android - 在 ListFragment 中没有事先关闭()的情况下完成游标

Question

我在关闭应用程序或只是让手机在应用程序打开时休眠后收到此错误消息。

当我让手机进入休眠状态时，我会收到 30 到 61 条有关此错误消息的日志条目。在加载 ListFragment 之前记录错误。我怀疑 fragment 已加载但错误记录在 fragment 的信息条目之前。

当我关闭应用程序时，我只得到 1 个错误条目，它是在 onLoaderReset() 调用之后记录的。我在应用程序关闭之前关闭了数据库，这似乎有所帮助。

该应用程序可以运行，但我担心它在各种手机上运行后会失败。

除 onLoaderReset() 中的 adapter.swapCursor(null) 外，我没有明确控制光标。

我很感激关于如何解决此错误的任何想法。

谢谢

public class ChildList extends ListFragment implements
    LoaderManager.LoaderCallbacks<Cursor>, DatabaseConstants, GoodiList {

private final String TAG = "ChildList";

// database columns that we will retreive
final String[] PROJECTION = new String[] { CHILD_ID_COLUMN,
        CHILD_NAME_COLUMN };

// selects all
final String SELECTION = null;

SimpleCursorAdapter adapter = null;

private ListParent parentActivity;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    Log.e(TAG, "on Create");
    String[] fromColumns = { CHILD_NAME_COLUMN, CHILD_ID_COLUMN };

    int[] toViews = { R.id.name_column, R.id.id_column };

    adapter=new SimpleCursorAdapter(
            getActivity(),
            R.layout.child_list_entry,
            null,
            fromColumns,
            toViews,
            0
            );

    setListAdapter(adapter);

    getLoaderManager().initLoader(0, null, this);

    Log.i(TAG, "finished on Create");
}


public void onActivityCreated(Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);

    LongClickListener longClickListener = new LongClickListener();

    getListView().setOnItemLongClickListener(longClickListener);
}

@Override
public void setListAdapter(ListAdapter adapter) {
    super.setListAdapter(adapter);
}

@Override
public Loader<Cursor> onCreateLoader(int arg0, Bundle arg1) {

    Log.v(TAG, "starting on create loader");

    Uri CHILD_URI = ChildContentProvider.CONTENT_URI;

    CursorLoader cursorLoader = new CursorLoader(getActivity(), CHILD_URI,
            PROJECTION, SELECTION, null, null);

    Log.v(TAG, "finished on create loader");

    return cursorLoader;
}

@Override
public void onLoadFinished(Loader<Cursor> arg0, Cursor newCursor) {
    adapter.swapCursor(newCursor);

    if (newCursor != null) {
        int rowCount = newCursor.getCount();

        Log.v(TAG, "--- onLoadFinished:  got " + rowCount + " children");
    }
}

/**
 * this used to delete. However, we need it to select usually. Now delete is
 * done by long click.
 */
@Override
public void onListItemClick(ListView l, View v, int position, long id) {
    super.onListItemClick(l, v, position, id);

    // delete child - remove child from list and database
    Object item = l.getItemAtPosition(position);

    Cursor cursor = (Cursor) item;

    int nameCol = cursor.getColumnIndex(CHILD_NAME_COLUMN);
    int idCol = cursor.getColumnIndex(CHILD_ID_COLUMN);

    final String name = cursor.getString(nameCol);

    final int childId = cursor.getInt(idCol);

    Log.i(TAG, "selected " + name + " id: " + childId + " at position "
            + position);

    cursor.close();

    parentActivity.listItemSelected(this, position, childId);

}

/**
 * Forces cursor to requery database and list to be update. Used when a new
 * child is entered in parent activity's EditText field.
 */
public void notifyDataChanged() {

    Log.i(TAG, "told adapter that data changed");

    getLoaderManager().restartLoader(0, null, this);

    adapter.notifyDataSetChanged();
}

/** tell adapter that cursor is no longer valid*/
@Override
public void onLoaderReset(Loader<Cursor> arg0) {
Log.i(TAG,"---- onLoaderReset -----");

adapter.swapCursor(null);

}

@Override
public void onAttach(Activity activity) {
    super.onAttach(activity);

    parentActivity = (ListParent) activity;

    parentActivity.setList(this);

}

Answer 1

我遇到了同样的问题，我通过仔细查看文档解决了这个问题。

根据文档，http://developer.android.com/reference/android/widget/CursorAdapter.html#swapCursor(android.database.Cursor)

swapCursor(Cursor data) 方法返回原始未关闭的游标。如果新游标与旧游标相同，或者不存在旧游标，则返回 null。

通过更改我的代码

@Override
public void onLoadFinished(Loader<Cursor> loader, Cursor data) {
    adapter.swapCursor(data);
}

到

@Override
public void onLoadFinished(Loader<Cursor> loader, Cursor data) {
    Cursor cursor = adapter.swapCursor(data);
    if (cursor != null) {
        cursor.close();
    }
}

我阻止了这些警告的出现。

注意:您也应该对 onLoaderReset() 方法执行相同的操作。因为即使您执行 adapter.swapCursor(null)，它也会返回旧光标。