android - ListFragment 中的异常 : The specified child already has a parent

Question

我正在制作一个下载器应用程序，但在 onCreateView 返回部分之后出现了 child 的 parent 错误。我尝试了很多东西，但没有任何帮助。我试过:((ViewGroup)dlistView.getParent()).removeView(dlistView);之后编译器说:

01-12 12:05:15.558: E/AndroidRuntime(10740): java.lang.RuntimeException: Your content must have a ListView whose id attribute is 'android.R.id.list'

或删除容器/我得到一个 npe/或删除 V 但 V.getParent() 为空。

Which view is the parent, and which is the child?

代码:

public static class DownloadingFragment extends ListFragment {
public static final String ARG_SECTION_NUMBER = "section_number";
        public DownloadingFragment() {
        }

        @Override
        public View onCreateView (LayoutInflater inflater, ViewGroup container,
                Bundle savedInstanceState) {
            View V = inflater.inflate (R.layout.list, null);    
            ListView dlistView = (ListView) V.findViewById(R.id.dlist);
            List<DownloadInfo> downloadInfo = new ArrayList<DownloadInfo>();
            downloadInfo.add(new DownloadInfo("File", 1000));
            DownloadInfoArrayAdapter diaa = new DownloadInfoArrayAdapter(
                    getActivity().getApplication(),R.layout.list, downloadInfo);
            dlistView.setAdapter(diaa);
        return dlistView; // throw exception 
        }
    }
//...
}

预先感谢您的帮助。

编辑:新代码:

public static class DownloadingFragment extends Fragment {
        public static final String ARG_SECTION_NUMBER = "section_number";
        public DownloadingFragment() {
        }
        @Override
        public View onCreateView (LayoutInflater inflater, ViewGroup container,
                Bundle savedInstanceState) {
            View V = inflater.inflate (R.layout.list, null);    
        return V;
        }

        @Override
        public void onStart() {
            // TODO Auto-generated method stub
            super.onStart();
            ListView dlistView = (ListView) getView().findViewById(R.id.dlist);
            List<DownloadInfo> downloadInfo = new ArrayList<DownloadInfo>();
            downloadInfo.add(new DownloadInfo("File", 1000));
            DownloadInfoArrayAdapter diaa = new DownloadInfoArrayAdapter(
                    getActivity().getApplication(),R.layout.list, downloadInfo);
            dlistView.setAdapter(diaa);
        }
    }
//...
}

Answer 1

那是因为您返回的 ListView 有一个父项(在 V 的布局树中的某处)。

对于任何类型的 fragment ，onCreateView 应该返回一个没有任何父级的 View 。

在这种情况下，因为它是一个 listFragment，所以创建 ListView (使用 xml 或以编程方式)，然后返回它。不允许它有任何 parent ，因为它需要有一个 parent 作为 fragment 。

阅读here了解更多信息:

The system calls this when it's time for the fragment to draw its user interface for the first time. To draw a UI for your fragment, you must return a View from this method that is the root of your fragment's layout. You can return null if the fragment does not provide a UI.