在Android中需要有關數據庫訪問的幫助

Question

我在我的應用程序中使用sqlite數據庫。 我在這樣的服務類中有這個dbhelper類。

    public class MushroomService {

        private int downloadprogress;
        private int databasesize;

        private DataBaseHelper myDbHelper;
    }

    public MushroomService(Context context)
    {
        myDbHelper = new DataBaseHelper(context);
        downloadprogress = 0;
    }

服務類是我的應用程序類的成員，如下所示：

public class fungifieldguideapplication extends Application {
    public MushroomService service = new MushroomService(this);
}

在我的活動類中，我訪問此應用程序並將其保留為本地變量，如下所示：

public class Cat_Genus extends Activity {
    fungifieldguideapplication appState;
    ListView list_Genus;

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        setContentView(R.layout.cat_genus);

        appState = ((fungifieldguideapplication)this.getApplication());

        Cursor cursor_genuslist = appState.service.GetGenusList(this);
        startManagingCursor(cursor_genuslist);
    }
}

我的服務電話如下所示：

public Cursor GetGenusList(Context context)
    {
        myDbHelper = new DataBaseHelper(context);
        Cursor cursor;
        try 
        {
            myDbHelper.openDataBase();
            SQLiteDatabase db = myDbHelper.myDataBase;
            cursor = db.query(true, "Mushrooms", GenusListColumns, null, null, "Genus", null, "Genus ASC", null);
        }
        catch(SQLException sqle)
        {
            throw sqle;
        }
        return cursor;
    }

我添加了這些替代，以消除我的內存泄漏。

@Override
    public void onDestroy() {
        list_Genus.setAdapter(null);
        appState.service.CloseDB();
        super.onDestroy();
    }

    @Override
    public void onPause() {
        appState.service.CloseDB();
        super.onPause();
    }

    @Override
    public void onResume() {
        appState.service.OpenDB();
        super.onResume();
    }

但是我無法阻止我的內存泄漏。 有人可以幫我弄清楚如何擺脫這些內存泄漏嗎？ 這些泄漏屬於以下類型：

07-27 17:38:44.613: ERROR/Database(26175): Leak found
07-27 17:38:44.613: ERROR/Database(26175): java.lang.IllegalStateException: /data/data/net.daleroy.fungifieldguide/databases/Mushrooms.db SQLiteDatabase created and never closed
07-27 17:38:44.613: ERROR/Database(26175):     at android.database.sqlite.SQLiteDatabase.<init>(SQLiteDatabase.java:1695)
07-27 17:38:44.613: ERROR/Database(26175):     at android.database.sqlite.SQLiteDatabase.openDatabase(SQLiteDatabase.java:739)
07-27 17:38:44.613: ERROR/Database(26175):     at net.daleroy.fungifieldguide.data.DataBaseHelper.openDataBase(DataBaseHelper.java:79)
07-27 17:38:44.613: ERROR/Database(26175):     at net.daleroy.fungifieldguide.services.MushroomService.GetSpeciesListByGenus(MushroomService.java:113)
07-27 17:38:44.613: ERROR/Database(26175):     at net.daleroy.fungifieldguide.activities.Cat_Species.onCreate(Cat_Species.java:46)
07-27 17:38:44.613: ERROR/Database(26175):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
07-27 17:38:44.613: ERROR/Database(26175):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2459)
07-27 17:38:44.613: ERROR/Database(26175):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2512)
07-27 17:38:44.613: ERROR/Database(26175):     at android.app.ActivityThread.access$2200(ActivityThread.java:119)
07-27 17:38:44.613: ERROR/Database(26175):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1863)
07-27 17:38:44.613: ERROR/Database(26175):     at android.os.Handler.dispatchMessage(Handler.java:99)
07-27 17:38:44.613: ERROR/Database(26175):     at android.os.Looper.loop(Looper.java:123)
07-27 17:38:44.613: ERROR/Database(26175):     at android.app.ActivityThread.main(ActivityThread.java:4363)
07-27 17:38:44.613: ERROR/Database(26175):     at java.lang.reflect.Method.invokeNative(Native Method)
07-27 17:38:44.613: ERROR/Database(26175):     at java.lang.reflect.Method.invoke(Method.java:521)
07-27 17:38:44.613: ERROR/Database(26175):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:860)
07-27 17:38:44.613: ERROR/Database(26175):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618)
07-27 17:38:44.613: ERROR/Database(26175):     at dalvik.system.NativeStart.main(Native Method)

Answer 1

也許我是錯的，但也許是因為您在與數據庫進行交互之后沒有關閉數據庫。 每當我在android上進行數據庫工作時，我都會在Try {} finally {}子句中包圍交互，該子句會在finally上關閉連接。

例如

try{
//database stuff
} finally{
   db.close
 }

Answer 2

您的程序正在終止，因為您兩次打開數據庫

    myDbHelper = new DataBaseHelper(context); // first here
    Cursor cursor;
    try 
    {
        myDbHelper.openDataBase(); //then here

您可能可以刪除“ myDbHelper.openDataBase（）;”