为什么在 onResume() 中的 View 上调用 getWidth() 返回 0? [英] Why does calling getWidth() on a View in onResume() return 0?

问题描述

我读过的所有内容都说您不能在构造函数中的 View 上调用 getWidth() 或 getHeight()，但是我在 onResume() 中调用它们.那个时候屏幕的布局不应该已经绘制了吗?

@Override受保护的无效 onResume() {super.onResume();填充数据()；}私有无效 populateData() {LinearLayout test = (LinearLayout) findViewById(R.id.myview);double widthpx = test.getWidth();}

解决方案

调用 onResume() 时视图仍未绘制，因此其宽度和高度均为 0.您可以当它的大小改变时使用 OnGlobalLayoutListener():

yourView.getViewTreeObserver().addOnGlobalLayoutListener(new OnGlobalLayoutListener() {@覆盖公共无效 onGlobalLayout() {//移除布局监听器以避免多次调用if(Build.VERSION.SDK_INT < Build.VERSION_CODES.JELLY_BEAN) {yourView.getViewTreeObserver().removeGlobalOnLayoutListener(this);}别的 {yourView.getViewTreeObserver().removeOnGlobalLayoutListener(this);}填充数据()；}});

有关其他信息，请查看 Android 获取宽度返回 0.>

Everything I've read says you can't call getWidth() or getHeight() on a View in a constructor, but I'm calling them in onResume(). Shouldn't the screen's layout have been drawn by then?

@Override
protected void onResume() {
    super.onResume();

    populateData();
}

private void populateData() {
    LinearLayout test = (LinearLayout) findViewById(R.id.myview);
    double widthpx = test.getWidth();
}

解决方案

A view still hasn't been drawn when onResume() is called, so its width and height are 0. You can "catch" when its size changes using OnGlobalLayoutListener():

yourView.getViewTreeObserver().addOnGlobalLayoutListener(new OnGlobalLayoutListener() {

    @Override
    public void onGlobalLayout() {

        // Removing layout listener to avoid multiple calls
        if(Build.VERSION.SDK_INT < Build.VERSION_CODES.JELLY_BEAN) {
            yourView.getViewTreeObserver().removeGlobalOnLayoutListener(this);
        }
        else {
            yourView.getViewTreeObserver().removeOnGlobalLayoutListener(this);
        }

        populateData();
    }
});

For additional info take a look at Android get width returns 0.

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