CircleLoadingView.java 文件源码

@Override
public Drawable createShadowShapeDrawable(Context context, final CircleLoadingView circleLoadingView, int shadowColor) {
    final float density = context.getResources().getDisplayMetrics().density;
    ShapeDrawable circle = new ShapeDrawable(new OvalShape());
    circle.getPaint().setColor(shadowColor);
    final float elevation = SHADOW_ELEVATION * density;
    circleLoadingView.setElevation(elevation);

    circleLoadingView.getViewTreeObserver().addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
        @Override
        public void onGlobalLayout() {
            ViewParent p = circleLoadingView.getParent();
            if(p instanceof ViewGroup) {
                final int margin = (int) elevation;
                ViewGroup.LayoutParams params = circleLoadingView.getLayoutParams();
                if(params instanceof ViewGroup.MarginLayoutParams){
                    ((ViewGroup.MarginLayoutParams) params).setMargins(margin, margin, margin, margin);
                }
            }

            circleLoadingView.getViewTreeObserver().removeOnGlobalLayoutListener(this);
        }
    });

    return circle;
}