iOS应用开发中使用UIScrollView控件来实现图片缩放

@interface MJViewController ()
{
    //在私有扩展中创建一个属性
    UIScrollView *_scrollView;
}
@end

@implementation MJViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
   
    // 1.创建UIScrollView
    UIScrollView *scrollView = [[UIScrollView alloc] init];
    scrollView.frame = CGRectMake(0, 0, 250, 250); // frame中的size指UIScrollView的可视范围
    scrollView.backgroundColor = [UIColor grayColor];
    [self.view addSubview:scrollView];
   
    // 2.创建UIImageView（图片）
    UIImageView *imageView = [[UIImageView alloc] init];
    imageView.image = [UIImage imageNamed:@"big.jpg"];
    CGFloat imgW = imageView.image.size.width; // 图片的宽度
    CGFloat imgH = imageView.image.size.height; // 图片的高度
    imageView.frame = CGRectMake(0, 0, imgW, imgH);
    [scrollView addSubview:imageView];
   
    // 3.设置scrollView的属性
   
    // 设置UIScrollView的滚动范围（内容大小）
    scrollView.cOntentSize= imageView.image.size;
   
    // 隐藏水平滚动条
    scrollView.showsHorizOntalScrollIndicator= NO;
    scrollView.showsVerticalScrollIndicator = NO;
   
    // 用来记录scrollview滚动的位置
//    scrollView.cOntentOffset= ;
   
    // 去掉弹簧效果
//    scrollView.bounces = NO;
   
    // 增加额外的滚动区域（逆时针，上、左、下、右）
    // top  left  bottom  right
    scrollView.cOntentInset= UIEdgeInsetsMake(20, 20, 20, 20);
   
    _scrollView = scrollView;
}

- (IBAction)down:(UIButton *)sender {
    [UIView animateWithDuration:1.0 animations:^{
        //三个步骤
        CGPoint offset = _scrollView.contentOffset;
        offset.y += 150;
        _scrollView.cOntentOffset= offset;
       
        //_scrollView.cOntentOffset= CGPointMake(0, 0);
    }];
}
@end

@interface YYViewController ()
{
    UIScrollView *_scrollview;
    UIImageView *_imageview;
}
@end

- (void)viewDidLoad
{
    [super viewDidLoad];
   
    //1添加 UIScrollView
    //设置 UIScrollView的位置与屏幕大小相同
    _scrollview=[[UIScrollView alloc]initWithFrame:self.view.bounds];
    [self.view addSubview:_scrollview];
   
    //2添加图片
    //有两种方式
    //(1)一般方式
//    UIImageView  *imageview=[[UIImageView alloc]init];
//    UIImage *image=[UIImage imageNamed:@"minion"];
//    imageview.image=image;
//    imageview.frame=CGRectMake(0, 0, image.size.width, image.size.height);
   
    //(2)使用构造方法
    UIImage *image=[UIImage imageNamed:@"minion"];
    _imageview=[[UIImageView alloc]initWithImage:image];
    //调用initWithImage:方法，它创建出来的imageview的宽高和图片的宽高一样
    [_scrollview addSubview:_imageview];
   
    //设置UIScrollView的滚动范围和图片的真实尺寸一致
    _scrollview.cOntentSize=image.size;
   
   
    //设置实现缩放
    //设置代理scrollview的代理对象
    _scrollview.delegate=self;
    //设置最大伸缩比例
    _scrollview.maximumZoomScale=2.0;
    //设置最小伸缩比例
    _scrollview.minimumZoomScale=0.5;
   
}

//告诉scrollview要缩放的是哪个子控件
-(UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView
{
    return _imageview;
}

@end

    UIImage *image=[UIImage imageNamed:@"minion"];

    imageview.image=image;

    imageview.frame=CGRectMake(0, 0, image.size.width, image.size.height);

    _imageview=[[UIImageViewalloc]initWithImage:image];