如果片段包含 AppBarLayout，BottomNavigationView 不会隐藏在片段内滚动

Question

我在 Android 中使用 coordinatorLayout 在片段内滚动和检测它时遇到很多问题。我有一个包含 3 个片段的 "MainActivity"。在其中一个片段中，我有一个 Appbar，它会在滚动片段时折叠。我设法做到了这一点，但如果我设置滚动行为以允许这样做，我的 bottomNavigationView（位于 mainactivity.xml 中）不会对滚动做出反应。代码是这样的：

Fragment1.xml

<android.support.design.widget.CoordinatorLayout
...
...>
    <android.support.design.widget.AppBarLayout
 ...
 ...>
        <android.support.design.widget.CollapsingToolbarLayout
                 app:layout_scrollFlags="scroll|exitUntilCollapsed"
   ...>
            <android.support.v7.widget.Toolbar
     .../>
        </android.support.design.widget.CollapsingToolbarLayout>
    </android.support.design.widget.AppBarLayout>

   <android.support.v4.widget.NestedScrollView
        app:layout_behavior="@string/appbar_scrolling_view_behavior">
   </android.support.v4.widget.NestedScrollView>

</android.support.design.widget.CoordinatorLayout>

MainActivity.xml

<android.support.design.widget.CoordinatorLayout
.../>
    <FrameLayout
        app:layout_behavior="@string/appbar_scrolling_view_behavior"
 .../>
    <android.support.design.widget.BottomNavigationView
      app:layout_behavior="@string/hide_bottom_view_on_scroll_behavior"
.../>
</android.support.design.widget.CoordinatorLayout>

现在，这很好用，因为当我在 fragment 中滚动时，我的 AppBar 折叠到标题中（这是我想要的），但我的 bottomNavigationView 对滚动没有反应。

我发现如果我添加行

app:layout_behavior="@string/appbar_scrolling_view_behavior"

到 AppBarLayout xml 声明我让 bottomView 在滚动事件上折叠（当我向上滚动时它再次显示）。所以基本上，要么我有能力在片段内折叠应用栏，要么我有能力在我检测到片段内的滚动事件时隐藏 BottomNavigationView。

如有任何帮助，我们将不胜感激。

Answer 1

为了隐藏底部导航以响应在片段内滚动修改fragment1.kt上的onCreateView方法如下

override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {

        ...

        // access the bottom nav which is on the main activity
        val bottomNav: BottomNavigationView = activity!!.findViewById(R.id.bottom_nav)

        // hide bottom nav when scrolling
        rvList.addOnScrollListener(object : RecyclerView.OnScrollListener() {

            override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) {
                if (dy > 0 || dy < 0) {
                    bottomNav.visibility = View.GONE
                }
            }

            override fun onScrollStateChanged(recyclerView: RecyclerView, newState: Int) {
                if (newState == RecyclerView.SCROLL_STATE_IDLE) {
                    bottomNav.visibility = View.VISIBLE
                }

                super.onScrollStateChanged(recyclerView, newState)
            }
        })

        return view
}

在Java

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {
        ...

    // access the bottom nav which is on the main activity
    BottomNavigationView bottomNav = getActivity.findViewById(R.id.bottom_nav);

    // hide bottom nav when scrolling
    recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener()
    {
        @Override
        public void onScrolled(RecyclerView recyclerView, int dx, int dy)
        {
             if (dy > 0 ||dy<0)
             {
                 bottomNav.setVisibility(View.GONE);
             }
        }

        @Override
        public void onScrollStateChanged(RecyclerView recyclerView, int newState)
        {
             if (newState == RecyclerView.SCROLL_STATE_IDLE)
             {
                  bottomNav.setVisibility(View.VISIBLE);
             }

             super.onScrollStateChanged(recyclerView, newState);
        }
    });

        return view;
 }

更新：

将侦听器代码提取到单独的函数，如下所示（在 Kotlin 中）

   public fun hideBottomNav(
        rvList: RecyclerView,
        bottomNav: BottomNavigationView
    ) {
        rvList.addOnScrollListener(object : RecyclerView.OnScrollListener() {

            override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) {
                if (dy > 0 || dy < 0) {
                    bottomNav.visibility = View.GONE
                }
            }

            override fun onScrollStateChanged(recyclerView: RecyclerView, newState: Int) {
                if (newState == RecyclerView.SCROLL_STATE_IDLE) {
                    bottomNav.visibility = View.VISIBLE
                }

                super.onScrollStateChanged(recyclerView, newState)
            }
        })
    }

Answer 2

将您的图书馆更新为 28.0.0 or above 或 androidx / material-1.0.0 并像下面那样更改您的 BottomNavigationView-

<BottomNavigationView
        android:id="@+id/navigation"
        .
        .
        .
        .
        app:layout_behavior="@string/hide_bottom_view_on_scroll_behavior" />

希望对您有所帮助。

如果片段包含 AppBarLayout，BottomNavigationView 不会隐藏在片段内滚动

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