Android:SQLite,cursor.moveToNext()始终返回false

Question

以下语句cursor.moveToNext()始终为false.我希望循环执行一次.我已经测试过查询实际返回的数据.

有谁知道是什么事吗？

    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

我知道您已经解决了问题，但以下是所发生情况的演练：

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().