ListPopupWindow 不遵守 WRAP_CONTENT 宽度规范

我正在尝试使用 ListPopupWindow 通过ArrayAdapter（最终这将是一个更复杂的自定义适配器）。代码如下。如截图所示，得到的结果ListPopupWindow看起来就像内容宽度为零一样。它显示了正确的项目数量，这些项目仍然是可点击的，并且点击成功会产生一个Toast，所以至少这么多工作正常。

一个有趣的注释：我可以提供以像素为单位的宽度popup.setWidth(...)代替ListPopupWindow.WRAP_CONTENT而且它会显示一些内容，但这看起来很不灵活。

我该如何制作ListPopupWindow包装其内容？

测试活动：

public class MainActivity extends Activity {

    private static final String[] STRINGS = {"Option1","Option2","Option3","Option4"};
    private View anchorView;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        getActionBar().setHomeButtonEnabled(true);
        setContentView(R.layout.activity_main);
        anchorView = findViewById(android.R.id.home);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.activity_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
            case android.R.id.home:
                showPopup();
                return true;
        }
        return super.onOptionsItemSelected(item);
    }

    private void showPopup() {
        ListPopupWindow popup = new ListPopupWindow(this);
        popup.setAdapter(new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, STRINGS));
        popup.setAnchorView(anchorView);
        popup.setWidth(ListPopupWindow.WRAP_CONTENT);
        popup.setOnItemClickListener(new OnItemClickListener() {

            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                Toast.makeText(MainActivity.this, "Clicked item " + position, Toast.LENGTH_SHORT).show();
            }
        });
        popup.show();
    }
}

截屏：

您可以测量适配器内容的宽度：

private int measureContentWidth(ListAdapter listAdapter) {
    ViewGroup mMeasureParent = null;
    int maxWidth = 0;
    View itemView = null;
    int itemType = 0;

    final ListAdapter adapter = listAdapter;
    final int widthMeasureSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED);
    final int heightMeasureSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED);
    final int count = adapter.getCount();
    for (int i = 0; i < count; i++) {
        final int positionType = adapter.getItemViewType(i);
        if (positionType != itemType) {
            itemType = positionType;
            itemView = null;
        }

        if (mMeasureParent == null) {
            mMeasureParent = new FrameLayout(mContext);
        }

        itemView = adapter.getView(i, itemView, mMeasureParent);
        itemView.measure(widthMeasureSpec, heightMeasureSpec);

        final int itemWidth = itemView.getMeasuredWidth();

        if (itemWidth > maxWidth) {
            maxWidth = itemWidth;
        }
    }

    return maxWidth;
}

在你的 showPopup() 函数中：

 ArrayAdapter arrayAdapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, STRINGS);
    popup.setAdapter(arrayAdapter);
    popup.setAnchorView(anchorView);
    popup.setContentWidth(measureContentWidth(arrayAdapter));