如何使Android ScrollView衰落边缘始终可见? [英] How to make Android ScrollView fading edge always visible?

问题描述

默认情况下，只有在可以朝该方向滚动时，滚动视图的衰落边缘才可见.如何使它始终可见?

By default scrollview's fading edge is visible only if it is possible to scroll in that direction. How can I make it visible at all times?

我不想将任何可绘制对象放在上面或类似的东西上.我想使用内置的衰落边缘来实现它，可能是通过重写一些scrollview函数来实现的.

I don't want to put any drawables on top or something like that. I want to accomplish it using the builtin fading edge, probably by overriding some scrollview functions.

推荐答案

是的，扩展ScrollView并重写这些方法(基于Donut-release2):

Yes, extend ScrollView and override these methods (based on Donut-release2):

@Override
protected float getTopFadingEdgeStrength() {
    if (getChildCount() == 0) {
        return 0.0f;
    }
    return 1.0f;
}

@Override
protected float getBottomFadingEdgeStrength() {
    if (getChildCount() == 0) {
        return 0.0f;
    }
    return 1.0f;
}

为了比较起见，这是原始代码，当您靠近列表末尾时，它会缩短褪色边缘:

For comparison's sake, this is the original code, which shortens the fading edge as you get close to the end of the list:

@Override
protected float getTopFadingEdgeStrength() {
    if (getChildCount() == 0) {
        return 0.0f;
    }

    final int length = getVerticalFadingEdgeLength();
    if (mScrollY < length) {
        return mScrollY / (float) length;
    }

    return 1.0f;
}

@Override
protected float getBottomFadingEdgeStrength() {
    if (getChildCount() == 0) {
        return 0.0f;
    }

    final int length = getVerticalFadingEdgeLength();
    final int bottomEdge = getHeight() - mPaddingBottom;
    final int span = getChildAt(0).getBottom() - mScrollY - bottomEdge;
    if (span < length) {
        return span / (float) length;
    }

    return 1.0f;
}

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