查询sqlite数据库并将选定的数据存储到2d数组

Question

我想查询sqlite数据库并将选定的数据存储到2d数组中。

我的问题是插入“WHERE字段='bordeaux'”到查询导致错误，“android.database.CursorIndexOutOfBoundsExeption：索引1请求，大小为1”。 没有它，查询和数组看起来工作得很好。

此外，我发现查询“WHERE ...”只能删除“c.moveToNext（）;”时只显示一个适当的记录。来自阵列部分。

可以肯定，我的sqlite数据库包含足够的数据匹配我的查询。

对不起，我的不好解释，但我只是不明白原因。 你能告诉我为什么？

我的代码如下。

公众的String [] [] 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

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"); 
    } 

Answer 2

是的，它看起来像你实际上并不返回五行......如果有的话。在if条件之后添加;使其无效。删除;，以确保你没有一个空指针，并且每增加一个迭代，你仍然可以有记录前检查：

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(); 
    }       
}