UIScrollView实现缩放和居中

UIScrollView可以实现缩放功能。

1. .h文件实现<UIScrollViewDelegate>协议。
2. 设置scrollView对象的两个属性maximumZoomScale和minimumZoomScale。
3. .m文件中实现代理方法viewForZoomingInScrollView: 。

完成上面三个步骤就基本实现了缩放功能。

.h文件

@interface MapViewController : UIViewController <UIScrollViewDelegate>

@end

.m文件

@implementation MapViewController

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        // Custom initialization
    }
    return self;
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    
    CGSize mainViewSize = CGSizeMake([[UIScreen mainScreen] bounds].size.width, [[UIScreen mainScreen] bounds].size.height - 20 - 44 - 49);
    
    //scrollView
    UIScrollView *scrollView = [[UIScrollView alloc] initWithFrame:CGRectMake(0, 0, mainViewSize.width, mainViewSize.height)];
    scrollView.delegate = self;
    //开启多点触摸
    scrollView.multipleTouchEnabled = YES;
    //设置最小缩放比例
    scrollView.minimumZoomScale = 1.0;
    //设置最大缩放比例
    scrollView.maximumZoomScale = 10.0;
    [self.view addSubview:scrollView];
    
    
    UIImage *mapImage = [UIImage imageNamed:@"mapLarge.png"];

    
    CGFloat imageView_X = (mapImage.size.width > mainViewSize.width ? mainViewSize.width : mapImage.size.width);
    CGFloat imageView_Y = (mapImage.size.height > mainViewSize.height ? mainViewSize.height : mapImage.size.height);
    if (mapImage.size.width > mainViewSize.width) {
        imageView_Y = mapImage.size.height * (mainViewSize.width / mapImage.size.width);
    }
    UIImageView *mapImageView = [[UIImageView alloc] initWithFrame:CGRectMake((mainViewSize.width - imageView_X) / 2, (mainViewSize.height - imageView_Y) / 2, imageView_X, imageView_Y)];
    mapImageView.tag = 101;
    [mapImageView setImage:mapImage];
    [scrollView addSubview:mapImageView];
    
    
    
}

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

#pragma mark -
#pragma mark UIScrollView Delegate
//实现图片在缩放过程中居中
- (void)scrollViewDidZoom:(UIScrollView *)scrollView
{
    CGFloat offsetX = (scrollView.bounds.size.width > scrollView.contentSize.width)?(scrollView.bounds.size.width - scrollView.contentSize.width)/2 : 0.0;
    CGFloat offsetY = (scrollView.bounds.size.height > scrollView.contentSize.height)?(scrollView.bounds.size.height - scrollView.contentSize.height)/2 : 0.0;
    [self.view viewWithTag:101].center = CGPointMake(scrollView.contentSize.width/2 + offsetX,scrollView.contentSize.height/2 + offsetY);
}

//返回缩放的是哪个ImageView
-(UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView{
    return [self.view viewWithTag:101];
}

@end