为什么在 NavigationView 中滚动取决于外部 xml 元素？

Question

我将 table 的内容菜单放在右侧的 NavigationView 中。这是我的有效代码：

<android.support.v4.widget.DrawerLayout
    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:id="@+id/drawer_layout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:fitsSystemWindows="true"
    android:layout_gravity="right"
    tools:openDrawer="start">

    <android.support.design.widget.AppBarLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:theme="@style/AppTheme.AppBarOverlay">

        <android.support.v7.widget.Toolbar
            android:id="@+id/top_nav_toolbar"
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize"
            android:background="?attr/colorPrimary"
            android:elevation="4dp"
            app:popupTheme="@style/ThemeOverlay.AppCompat.Light">
        </android.support.v7.widget.Toolbar>
    </android.support.design.widget.AppBarLayout>

    <!-- The main content gets loaded in here. -->
    <LinearLayout
        xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:tools="http://schemas.android.com/tools"
        xmlns:app="http://schemas.android.com/apk/res-auto"
        android:id="@+id/grandparent_layout"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical"
        tools:context="my.Activity">

        <FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
            android:id="@+id/fragment_container"
            android:layout_width="match_parent"
            android:layout_height="match_parent">
        </FrameLayout>
    </LinearLayout>

    <android.support.design.widget.NavigationView
        android:id="@+id/toc_drawer_view"
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:layout_gravity="end"
        android:fitsSystemWindows="true"
        app:headerLayout="@layout/burger_menu_header"
        app:theme="@style/TableOfContents_TextAppearance"
        app:menu="@menu/burger_menu_drawer_items"
        >
    </android.support.design.widget.NavigationView>
</android.support.v4.widget.DrawerLayout>

在以前版本的代码中，我在主要内容保持 LinearLayout 上方设置了 NavigationView。像这样：

<android.support.v4.widget.DrawerLayout
    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:id="@+id/drawer_layout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:fitsSystemWindows="true"
    android:layout_gravity="right"
    tools:openDrawer="start">

    <android.support.design.widget.AppBarLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:theme="@style/AppTheme.AppBarOverlay">

        <android.support.v7.widget.Toolbar
            android:id="@+id/top_nav_toolbar"
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize"
            android:background="?attr/colorPrimary"
            android:elevation="4dp"
            app:popupTheme="@style/ThemeOverlay.AppCompat.Light">
        </android.support.v7.widget.Toolbar>
    </android.support.design.widget.AppBarLayout>

    <android.support.design.widget.NavigationView
        android:id="@+id/toc_drawer_view"
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:layout_gravity="end"
        android:fitsSystemWindows="true"
        app:headerLayout="@layout/burger_menu_header"
        app:theme="@style/TableOfContents_TextAppearance"
        app:menu="@menu/burger_menu_drawer_items"
        >
    </android.support.design.widget.NavigationView>

    <!-- The main content gets loaded in here. -->
    <LinearLayout
        xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:tools="http://schemas.android.com/tools"
        xmlns:app="http://schemas.android.com/apk/res-auto"
        android:id="@+id/grandparent_layout"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical"
        tools:context="my.Activity">

        <FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
            android:id="@+id/fragment_container"
            android:layout_width="match_parent"
            android:layout_height="match_parent">
        </FrameLayout>
    </LinearLayout>

</android.support.v4.widget.DrawerLayout>

在那个版本中，系统（在模拟器和硬件测试设备上）显示右侧抽屉，并显示菜单的前几个元素，但我无法滚动到菜单底部。如果我在 xml 代码中手动打开滚动条，它会出现，但它不知道除了立即可见之外还有任何内容。

我的问题是为什么？使滚动魔法起作用的幕后绘图逻辑是什么？

为了完整起见，burger_menu_header.xml 看起来像这样：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="@drawable/toc_nav_bar"
android:gravity="bottom"
android:orientation="vertical"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:theme="@style/ThemeOverlay.AppCompat.Dark">
<TextView
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:paddingTop="@dimen/nav_header_vertical_spacing"
    android:text="Table of Contents"
    android:textAppearance="@style/TextAppearance.AppCompat.Body1"/>
</LinearLayout>

和 burger_menu_drawer_items.xml 看起来像：

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android">
    <item
        android:id="@+id/nav_chapter_0"
        android:icon="@drawable/ic_radio_button_unchecked_black_24dp"
        android:title="Introduction"/>

    <item
        android:id="@+id/nav_chapter_1"
        android:icon="@drawable/ic_radio_button_unchecked_black_24dp"
        android:title="Chapter 1 - The Adventure"/>
    <item
        android:id="@+id/nav_chapter_2"
        android:icon="@drawable/ic_radio_button_unchecked_black_24dp"
        android:title="Chapter 2 - Our Heroes Go Sailing"/>
    <item
        android:id="@+id/nav_chapter_3"
        android:icon="@drawable/ic_radio_button_unchecked_black_24dp"
        android:title="Chapter 3 - The Ship Is LostAtSeaFarAway"/>
    <item
        android:id="@+id/nav_chapter_4"
        android:icon="@drawable/ic_radio_button_unchecked_black_24dp"
        android:title="Chapter 4 - Skipper Wins!"/>
    <item
        android:id="@+id/nav_chapter_5"
        android:icon="@drawable/ic_radio_button_unchecked_black_24dp"
        android:title="Chapter 5"/>
    <item
        android:id="@+id/nav_chapter_6"
        android:icon="@drawable/ic_radio_button_unchecked_black_24dp"
        android:title="Chapter 6"/>
    <item
        android:id="@+id/nav_chapter_7"
        android:icon="@drawable/ic_radio_button_unchecked_black_24dp"
        android:title="Chapter 7"/>
    <item
        android:id="@+id/nav_chapter_8"
        android:icon="@drawable/ic_radio_button_unchecked_black_24dp"
        android:title="Chapter 8"/>
    <item
        android:id="@+id/nav_chapter_9"
        android:icon="@drawable/ic_radio_button_unchecked_black_24dp"
        android:title="Chapter 9"/>
    <item
        android:id="@+id/nav_chapter_10"
        android:icon="@drawable/ic_radio_button_unchecked_black_24dp"
        android:title="Chapter 10"/>
    <item
        android:id="@+id/nav_chapter_11"
        android:icon="@drawable/ic_radio_button_unchecked_black_24dp"
        android:title="Chapter 11 - No Way Is This Happening, She Cried"/>
    <item
        android:id="@+id/nav_chapter_12"
        android:icon="@drawable/ic_radio_button_unchecked_black_24dp"
        android:title="Chapter 12 - The End?"/>
    <item
        android:id="@+id/nav_chapter_13"
        android:icon="@drawable/ic_radio_button_unchecked_black_24dp"
        android:title="Chapter 13 - But Wait..."/>
    <item
        android:id="@+id/nav_chapter_14"
        android:icon="@drawable/ic_radio_button_unchecked_black_24dp"
        android:title="Chapter 14 - But Wait..."/>
    <item
        android:id="@+id/nav_chapter_15"
        android:icon="@drawable/ic_radio_button_unchecked_black_24dp"
        android:title="Chapter 14 - Nah, It Was Nothing"/>
</menu>

Answer 1

大约

Z-Index

哥谭绿。

<item num1
<item num2 is above 1
<item num3 is above 2

So it is important that the item that needs touch or focus gets the touch or focus. This is determined first by z-index. In the example above item 3 has the greatest z-index and gets first attempt at handling the touch before it is passed to item 2 and then if item 2 doesn't handle the touch it will go to item 1.

想象一下你有

<content>
<drawerNav>

drawerNav 首次尝试处理触摸并将 open/close 等触摸或滑动。如果不需要处理，它将传递到内容视图。

现在让我们考虑一下

<drawerNav>
<content>

内容是全屏的，每次都会消耗触摸，永远不会传递到抽屉，所以抽屉只能通过汉堡菜单工作，而不是滑动，即使那样也很不确定。

如您所见，它与通过 zindex 的触摸处理顺序有关。

为什么在 NavigationView 中滚动取决于外部 xml 元素？

Why is scrolling in NavigationView dependent on outside xml elements?

android

xml

scroll

navigationview