A CoordinatorLayout.Behavior for showing/hiding a CircleImageView anchored to an AppBarLayout

CircleImageViewBehavior.java

package android.support.design.widget;

import android.graphics.Rect;
import android.view.View;
import de.hdodenhof.circleimageview.CircleImageView;

/**
 * Layout Behavior to show/hide a CircleImageView anchored to a AppBarLayout
 */
public class CircleImageViewBehavior extends CoordinatorLayout.Behavior<CircleImageView> {

  private Rect mTmpRect;

  @Override
  public boolean layoutDependsOn(CoordinatorLayout parent, CircleImageView child, View dependency) {
    // check that our dependency is the AppBarLayout
    return dependency instanceof AppBarLayout;
  }

  @Override public boolean onDependentViewChanged(CoordinatorLayout parent, CircleImageView child,
      View dependency) {
    if (dependency instanceof AppBarLayout) {
      return updateCircleImageViewVisibility(parent, (AppBarLayout) dependency, child);
    }
    return false;
  }

  private boolean updateCircleImageViewVisibility(CoordinatorLayout parent,
      AppBarLayout appBarLayout, CircleImageView child) {
    final CoordinatorLayout.LayoutParams lp =
        (CoordinatorLayout.LayoutParams) child.getLayoutParams();
    if (lp.getAnchorId() != appBarLayout.getId()) {
      // The anchor ID doesn't match the dependency, so we won't automatically
      // show/hide the FAB
      return false;
    }

    if (mTmpRect == null) {
      mTmpRect = new Rect();
    }

    // First, let's get the visible rect of the dependency
    final Rect rect = mTmpRect;
    ViewGroupUtils.getDescendantRect(parent, appBarLayout, rect);

    if (rect.bottom <= appBarLayout.getMinimumHeightForVisibleOverlappingContent()) {
      // If the anchor's bottom is below the seam, hide it
      child.setVisibility(View.INVISIBLE);
    } else {
      // Else, show it
      child.setVisibility(View.VISIBLE);
    }
    return true;
  }
}