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如何修复“请确保在光标上显式调用 close()”？

发布于 2024-10-20 17:26:03 字数 8111 浏览 4 评论 0原文

我正在构建一个具有以下代码的 Activity 的 Android 应用程序：

public class SavedSalesActivity extends Activity {

    protected ListView mSalesList;
    protected Cursor mSalesCursor;
    protected SalesCursorAdapter mSalesAdapter;
    protected SalesDbAdapter mDb;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.sales_list);

        mDb = new SalesDbAdapter(this);
        mDb.open();
        mSalesCursor = mDb.getSaved();
        startManagingCursor(mSalesCursor);

        mSalesAdapter = new SalesCursorAdapter(this, R.layout.sales_list_item, mSalesCursor,
                new String[0], new int[0]);

        mSalesList = (ListView)findViewById(R.id.sales_listview);
        mSalesList.setAdapter(mSalesAdapter);
        mSalesList.setEmptyView(findViewById(android.R.id.empty));
        mSalesList.setOnItemClickListener(new OnItemClickListener() {...});
    }

    @Override
    protected void onStart() {
        Log.v(TAG, "Starting SavedSalesActivity");

        mDb.open();

        mSalesCursor = mDb.getSaved();
        startManagingCursor(mSalesCursor);

        super.onStart();
    }

    @Override
    protected void onStop() {
        Log.v(TAG, "Stopping SavedSalesActivity");

        mSalesCursor.close();

        mDb.close();

        super.onStop();
    }
}

根据我的理解，这应该足以正确关闭我的所有资源，但是如果我打开此 Activity 并使用 Android 设备后退按钮退出它，我会得到经过一段短（可变）时间后，Logcat 中会出现此情况。

03-08 19:33:58.492: WARN/SQLiteCompiledSql(5169): Releasing statement in a finalizer. Please ensure that you explicitly call close() on your cursor: SELECT * FROM sales ORDER BY featured DESC
03-08 19:33:58.492: WARN/SQLiteCompiledSql(5169): android.database.sqlite.DatabaseObjectNotClosedException: Application did not close the cursor or database object that was opened here
03-08 19:33:58.492: WARN/SQLiteCompiledSql(5169):     at android.database.sqlite.SQLiteCompiledSql.<init>(SQLiteCompiledSql.java:62)
03-08 19:33:58.492: WARN/SQLiteCompiledSql(5169):     at android.database.sqlite.SQLiteProgram.<init>(SQLiteProgram.java:80)
03-08 19:33:58.492: WARN/SQLiteCompiledSql(5169):     at android.database.sqlite.SQLiteQuery.<init>(SQLiteQuery.java:46)
03-08 19:33:58.492: WARN/SQLiteCompiledSql(5169):     at android.database.sqlite.SQLiteDirectCursorDriver.query(SQLiteDirectCursorDriver.java:42)
03-08 19:33:58.492: WARN/SQLiteCompiledSql(5169):     at android.database.sqlite.SQLiteDatabase.rawQueryWithFactory(SQLiteDatabase.java:1345)
03-08 19:33:58.492: WARN/SQLiteCompiledSql(5169):     at android.database.sqlite.SQLiteDatabase.queryWithFactory(SQLiteDatabase.java:1229)
03-08 19:33:58.492: WARN/SQLiteCompiledSql(5169):     at android.database.sqlite.SQLiteDatabase.query(SQLiteDatabase.java:1184)
03-08 19:33:58.492: WARN/SQLiteCompiledSql(5169):     at android.database.sqlite.SQLiteDatabase.query(SQLiteDatabase.java:1264)
03-08 19:33:58.492: WARN/SQLiteCompiledSql(5169):     at com.maps.app.classifiedconcepts.sale.SalesDbAdapter.getSaved(SalesDbAdapter.java:149)
03-08 19:33:58.492: WARN/SQLiteCompiledSql(5169):     at com.maps.app.classifiedconcepts.sale.SavedSalesActivity.onCreate(SavedSalesActivity.java:113)
03-08 19:33:58.492: WARN/SQLiteCompiledSql(5169):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
03-08 19:33:58.492: WARN/SQLiteCompiledSql(5169):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)
03-08 19:33:58.492: WARN/SQLiteCompiledSql(5169):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
03-08 19:33:58.492: WARN/SQLiteCompiledSql(5169):     at android.app.ActivityThread.access$2300(ActivityThread.java:125)
03-08 19:33:58.492: WARN/SQLiteCompiledSql(5169):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
03-08 19:33:58.492: WARN/SQLiteCompiledSql(5169):     at android.os.Handler.dispatchMessage(Handler.java:99)
03-08 19:33:58.492: WARN/SQLiteCompiledSql(5169):     at android.os.Looper.loop(Looper.java:123)
03-08 19:33:58.492: WARN/SQLiteCompiledSql(5169):     at android.app.ActivityThread.main(ActivityThread.java:4627)
03-08 19:33:58.492: WARN/SQLiteCompiledSql(5169):     at java.lang.reflect.Method.invokeNative(Native Method)
03-08 19:33:58.492: WARN/SQLiteCompiledSql(5169):     at java.lang.reflect.Method.invoke(Method.java:521)
03-08 19:33:58.492: WARN/SQLiteCompiledSql(5169):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
03-08 19:33:58.492: WARN/SQLiteCompiledSql(5169):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
03-08 19:33:58.492: WARN/SQLiteCompiledSql(5169):     at dalvik.system.NativeStart.main(Native Method)
03-08 19:33:58.503: ERROR/Database(5169): close() was never explicitly called on database '/data/data/com.maps.app.classifiedconcepts/databases/classified_concepts' 
03-08 19:33:58.503: ERROR/Database(5169): android.database.sqlite.DatabaseObjectNotClosedException: Application did not close the cursor or database object that was opened here
03-08 19:33:58.503: ERROR/Database(5169):     at android.database.sqlite.SQLiteDatabase.<init>(SQLiteDatabase.java:1810)
03-08 19:33:58.503: ERROR/Database(5169):     at android.database.sqlite.SQLiteDatabase.openDatabase(SQLiteDatabase.java:817)
03-08 19:33:58.503: ERROR/Database(5169):     at android.database.sqlite.SQLiteDatabase.openOrCreateDatabase(SQLiteDatabase.java:851)
03-08 19:33:58.503: ERROR/Database(5169):     at android.database.sqlite.SQLiteDatabase.openOrCreateDatabase(SQLiteDatabase.java:844)
03-08 19:33:58.503: ERROR/Database(5169):     at android.app.ContextImpl.openOrCreateDatabase(ContextImpl.java:540)
03-08 19:33:58.503: ERROR/Database(5169):     at android.content.ContextWrapper.openOrCreateDatabase(ContextWrapper.java:203)
03-08 19:33:58.503: ERROR/Database(5169):     at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:112)
03-08 19:33:58.503: ERROR/Database(5169):     at com.maps.app.classifiedconcepts.sale.SalesDbAdapter.open(SalesDbAdapter.java:163)
03-08 19:33:58.503: ERROR/Database(5169):     at com.maps.app.classifiedconcepts.sale.SavedSalesActivity.onCreate(SavedSalesActivity.java:112)
03-08 19:33:58.503: ERROR/Database(5169):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
03-08 19:33:58.503: ERROR/Database(5169):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)
03-08 19:33:58.503: ERROR/Database(5169):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
03-08 19:33:58.503: ERROR/Database(5169):     at android.app.ActivityThread.access$2300(ActivityThread.java:125)
03-08 19:33:58.503: ERROR/Database(5169):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
03-08 19:33:58.503: ERROR/Database(5169):     at android.os.Handler.dispatchMessage(Handler.java:99)
03-08 19:33:58.503: ERROR/Database(5169):     at android.os.Looper.loop(Looper.java:123)
03-08 19:33:58.503: ERROR/Database(5169):     at android.app.ActivityThread.main(ActivityThread.java:4627)
03-08 19:33:58.503: ERROR/Database(5169):     at java.lang.reflect.Method.invokeNative(Native Method)
03-08 19:33:58.503: ERROR/Database(5169):     at java.lang.reflect.Method.invoke(Method.java:521)
03-08 19:33:58.503: ERROR/Database(5169):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
03-08 19:33:58.503: ERROR/Database(5169):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
03-08 19:33:58.503: ERROR/Database(5169):     at dalvik.system.NativeStart.main(Native Method)

mSalesCursor = mDb.getSaved(); 行在我的 SalesDbAdapter 中调用以下代码：

public Cursor getSaved() {
return mDb.query(TABLE_NAME, null, null, null, null, null, KEY_FEATURED + " DESC"); 
}

我做错了什么？为什么我会遇到这些异常？我特别困惑，因为我认为在初始化 mSalesCursor 之后立即调用 startManagingCursor(mSalesCursor) 将使我无需在任何活动生命周期方法中关闭游标。

原文

I'm building an Android application with an activity that has the following code:

public class SavedSalesActivity extends Activity {

    protected ListView mSalesList;
    protected Cursor mSalesCursor;
    protected SalesCursorAdapter mSalesAdapter;
    protected SalesDbAdapter mDb;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.sales_list);

        mDb = new SalesDbAdapter(this);
        mDb.open();
        mSalesCursor = mDb.getSaved();
        startManagingCursor(mSalesCursor);

        mSalesAdapter = new SalesCursorAdapter(this, R.layout.sales_list_item, mSalesCursor,
                new String[0], new int[0]);

        mSalesList = (ListView)findViewById(R.id.sales_listview);
        mSalesList.setAdapter(mSalesAdapter);
        mSalesList.setEmptyView(findViewById(android.R.id.empty));
        mSalesList.setOnItemClickListener(new OnItemClickListener() {...});
    }

    @Override
    protected void onStart() {
        Log.v(TAG, "Starting SavedSalesActivity");

        mDb.open();

        mSalesCursor = mDb.getSaved();
        startManagingCursor(mSalesCursor);

        super.onStart();
    }

    @Override
    protected void onStop() {
        Log.v(TAG, "Stopping SavedSalesActivity");

        mSalesCursor.close();

        mDb.close();

        super.onStop();
    }
}

According to my understanding this should be more than sufficient to properly close all my resources, however if I open this activity and exit it with the Android device back button I get this in Logcat after a short (variable) period of time.

03-08 19:33:58.492: WARN/SQLiteCompiledSql(5169): Releasing statement in a finalizer. Please ensure that you explicitly call close() on your cursor: SELECT * FROM sales ORDER BY featured DESC
03-08 19:33:58.492: WARN/SQLiteCompiledSql(5169): android.database.sqlite.DatabaseObjectNotClosedException: Application did not close the cursor or database object that was opened here
03-08 19:33:58.492: WARN/SQLiteCompiledSql(5169):     at android.database.sqlite.SQLiteCompiledSql.<init>(SQLiteCompiledSql.java:62)
03-08 19:33:58.492: WARN/SQLiteCompiledSql(5169):     at android.database.sqlite.SQLiteProgram.<init>(SQLiteProgram.java:80)
03-08 19:33:58.492: WARN/SQLiteCompiledSql(5169):     at android.database.sqlite.SQLiteQuery.<init>(SQLiteQuery.java:46)
03-08 19:33:58.492: WARN/SQLiteCompiledSql(5169):     at android.database.sqlite.SQLiteDirectCursorDriver.query(SQLiteDirectCursorDriver.java:42)
03-08 19:33:58.492: WARN/SQLiteCompiledSql(5169):     at android.database.sqlite.SQLiteDatabase.rawQueryWithFactory(SQLiteDatabase.java:1345)
03-08 19:33:58.492: WARN/SQLiteCompiledSql(5169):     at android.database.sqlite.SQLiteDatabase.queryWithFactory(SQLiteDatabase.java:1229)
03-08 19:33:58.492: WARN/SQLiteCompiledSql(5169):     at android.database.sqlite.SQLiteDatabase.query(SQLiteDatabase.java:1184)
03-08 19:33:58.492: WARN/SQLiteCompiledSql(5169):     at android.database.sqlite.SQLiteDatabase.query(SQLiteDatabase.java:1264)
03-08 19:33:58.492: WARN/SQLiteCompiledSql(5169):     at com.maps.app.classifiedconcepts.sale.SalesDbAdapter.getSaved(SalesDbAdapter.java:149)
03-08 19:33:58.492: WARN/SQLiteCompiledSql(5169):     at com.maps.app.classifiedconcepts.sale.SavedSalesActivity.onCreate(SavedSalesActivity.java:113)
03-08 19:33:58.492: WARN/SQLiteCompiledSql(5169):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
03-08 19:33:58.492: WARN/SQLiteCompiledSql(5169):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)
03-08 19:33:58.492: WARN/SQLiteCompiledSql(5169):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
03-08 19:33:58.492: WARN/SQLiteCompiledSql(5169):     at android.app.ActivityThread.access$2300(ActivityThread.java:125)
03-08 19:33:58.492: WARN/SQLiteCompiledSql(5169):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
03-08 19:33:58.492: WARN/SQLiteCompiledSql(5169):     at android.os.Handler.dispatchMessage(Handler.java:99)
03-08 19:33:58.492: WARN/SQLiteCompiledSql(5169):     at android.os.Looper.loop(Looper.java:123)
03-08 19:33:58.492: WARN/SQLiteCompiledSql(5169):     at android.app.ActivityThread.main(ActivityThread.java:4627)
03-08 19:33:58.492: WARN/SQLiteCompiledSql(5169):     at java.lang.reflect.Method.invokeNative(Native Method)
03-08 19:33:58.492: WARN/SQLiteCompiledSql(5169):     at java.lang.reflect.Method.invoke(Method.java:521)
03-08 19:33:58.492: WARN/SQLiteCompiledSql(5169):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
03-08 19:33:58.492: WARN/SQLiteCompiledSql(5169):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
03-08 19:33:58.492: WARN/SQLiteCompiledSql(5169):     at dalvik.system.NativeStart.main(Native Method)
03-08 19:33:58.503: ERROR/Database(5169): close() was never explicitly called on database '/data/data/com.maps.app.classifiedconcepts/databases/classified_concepts' 
03-08 19:33:58.503: ERROR/Database(5169): android.database.sqlite.DatabaseObjectNotClosedException: Application did not close the cursor or database object that was opened here
03-08 19:33:58.503: ERROR/Database(5169):     at android.database.sqlite.SQLiteDatabase.<init>(SQLiteDatabase.java:1810)
03-08 19:33:58.503: ERROR/Database(5169):     at android.database.sqlite.SQLiteDatabase.openDatabase(SQLiteDatabase.java:817)
03-08 19:33:58.503: ERROR/Database(5169):     at android.database.sqlite.SQLiteDatabase.openOrCreateDatabase(SQLiteDatabase.java:851)
03-08 19:33:58.503: ERROR/Database(5169):     at android.database.sqlite.SQLiteDatabase.openOrCreateDatabase(SQLiteDatabase.java:844)
03-08 19:33:58.503: ERROR/Database(5169):     at android.app.ContextImpl.openOrCreateDatabase(ContextImpl.java:540)
03-08 19:33:58.503: ERROR/Database(5169):     at android.content.ContextWrapper.openOrCreateDatabase(ContextWrapper.java:203)
03-08 19:33:58.503: ERROR/Database(5169):     at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:112)
03-08 19:33:58.503: ERROR/Database(5169):     at com.maps.app.classifiedconcepts.sale.SalesDbAdapter.open(SalesDbAdapter.java:163)
03-08 19:33:58.503: ERROR/Database(5169):     at com.maps.app.classifiedconcepts.sale.SavedSalesActivity.onCreate(SavedSalesActivity.java:112)
03-08 19:33:58.503: ERROR/Database(5169):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
03-08 19:33:58.503: ERROR/Database(5169):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)
03-08 19:33:58.503: ERROR/Database(5169):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
03-08 19:33:58.503: ERROR/Database(5169):     at android.app.ActivityThread.access$2300(ActivityThread.java:125)
03-08 19:33:58.503: ERROR/Database(5169):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
03-08 19:33:58.503: ERROR/Database(5169):     at android.os.Handler.dispatchMessage(Handler.java:99)
03-08 19:33:58.503: ERROR/Database(5169):     at android.os.Looper.loop(Looper.java:123)
03-08 19:33:58.503: ERROR/Database(5169):     at android.app.ActivityThread.main(ActivityThread.java:4627)
03-08 19:33:58.503: ERROR/Database(5169):     at java.lang.reflect.Method.invokeNative(Native Method)
03-08 19:33:58.503: ERROR/Database(5169):     at java.lang.reflect.Method.invoke(Method.java:521)
03-08 19:33:58.503: ERROR/Database(5169):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
03-08 19:33:58.503: ERROR/Database(5169):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
03-08 19:33:58.503: ERROR/Database(5169):     at dalvik.system.NativeStart.main(Native Method)

The line mSalesCursor = mDb.getSaved(); calls the following code in my SalesDbAdapter:

public Cursor getSaved() {
return mDb.query(TABLE_NAME, null, null, null, null, null, KEY_FEATURED + " DESC"); 
}

What am I doing wrong? Why am I getting these exceptions? I'm especially puzzled because I thought that calling startManagingCursor(mSalesCursor) right after initializing mSalesCursor would save me from the need to close the Cursor in any of the Activity Lifecycle methods.

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评论（3）

仄言 2024-10-27 17:26:03

对于其他查看此答案的人，我总是用 try/catch/finally 语句包装我的游标用法。这提供了无论发生什么情况游标都会关闭的确定性。

我经常使用它，甚至制作了一个 Eclipse 模板。

例子：

void foo() {
    Cursor c = null;
    try {
        c = db.get_somthing();
        do_something©;
    }       

    catch (Exception e) {
        print_err_msg(e);
    }

    finally {
        if (c != null) {
            c.close();
            c = null;
        }
    }
}

For other people looking at this answer, I always wrap my Cursor usage with try/catch/finally statements. This provides certainty that the cursor gets closed, regardless of what happens.

I use this so often that I've even made an Eclipse template.

example:

void foo() {
    Cursor c = null;
    try {
        c = db.get_somthing();
        do_something©;
    }       

    catch (Exception e) {
        print_err_msg(e);
    }

    finally {
        if (c != null) {
            c.close();
            c = null;
        }
    }
}
回复 原文
赠我空喜 2024-10-27 17:26:03

对于这些类型，您应该重写 onResume() 和 onPause() 而不是 onStart() 和 onStop()的事情。查看活动生命周期文档。

You should override onResume() and onPause() instead of onStart() and onStop() for these kinds of things. Check out the Activity Lifecycle documentation.

回复 原文
静谧幽蓝 2024-10-27 17:26:03

考虑调用 startManagingCursor() 。

Consider calling startManagingCursor().

回复 原文
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