UIScrollView图片比较大

下面代码显示了scrollView，但是需要显示的图片（tutorial）比view大。
tutorial.png的尺寸是280X1200。

tipScroll = [[UIScrollView alloc]initWithFrame:CGRectMake(20, 10, 280, 1200)];
tipScroll.showsVerticalScrollIndicator = YES;
tipScroll.scrollEnabled = YES;
tipScroll.userInteractionEnabled = YES;

UIImageView *tutorialImageView = [[UIImageView alloc]initWithImage:[UIImage imageNamed:@"tutorial"]];

tipScroll.contentMode = UIViewContentModeScaleAspectFit;
tutorialImageView.contentMode = UIViewContentModeScaleAspectFit;

tipScroll.contentSize = tutorialImageView.frame.size;

[self.view addSubview:tipScroll];
[tipScroll addSubview:tutorialImageView];

试试：

tipScroll = [[UIScrollView alloc]initWithFrame:CGRectMake(20, 10, 280, 1200)];
tipScroll.showsVerticalScrollIndicator = YES;
tipScroll.scrollEnabled = YES;
tipScroll.userInteractionEnabled = YES;

UIImageView *tutorialImageView = [[UIImageView alloc]initWithFrame:CGRectMake(0, 0, 280, 1200)];
tutorialImageView.image = [UIImage imageNamed:@"tutorial"];

tipScroll.contentSize = tutorialImageView.frame.size;
[tipScroll addSubview:tutorialImageView];
[self.view addSubview:tipScroll];