android - 在自定义 ViewGroup 中使用 onLayout 正确布局子项

Question

我正在创建自定义 ViewGroup。我确实需要一个在另一个之上的 2 FrameLayout；留在底部的一个必须为 20dp，而另一个必须覆盖 View 的其余部分。

测量

@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
    int widthMode = MeasureSpec.getMode(widthMeasureSpec);
    int heightMode = MeasureSpec.getMode(heightMeasureSpec);
    int widthSize = MeasureSpec.getSize(widthMeasureSpec);
    int heightSize = MeasureSpec.getSize(heightMeasureSpec);
    setMeasuredDimension(widthSize, heightSize);

    final View content = getChildAt(CONTENT_INDEX);
    final View bar = getChildAt(BAR_INDEX);

    content.measure(
        MeasureSpec.makeMeasureSpec(widthSize, MeasureSpec.EXACTLY),
        MeasureSpec.makeMeasureSpec(heightSize - getPixels(BAR_HEIGHT), MeasureSpec.EXACTLY)
    );

    bar.measure(
        MeasureSpec.makeMeasureSpec(widthSize, MeasureSpec.EXACTLY),
        MeasureSpec.makeMeasureSpec(getPixels(BAR_HEIGHT), MeasureSpec.EXACTLY)
    );

onLayout

@Override
protected void onLayout(boolean changed, int l, int t, int r, int b) {
    mInLayout = true;

    final View content = getChildAt(CONTENT_INDEX);
    final View bar = getChildAt(BAR_INDEX);

    if (content.getVisibility() != GONE) {
        content.layout(0, 0, content.getMeasuredWidth(), content.getMeasuredHeight());
     }

     if (bar.getVisibility() != GONE) {
         bar.layout(0, content.getMeasuredHeight(), bar.getMeasuredWidth(), 0);
     }

     mInLayout = false;
     mFirstLayout = false;
 }
    }

我添加到这个自定义 ViewGroup 的 View

LayoutParams lp = new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT);

mContentContainer = new FrameLayout(getContext());
mContentContainer.setLayoutParams(lp);

mBarContainer = new FrameLayout(getContext());
mBarContainer.setLayoutParams(lp);

// ... adding stuff to both containers ....

addView(mContentContainer, 0);
addView(mBarContainer, 1);

问题

mContentContainer 得到正确呈现(从 top=0 到 bottom=(totalHeight - bar height) 并匹配父级的宽度)，而 bar 没有呈现。

Answer 1

View#layout() 方法中的最后一个参数是View 的底部。对于您的 bar，您传递的是 0，但它应该是您的自定义 View 的高度，您可以从 >t 和 b 值传递到 onLayout()。

bar.layout(0, content.getMeasuredHeight(), bar.getMeasuredWidth(), b - t);