UIScrollView contentSize

UISrollView

UIScrollView的基本使用

UIScrollView的用法很简单
将需要展示的内容添加到UIScrollView中
设置UIScrollView的contentSize属性，告诉UIScrollView所有内容的尺寸，也就是告诉它滚动的范围（能滚多远，滚到哪里是尽头）

UIScrollView显示内容的小细节
超出UIScrollView边框的内容会被自动隐藏
用户可以用过手势拖动来查看超出边框并被隐藏的内容

  self.scrollView.contentSize=CGSizeMake(0, 900);
    self.scrollView.scrollEnabled=YES;
    

UIScrollView无法滚动的解决办法

如果UIScrollView无法滚动，可能是以下原因：
没有设置contentSize
scrollEnabled = NO
没有接收到触摸事件:userInteractionEnabled = NO
… …

@interface ViewController ()
@property (weak, nonatomic) IBOutlet UIScrollView *scrollView;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    UIImageView *imageView=[[UIImageView alloc]initWithImage:[UIImage imageNamed:@"minion"]];
    [self.scrollView addSubview:imageView];
    
    self.scrollView.contentSize=imageView.image.size;
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

- (IBAction)left:(id)sender {
    
    self.scrollView.contentOffset = CGPointMake(0, self.scrollView.contentOffset.y);
}

- (IBAction)top:(id)sender {
    
    self.scrollView.contentOffset=CGPointMake(self.scrollView.contentOffset.y, 0);
    
}
- (IBAction)bottom:(id)sender {
    
    [UIView beginAnimations:nil context:nil];
    CGFloat  offSetY=self.scrollView.contentSize.height-self.scrollView.frame.size.height;
    
      self.scrollView.contentOffset=CGPointMake(self.scrollView.contentOffset.y, offSetY);
    [UIView commitAnimations];
    
}
- (IBAction)right:(id)sender {
    [UIView beginAnimations:nil context:nil];
    CGFloat offsetX = self.scrollView.contentSize.width - self.scrollView.frame.size.width;
    self.scrollView.contentOffset = CGPointMake(offsetX, self.scrollView.contentOffset.y);
    [UIView commitAnimations];
}

@end