我正在尝试构建一个聊天应用程序。 我需要执行一个SQLite查询，该查询返回用户所属的所有组。然后使用这些组，每个组都需要一些数据。
这两种方法都是
public List<Contact_class> getAllGroupsFromUser() {
List<String> grupos = new ArrayList<>();
String user = ClassCOM.getUserLogged(context);
SQLiteDatabase db = this.getReadableDatabase();
String select_query = "SELECT gr."+KEY_GROUP+" FROM "+TABLE_GROUPS+" gr JOIN "+TABLE_USER_GROUP_REL+" rel ON rel."+KEY_ID_GROUP+" = gr."+KEY_ID_GROUP+" JOIN "+ TABLE_USERS +" user ON user."+KEY_ID_USER+" = rel."+KEY_ID_USER+" WHERE user." + KEY_USER + " = '"+user+"'";
String grupo;
Cursor cursor = db.rawQuery(select_query, null);
if (cursor.moveToFirst()) {
do {
grupo = cursor.getString(0);
grupos.add(grupo);
} while (cursor.moveToNext());
}
cursor.close();
db.close();
return getGroupLastMessage(grupos);
}
private List<Contacto_class> getGroupLastMessage(List<String> grupos){
List<Contacto_class> lista = new ArrayList<>();
SQLiteDatabase db = this.getReadableDatabase();
String fecha, mensaje, usuario;
for(String gr : grupos){
String select_query = "SELECT "+KEY_DATE+", "+KEY_USER+", "+KEY_MENSAJE+" FROM "+TABLE_MESSAGES+" WHERE "+KEY_ID_GROUP+"='"+getGroupId(gr)+"' ORDER BY "+KEY_DATE +" DESC LIMIT 1";
Cursor cursor = db.rawQuery(select_query, null);
if (cursor.moveToFirst()) {
fecha = cursor.getString(0);
usuario = cursor.getString(1);
mensaje = cursor.getString(2);
Contacto_class contacto_class = new Contacto_class(gr, usuario, fecha, mensaje);
lista.add(contacto_class);
}
cursor.close();
}
db.close();
return lista;
}
运行代码时，出现此错误：
E/AndroidRuntime: FATAL EXCEPTION: main
Process: es.monlau.smartschool, PID: 5719
java.lang.IllegalStateException: attempt to re-open an already-closed object: SQLiteDatabase: /data/user/0/es.monlau.smartschool/databases/Smartschool
at android.database.sqlite.SQLiteClosable.acquireReference(SQLiteClosable.java:55)
at android.database.sqlite.SQLiteDatabase.rawQueryWithFactory(SQLiteDatabase.java:1314)
at android.database.sqlite.SQLiteDatabase.rawQuery(SQLiteDatabase.java:1257)
at es.monlau.smartschool.handler.DBHandler.getGroupLastMessage(DBHandler.java:327)
at es.monlau.smartschool.handler.DBHandler.getAllGroupsFromUser(DBHandler.java:315)
at es.monlau.smartschool.Mensajeria.showContactList(Mensajeria.java:89)
at es.monlau.smartschool.Mensajeria.onCreateView(Mensajeria.java:54)
at android.support.v4.app.Fragment.performCreateView(Fragment.java:2346)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1428)
at android.support.v4.app.FragmentManagerImpl.moveFragmentToExpectedState(FragmentManager.java:1759)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1827)
at android.support.v4.app.BackStackRecord.executeOps(BackStackRecord.java:797)
at android.support.v4.app.FragmentManagerImpl.executeOps(FragmentManager.java:2596)
at android.support.v4.app.FragmentManagerImpl.executeOpsTogether(FragmentManager.java:2383)
at android.support.v4.app.FragmentManagerImpl.removeRedundantOperationsAndExecute(FragmentManager.java:2338)
at android.support.v4.app.FragmentManagerImpl.execSingleAction(FragmentManager.java:2215)
at android.support.v4.app.BackStackRecord.commitNowAllowingStateLoss(BackStackRecord.java:649)
at android.support.v4.app.FragmentPagerAdapter.finishUpdate(FragmentPagerAdapter.java:145)
at android.support.v4.view.ViewPager.populate(ViewPager.java:1238)
at android.support.v4.view.ViewPager.populate(ViewPager.java:1086)
at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1616)
at android.view.View.measure(View.java:22002)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6580)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1514)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:806)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:685)
at android.view.View.measure(View.java:22002)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6580)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:185)
at android.view.View.measure(View.java:22002)
at android.support.v4.widget.DrawerLayout.onMeasure(DrawerLayout.java:1059)
at android.view.View.measure(View.java:22002)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6580)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:185)
at android.support.v7.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:141)
at android.view.View.measure(View.java:22002)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6580)
at android.support.v7.widget.ActionBarOverlayLayout.onMeasure(ActionBarOverlayLayout.java:400)
at android.view.View.measure(View.java:22002)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6580)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:185)
at android.view.View.measure(View.java:22002)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6580)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1514)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:806)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:685)
at android.view.View.measure(View.java:22002)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6580)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:185)
at com.android.internal.policy.DecorView.onMeasure(DecorView.java:721)
at android.view.View.measure(View.java:22002)
at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2410)
E/AndroidRuntime: at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1498)
at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1751)
at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1386)
at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6733)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:911)
at android.view.Choreographer.doCallbacks(Choreographer.java:723)
at android.view.Choreographer.doFrame(Choreographer.java:658)
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:897)
at android.os.Handler.handleCallback(Handler.java:789)
at android.os.Handler.dispatchMessage(Handler.java:98)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6541)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)
在这一行：
Cursor cursor = db.rawQuery(select_query, null);
我的猜测是问题是我在第一次迭代中打开了游标，然后将其关闭并再次打开以进行第二次插入。我不能那样做吗？我该如何解决这种“双重查询”情况？
谢谢。
答案 0 :(得分：0)
java.lang.IllegalStateException：尝试重新打开一个已经关闭的 对象：SQLiteDatabase
主要是由于cursor.close();导致的。您的代码将是
Cursor cursor = db.rawQuery(select_query, null);
if (cursor.moveToFirst()) {
do {
grupo = cursor.getString(0);
grupos.add(grupo);
} while (cursor.moveToNext());
}
return getGroupLastMessage(grupos);
和
if (cursor.moveToFirst()) {
do {
fecha = cursor.getString(0);
usuario = cursor.getString(1);
mensaje = cursor.getString(2);
Contacto_class contacto_class = new Contacto_class(gr, usuario, fecha, mensaje);
lista.add(contacto_class);
} while (cursor.moveToNext());
}
cursor.close();
// close db connection
db.close();
如果此问题仍然存在，请添加Break-Point并执行调试。