Android - 尝试重新打开已经关闭的对象:使用loaderManager的SQLiteQuery

Question

我对Android很新,我对过滤的listView和从横向模式更改为纵向模式或反之亦然的活动有一些问题.我有一个editText用于过滤"drinkSearch",只要我不改变视角(人像与风景),这个过滤就有效.这是我得到的错误:

java.lang.IllegalStateException:尝试重新打开已经关闭的对象:SQLiteQuery:SELECT _id,name FROM drinks

正如您在下面的代码中看到的,我使用了接口LoaderManager.LoaderCallbacks,这个概念对我来说有点新,我不确定哪里出了问题.我将非常感谢所有的帮助,在此先感谢!

public class Drinks_Fragment extends Fragment实现LoaderManager.LoaderCallbacks {

private static final int DRINKS_LIST_LOADER = 0x01;
private SimpleCursorAdapter adapter;
private ListView drinksList;
private String LOG;
private EditText drinkSearch;

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {

    View view = inflater.inflate(R.layout.drinks_list, container, false);
    drinkSearch = (EditText)view.findViewById(R.id.drinkInputSearch);
    drinksList = (ListView) view.findViewById(R.id.drinksList);
    drinksList.setEmptyView(view.findViewById(R.id.empty_list_view));

    String[] from = {DrinksTable.COLUMN_NAME};
    int[] to = {R.id.drinkName};
    getLoaderManager().initLoader(DRINKS_LIST_LOADER, null, this);
    adapter = new SimpleCursorAdapter(getActivity().getApplicationContext(), R.layout.drinks_list_item,null, from, to, 0);
    drinksList.setAdapter(adapter);

在这部分中,我根据searchDrink editText中输入的字符串向contentProvider询问新的Cursor.(以下代码,直到"返回视图"正好在上面的部分下方,同样的onCreateView方法)

    drinkSearch.addTextChangedListener(new TextWatcher() {

        @Override
        public void onTextChanged(CharSequence s, int arg1, int arg2, int arg3) {
            // When user changed the Text
            adapter.getFilter().filter(s.toString());
        }

        @Override
        public void beforeTextChanged(CharSequence arg0, int arg1, int arg2, int arg3) {
            // TODO Auto-generated method stub

        }

        @Override
        public void afterTextChanged(Editable arg0) {
            // TODO Auto-generated method stub
        }
    });

    adapter.setFilterQueryProvider(new FilterQueryProvider() {

        public Cursor runQuery(CharSequence constraint) {
            String value = "%"+constraint.toString()+"%";
            ContentResolver content = getActivity().getContentResolver();
            return content.query(CupProvider.DRINKS_URI,new String[]{DrinksTable.COLUMN_ID,DrinksTable.COLUMN_NAME},DrinksTable.COLUMN_NAME + " LIKE ?",new String[]{value},null);
        }
    });

    return view;
}

@Override
public void onCreateContextMenu(ContextMenu menu, View v, ContextMenu.ContextMenuInfo menuInfo) {
    super.onCreateContextMenu(menu,v,menuInfo);
    MenuInflater inflater = getActivity().getMenuInflater();
    inflater.inflate(R.menu.drink_actions,menu);
}


@Override
public Loader<Cursor> onCreateLoader(int i, Bundle bundle) {
    String[] projection = {DrinksTable.COLUMN_ID, DrinksTable.COLUMN_NAME};
    CursorLoader cursorLoader = new CursorLoader(getActivity(), CupProvider.DRINKS_URI, projection, null, null, null);
    return cursorLoader;
}

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

}

@Override
public void onLoaderReset(Loader<Cursor> cursorLoader) {
    // data is not available anymore, delete reference
    adapter.swapCursor(null);
}

}

这里有2张图片展示了当下的样子:http ://oi42.tinypic.com/dfc702.jpg http://oi43.tinypic.com/2ylqkqa.jpg

Answer 1

由于格式不佳,您的代码有点难以理解.

无论如何,提供的答案实际上不是解决方法.onLoadFinished应保证返回的光标不会被关闭,因此您将以错误的方式加载光标.具体来说,当你打电话

adapter.getFilter().filter(s.toString());

我真的不明白这里发生了什么,但我明白你应该做点什么.只需将查询过滤器存储在您的Fragment运行中的字段中即可getLoaderManager().restartLoader(DRINKS_LIST_LOADER, null, this);.请注意,您运行restartLoader,而不是initLoader,因为您有不同的数据要查询.

在你的onCreateLoader,你应该使用你存储的过滤器作为实例变量selection.

一些背景

initLoader加载上次运行中加载的数据(如果之前已运行).这就是你在Fragment/Activity的初始化方法中调用的原因.这很方便,因为您不必重新查询方向更改.

restartLoader清理以前加载的数据,以便您获得一个新的Loader(可能)不同的数据.

如果您还不确定自己在做什么,请务必阅读本文,这是一篇关于Loaders的非常好的介绍性文章,示例代码非常类似于您想要实现的内容.装载机起初非常神秘,但是一旦掌握了它,它就会顺利航行.