Question

我希望从sqlite db中获取一行。

我使用以下代码来获取值。

public ShipmentStatusDao getShipmentStatusRow(int id) {
        SQLiteDatabase db = this.getReadableDatabase();

        Cursor cursor = db.query(TABLE_SHIPMENTSTATUS, new String[]{KEY_NOTES,
                        KEY_PHOTOS, KEY_DOCUMENTS}, KEY_ID + "=?",
                new String[]{String.valueOf(id)}, null, null, null, null);
        if (cursor != null)
            cursor.moveToFirst();

        ShipmentStatusDao notification = new ShipmentStatusDao(cursor.getInt(0),
                cursor.getString(1), cursor.getString(2), cursor.getString(3), cursor.getString(4), cursor.getString(5), cursor.getString(6), cursor.getString(7), cursor.getString(8));

        return notification;
    }

我使用以下代码调用上述方法，

 ShipmentStatusDao shipmentStatusRow = db.getShipmentStatusRow(1);
 shipmentStatusRow.getDate();

我收到以下错误，

java.lang.IllegalStateException：无法读取第0行，第3列 CursorWindow。确保之前正确初始化了Cursor 从中访问数据。在android.database.CursorWindow.nativeGetString（本机方法）在android.database.CursorWindow.getString（CursorWindow.java:438）在android.database.AbstractWindowedCursor.getString（AbstractWindowedCursor.java:51）在com.vaighai.handlers.NotificationDbHandler.getShipmentStatusRow（NotificationDbHandler.java:364）在com.vaighai.fragments.StatusFragment $ 5.onItemClick（StatusFragment.java:237）在android.widget.AdapterView.performItemClick（AdapterView.java:301）在android.widget.AbsListView.performItemClick（AbsListView.java:1510）在android.widget.AbsListView $ PerformClick.run（AbsListView.java:3339）在android.os.Handler.handleCallback（Handler.java:730）在android.os.Handler.dispatchMessage（Handler.java:92）在android.os.Looper.loop（Looper.java:176）在android.app.ActivityThread.main（ActivityThread.java:5419） at java.lang.reflect.Method.invokeNative（Native Method）在java.lang.reflect.Method.invoke（Method.java:525）在com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run（ZygoteInit.java:1046）在com.android.internal.os.ZygoteInit.main（ZygoteInit.java:862）在dalvik.system.NativeStart.main（Native Method）03-16 14：54：32.826 2337-7411 /？ I / ActivityManager：通知ApplicationCrash

我怎样才能纠正上述错误？

Answer 1

您只查询三个字段（KEY_NOTES， KEY_PHOTOS，KEY_DOCUMENTS）。所以cursor.getString（3）会抛出错误。

Answer 2

您只检查Cursor是否为空，但不检查它是否为空

moveToFirst()会返回boolean，因此您知道它是空的。你可以改变这个

if (cursor != null)
        cursor.moveToFirst();

ShipmentStatusDao notification = new ShipmentStatusDao(cursor.getInt(0),
            cursor.getString(1), cursor.getString(2), cursor.getString(3), cursor.getString(4), cursor.getString(5), cursor.getString(6), cursor.getString(7), cursor.getString(8));

return notification;

进入这个

if (cursor != null && cursor.moveToFirst()) {
    ShipmentStatusDao notification = new ShipmentStatusDao(cursor.getInt(0),
            cursor.getString(1), cursor.getString(2), cursor.getString(3), cursor.getString(4), cursor.getString(5), cursor.getString(6), cursor.getString(7), cursor.getString(8));

    cursor.close(); // Don't forget to close BTW
    return notification;
}  else {
    // Cursor is null or empty, you need to do something with this
    return null;
}

<强>更新
此外，通过在查询中提供new String[]{KEY_NOTES, KEY_PHOTOS, KEY_DOCUMENTS}，您的选择中只有三列。如果您将其更改为null，则Cursor包含所有列。这应该可以解决您的错误

Answer 3

所有与游标相关的代码/查询都应该包含在一个代码块中。

Cursor cursor = db.query(TABLE_SHIPMENTSTATUS, new String[]{KEY_NOTES,
                        KEY_PHOTOS, KEY_DOCUMENTS}, KEY_ID + "=?",
                new String[]{String.valueOf(id)}, null, null, null, null);
if (cursor != null) { 
    while (cursor.moveToNext()) {
    ... // simply do this 
    }
}

希望这有帮助！

根据id从数据库中获取单行会导致错误

3 个答案: