Android 为什么setSelection方法在onLoadFinished中不起作用？

我想在onLoadFinished方法中的我的ListFragment中设置选择，但是Log.vTAG，onLoadFinished:Selected id->+getSelectedItemId；行返回onLoadFinished:所选id->-9223372036854775808

问题是什么

 public void onLoadFinished(Loader<LoaderResult> loader, LoaderResult data) {
    adapter.swapCursor(data.cursor);

    // The list should now be shown.
    if (isResumed()) {
        setListShown(true);
    } else {
        setListShownNoAnimation(true);
    }
    if (data.cursor.getCount() > 0) {
        setSelection(0);
        Log.v(TAG, " onLoadFinished: Selected id -> " + getSelectedItemId());
    }        
}

谢谢