自动滚动scrollview的问题

使用setContentOffset:animated:

UIScrollView *scrollView = ...;
CGPoint newOffset = scrollView.contentOffset;
newOffset.y = 0;
[scrollView setContentOffset:newOffset animated:YES];

如果你想要开场动画的效果，在scrollView的viewcontroller实现

- (void)viewDidLoad
{
    [super viewDidLoad];

    // ...

    CGPoint bottomOffset = CGPointMake(self.scrollView.contentOffset.x, self.scrollView.contentSize.height - self.scrollView.bounds.size.height);
    [self.scrollView setContentOffset:bottomOffset animated:NO];
}
- (void)viewDidAppear:(BOOL)animated
{
    [super viewDidAppear:animated];

    CGPoint newOffset = self.scrollView.contentOffset;
    newOffset.y = 0;
    [self.scrollView setContentOffset:newOffset animated:YES];
}

补充：

移动的慢点，用timer实现：

- (void)viewDidLoad
{
    [super viewDidLoad];

    // ...

    CGPoint bottomOffset = CGPointMake(self.scrollView.contentOffset.x, self.scrollView.contentSize.height - self.scrollView.bounds.size.height);
    [self.scrollView setContentOffset:bottomOffset animated:NO];
}


- (void)viewDidAppear:(BOOL)animated
{    
    [super viewDidAppear:animated];

    CGPoint bottomOffset = CGPointMake(self.scrollView.contentOffset.x, self.scrollView.contentSize.height - self.scrollView.bounds.size.height);

    //设置延迟时间
    float scrollDurationInSeconds = 4.0;

    //计算timer间隔


    float totalScrollAmount = bottomOffset.y;
    float timerInterval = scrollDurationInSeconds / totalScrollAmount;

    [NSTimer scheduledTimerWithTimeInterval:timerInterval target:self selector:@selector(scrollScrollView:) userInfo:nil repeats:YES];
}

- (void)scrollScrollView:(NSTimer *)timer
{
    CGPoint newScrollViewContentOffset = self.scrollView.contentOffset;

    //向上移动 1px
    newScrollViewContentOffset.y -= 1;


    newScrollViewContentOffset.y = MAX(0, newScrollViewContentOffset.y);

    //如果到顶了，timer中止
    if (newScrollViewContentOffset.y == 0) {
        [timer invalidate];
    }

    //最后设置scollView's contentOffset
    self.scrollView.contentOffset = newScrollViewContentOffset;
}