Question

我正在使用android和sqlite数据库，我想从列nomMission获取数据这就是我所做的，但它不起作用

 public List<Missions> getMissions() {
    List<Missions> mission = new ArrayList<Missions>();

    Cursor cursor = mDb.rawQuery("select nomMission from Missions", null);

    cursor.moveToFirst();
    while (!cursor.isAfterLast()) {
        Missions missionss = cursorToMission(cursor);
        mission.add(missionss);
        cursor.moveToNext();
    }
    // make sure to close the cursor
    cursor.close();
    return mission;
}

private Missions cursorToMission(Cursor cursor) {
    Missions missions = new Missions(null, null);
    missions.setNomMission(cursor.getString(1));
    missions.setDateMission(cursor.getString(2));
    return missions;
}

错误日志：

04-29 16:04:52.347: E/AndroidRuntime(4864): FATAL EXCEPTION: main
04-29 16:04:52.347: E/AndroidRuntime(4864): java.lang.RuntimeException: Unable to start activity ComponentInfo{tn.pfe.ybn.sigl/tn.pfe.ybn.sigl.DataManip.MissionAct}: java.lang.IllegalStateException: Couldn't read row 0, col 1 from CursorWindow.  Make sure the Cursor is initialized correctly before accessing data from it.
04-29 16:04:52.347: E/AndroidRuntime(4864):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2077)
04-29 16:04:52.347: E/AndroidRuntime(4864):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2104)
04-29 16:04:52.347: E/AndroidRuntime(4864):     at android.app.ActivityThread.access$600(ActivityThread.java:134)
04-29 16:04:52.347: E/AndroidRuntime(4864):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1247)
04-29 16:04:52.347: E/AndroidRuntime(4864):     at android.os.Handler.dispatchMessage(Handler.java:99)
04-29 16:04:52.347: E/AndroidRuntime(4864):     at android.os.Looper.loop(Looper.java:154)
04-29 16:04:52.347: E/AndroidRuntime(4864):     at android.app.ActivityThread.main(ActivityThread.java:4624)
04-29 16:04:52.347: E/AndroidRuntime(4864):     at java.lang.reflect.Method.invokeNative(Native Method)
04-29 16:04:52.347: E/AndroidRuntime(4864):     at java.lang.reflect.Method.invoke(Method.java:511)
04-29 16:04:52.347: E/AndroidRuntime(4864):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:809)
04-29 16:04:52.347: E/AndroidRuntime(4864):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:576)
04-29 16:04:52.347: E/AndroidRuntime(4864):     at dalvik.system.NativeStart.main(Native Method)
04-29 16:04:52.347: E/AndroidRuntime(4864): Caused by: java.lang.IllegalStateException: Couldn't read row 0, col 1 from CursorWindow.  Make sure the Cursor is initialized correctly before accessing data from it.

Answer 1

因为光标实际上只包含一列哪个索引 0 （表格列基于0）。

您指定：

Cursor cursor = mDb.rawQuery("select nomMission from Missions", null);

（一栏）

但是你试着访问

missions.setNomMission(cursor.getString(1));
missions.setDateMission(cursor.getString(2));

在您的情况下，您只能访问：

missions.setNomMission(cursor.getString(0));

或者更好，

missions.setNomMission(cursor.getString(cursor.getColumnIndex("nomMission")));

您可以通过名称引用列，而不是索引

Answer 2

如果您的查询只选择一列，它只会返回一个索引为0的列。现在的方式，您可以调用cursor.getString(0)，而且确实如此。如果你想获得NomMission和DateMission，你应该致电

`Cursor cursor = mDB.rawQuery（＆＃34; SELECT nomMission AND dateMission FROM Missions＆＃34;，null）;

就个人而言，我更喜欢使用SQLiteDatabase＆＃39; query method here。

对你而言，这看起来像是

Cursor cursor = mDb.query("Missions, new String[]{"nomMission", "dateMission"},null, null, null, null, null, null);

我也是一个菜鸟，所以任何人都可以随意纠正任何事情。

从sqlite数据库获取数据

2 个答案: