添加到 CollapsingToolbarLayout 的滚动标志，如下所示：
<android.support.design.widget.CollapsingToolbarLayout
android:id="@+id/collapsingToolbarLayout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:clipChildren="false"
android:clipToPadding="false"
android:fitsSystemWindows="true"
app:layout_scrollFlags="scroll|exitUntilCollapsed|snap|enterAlways"
app:statusBarScrim="?attr/colorPrimaryDark">
enterAlways 不会导致应用栏在关闭时打开，因为您正在抑制该功能，但可以正常工作。
问题 #2： 当应用栏完全展开时，不应允许 RecyclerView 向上滚动。这恰好是问题 #1 的不同问题。
[已更新] 要更正此问题，请修改 RecyclerView 的行为以在 RecyclerView 尝试向上滚动和应用栏时消耗滚动已完全展开或将在 scroll(dy) 被消耗后完全展开。 RecyclerView 可以向上滚动，但它永远不会看到该操作，因为它的行为 SlidingPanelBehavior 会消耗滚动。如果应用栏未完全展开但会在当前滚动条被消耗后展开，该行为会通过调用修改 dy 并在完全消耗滚动条之前调用 super 来强制应用栏完全展开。 （参见 SlidingPanelBehavior#onNestedPreScroll()）。 （在之前的回答中，修改了 appBar 行为。将行为更改放在 RecyclerView 上是更好的选择。）
问题 #3： 当嵌套滚动已处于所需状态时，将 RecyclerView 的嵌套滚动设置为 enable/disabled 会导致问题。为避免这些问题，只有在 ScrollingActivity:
private void setExpandAndCollapseEnabled(boolean enabled) {
if (mNestedView.isNestedScrollingEnabled() != enabled) {
mNestedView.setNestedScrollingEnabled(enabled);
}
}
这是测试应用程序在进行上述更改后的行为方式：
有上述变化的模块在post.
的末尾How can I make the top view be replaced with a smaller one when collapsed (and back to large one when expanded), instead of completely disappear ?
[更新] 使较小的视图成为 CollapsingToolbarLayout 的直接子视图，因此它是 Toolbar 的兄弟视图。下面是这种方法的演示。较小视图的 collapseMode 设置为 pin。较小视图的边距以及工具栏的边距都进行了调整，因此较小的视图紧靠工具栏下方。由于 CollapsingToolbarLayout 是一个 FrameLayout，视图堆栈和 FrameLayout 的高度刚好成为最高子视图的高度。 这种结构可以避免insets需要调整的问题和点击效果缺失的问题。
最后一个问题仍然存在，向下拖动应用栏应该打开它，假设向下拖动较小的视图不应该打开应用栏。使用 AppBarLayout.Behavior 的 setDragCallback 允许应用栏在拖动时打开。由于较小的视图已合并到 appBar 中，因此将其向下拖动将打开 appbar。为防止这种情况，应用栏附加了一个名为 MyAppBarBehavior 的新行为。此行为与 MainActivity 中的代码结合可防止拖动较小的视图以打开应用栏，但允许拖动工具栏。
activity_main.xml
<android.support.design.widget.CoordinatorLayout
android:id="@+id/coordinatorLayout"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<android.support.design.widget.AppBarLayout
android:id="@+id/app_bar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:fitsSystemWindows="true"
android:stateListAnimator="@null"
android:theme="@style/AppTheme.AppBarOverlay"
app:expanded="false"
app:layout_behavior=".MyAppBarBehavior"
tools:targetApi="lollipop">
<android.support.design.widget.CollapsingToolbarLayout
android:id="@+id/collapsingToolbarLayout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:clipChildren="false"
android:clipToPadding="false"
android:fitsSystemWindows="true"
app:layout_scrollFlags="scroll|exitUntilCollapsed|snap|enterAlways"
app:statusBarScrim="?attr/colorPrimaryDark">
<!--large view -->
<LinearLayout
android:id="@+id/largeView"
android:layout_width="match_parent"
android:layout_height="280dp"
android:layout_marginTop="?attr/actionBarSize"
android:orientation="vertical"
app:layout_collapseMode="parallax"
app:layout_collapseParallaxMultiplier="1.0">
<TextView
android:id="@+id/largeTextView"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_gravity="center"
android:background="?attr/selectableItemBackgroundBorderless"
android:clickable="true"
android:focusable="true"
android:focusableInTouchMode="false"
android:gravity="center"
android:text="largeView"
android:textSize="14dp"
tools:background="?attr/colorPrimary"
tools:layout_gravity="top|center_horizontal"
tools:layout_height="40dp"
tools:layout_width="40dp"
tools:text="1" />
</LinearLayout>
<!--top toolbar-->
<android.support.v7.widget.Toolbar
android:id="@+id/toolbar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginBottom="@dimen/small_view_height"
app:contentInsetStart="0dp"
app:layout_collapseMode="pin"
app:popupTheme="@style/AppTheme.PopupOverlay">
<android.support.constraint.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:clickable="true"
android:focusable="true">
<LinearLayout
android:id="@+id/expandCollapseButton"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:background="?android:selectableItemBackground"
android:gravity="center_vertical"
android:orientation="horizontal"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent">
<TextView
android:id="@+id/titleTextView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:ellipsize="end"
android:gravity="center"
android:maxLines="1"
android:text="title"
android:textAppearance="@style/TextAppearance.Widget.AppCompat.Toolbar.Title"
android:textColor="@android:color/white" />
<ImageView
android:id="@+id/arrowImageView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="8dp"
android:layout_marginStart="8dp"
app:srcCompat="@android:drawable/arrow_up_float"
tools:ignore="ContentDescription,RtlHardcoded" />
</LinearLayout>
</android.support.constraint.ConstraintLayout>
</android.support.v7.widget.Toolbar>
<!--small view-->
<LinearLayout
android:id="@+id/smallLayout"
android:layout_width="match_parent"
android:layout_height="@dimen/small_view_height"
android:layout_marginTop="?attr/actionBarSize"
android:clipChildren="false"
android:clipToPadding="false"
android:orientation="horizontal"
app:layout_collapseMode="pin"
tools:background="#ff330000"
tools:layout_height="@dimen/small_view_height">
<TextView
android:id="@+id/smallTextView"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_gravity="center"
android:background="?attr/selectableItemBackgroundBorderless"
android:clickable="true"
android:focusable="true"
android:focusableInTouchMode="false"
android:gravity="center"
android:text="smallView"
android:textSize="14dp"
tools:background="?attr/colorPrimary"
tools:layout_gravity="top|center_horizontal"
tools:layout_height="40dp"
tools:layout_width="40dp"
tools:text="1" />
</LinearLayout>
</android.support.design.widget.CollapsingToolbarLayout>
</android.support.design.widget.AppBarLayout>
<com.example.expandedtopviewtestupdate.MyRecyclerView
android:id="@+id/nestedView"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_behavior="@string/appbar_scrolling_view_behavior"
tools:context=".SlidingPanelBehavior" />
</android.support.design.widget.CoordinatorLayout>
最后，在 addOnOffsetChangedListener 中添加以下代码以在应用栏扩展和收缩时在较小的视图中淡出 out/fade。一旦视图的 alpha 为零（不可见），将其可见性设置为 View.INVISIBLE，这样就无法单击它。一旦视图的 alpha 增加到零以上，通过将其可见性设置为 View.VISIBLE.
mSmallLayout.setAlpha((float) -verticalOffset / totalScrollRange);
// If the small layout is not visible, make it officially invisible so
// it can't receive clicks.
if (alpha == 0) {
mSmallLayout.setVisibility(View.INVISIBLE);
} else if (mSmallLayout.getVisibility() == View.INVISIBLE) {
mSmallLayout.setVisibility(View.VISIBLE);
}
结果如下：
这是合并了上述所有更改的新模块。
MainActivity.java
public class MainActivity extends AppCompatActivity
implements MyRecyclerView.AppBarTracking {
private MyRecyclerView mNestedView;
private int mAppBarOffset = 0;
private boolean mAppBarIdle = true;
private int mAppBarMaxOffset = 0;
private AppBarLayout mAppBar;
private boolean mIsExpanded = false;
private ImageView mArrowImageView;
private LinearLayout mSmallLayout;
@Override
protected void onCreate(Bundle savedInstanceState) {
LinearLayout expandCollapse;
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = findViewById(R.id.toolbar);
expandCollapse = findViewById(R.id.expandCollapseButton);
mArrowImageView = findViewById(R.id.arrowImageView);
mNestedView = findViewById(R.id.nestedView);
mAppBar = findViewById(R.id.app_bar);
mSmallLayout = findViewById(R.id.smallLayout);
// Log when the small text view is clicked
findViewById(R.id.smallTextView).setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Log.d(TAG, "<<<<click small layout");
}
});
// Log when the big text view is clicked.
findViewById(R.id.largeTextView).setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Log.d(TAG, "<<<<click big view");
}
});
setSupportActionBar(toolbar);
ActionBar ab = getSupportActionBar();
if (ab != null) {
getSupportActionBar().setDisplayShowTitleEnabled(false);
}
mAppBar.post(new Runnable() {
@Override
public void run() {
mAppBarMaxOffset = -mAppBar.getTotalScrollRange();
CoordinatorLayout.LayoutParams lp =
(CoordinatorLayout.LayoutParams) mAppBar.getLayoutParams();
MyAppBarBehavior behavior = (MyAppBarBehavior) lp.getBehavior();
// Only allow drag-to-open if the drag touch is on the toolbar.
// Once open, all drags are allowed.
if (behavior != null) {
behavior.setCanOpenBottom(findViewById(R.id.toolbar).getHeight());
}
}
});
mNestedView.setAppBarTracking(this);
mNestedView.setLayoutManager(new LinearLayoutManager(this));
mNestedView.setAdapter(new RecyclerView.Adapter<RecyclerView.ViewHolder>() {
@Override
public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
return new ViewHolder(
LayoutInflater.from(parent.getContext())
.inflate(android.R.layout.simple_list_item_1, parent, false));
}
@SuppressLint("SetTextI18n")
@Override
public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
((TextView) holder.itemView.findViewById(android.R.id.text1))
.setText("Item " + position);
}
@Override
public int getItemCount() {
return 200;
}
class ViewHolder extends RecyclerView.ViewHolder {
public ViewHolder(View view) {
super(view);
}
}
});
mAppBar.addOnOffsetChangedListener(new AppBarLayout.OnOffsetChangedListener() {
@Override
public void onOffsetChanged(AppBarLayout appBarLayout, int verticalOffset) {
mAppBarOffset = verticalOffset;
int totalScrollRange = appBarLayout.getTotalScrollRange();
float progress = (float) (-verticalOffset) / (float) totalScrollRange;
mArrowImageView.setRotation(-progress * 180);
mIsExpanded = verticalOffset == 0;
mAppBarIdle = mAppBarOffset >= 0 || mAppBarOffset <= mAppBarMaxOffset;
float alpha = (float) -verticalOffset / totalScrollRange;
mSmallLayout.setAlpha(alpha);
// If the small layout is not visible, make it officially invisible so
// it can't receive clicks.
if (alpha == 0) {
mSmallLayout.setVisibility(View.INVISIBLE);
} else if (mSmallLayout.getVisibility() == View.INVISIBLE) {
mSmallLayout.setVisibility(View.VISIBLE);
}
}
});
expandCollapse.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
setExpandAndCollapseEnabled(true);
if (mIsExpanded) {
setExpandAndCollapseEnabled(false);
}
mIsExpanded = !mIsExpanded;
mNestedView.stopScroll();
mAppBar.setExpanded(mIsExpanded, true);
}
});
}
private void setExpandAndCollapseEnabled(boolean enabled) {
if (mNestedView.isNestedScrollingEnabled() != enabled) {
mNestedView.setNestedScrollingEnabled(enabled);
}
}
@Override
public boolean isAppBarExpanded() {
return mAppBarOffset == 0;
}
@Override
public boolean isAppBarIdle() {
return mAppBarIdle;
}
private static final String TAG = "MainActivity";
}
SlidingPanelBehavior.java
public class SlidingPanelBehavior extends AppBarLayout.ScrollingViewBehavior {
private AppBarLayout mAppBar;
public SlidingPanelBehavior() {
super();
}
public SlidingPanelBehavior(Context context, AttributeSet attrs) {
super(context, attrs);
}
@Override
public boolean layoutDependsOn(final CoordinatorLayout parent, View child, View dependency) {
if (mAppBar == null && dependency instanceof AppBarLayout) {
// Capture our appbar for later use.
mAppBar = (AppBarLayout) dependency;
}
return dependency instanceof AppBarLayout;
}
@Override
public boolean onInterceptTouchEvent(CoordinatorLayout parent, View child, MotionEvent event) {
int action = event.getAction();
if (event.getAction() != MotionEvent.ACTION_DOWN) { // Only want "down" events
return false;
}
if (getAppBarLayoutOffset(mAppBar) == -mAppBar.getTotalScrollRange()) {
// When appbar is collapsed, don't let it open through nested scrolling.
setNestedScrollingEnabledWithTest((NestedScrollingChild2) child, false);
} else {
// Appbar is partially to fully expanded. Set nested scrolling enabled to activate
// the methods within this behavior.
setNestedScrollingEnabledWithTest((NestedScrollingChild2) child, true);
}
return false;
}
@Override
public boolean onStartNestedScroll(@NonNull CoordinatorLayout coordinatorLayout, @NonNull View child,
@NonNull View directTargetChild, @NonNull View target,
int axes, int type) {
//noinspection RedundantCast
return ((NestedScrollingChild2) child).isNestedScrollingEnabled();
}
@Override
public void onNestedPreScroll(@NonNull CoordinatorLayout coordinatorLayout, @NonNull View child,
@NonNull View target, int dx, int dy, @NonNull int[] consumed,
int type) {
// How many pixels we must scroll to fully expand the appbar. This value is <= 0.
final int appBarOffset = getAppBarLayoutOffset(mAppBar);
// Check to see if this scroll will expand the appbar 100% or collapse it fully.
if (dy <= appBarOffset) {
// Scroll by the amount that will fully expand the appbar and dispose of the rest (dy).
super.onNestedPreScroll(coordinatorLayout, mAppBar, target, dx,
appBarOffset, consumed, type);
consumed[1] += dy;
} else if (dy >= (mAppBar.getTotalScrollRange() + appBarOffset)) {
// This scroll will collapse the appbar. Collapse it and dispose of the rest.
super.onNestedPreScroll(coordinatorLayout, mAppBar, target, dx,
mAppBar.getTotalScrollRange() + appBarOffset,
consumed, type);
consumed[1] += dy;
} else {
// This scroll will leave the appbar partially open. Just do normal stuff.
super.onNestedPreScroll(coordinatorLayout, child, target, dx, dy, consumed, type);
}
}
/**
* {@code onNestedPreFling()} is overriden to address a nested scrolling defect that was
* introduced in API 26. This method prevent the appbar from misbehaving when scrolled/flung.
* <p>
* Refer to <a href="https://issuetracker.google.com/issues/65448468" target="_blank">"Bug in design support library"</a>
*/
@Override
public boolean onNestedPreFling(@NonNull CoordinatorLayout coordinatorLayout,
@NonNull View child, @NonNull View target,
float velocityX, float velocityY) {
//noinspection RedundantCast
if (((NestedScrollingChild2) child).isNestedScrollingEnabled()) {
// Just stop the nested fling and let the appbar settle into place.
((NestedScrollingChild2) child).stopNestedScroll(ViewCompat.TYPE_NON_TOUCH);
return true;
}
return super.onNestedPreFling(coordinatorLayout, child, target, velocityX, velocityY);
}
private static int getAppBarLayoutOffset(AppBarLayout appBar) {
final CoordinatorLayout.Behavior behavior =
((CoordinatorLayout.LayoutParams) appBar.getLayoutParams()).getBehavior();
if (behavior instanceof AppBarLayout.Behavior) {
return ((AppBarLayout.Behavior) behavior).getTopAndBottomOffset();
}
return 0;
}
// Something goes amiss when the flag it set to its current value, so only call
// setNestedScrollingEnabled() if it will result in a change.
private void setNestedScrollingEnabledWithTest(NestedScrollingChild2 child, boolean enabled) {
if (child.isNestedScrollingEnabled() != enabled) {
child.setNestedScrollingEnabled(enabled);
}
}
@SuppressWarnings("unused")
private static final String TAG = "SlidingPanelBehavior";
}
MyRecyclerView.kt
/**A RecyclerView that allows temporary pausing of casuing its scroll to affect appBarLayout, based on */
class MyRecyclerView @JvmOverloads constructor(context: Context, attrs: AttributeSet? = null, defStyle: Int = 0) : RecyclerView(context, attrs, defStyle) {
private var mAppBarTracking: AppBarTracking? = null
private var mView: View? = null
private var mTopPos: Int = 0
private var mLayoutManager: LinearLayoutManager? = null
interface AppBarTracking {
fun isAppBarIdle(): Boolean
fun isAppBarExpanded(): Boolean
}
override fun dispatchNestedPreScroll(dx: Int, dy: Int, consumed: IntArray?, offsetInWindow: IntArray?, type: Int): Boolean {
if (type == ViewCompat.TYPE_NON_TOUCH && mAppBarTracking!!.isAppBarIdle()
&& isNestedScrollingEnabled) {
if (dy > 0) {
if (mAppBarTracking!!.isAppBarExpanded()) {
consumed!![1] = dy
return true
}
} else {
mTopPos = mLayoutManager!!.findFirstVisibleItemPosition()
if (mTopPos == 0) {
mView = mLayoutManager!!.findViewByPosition(mTopPos)
if (-mView!!.top + dy <= 0) {
consumed!![1] = dy - mView!!.top
return true
}
}
}
}
if (dy < 0 && type == ViewCompat.TYPE_TOUCH && mAppBarTracking!!.isAppBarExpanded()) {
consumed!![1] = dy
return true
}
val returnValue = super.dispatchNestedPreScroll(dx, dy, consumed, offsetInWindow, type)
if (offsetInWindow != null && !isNestedScrollingEnabled && offsetInWindow[1] != 0)
offsetInWindow[1] = 0
return returnValue
}
override fun setLayoutManager(layout: RecyclerView.LayoutManager) {
super.setLayoutManager(layout)
mLayoutManager = layoutManager as LinearLayoutManager
}
fun setAppBarTracking(appBarTracking: AppBarTracking) {
mAppBarTracking = appBarTracking
}
override fun fling(velocityX: Int, velocityY: Int): Boolean {
var velocityY = velocityY
if (!mAppBarTracking!!.isAppBarIdle()) {
val vc = ViewConfiguration.get(context)
velocityY = if (velocityY < 0) -vc.scaledMinimumFlingVelocity
else vc.scaledMinimumFlingVelocity
}
return super.fling(velocityX, velocityY)
}
}
MyAppBarBehavior.java
/**
* Attach this behavior to AppBarLayout to disable the bottom portion of a closed appBar
* so it cannot be touched to open the appBar. This behavior is helpful if there is some
* portion of the appBar that displays when the appBar is closed, but should not open the appBar
* when the appBar is closed.
*/
public class MyAppBarBehavior extends AppBarLayout.Behavior {
// Touch above this y-axis value can open the appBar.
private int mCanOpenBottom;
// Determines if the appBar can be dragged open or not via direct touch on the appBar.
private boolean mCanDrag = true;
@SuppressWarnings("unused")
public MyAppBarBehavior() {
init();
}
@SuppressWarnings("unused")
public MyAppBarBehavior(Context context, AttributeSet attrs) {
super(context, attrs);
init();
}
private void init() {
setDragCallback(new AppBarLayout.Behavior.DragCallback() {
@Override
public boolean canDrag(@NonNull AppBarLayout appBarLayout) {
return mCanDrag;
}
});
}
@Override
public boolean onInterceptTouchEvent(CoordinatorLayout parent,
AppBarLayout child,
MotionEvent event) {
if (event.getAction() == MotionEvent.ACTION_DOWN) {
// If appBar is closed. Only allow scrolling in defined area.
if (child.getTop() <= -child.getTotalScrollRange()) {
mCanDrag = event.getY() < mCanOpenBottom;
}
}
return super.onInterceptTouchEvent(parent, child, event);
}
public void setCanOpenBottom(int bottom) {
mCanOpenBottom = bottom;
}
}