FC當在SQLite中查找記錄時

Question

我有幾種方法可以在我的應用程序中獲取記錄
但由於某種原因，這個人一直給我FC！ 我用下面的方法來獲得光標：

Cursor c=helper.getRecordById(num); 

這是實現如下：

public Cursor getRecordById(int rowId) { 
    String rowIDs=""+rowId; 
    String SelectById = "SELECT id, OrderName, OrderLink, DateYear, DateMonth, DateDay, OrderPrice FROM Orders WHERE id=?"; 
    String[] args={rowIDs}; 
    return(getReadableDatabase().rawQuery(SelectById, args)); 
} 

我曾嘗試也無需轉換詮釋爲String，但我剛剛離開這種方式..兩種方式得到相同的錯誤。

每當我到下面一行：

String name=c.getString(c.getColumnIndexOrThrow("OrderName")); 

我得到的FC。 GetColumnIndex工作得很好......我已經完全測試了它。 但getString引發錯誤。 ！

06-02 21:07:13.656: W/KeyCharacterMap(4329): Using default keymap: /system/usr/keychars/qwerty.kcm.bin 
06-02 21:07:16.006: D/AndroidRuntime(4329): Shutting down VM 
06-02 21:07:16.006: W/dalvikvm(4329): threadid=1: thread exiting with uncaught exception (group=0x4001d800) 
06-02 21:07:16.026: E/AndroidRuntime(4329): FATAL EXCEPTION: main 
06-02 21:07:16.026: E/AndroidRuntime(4329): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.Sagi.MyOrders/com.Sagi.MyOrders.DisplayRecord}: android.database.CursorIndexOutOfBoundsException: Index -1 requested, with a size of 0 
06-02 21:07:16.026: E/AndroidRuntime(4329):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663) 
06-02 21:07:16.026: E/AndroidRuntime(4329):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679) 
06-02 21:07:16.026: E/AndroidRuntime(4329):  at android.app.ActivityThread.access$2300(ActivityThread.java:125) 
06-02 21:07:16.026: E/AndroidRuntime(4329):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033) 
06-02 21:07:16.026: E/AndroidRuntime(4329):  at android.os.Handler.dispatchMessage(Handler.java:99) 
06-02 21:07:16.026: E/AndroidRuntime(4329):  at android.os.Looper.loop(Looper.java:123) 
06-02 21:07:16.026: E/AndroidRuntime(4329):  at android.app.ActivityThread.main(ActivityThread.java:4627) 
06-02 21:07:16.026: E/AndroidRuntime(4329):  at java.lang.reflect.Method.invokeNative(Native Method) 
06-02 21:07:16.026: E/AndroidRuntime(4329):  at java.lang.reflect.Method.invoke(Method.java:521) 
06-02 21:07:16.026: E/AndroidRuntime(4329):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868) 
06-02 21:07:16.026: E/AndroidRuntime(4329):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626) 
06-02 21:07:16.026: E/AndroidRuntime(4329):  at dalvik.system.NativeStart.main(Native Method) 
06-02 21:07:16.026: E/AndroidRuntime(4329): Caused by: android.database.CursorIndexOutOfBoundsException: Index -1 requested, with a size of 0 
06-02 21:07:16.026: E/AndroidRuntime(4329):  at android.database.AbstractCursor.checkPosition(AbstractCursor.java:580) 
06-02 21:07:16.026: E/AndroidRuntime(4329):  at android.database.AbstractWindowedCursor.checkPosition(AbstractWindowedCursor.java:214) 
06-02 21:07:16.026: E/AndroidRuntime(4329):  at android.database.AbstractWindowedCursor.getString(AbstractWindowedCursor.java:41) 
06-02 21:07:16.026: E/AndroidRuntime(4329):  at com.Sagi.MyOrders.DisplayRecord.onCreate(DisplayRecord.java:48) 
06-02 21:07:16.026: E/AndroidRuntime(4329):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047) 
06-02 21:07:16.026: E/AndroidRuntime(4329):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627) 
06-02 21:07:16.026: E/AndroidRuntime(4329):  ... 11 more 
06-02 21:12:16.126: I/Process(4329): Sending signal. PID: 4329 SIG: 9 

有趣的是我複製了完全相同的查詢方法，我在另一個地方，其工作只是正常使用的，我甚至試圖給它一個恆定的尋找，我知道存在只是爲了檢查。但沒有。一遍又一遍的錯誤！

謝謝！

Answer 1

一個Cursor最初指向一記開始前，允許這種代碼：

final Cursor cursor = /* get cursor */; 
while(cursor.moveToNext()) { 
    /* do something with cursor */ 
} 

如果只期待一個記錄，你一定會有一個記錄，然後accesing之前你Cursor做：

cursor.moveToNext(); 

或：

cursor.moveToFirst();