下拉tableView实现相仿微信中带图的灰色背景

UIView *topView = [[UIView alloc]initWithFrame:CGRectMake(0, -480, ScreenWidth, 480)];    UIImageView *iconImage = [[UIImageView alloc]initWithFrame:CGRectMake((ScreenWidth - 35)/2.0,380, 35, 35)];    iconImage.image = [UIImage imageNamed:@"pic_dropdown.png"];    iconImage.contentMode = UIViewContentModeCenter;    [topView addSubview:iconImage];    topView.backgroundColor = [UIColor colorWithRed:246/255.0 green:246/255.0 blue:246/255.0 alpha:1];    [_tableView addSubview:topView];