[MaterialToolbar] Shadow is drawn over content with the same elevation

[carloshwa]

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Description: The shadow from a MaterialToolbar will draw over content below it even if it is of the same elevation. For example, if I have a MaterialCardView with cardElevation=4dp that is directly below a MaterialToolbar with elevation=4dp, there will be a shadow cast on the MaterialCardView from the MaterialToolbar.

Expected behavior: I would expect that there is no shadow over the card, since it is the same elevation as the app bar.

Source code: Modify cat_topappbar_action_bar_activity.xml from the catalog app so that the contents is within a MaterialCardView:

<com.google.android.material.card.MaterialCardView
  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"
  app:strokeWidth="0dp"
  app:cardElevation="4dp">
  <LinearLayout
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:orientation="vertical">

    <TextView
        android:id="@+id/action_bar_demo_description"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:padding="16dp"/>
      <Button
          android:id="@+id/action_bar_demo_action_mode_button"
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          android:layout_gravity="center_horizontal"
          android:text="@string/cat_topappbar_action_bar_toggle_action_mode_button"/>
  </LinearLayout>
</com.google.android.material.card.MaterialCardView>

Then open the Action Bar Demo in the Catalog app.

Android API version: 31

Material Library version: 1.7.0-beta01

Device: Google Pixel 4a