Question

由于数据库出现问题，我的应用程序崩溃了。我不确定是什么导致了这个问题。以下是更多细节。

我在 Logcat：

中收到以下错误

07-24 19:05:29.471: E/AndroidRuntime(23786): FATAL EXCEPTION: Thread-24967
07-24 19:05:29.471: E/AndroidRuntime(23786): Process: com.example.brianapp, PID: 23786
07-24 19:05:29.471: E/AndroidRuntime(23786): android.database.CursorIndexOutOfBoundsException: Index 0 requested, with a size of 0
07-24 19:05:29.471: E/AndroidRuntime(23786):    at android.database.AbstractCursor.checkPosition(AbstractCursor.java:426)
07-24 19:05:29.471: E/AndroidRuntime(23786):    at android.database.AbstractWindowedCursor.checkPosition(AbstractWindowedCursor.java:136)
07-24 19:05:29.471: E/AndroidRuntime(23786):    at android.database.AbstractWindowedCursor.getString(AbstractWindowedCursor.java:50)
07-24 19:05:29.471: E/AndroidRuntime(23786):    at com.example.brianapp.DatabaseHelper.getScore(DatabaseHelper.java:116)
07-24 19:05:29.471: E/AndroidRuntime(23786):    at com.example.brianapp.Meditation.writeToDatabase(Meditation.java:626)
07-24 19:05:29.471: E/AndroidRuntime(23786):    at com.example.brianapp.Meditation$2.run(Meditation.java:139)

首先在我的数据库助手类中引用 this method ：

// Getting single score (i.e. not the full db)  
    Score getScore(String name) {
        SQLiteDatabase db = this.getReadableDatabase();

        Cursor cursor = db.query(TABLE_SCORE, new String[] {COL_SESSION, COL_GAMETITLE, 
                COL_NAME, COL_MED, COL_MAX, COL_AVGATT, COL_MAXATT, COL_SCORE, COL_DATE }, COL_SESSION + "=?",
                new String[] { String.valueOf(name) }, null, null,null,null); 
        if (cursor != null)
            cursor.moveToFirst();

        Score score = new Score(Integer.parseInt(cursor
                .getString(0)),cursor.getString(1),cursor.getString(2),Integer.parseInt(cursor
                .getString(3)),Integer.parseInt(cursor.getString(4)),Integer.parseInt(cursor.getString(5)),
                Integer.parseInt(cursor.getString(6)),
                Integer.parseInt(cursor.getString(7)), cursor.getString(8));
        // return contact
        return score;
    }

以及此代码部分，我在其他活动中使用此方法：

public void writeToDatabase(){

            DatabaseHelper db = new DatabaseHelper(this);



            /**
             * CRUD Operations
             * */

            SimpleDateFormat df= new SimpleDateFormat("dd/MM/yyyy"); //change back to original if not working (see SO)

            //myDate will be used to enter into DB
            String myDate= df.format(new Date()); 


            //getting random number for sessionid (WILL BE CHANGED EVENTUALLY)
            Random ran = new Random();
            int x = ran.nextInt(1) + 3000;

            //Adding the new Score to the database. NOTE: SESSIONID NEEDS TO BE SORTED
            db.addScore(new Score(x, "Multiplication", UserName.getUserName(), averageMedLevel,medMax, 
                    averageAttLevel,attMax, score,myDate));

            //single score, used for passing to the results screen
            single = db.getScore(UserName.getUserName());


            //list of all the scores in the database
            List<Score> scores = db.getAllScores();

Answer 1

好像你的光标是空的，我建议你只在非空时从光标读取数据。在您的代码中，您已经拥有了所需的一切。只需进行下一次更改：

Score getScore(String name) {
    SQLiteDatabase db = this.getReadableDatabase();

    Cursor cursor = db.query(TABLE_SCORE, new String[] {COL_SESSION, COL_GAMETITLE, 
            COL_NAME, COL_MED, COL_MAX, COL_AVGATT, COL_MAXATT, COL_SCORE, COL_DATE }, COL_SESSION + "=?",
            new String[] { String.valueOf(name) }, null, null,null,null); 
    //Just add brackets to this validation so you only read the Cursor when is not empty
    if (cursor != null) {
        cursor.moveToFirst();

        Score score = new Score(Integer.parseInt(cursor
            .getString(0)),cursor.getString(1),cursor.getString(2),Integer.parseInt(cursor
            .getString(3)),Integer.parseInt(cursor.getString(4)),Integer.parseInt(cursor.getString(5)),
            Integer.parseInt(cursor.getString(6)),
            Integer.parseInt(cursor.getString(7)), cursor.getString(8));

        return score;
    }
    //Otherwise return null or change this to whatever you want
    else
        return null
}

Answer 2

当查询未返回任何数据时，没有第一行要移动，moveToFirst()返回false。你必须检查一下：

Cursor cursor = db.query(...);
if (!cursor.moveToFirst()) {
    // nothing found in DB
    return null; // or whatever is appropiate for this error
}
... cursor.getXxx() ...
return score;

（注意：query()永远不会返回null。）

SQlite数据库错误：CursorIndexOutofBounds？

2 个答案: