FadingEdgeScrollView.java 文件源码

@Override
protected void dispatchDraw(Canvas canvas) {
    super.dispatchDraw(canvas);
    setVerticalFadingEdgeEnabled(true);
    float topShadowStrength = getTopFadingEdgeStrength();
    float bottomShadowStrength = getBottomFadingEdgeStrength();
    float shadowHeight = getVerticalFadingEdgeLength();
    setVerticalFadingEdgeEnabled(false);

    if (mDrawTopShadow) {
        mFadingShadow.drawShadow(this, canvas, FadingShadow.POSITION_TOP,
                shadowHeight, topShadowStrength);
    }

    if (mDrawBottomShadow) {
        mFadingShadow.drawShadow(this, canvas, FadingShadow.POSITION_BOTTOM,
                shadowHeight, bottomShadowStrength);
    }
}