FloatingActionButton.java 文件源码

private Drawable createInnerStrokesDrawable(final int color, float strokeWidth) {
        if (!mStrokeVisible) {
                return new ColorDrawable(Color.TRANSPARENT);
        }

        ShapeDrawable shapeDrawable = new ShapeDrawable(new OvalShape());

        final int bottomStrokeColor = darkenColor(color);
        final int bottomStrokeColorHalfTransparent = halfTransparent(bottomStrokeColor);
        final int topStrokeColor = lightenColor(color);
        final int topStrokeColorHalfTransparent = halfTransparent(topStrokeColor);

        final Paint paint = shapeDrawable.getPaint();
        paint.setAntiAlias(true);
        paint.setStrokeWidth(strokeWidth);
        paint.setStyle(Style.STROKE);
        shapeDrawable.setShaderFactory(new ShaderFactory() {
                @Override
                public Shader resize(int width, int height) {
                        return new LinearGradient(width / 2, 0, width / 2, height,
                                new int[]{topStrokeColor, topStrokeColorHalfTransparent, color, bottomStrokeColorHalfTransparent, bottomStrokeColor},
                                new float[]{0f, 0.2f, 0.5f, 0.8f, 1f},
                                TileMode.CLAMP
                        );
                }
        });

        return shapeDrawable;
}