扩展FrameLayout,子视图将不再显示

Question

这是我的代码FrameLayout:

<FrameLayout
        android:layout_width="fill_parent" android:layout_height="wrap_content">
    <ImageView
            android:id="@+id/frameView"
            android:layout_width="fill_parent"
            android:layout_height="fill_parent"
            android:src="@drawable/image1"
            />
</FrameLayout>

ImageView很好.

现在我有一个从FrameLayout扩展的自定义布局,例如MyFrameLayout.

在MyFrameLayout中,我希望布局的高度始终是宽度的一半,所以我的代码是:

public class MyFrameLayout extends FrameLayout {

     // 3 constructors just call super

     @Override
     protected void onMeasure(int widthMeasureSpec,
                         int heightMeasureSpec) {
        int width = MeasureSpec.getSize(widthMeasureSpec);
        int height = (int) (width * 0.5);
        setMeasuredDimension(width, height);
    }
}

然后在xml中使用它:

<com.test.MyFrameLayout
        android:layout_width="fill_parent" android:layout_height="wrap_content">
    <ImageView
            android:id="@+id/frameView"
            android:layout_width="fill_parent"
            android:layout_height="fill_parent"
            android:src="@drawable/image1"
            />
</com.test.MyFrameLayout>

但现在内部的ImageView消失了.

我想我没有实现onMeasure或onLayout正确.我想我也需要调整子视图的大小.但我现在不知道该怎么做.

---

UPDATE

根据TheDimasig的评论,我刚检查了我的代码并更新了我的问题.谢谢

Answer 1

最简单的方法是更改​​onMeasure中的measurespec,但仍然调用super:

 @Override
 protected void onMeasure(int widthMeasureSpec,
                     int heightMeasureSpec) {
    int width = MeasureSpec.getSize(widthMeasureSpec);
    int height = (int) (width * 0.5);
    heightMeasureSpec = MeasureSpec.makeMeasureSpec(height, MeasureSpec.EXACTLY);
    super.onMeasure(widthMeasureSpec, heightMeasureSpec);
}

这样您就可以获得所需的尺寸,但不必手动测量子尺寸.

Answer 2

您没有看到任何子视图,因为您没有onMeasure正确覆盖该方法.您可以让超类实现逻辑(因此将显示子视图),然后重置计算的宽度和高度MyFrameLayout:

@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
    // let the super class handle calculations
    super.onMeasure(widthMeasureSpec, heightMeasureSpec);
    // set again the dimensions, this time calculated as we want
    setMeasuredDimension(getMeasuredWidth(), getMeasuredHeight() / 2);
    // this is required because the children keep the super class calculated dimensions (which will not work with the new MyFrameLayout sizes) 
    final int count = getChildCount();
    for (int i = 0; i < count; i++) {
        final View v = getChildAt(i);
        // this works because you set the dimensions of the ImageView to FILL_PARENT          
        v.measure(MeasureSpec.makeMeasureSpec(getMeasuredWidth(),
                MeasureSpec.EXACTLY), MeasureSpec.makeMeasureSpec(
                getMeasuredHeight(), MeasureSpec.EXACTLY));
    }
}

如果您发布的布局不是您的完整布局,那么我的代码可能无效.

Answer 3

我想在你的onMeasure方法中你忘记对所有子视图调用 onMeasure，包括你的 ImageView。您必须检查所有子视图并对它们调用 onMeasure ，如下所示：

    for (int i = 0; i < getChildCount(); i++) {
        getChildAt(i).measure(....);
    }