Android Sqlite Cursor没有返回正确的值

Question

我在sqlite db上使用了游标来获取记录。

我的代码如下：

btnnext.setOnClickListener(new OnClickListener() {
    public void onClick(View v) {
        displayQuestion();
    });
}   

private void displayQuestion() {
    db.openDataBase();
    SQLiteDatabase sqlitedatabase = db.getWritableDatabase();

    Cursor cur;
    cur = sqlitedatabase.rawQuery("select quiz_id, opt_ans from options" ,null);
    cur.moveToFirst();
    db.close();

    radioGroup.removeAllViews();
    for (int i = 0; i <= 3; i++) {
        l++;
        Log.v("value of l",l+"");
        radioButton = new RadioButton(this);
        String str_opt = cur.getString(cur.getColumnIndex(Database_helper_class.OPT_ID));
        radioButton.setText(str_opt);
        Log.v("value of l",l+""+str_opt);
        radioButton.setId(i);
        cur.moveToPosition(l);
        radioGroup.addView(radioButton);
    }
}

我得到的日志是：

03-07 18:32:03.190: V/value of l(28903): 1video
03-07 18:32:03.200: V/value of l(28903): 2
03-07 18:32:03.210: V/value of l(28903): 2sound
03-07 18:32:03.210: V/value of l(28903): 3
03-07 18:32:03.221: V/value of l(28903): 3image
03-07 18:32:03.231: V/value of l(28903): 4
03-07 18:32:03.240: V/value of l(28903): 4word document
03-07 18:32:05.561: V/value of l(28903): 5
03-07 18:32:05.571: V/value of l(28903): 5video
03-07 18:32:05.580: V/value of l(28903): 6
03-07 18:32:05.590: V/value of l(28903): 6A process
03-07 18:32:05.590: V/value of l(28903): 7
03-07 18:32:05.601: V/value of l(28903): 7A system software
03-07 18:32:05.601: V/value of l(28903): 8
03-07 18:32:05.610: V/value of l(28903): 8A document

我正在使用的数据库是

opt_ans,"opt_id","quiz_id"
    video,"1","1"
    sound,"2","2"
    image,"3","3"
    word document,"4","4"
    appliction,"5","5"
    A process,"6","6"
    A system software,"7","7"
    A document,"8","8"
    hgfhgfh,"9","9"
    hgfhgf,"10","10"
    tytrytr,"11","11"
    ytrytrytr,"12","12"
    tytrytrytr,"13","13"
    tytrytryt,"14","14"
    tytyt,"15","15"
    ytytyt,"16","16"
    ytytryt,"17","17"
    tytytr,"18","18"
    tytytryt,"19","19"
    htghyt,"20","20"

现在我的问题：

为什么我在第5和第9个索引上获得视频，同时在这些索引上有不同的值？

Answer 1

除非您指定，否则SQL不保证返回行的任何顺序。基本上，您的结果可能是随机顺序。因此，您需要按如下方式更改查询：

cur = sqlitedatabase.rawQuery("select quiz_id, opt_ans from options order by quiz_id asc" ,null);

修改
另外我猜你没有正确地迭代光标，试试这个：

int i = 0;
for (boolean hasItem = cur.moveToFirst(); hasItem; hasItem = cur.moveToNext()) {
    if (i < 4) {
        radioButton = new RadioButton(this);
        String str_opt = cur.getString(cur.getColumnIndex(Database_helper_class.OPT_ID));
        radioButton.setText(str_opt);
        radioButton.setId(i);
        radioGroup.addView(radioButton);
        Log.v("Value of button " + i + " is: " + str_opt);
        i++;
    }
    else {
        break;
    }
}