android - Android: SQLite, cursor.moveToNext() always returns false

Question

The following statement cursor.moveToNext() is always false. I expect the loop to execute once. I've tested that the query actually returns data.

Does anyone know what is the matter?

    String query ="SELECT(SELECT COUNT(*) FROM Table1) as count1, (SELECT COUNT(*) FROM Table2) as count2;";

    Cursor mCursor = mDb.rawQuery(query, null);

    if (mCursor != null) {
        mCursor.moveToFirst();
    }

    while (cursor.moveToNext()) {   //<---------------return false here???
        String result_0=cursor.getString(0);
    }

Answer 1

您可以通过这种方式迭代光标。

    if(moveCursor.moveToFirst()){
        do{
            //your code

        }while(moveCursor.moveToNext());
    }               

Answer 2

我知道你已经解决了你的问题，但这里是发生的事情的演练：

Cursor mCursor = mDb.rawQuery(query, null);

// At this point mCursor is positioned at just before the first record.

if (mCursor != null) {
    mCursor.moveToFirst();
    // mCursor is now pointing at the first (and only) record
}

while (mCursor.moveToNext()) {
    String result_0=cursor.getString(0);
}

// The loop above was skipped because `.moveToNext()` caused mCursor
// to move past the last record.

因此，在您只需要一条记录的情况下，您只需要mCursor.moveToFirst() OR您的mCursor.moveToNext().