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;
}