使用CursorLoader在ListFragment数据库中查询SQLite的最佳实践?

I'm using Android Compatibility Library in my project. I've set up ListFragment as described in the DevGuide (http://developer.android.com/reference/android/app/Fragment.html), and using a simple CursorLoader Christian made be used without content provider (CursorLoader usage without ContentProvider).

我在我的项目中使用Android兼容性库。我已经按照DevGuide (http://developer.android.com/reference/android/app/Fragment.html)中描述的那样设置了ListFragment，并使用一个简单的CursorLoader Christian，使其不使用内容提供程序(CursorLoader使用而不使用内容提供程序)。

The question is where, in my ListFragment / parent Activity, should I open database, return the Cursor, create Adapter and setListAdapter?

问题是，在我的ListFragment / parent活动中，我应该在哪里打开数据库，返回光标，创建适配器和setListAdapter?

So in my app, I have TitlesFragment, DetailsFragment, FragmentLayoutActivity, DetailsLayoutActivity.

在我的应用中，我有TitlesFragment fragment fragment片段，FragmentLayoutActivity, DetailsLayoutActivity。

Is the best practice...

练习是最好的……

to open database in ListFragment's onActivityCreatedand close it in ListFragment's onDestroy like in code sample below

打开ListFragment’s onactivitycreated并关闭ListFragment’s onDestroy，如下面的代码示例所示

@Override
public void onActivityCreated(Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);
    // Open database
    playersDatabaseHelper = new PlayersDBAdapter(getActivity());
    playersDatabaseHelper.open();
    getLoaderManager().initLoader(0, null, this);
    ...
}

@Override
public void onDestroy() {
    super.onDestroy();
    if (playersDatabaseHelper != null) {
        playersDatabaseHelper.close();
    }
}

query database and return the cursor in onCreateLoader, and create the Adapter and setListAdapter in onLoadFinished like in code sample below

查询数据库并在onCreateLoader中返回光标，并在onLoadFinished中创建适配器和setListAdapter，如下面的代码示例所示

@Override
public Loader<Cursor> onCreateLoader(int id, Bundle args) {
    // Now create and return a CursorLoader that will take care of
    // creating a Cursor for the data being displayed.
    return new MyCursorLoader(getActivity()) {
        @Override
        public Cursor loadInBackground() {
            playersCursor = playersDatabaseHelper.getAllPlayers();
            return playersCursor;
        }
    };

}

@Override
public void onLoadFinished(Loader<Cursor> loader, Cursor cursor) {      
    // Create an empty adapter we will use to display the loaded data.
    playersAdapter = new RowAdapter(getActivity(), playersCursor, R.layout.players_overview_row);

    // Allocate the adapter to the List displayed within this fragment.
    setListAdapter(playersAdapter);

    playersAdapter.swapCursor(cursor);

    // The list should now be shown.
    if (isResumed()) {
        setListShown(true);
    } else {
        setListShownNoAnimation(true);
    }
}

Am I on the right track or should I move some of those somewhere? Thanks for your time!

我是在正确的轨道上还是应该把其中的一些移到别的地方?谢谢你的时间!

1 个解决方案

#1

Sorry no experience in CursorLoader yet and Fragment, but I already experienced use of SQLiteOpenHelper in the context of concurrent access by different threads & activities.

对不起，我还没有使用CursorLoader和Fragment，但是我已经在使用SQLiteOpenHelper时遇到过不同线程和活动并发访问的情况。

I will assume that PlayersDBAdapter is internally using a SQLiteOpenHelper class. but it is not clear what your methods open() and close() are doing?

我将假设PlayersDBAdapter在内部使用SQLiteOpenHelper类。但是不清楚open()和close()方法在做什么?

What I did:

我所做的:

define your SQLiteOpenHelper as an application wide singleton, not activity wide as you seem to do
将您的SQLiteOpenHelper定义为应用程序范围的单例，而不是像您看起来那样的活动范围
instantiate SQLiteOpenHelper single instance in your Application onCreate
在您的应用程序中实例化SQLiteOpenHelper单个实例。
DON'T release SQLiteOpenHelper instance in any activity onDestroy, as when an activity stops, another one might still have to open the DB
不要在任何活动中释放SQLiteOpenHelper实例，因为当活动停止时，另一个活动可能仍然需要打开DB。
I guess SQLiteOpenHelper instance should be cleared in application onTerminate (not sure as onTerminate is in practice almost never called)
我想SQLiteOpenHelper应该在onTerminate应用程序中清除(不确定onTerminate在实践中几乎从未调用过)
I have DBAdapter object which gets a SQLiteDatabase reference with mySQLiteOpenHelper.getWritableDatabase()
我有一个DBAdapter对象，它通过mySQLiteOpenHelper.getWritableDatabase()获得一个SQLiteDatabase引用
these DBAdapter are typically allocated in activity onCreate and released in onDestroy
这些DBAdapter通常在活动onCreate中分配，并在onDestroy中释放

At least this works, no crashs in an application with several thousands users. Suggestions to improve that are welcome :-)

至少这是可行的，在一个拥有数千用户的应用程序中没有碰撞。建议改善，欢迎:

#1