UIScrollView实现缩放和居中

UIScrollView可以实现缩放功能。

.h文件实现<UIScrollViewDelegate>协议。
设置scrollView对象的两个属性maximumZoomScale和minimumZoomScale。
.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

1 @interface MapViewController : UIViewController <UIScrollViewDelegate>
2 
3 @end

.m文件

 1 @implementation MapViewController
 2 
 3 - (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
 4 {
 5     self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
 6     if (self) {
 7         // Custom initialization
 8     }
 9     return self;
10 }
11 
12 - (void)viewDidLoad
13 {
14     [super viewDidLoad];
15     
16     CGSize mainViewSize = CGSizeMake([[UIScreen mainScreen] bounds].size.width, [[UIScreen mainScreen] bounds].size.height - 20 - 44 - 49);
17     
18     //scrollView
19     UIScrollView *scrollView = [[UIScrollView alloc] initWithFrame:CGRectMake(0, 0, mainViewSize.width, mainViewSize.height)];
20     scrollView.delegate = self;
21     //开启多点触摸
22     scrollView.multipleTouchEnabled = YES;
23     //设置最小缩放比例
24     scrollView.minimumZoomScale = 1.0;
25     //设置最大缩放比例
26     scrollView.maximumZoomScale = 10.0;
27     [self.view addSubview:scrollView];
28     
29     
30     UIImage *mapImage = [UIImage imageNamed:@"mapLarge.png"];
31 
32     
33     CGFloat imageView_X = (mapImage.size.width > mainViewSize.width ? mainViewSize.width : mapImage.size.width);
34     CGFloat imageView_Y = (mapImage.size.height > mainViewSize.height ? mainViewSize.height : mapImage.size.height);
35     if (mapImage.size.width > mainViewSize.width) {
36         imageView_Y = mapImage.size.height * (mainViewSize.width / mapImage.size.width);
37     }
38     UIImageView *mapImageView = [[UIImageView alloc] initWithFrame:CGRectMake((mainViewSize.width - imageView_X) / 2, (mainViewSize.height - imageView_Y) / 2, imageView_X, imageView_Y)];
39     mapImageView.tag = 101;
40     [mapImageView setImage:mapImage];
41     [scrollView addSubview:mapImageView];
42     
43     
44     
45 }
46 
47 - (void)didReceiveMemoryWarning
48 {
49     [super didReceiveMemoryWarning];
50     // Dispose of any resources that can be recreated.
51 }
52 
53 #pragma mark -
54 #pragma mark UIScrollView Delegate
55 //实现图片在缩放过程中居中
56 - (void)scrollViewDidZoom:(UIScrollView *)scrollView
57 {
58     CGFloat offsetX = (scrollView.bounds.size.width > scrollView.contentSize.width)?(scrollView.bounds.size.width - scrollView.contentSize.width)/2 : 0.0;
59     CGFloat offsetY = (scrollView.bounds.size.height > scrollView.contentSize.height)?(scrollView.bounds.size.height - scrollView.contentSize.height)/2 : 0.0;
60     [self.view viewWithTag:101].center = CGPointMake(scrollView.contentSize.width/2 + offsetX,scrollView.contentSize.height/2 + offsetY);
61 }
62 
63 //返回缩放的是哪个ImageView
64 -(UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView{
65     return [self.view viewWithTag:101];
66 }
67 
68 @end