android.database.CursorIndexOutOfBoundsException

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再見小時候
再見小時候 2021-02-14 15:21

The data access code in my Android app raises an exception.

Here is the code that causes the exception:

String getPost = \"SELECT * FROM \" + TABLE_POST          


        
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3条回答
  • 2021-02-14 15:41

    This arises in the case our Cursor has data but not yet pointing to first index in the data list.

    To get avoid this exception, we first should check:

    if (!cursor.moveToFirst())
            cursor.moveToFirst();
    

    And then carry the further actions.

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  • 2021-02-14 15:48

    You havent moved cursor index to first .. Try like this below

     String getPost = "SELECT * FROM " + TABLE_POST + ";";
        Cursor result = getReadableDatabase().rawQuery(getPost, null);
        List posts = new ArrayList();{
        Log.d("count", result.getCount() + " post rows");
    
        if (result .moveToFirst()) {
            do {
                 Post post = new Post();
                 post.setPostId(result.getInt(0));
                 posts.add(post);
                  ....
            } while (result .moveToNext());
        }
        result .close();
    
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  • 2021-02-14 15:49

    You are attempting to retrieve an item on index 2 but this index really doesn't exist (Cursor size is 2 so indexes are 0,1).

    Change your loop:

    if (result != null && result.moveToFirst()){
        do {
           Post post = new Post();
           post.setPostId(result.getInt(0));
           posts.add(post);
           ....
        } while (result.moveToNext());
    }
    

    Now it should work correctly.

    Note: Don't forget to call moveToFirst() method that moves Cursor into the first record (implicitly is positioned before the first row) and prepares it for reading. This is also a handy method for testing whether Cursor is valid or not.

    Note 2: Don't use column indexes, you can simply make a mistake in counting. Instead of use column names - this approach is generally recommended e.q. cursor.getColumnIndex("<columnName>")

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