КоординаторLayout и AppBarLayout

Я создал макет AppBar, как этот

<android.support.design.widget.AppBarLayout
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/appbar_layout"
    android:layout_height="@dimen/app_bar_height"
    android:layout_width="match_parent"
    android:fitsSystemWindows="true"
    android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
    app:elevation="20dp">

    <android.support.design.widget.CollapsingToolbarLayout...>
</android.support.design.widget.AppBarLayout>

он работает и бросает тень в LinearLayout:

<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <include layout="@layout/app_bar_large" />
</LinearLayout>

Однако, когда я помещаю его в shadow CoordinatorLayout, уходит:

<android.support.design.widget.CoordinatorLayout
    xmlns:android="http://schemas.android.com/apk/res/android" 
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <include layout="@layout/app_bar_large" />
</android.support.design.widget.CoordinatorLayout>

Как я могу заставить панель приложений снова показать свою тень?

Ответы

if (Math.abs(verticalOffset) == scrollRange) {
  // If we have some pinned children, and we're offset to only show those views,
  // we want to be elevate
  ViewCompat.setElevation(layout, layout.getTargetElevation());
} else {
  // Otherwise, we're inline with the content
  ViewCompat.setElevation(layout, 0f);
}

appBarLayout.addOnOffsetChangedListener(new AppBarLayout.OnOffsetChangedListener() {
        @Override
        public void onOffsetChanged(AppBarLayout appBarLayout, int verticalOffset) {
            //some other code here
            ViewCompat.setElevation(appBarLayout, The Elevation In Px);
        }
    });