bounds.origin.x = fmax(minBoundsOriginX, fmin(newBoundsOriginX, maxBoundsOriginX));
CGFloat newBoundsOriginY = bounds.origin.y - translation.y;
CGFloat minBoundsOriginY = 0.0;
CGFloat maxBoundsOriginY = self.contentSize.height - bounds.size.height;
bounds.origin.y = fmax(minBoundsOriginY, fmin(newBoundsOriginY, maxBoundsOriginY));
self.bounds = bounds;
[gestureRecognizer setTranslation:CGPointZero inView:self];
}
@end
和真正的UIScrollView一样，我们的类也有一个contentSize属性，你必须从外部来设置这个值来指定可以滚动的区域，当我们改变bounds的大小时我们要确保设置的值是有效的。
结果：
UIScrollView常用操作方法整理
复制代码
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view.
// 创建一个滚动视图
self.scrollView = [[UIScrollView alloc] initWithFrame:CGRectMake(0, 64, 320, 568-64)];
// 设置代理
self.scrollView.delegate = self;
self.scrollView.backgroundColor = [UIColor redColor];
[self.view addSubview:_scrollView];
/**
* CGPoint contentOffSet 监控目前滚动的位置
* CGSize contentSize 滚动范围大小(主属性)
