怎样关闭游标和数据库安全？ [英] How do I close the Cursor and Database safely?

问题描述

我取的数据库使用游标的记录。它的工作完美。但是，我在logcat中已经一些错误，而我使用这个code

I've fetched the records from Database using Cursor. It's work perfect. But, I've some errors in Logcat while i'm using this code

public Cursor fetchAll()
{
    SQLiteDatabase db = this.getReadableDatabase();
    Cursor cursor = db.query(t1, new String[] {"_id",name, date, prior, time, dateformat}, null, null, null, null, prior); 
    return cursor;
}

我的logcat的是 -

My logcat is -

12-16 14:49:20.774: E/Database(18611): close() was never explicitly called on database '/data/data/com.android.application/databases/appZ.db' 
12-16 14:49:20.774: E/Database(18611): android.database.sqlite.DatabaseObjectNotClosedException: Application did not close the cursor or database object that was opened here
12-16 14:49:20.774: E/Database(18611):  at android.database.sqlite.SQLiteDatabase.<init>(SQLiteDatabase.java:1810)
12-16 14:49:20.774: E/Database(18611):  at android.database.sqlite.SQLiteDatabase.openDatabase(SQLiteDatabase.java:817)
12-16 14:49:20.774: E/Database(18611):  at android.database.sqlite.SQLiteDatabase.openOrCreateDatabase(SQLiteDatabase.java:851)
12-16 14:49:20.774: E/Database(18611):  at android.database.sqlite.SQLiteDatabase.openOrCreateDatabase(SQLiteDatabase.java:844)
12-16 14:49:20.774: E/Database(18611):  at android.app.ContextImpl.openOrCreateDatabase(ContextImpl.java:540)
12-16 14:49:20.774: E/Database(18611):  at android.content.ContextWrapper.openOrCreateDatabase(ContextWrapper.java:203)
12-16 14:49:20.774: E/Database(18611):  at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:98)
12-16 14:49:20.774: E/Database(18611):  at android.database.sqlite.SQLiteOpenHelper.getReadableDatabase(SQLiteOpenHelper.java:158)
12-16 14:49:20.774: E/Database(18611):  at com.android.todoapplication.DBHelper.fetchAll(DBHelper.java:91)
12-16 14:49:20.774: E/Database(18611):  at com.android.todoapplication.ApplicationActivity.sc_adapter(ApplicationActivity.java:1210)
12-16 14:49:20.774: E/Database(18611):  at com.android.todoapplication.ApplicationActivity.refresh_data(ApplicationActivity.java:1195)
12-16 14:49:20.774: E/Database(18611):  at com.android.todoapplication.ApplicationActivity.onKeyDown(ApplicationActivity.java:1440)
12-16 14:49:20.774: E/Database(18611):  at android.view.KeyEvent.dispatch(KeyEvent.java:1037)
12-16 14:49:20.774: E/Database(18611):  at android.app.Activity.dispatchKeyEvent(Activity.java:2068)
12-16 14:49:20.774: E/Database(18611):  at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchKeyEvent(PhoneWindow.java:1643)
12-16 14:49:20.774: E/Database(18611):  at android.view.ViewRoot.deliverKeyEventToViewHierarchy(ViewRoot.java:2471)
12-16 14:49:20.774: E/Database(18611):  at android.view.ViewRoot.handleFinishedEvent(ViewRoot.java:2441)
12-16 14:49:20.774: E/Database(18611):  at android.view.ViewRoot.handleMessage(ViewRoot.java:1735)
12-16 14:49:20.774: E/Database(18611):  at android.os.Handler.dispatchMessage(Handler.java:99)
12-16 14:49:20.774: E/Database(18611):  at android.os.Looper.loop(Looper.java:123)
12-16 14:49:20.774: E/Database(18611):  at android.app.ActivityThread.main(ActivityThread.java:4627)
12-16 14:49:20.774: E/Database(18611):  at java.lang.reflect.Method.invokeNative(Native Method)
12-16 14:49:20.774: E/Database(18611):  at java.lang.reflect.Method.invoke(Method.java:521)
12-16 14:49:20.774: E/Database(18611):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
12-16 14:49:20.774: E/Database(18611):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
12-16 14:49:20.774: E/Database(18611):  at dalvik.system.NativeStart.main(Native Method)

我refered东西从<一个href="http://stackoverflow.com/questions/4872583/how-to-avoid-db-not-close-and-cursor-exception">here.他们告诉记者，使用getReadableDatabase（）。我使用的方法也。而且，我也用这个方法，

I refered something from here. They told that use getReadableDatabase(). I'm using that method also. And, i've also use this method,

public Cursor fetchAll()
{
    SQLiteDatabase db = this.getReadableDatabase();
    Cursor cursor = db.query(t1, new String[] {"_id",name, date, prior, time, dateformat}, null, null, null, null, prior); 
   if (cursor!=null)
    {
        cursor.close();
    }
   if (db!=null)
    {
        db.close();
    }
    return cursor;
}

在那之后有错误，如 -

after that having error like -

Database wasn't open.

之后，还我在我的数据库已经这样的错误。因此，任何人告诉我，我该如何获取获取记录后的安全性密切的光标和数据库。

After, also i've this errors in my Database. So anyone tell me How do I acquire the safety close for Cursor and Database after fetching the records.

推荐答案

编辑：如果您返回游标已经关闭，您不能使用它。调用方法前，打开数据库，然后调用方法后关闭游标，然后在数据库中。

If you return a cursor that is already closed, you can't use it. Open the database before calling the method, then close the cursor and then the database after calling the method.

您可以关闭游标后，你与它这样做的：

You can close the cursor after you're done with it like this:

Cursor cursor = fetchAll();
... // Do your work with the cursor
cursor.close();

或者如果你使用鼠标从一个活动，并且需要重新查询（当活动重新启动，停止......），你可以使用这个：

Or if you're using the cursor from an activity, and need to requery (when the activity is restarted, stopped...) you can use this:

Cursor cursor = fetchAll();
startManagingCursor(cursor); // Android will take care of the cursor for you
// Do your work with the cursor

要关闭数据库（关闭游标后，如果在活动里面的onDestroy（） preferably）：

To close database (after closing the cursor, or if inside an activity in onDestroy() preferably):

dbhelper.close();

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