sqlite android查詢（光標）

我開發了一個應用程序，允許用戶保存他最喜歡的兩個停車位。它使用服務從sqlite數據庫中檢索相關的停車信息。在數據庫中我有這樣的方法找到的第一個條目：sqlite android查詢（光標）

public Cursor firstentry(){ 
     String select = "SELECT PREF1, PREF2 FROM parking_table WHERE id =1"; 
     Cursor cursor = db.rawQuery(select, null); 
    return cursor;

每次我跑我的應用程序出現強制關閉的錯誤，當服務嘗試使用命令調用這個方法：

Cursor c = dh.firstentry();

當我評論它時，它會給出錯誤，這些應用程序完美無缺。

以下是錯誤的logcat的：

04-08 18:56:38.673: E/AndroidRuntime(13166): FATAL EXCEPTION: Timer-0 
04-08 18:56:38.673: E/AndroidRuntime(13166): java.lang.NullPointerException 
04-08 18:56:38.673: E/AndroidRuntime(13166): at stefan.testservice.ConnectionService$1.run(ConnectionService.java:64) 
04-08 18:56:38.673: E/AndroidRuntime(13166): at java.util.Timer$TimerImpl.run(Timer.java:284) 
04-08 18:56:39.654: E/ActivityThread(13166): Activity stefan.testservice.TestserviceActivity has leaked IntentReceiver [email protected] that was originally registered here. Are you missing a call to unregisterReceiver()? 
04-08 18:56:39.654: E/ActivityThread(13166): android.app.IntentReceiverLeaked: Activity stefan.testservice.TestserviceActivity has leaked IntentReceiver [email protected] that was originally registered here. Are you missing a call to unregisterReceiver()? 
04-08 18:56:39.654: E/ActivityThread(13166): at android.app.LoadedApk$ReceiverDispatcher.<init>(LoadedApk.java:756) 
04-08 18:56:39.654: E/ActivityThread(13166): at android.app.LoadedApk.getReceiverDispatcher(LoadedApk.java:551) 
04-08 18:56:39.654: E/ActivityThread(13166): at android.app.ContextImpl.registerReceiverInternal(ContextImpl.java:795) 
04-08 18:56:39.654: E/ActivityThread(13166): at android.app.ContextImpl.registerReceiver(ContextImpl.java:782) 
04-08 18:56:39.654: E/ActivityThread(13166): at android.app.ContextImpl.registerReceiver(ContextImpl.java:776) 
04-08 18:56:39.654: E/ActivityThread(13166): at android.content.ContextWrapper.registerReceiver(ContextWrapper.java:318) 
04-08 18:56:39.654: E/ActivityThread(13166): at stefan.testservice.TestserviceActivity$1.onServiceConnected(TestserviceActivity.java:280) 
04-08 18:56:39.654: E/ActivityThread(13166): at android.app.LoadedApk$ServiceDispatcher.doConnected(LoadedApk.java:1064) 
04-08 18:56:39.654: E/ActivityThread(13166): at android.app.LoadedApk$ServiceDispatcher$RunConnection.run(LoadedApk.java:1081) 
04-08 18:56:39.654: E/ActivityThread(13166): at android.os.Handler.handleCallback(Handler.java:587) 
04-08 18:56:39.654: E/ActivityThread(13166): at android.os.Handler.dispatchMessage(Handler.java:92) 
04-08 18:56:39.654: E/ActivityThread(13166): at android.os.Looper.loop(Looper.java:123) 
04-08 18:56:39.654: E/ActivityThread(13166): at android.app.ActivityThread.main(ActivityThread.java:3683) 
04-08 18:56:39.654: E/ActivityThread(13166): at java.lang.reflect.Method.invokeNative(Native Method) 
04-08 18:56:39.654: E/ActivityThread(13166): at java.lang.reflect.Method.invoke(Method.java:507) 
04-08 18:56:39.654: E/ActivityThread(13166): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839) 
04-08 18:56:39.654: E/ActivityThread(13166): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597) 
04-08 18:56:39.654: E/ActivityThread(13166): at dalvik.system.NativeStart.main(Native Method) 
04-08 18:56:40.054: E/ActivityThread(13166): Activity stefan.testservice.TestserviceActivity has leaked ServiceConnection [email protected] that was originally bound here 
04-08 18:56:40.054: E/ActivityThread(13166): android.app.ServiceConnectionLeaked: Activity stefan.testservice.TestserviceActivity has leaked ServiceConnection [email protected] that was originally bound here 
04-08 18:56:40.054: E/ActivityThread(13166): at android.app.LoadedApk$ServiceDispatcher.<init>(LoadedApk.java:938) 
04-08 18:56:40.054: E/ActivityThread(13166): at android.app.LoadedApk.getServiceDispatcher(LoadedApk.java:833) 
04-08 18:56:40.054: E/ActivityThread(13166): at android.app.ContextImpl.bindService(ContextImpl.java:867) 
04-08 18:56:40.054: E/ActivityThread(13166): at android.content.ContextWrapper.bindService(ContextWrapper.java:347) 
04-08 18:56:40.054: E/ActivityThread(13166): at stefan.testservice.TestserviceActivity.doBindService(TestserviceActivity.java:290) 
04-08 18:56:40.054: E/ActivityThread(13166): at stefan.testservice.TestserviceActivity$DownloadTask.onPostExecute(TestserviceActivity.java:193) 
04-08 18:56:40.054: E/ActivityThread(13166): at android.os.AsyncTask.finish(AsyncTask.java:417) 
04-08 18:56:40.054: E/ActivityThread(13166): at android.os.AsyncTask.access$300(AsyncTask.java:127) 
04-08 18:56:40.054: E/ActivityThread(13166): at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:429) 
04-08 18:56:40.054: E/ActivityThread(13166): at android.os.Handler.dispatchMessage(Handler.java:99) 
04-08 18:56:40.054: E/ActivityThread(13166): at android.os.Looper.loop(Looper.java:123) 
04-08 18:56:40.054: E/ActivityThread(13166): at android.app.ActivityThread.main(ActivityThread.java:3683) 
04-08 18:56:40.054: E/ActivityThread(13166): at java.lang.reflect.Method.invokeNative(Native Method) 
04-08 18:56:40.054: E/ActivityThread(13166): at java.lang.reflect.Method.invoke(Method.java:507) 
04-08 18:56:40.054: E/ActivityThread(13166): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839) 
04-08 18:56:40.054: E/ActivityThread(13166): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597) 
04-08 18:56:40.054: E/ActivityThread(13166): at dalvik.system.NativeStart.main(Native Method)

任何幫助，因爲我什麼都試過和似乎沒有任何工作是非常讚賞。提前致謝！

編輯：

停車表代碼：

public void onCreate(SQLiteDatabase db) { 
    db.execSQL("CREATE TABLE " + TABLE_NAME + "(id INTEGER PRIMARY KEY, PREF1 TEXT, PREF2 TEXT)"); 
    }

來源

2012-04-08 progdoc

發表您的parking_table定義。你是否跟着光標要求表的ID完全被_ID引用？ – hovanessyan 2012-04-08 17:08:58

如果我錯誤地理解了你，請糾正我，你是否建議我需要'_id = 1'而不是'id = 1'？ – progdoc 2012-04-08 17:11:36

ConnectionService.java line 64..post that line .. – 2012-04-08 17:14:57

我設法解決它，一切都很好，我只需要啓動類對象。下面是代碼所需的行：在我的情況

this.yourobject = new class(this);

是：

this.dh = new SQLHelper(this);

希望它能幫助:)

來源

2012-04-11 10:49:32 progdoc

其一個nullpointerexception意思大概是沒有在數據庫在那個時候。如果光標爲空，則需要處理

單步執行代碼實際上是查看確切內容爲空的唯一方法。更多的代碼是絕對必要但其很難告訴你貼什麼

來源

2012-04-08 17:15:17 tyczj

嗨，有數據，因爲服務開始延遲，我也通過自己插入虛擬數據來測試它，以確保空數據庫不是我的問題的來源。 – progdoc 2012-04-08 17:18:09

你rawsql運行，以便檢查是否準確的查詢的有效期爲您的數據庫，SELECT PREF1, PREF2 FROM parking_table WHERE id =1

是PREF1準確（與案例）列名??

來源

2012-04-08 17:29:02

是的，sql是正確的，所以列的名字 – progdoc 2012-04-08 17:31:20

如果你沒有一個SQLite的瀏覽器軟件，獲得一個位置： SQLite Browser

它有助於當我與SQLite的工作。我之前遇到過這個問題，我通過將id參數添加到查詢中來解決此問題。從本質上講，你要查詢更改爲：

public Cursor firstentry(){ 
    String select = "SELECT id, PREF1, PREF2 FROM parking_table WHERE id =1"; 
    Cursor cursor = db.rawQuery(select, null); 
return cursor;

不要忘記調用c.moveToFirst()如果c是遊標的名稱。

來源

2012-04-08 17:52:18

試過了，沒有工作：/ – progdoc 2012-04-08 19:42:39

sqlite android查詢（光標）

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