iOS表头图片随着下拉缩放

App中经常可以看到一种效果如下

表头动画.gif

在UIView上添加一个UIImageView，代码如下

- (UIView *)myHeaderView
{
    if (_myHeaderView == nil) {
        _myHeaderView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, [UIScreen mainScreen].bounds.size.width, 229)];
        _myHeaderView.backgroundColor = [UIColor clearColor];
        _myHeaderView.clipsToBounds = NO;
        
        [_myHeaderView addSubview:self.myHeaderImgView];
    }
    
    return _myHeaderView;
}

- (UIImageView *)myHeaderImgView
{
    if (_myHeaderImgView == nil) {
        _myHeaderImgView = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, [UIScreen mainScreen].bounds.size.width, 229)];
        _myHeaderImgView.backgroundColor = [UIColor clearColor];
        _myHeaderImgView.image = [UIImage imageNamed:@"cover"];
        _myHeaderImgView.contentMode = UIViewContentModeScaleAspectFill;
        _myHeaderImgView.clipsToBounds = YES;
    }
    
    return _myHeaderImgView;
}

将myHeaderView设置成tableview的headerview

- (void)viewDidAppear:(BOOL)animated
{
    [super viewDidAppear:animated];
    [self.view addSubview:self.myTableView];
    self.myTableView.frame = [UIScreen mainScreen].bounds;
    self.myTableView.tableHeaderView = self.myHeaderView;
}

在滑动的过程中修改myHeaderImgView的frame

#pragma mark - UIScrollViewDelegate method
- (void)scrollViewDidScroll:(UIScrollView *)scrollView
{
    CGFloat offsetY = scrollView.contentOffset.y;
    if (offsetY < 0) {
        self.myHeaderImgView.frame = CGRectMake(0, offsetY, [UIScreen mainScreen].bounds.size.width, 229 - offsetY);
    } else {
        self.myHeaderImgView.frame = CGRectMake(0, 0, [UIScreen mainScreen].bounds.size.width, 229);
    }
}

就可以实现gif的效果啦~