获取cell相对viewcontroller坐标

-(UICollectionViewCell*)collectionView:(UICollectionView*)collectionView cellForItemAtIndexPath:(NSIndexPath*)indexPath{

    FH_HomeButtonCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:FH_HomeButtonCellID forIndexPath:indexPath];

    cell.fh_QZIconModel=_dataArr[indexPath.item];

    if(indexPath.item==2) {

        CGRectcellRect = [collectionViewconvertRect:cell.frametoView:collectionView];

        //cell在当前屏幕的位置

        UIWindow * window=[[[UIApplication sharedApplication] delegate] window];

        CGRectrect2 = [_collectionViewconvertRect:cellRecttoView:window];

        NSNumber *obj1 = [NSNumber numberWithFloat:rect2.origin.x];

        NSNumber *obj2 = [NSNumber numberWithFloat:rect2.origin.y];

        NSNotification * notice = [NSNotification notificationWithName:@"userguide" object:nil userInfo:@{@"Rect1":obj1,@"Rect2":obj2}];

        [[NSNotificationCenter defaultCenter]postNotification:notice];

        NSLog(@"--------22222222------- %f - %f # %f - %f",rect2.origin.x,rect2.origin.y,rect2.size.width,rect2.size.height);

    }

    returncell;

}