IllegalStateException:数据库已关闭(使用ViewPager)

Question

我对导致此错误的原因感到困惑,因为我已确保正在关闭我的数据库适配器(至少我认为我是).这就是LogCat的说法(所有这些标签都是AndroidRuntime):

致命异常:主java.lang.IllegalStateException:数据库/data/data/com.acedit.assignamo/databases/data.db(conn#0)已在android.database.sqlite.SQLiteDatabase.verifyDbIsOpen关闭(SQLiteDatabase.java:2082 )在android.database.sqlite.SQLiteDatabase.lock(SQLiteDatabase.java:413)的android.database.sqlite.SQLiteDatabase.lock(SQLiteDatabase.java:400)android.database.sqlite.SQLiteQuery.fillWindow(SQLiteQuery.java: 79)在Android.database.AbstractCursor.moveToPosition(AbstractCursor.java:178)的android.database.sqlite.SQLiteCursor.onMove(SQLiteCursor.java:147)的android.database.sqlite.SQLiteCursor.fillWindow(SQLiteCursor.java:164) )在android.view.View.dispatchSaveInstanceState(View.java:9868)的android.widget.AbsListView.onSaveInstanceState(AbsListView.java:1569)上的android.support.v4.widget.CursorAdapter.getItemId(CursorAdapter.java:225)在Android.widget.AdapterView.dispatchSaveInstanceState(Adapt)的android.view.ViewGroup.dispatchFreezeSelfOnly(ViewGroup.java:2310)erView.java:770)在android.view.View.View.saveInstanceState(ViewGroup.java:2296)的android.view.View.save.Stava上的android.view.View.SaveHsty状态(View.java:9851),android.support.v4.app.FragmentManagerImpl.saveFragmentViewState(FragmentManager)的.java:1561)在android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:962)在android.support.v4.app.FragmentManagerImpl.detachFragment(FragmentManager.java:1233)在android.support.v4. app.BackStackRecord.run(BackStackRecord.java:620)在android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1431)的android.support.v4.app.FragmentManagerImpl.executePendingTransactions(FragmentManager.java:431)在android.support.v4.app.FragmentPagerAdapter.finishUpdate(FragmentPagerAdapter.java:141)在android.support.v4.view.ViewPager.populate(ViewPager.java:895)在android.support.v4.view.ViewPager.populate (ViewPager.java:772)在android.support.v4.view.V上的android.support.v4.view.ViewPager.completeScroll(ViewPager.java:1539)iewPager.computeScroll(ViewPager.java:1422)在android.view.View.getDisplayList(View.java:10406)在android.view.ViewGroup.dispatchGetDisplayList(ViewGroup.java:2597)在android.view.View.getDisplayList(查看的.java:10380)在android.view.ViewGroup.dispatchGetDisplayList(ViewGroup.java:2597)在android.view.View.getDisplayList(View.java:10380)在android.view.ViewGroup.dispatchGetDisplayList(ViewGroup.java:2597)在Android.view上的android.view.View.get.get.目录(View.java:10380)的android.view.View.get.getDisplayList(ViewGroup.java:2597)上的android.view.View.getDisplayList(View.java:10380).在Android.view.ViewRootImpl.handleMessage的android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1634)的android.view.ViewRootImpl.draw(ViewRootImpl.java:1910)上的HardwareRenderer $ GlRenderer.draw(HardwareRenderer.java:875) (ViewRootImpl.java:2442)android.app.Handler.dispatchMessage(Handler.java:99)android.app.Looper.loop(Looper.java:137)android.app.ActivityThread.main(Activi)tyThread.java:4575)在java.lang.reflect.Method.invokeNative(本机方法)在java.lang.reflect.Method.invoke(Method.java:511)在com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.在dalvik.system.NativeStart.main(本机方法)的com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)上运行(ZygoteInit.java:786)

我的代码:

public Cursor fetchIncompleteAssignments(Short course) {
    DbAdapter adapter = new DbAdapter(context, null, Values.ASSIGNMENT_TABLE);
    adapter.open();

    Cursor r;
    if (course == null) // Fetching from all courses
        r = adapter.fetchAllWhere(Values.ASSIGNMENT_LIST_FETCH, Values.ASSIGNMENT_KEY_STATUS + "=" + 0, Values.ASSIGNMENT_KEY_DUE_DATE);
    else
        r = adapter.fetchAllWhere(Values.ASSIGNMENT_LIST_FETCH, Values.ASSIGNMENT_KEY_COURSE + "=" + course
            + " AND " + Values.ASSIGNMENT_KEY_STATUS + "=" + 0, Values.ASSIGNMENT_KEY_DUE_DATE);
    adapter.close();
    return r;
}

// Part of DbAdapter:
public DbAdapter open() throws SQLException {
    dbHelper = new DatabaseHelper(context);
    db = dbHelper.getWritableDatabase();
    return this;
}

public void close() {
    if (db != null) {
        try {
            db.close();
            dbHelper.close();
        } catch (NullPointerException e) {
            Log.e("Close", "Error: " + e + " " + e.getMessage());
        }
    } else
        Log.e("Close", "Error! db \"" + DATABASE_TABLE + "\" is null.");
}

在Cursor从返回fetchAllAssignments()被用来填充ListView通过自定义CursorAdapter.这ListView是a的内容ListFragment,并且在ViewPager的每个页面中显示了此ListFragment的多个实例(一个用于显示所有课程的作业,然后是每个单独课程的页面).

关于什么是错的任何想法？据我所知,我正在关闭我的数据库.如果您需要更多代码,请与我们联系.提前致谢!

编辑:数据从数据库中拉出来,并且它也填充了ListView.我可以浏览各个页面,但只要Fragment停止,它就会崩溃.当我开始另一个Activity时,它经常会崩溃,但并非总是如此.当我浏览页面时,它偶尔也会崩溃,尽管很少.这是我的片段的onPause()方法(我没有onStop()或onDestroy()):

public void onPause() {
    super.onPause();
    if (!assignmentsCursor.isClosed()) {
        assignmentsCursor.close();
        assignmentsCursor = null;
    }
}

在我,onResume()我只是从数据库重新加载列表,并获得上下文的新副本getActivity().也许有些东西被清除了(出于记忆目的)而且我没有重新加载它？我没有得到任何类型的NullPointerException,所以这似乎不太可能......

Answer 1

这个异常实际上是因为你双重关闭数据库而引发的，而不是因为你没有关闭它。

所以..

在您的close()方法中，替换代码中的以下行：

if (db != null) {

和：

if (db != null && db.isOpen()) {