CoordinatorLayout and AppBarLayout elevation

setTargetElevation() is now deprecated for AppBarLayout.

The new correct implementation for applying custom elevation to an AppBarLayout based on the state of the layout is to use a StateListAnimator. material-components uses this as you can see here

I've added an example implementation of always showing AppBarLayout elevation here in this gist.

All you need is to 1. create a custom state list animator under /res/animator and 2. set the AppBarLayout's StateListAnimator like so:

appBarLayout.stateListAnimator = AnimatorInflater.loadStateListAnimator(context, R.animator.appbar_always_elevated_state_list_animator)

This is actually an implementation detail of CollapsingToolbarLayout, as seen in the source code:

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);
}

Which removes the elevation when the CollapsingToolbarLayout is showing non-pinned elements - by default, it'll only have elevation when only pinned children are visible.

The solution is to use app:elevation=0dp to remove the default elevation and set android:translationZ to the elevation you want.

Note : The code below uses the latest AndroidX / Material libraries and might not work if you're using the old support library

<com.google.android.material.appbar.AppBarLayout
    android:layout_height="wrap_content"
    android:layout_width="match_parent"
    android:translationZ="8dp"
    app:elevation="0dp">

    <!--
      * `app:elevation=0dp` disables the default shadow that is automatically added on
      scroll ; other values e.g. `6dp` are ignored despite what the official doc says
      (see below)
      * so instead we're using `android:translationZ` to add a shadow with a custom
      elevation
    -->

The documentation for AppBarLayout # setTargetElevation() states that you can set a custom elevation value using the app:elevation attribute, but it didn't work for me for values greater than 0dp, so I'm using translationZ as a workaround.

the reason is above,try this to solve:

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