关于查询数据库返回cursor!=null但是getcount为0的有关问题

mUri = getContentResolver().insert(mUri, values);//已经插入数据库成功，在数据库里看到了
mCursor = managedQuery(mUri, PROJECTION, null, null, null);//查询
if (mCursor != null) {
            Log.i(LOG_TAG, Integer.toString(mCursor.getCount()));/////////////数据结果为0
            if(!mCursor.moveToFirst())
            {
                Log.i(LOG_TAG, "MCursor movetofirst failed....");/////////////显示failed
                }
            String note = mCursor.getString(0);//报错：android.database.CursorIndexOutOfBoundsException: Index 0 requested, with a size of 0
            }