FloatingActionButton.java 文件源码

private Drawable createCircleDrawable(int color, float strokeWidth) {
  int alpha = Color.alpha(color);
  int opaqueColor = opaque(color);

  ShapeDrawable fillDrawable = new ShapeDrawable(new OvalShape());

  final Paint paint = fillDrawable.getPaint();
  paint.setAntiAlias(true);
  paint.setColor(opaqueColor);

  Drawable[] layers = {
      fillDrawable,
      createInnerStrokesDrawable(opaqueColor, strokeWidth)
  };

  LayerDrawable drawable = alpha == 255 || !mStrokeVisible
      ? new LayerDrawable(layers)
      : new TranslucentLayerDrawable(alpha, layers);

  int halfStrokeWidth = (int) (strokeWidth / 2f);
  drawable.setLayerInset(1, halfStrokeWidth, halfStrokeWidth, halfStrokeWidth, halfStrokeWidth);

  return drawable;
}