如何在focusArea周围的TextureView上添加阴影

<!-- shadow_drawable.xml -->
<shape xmlns:android="http://schemas.android.com/apk/res/android">
    <solid android:color="#FFFFFF" /> <!-- 设置矩形的填充颜色 -->
    <corners android:radius="8dp" /> <!-- 设置矩形的圆角半径 -->
    <padding android:left="8dp" android:top="8dp" android:right="8dp" android:bottom="8dp" /> <!-- 设置矩形的内边距 -->
    <size android:width="match_parent" android:height="match_parent" /> <!-- 设置矩形的大小 -->
    <stroke android:color="#000000" android:width="1dp" /> <!-- 设置矩形的边框 -->
</shape>

<!-- layout.xml -->
<FrameLayout
    android:id="@+id/container"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <TextureView
        android:id="@+id/textureView"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

</FrameLayout>

// MainActivity.java
public class MainActivity extends AppCompatActivity {
    private FrameLayout container;
    private TextureView textureView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        container = findViewById(R.id.container);
        textureView = findViewById(R.id.textureView);

        Drawable shadowDrawable = ContextCompat.getDrawable(this, R.drawable.shadow_drawable);
        container.setBackground(shadowDrawable);
    }
}