查询sqlite数据库并将所选数据存储到二维数组中

Question

我正在尝试查询 sqlite 数据库并将所选数据存储到二维数组中。

我的问题是在查询中插入“WHERE field='bordeaux'”会导致错误，“android.database.CursorIndexOutOfBoundsExeption：请求索引 1，大小为 1。” 没有它，查询和数组似乎运行良好。

另外，我发现当我删除“c.moveToNext();”时，带有“WHERE...”的查询只能显示一个合适的记录。从数组部分。

可以肯定的是，我的 sqlite 数据库包含与我的查询匹配的足够数据。

对不起，我的解释很糟糕，但我就是不明白原因。 你能告诉我为什么吗？？

我的代码如下。

公共字符串[][] onQuestion(){

    mDbHelper = new MySQLHelper(this);
    db = mDbHelper.getWritableDatabase();  
    Cursor c = db.rawQuery("SELECT field, question, choice1, choice2, choice3, choice4, answer FROM WineQuiz WHERE field= 'bordeaux' ORDER BY RANDOM() LIMIT 5", null);

    if(c.moveToFirst());{
                    for (int ii = 0; ii < array.length; ii++) {
                    array[ii][0] = c.getString(c.getColumnIndex("field"));
                    array[ii][1] = c.getString(c.getColumnIndex("question"));
                    array[ii][2] = c.getString(c.getColumnIndex("choice1"));
                    array[ii][3] = c.getString(c.getColumnIndex("choice2"));
                    array[ii][4] = c.getString(c.getColumnIndex("choice3"));
                    array[ii][5] = c.getString(c.getColumnIndex("choice4"));
                    array[ii][6] = c.getString(c.getColumnIndex("answer"));
                    c.moveToNext();
                    }                          
        db.close();

    }
    }
        return array;
}

Answer 1

是的，看起来您实际上并没有返回五行......如果有的话。在if 条件之后添加; 会使它变得无用。删除 ; 以确保您没有空游标，并在每次额外迭代之前检查您是否仍有可用记录：

if( c.moveToFirst() ) {
    for (int ii = 0; ii < array.length && !c.isAfterLast(); ii++) {
        array[ii][0] = c.getString(c.getColumnIndex( "field"));
        array[ii][1] = c.getString(c.getColumnIndex( "question" ));
        array[ii][2] = c.getString(c.getColumnIndex( "choice1" ));
        array[ii][3] = c.getString(c.getColumnIndex( "choice2" ));
        array[ii][4] = c.getString(c.getColumnIndex( "choice3" ));
        array[ii][5] = c.getString(c.getColumnIndex( "choice4" ));
        array[ii][6] = c.getString(c.getColumnIndex( "answer" ));
        c.moveToNext();
    }                          
}

Answer 2

你应该试试这个...

    mDbHelper = new MySQLHelper(this);
    db = mDbHelper.getWritableDatabase();
    int cPos; // for cursor position
    Cursor c = db.rawQuery("SELECT field, question, choice1, choice2, "
            + "choice3, choice4, answer FROM WineQuiz "
            + "WHERE field= 'bordeaux' ORDER BY RANDOM() LIMIT 5", null);
    if (c.getCount() > 0) { // If cursor has atleast one row
        String[][] array = new String[c.getCount()][7]; // Dynamic string array
        c.moveToFirst();
        do { // always prefer do while loop while you deal with database
            cPos = c.getPosition();
            array[cPos][0] = c.getString(c.getColumnIndex("field"));
            array[cPos][1] = c.getString(c.getColumnIndex("question"));
            array[cPos][2] = c.getString(c.getColumnIndex("choice1"));
            array[cPos][3] = c.getString(c.getColumnIndex("choice2"));
            array[cPos][4] = c.getString(c.getColumnIndex("choice3"));
            array[cPos][5] = c.getString(c.getColumnIndex("choice4"));
            array[cPos][6] = c.getString(c.getColumnIndex("answer"));
            c.moveToNext();
        } while (!c.isAfterLast());
    } else {
        Log.e("SQL Query Error", "Cursor has no data");
    }