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是 20dp，而另一个必须覆盖视图的其余部分。

onMeasure

@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 的视图

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

Answer 1

View#layout() 方法中的最后一个参数是View 的底部。对于你的 bar，你超过了 0，但它应该是你自定义的 View 的高度，你可以从 t 和 b 中计算出来传递给 onLayout().

的值

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

在自定义 ViewGroup 中使用 onLayout 正确布局子项

Correctly layout children with onLayout in Custom ViewGroup

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android-custom-view

android-viewgroup