android sqlite android.database.CursorIndexOutOfBoundsException: Index 5 requested, with a size of 5

Cursor c = db.query("user",null,null,null,null,null,null);//查詢並得到遊標
if(c.moveToFirst()){//判斷遊標是否爲空
    for(int i=0;i<c.getCount();i++){
        c.move(i);//移動到指定記錄
        String username = c.getString(c.getColumnIndex("username");
        String password = c.getString(c.getColumnIndex("password"));
    }
}

在經過以上代碼讀取sqlite user表中多條數據時，就會發生錯誤:android sqlite android.database.CursorIndexOutOfBoundsException: Index 5 requested, with a size of 5。我把上面代碼改爲如下：

Cursor c = db.query("user",null,null,null,null,null,null);//查詢並得到遊標

    for(int i=0;i<c.getCount() && c!=null ;i++){
if(c.moveToFirst()){//判斷遊標是否爲空
        c.move(i);//移動到指定記錄
        String username = c.getString(c.getColumnIndex("username");
        String password = c.getString(c.getColumnIndex("password"));
    }
}

OK，睡覺了。