added in version 24.1.0
belongs to Maven artifact


public final class ShadowOverlayHelper
extends Object


ShadowOverlayHelper is a helper class for shadow, overlay color and rounded corner. There are many choices to implement Shadow, overlay color. Initialize it with ShadowOverlayHelper.Builder and it decides the best strategy based on options user choose and current platform version.

  • For shadow: it may use 9-patch with opticalBounds or Z-value based shadow for API >= 21. When 9-patch is used, it requires a ShadowOverlayContainer to include 9-patch views.
  • For overlay: it may use ShadowOverlayContainer which overrides draw() or it may use setForeground(new ColorDrawable()) for API>=23. The foreground support might be disabled if rounded corner is applied due to performance reason.
  • For rounded-corner: it uses a ViewOutlineProvider for API>=21. There are two different strategies: use Wrapper with a ShadowOverlayContainer; or apply rounded corner, overlay and rounded-corner to the view itself. Below is an example of how helper is used. ShadowOverlayHelper mHelper = new ShadowOverlayHelper.Builder(). .needsOverlay(true).needsRoundedCorner(true).needsShadow(true) .build(); mHelper.prepareParentForShadow(parentView); // apply optical-bounds for 9-patch shadow. mHelper.setOverlayColor(view, Color.argb(0x80, 0x80, 0x80, 0x80)); mHelper.setShadowFocusLevel(view, 1.0f); ... View initializeView(View view) { if (mHelper.needsWrapper()) { ShadowOverlayContainer wrapper = mHelper.createShadowOverlayContainer(context); wrapper.wrap(view); return wrapper; } else { mHelper.onViewCreated(view); return view; } } ...


    Nested classes

    class ShadowOverlayHelper.Builder

    Builder for creating ShadowOverlayHelper. 

    class ShadowOverlayHelper.Options

    Option values for ShadowOverlayContainer. 



    Shadows depend on the size, shape, and position of the view.


    No shadow.


    Shadows are fixed.

    Public methods

    ShadowOverlayContainer createShadowOverlayContainer(Context context)

    Create ShadowOverlayContainer for this helper.

    int getShadowType()
    boolean needsOverlay()
    boolean needsRoundedCorner()
    boolean needsWrapper()

    Returns true if a "wrapper" ShadowOverlayContainer is needed.

    void onViewCreated(View view)

    Must be called when view is created for cases needsWrapper() is false.

    void prepareParentForShadow(ViewGroup parent)

    prepareParentForShadow(ViewGroup) must be called on parent of container before using shadow.

    static void setNoneWrapperOverlayColor(View view, int color)

    Set overlay color for view other than ShadowOverlayContainer.

    static void setNoneWrapperShadowFocusLevel(View view, float level)

    Set shadow focus level (0 to 1).

    void setOverlayColor(View view, int color)

    Set overlay color for view, it can be a ShadowOverlayContainer if needsWrapper() is true, or other view type.

    void setShadowFocusLevel(View view, float level)

    Set shadow focus level (0 to 1).

    static boolean supportsDynamicShadow()

    Returns true if the platform sdk supports dynamic shadows.

    static boolean supportsForeground()

    Returns true if view.setForeground() is supported.

    static boolean supportsRoundedCorner()

    Returns true if the platform sdk supports rounded corner through outline.

    static boolean supportsShadow()

    Return true if the platform sdk supports shadow.