如何缩放填充屏幕的 UIImageView

Posted 2023-03-16

【中文标题】如何缩放填充屏幕的 UIImageView

【英文标题】：How to Zoom a UIImageView that fills the screen

【发布时间】：2012-11-09 15:27:18

【问题描述】：

我只是想缩放我在 UIScrollView 上的 UIImageView 上设置的照片。也许是因为图像与屏幕大小相同，但在我下面的代码中既没有调用viewForZoomingInScrollView，也没有调用scrollViewDidZoom。请帮我解决这个问题，以便我可以放大图像。谢谢：

界面：

#import <UIKit/UIKit.h>

@interface ViewController : UIViewController <UIScrollViewDelegate>

@property (strong, nonatomic) UIScrollView* scrollView;
@property (strong, nonatomic) UIImageView *imageHolder;

@end

实施：

#import "ViewController.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad

[super viewDidLoad];

// Tell the scroll view the size of the contents
self.scrollView.contentSize = self.view.frame.size;

self.scrollView.delegate = self;
self.scrollView.scrollEnabled = YES;

_imageHolder = [[UIImageView alloc]initWithFrame:self.view.frame];
_scrollView = [[UIScrollView alloc]initWithFrame:self.view.frame];

[self.imageHolder setImage:[UIImage imageNamed:@"P1020486.png"]];

[self.scrollView addSubview:_imageHolder];
[self.view addSubview:self.scrollView];

//Keep the proportion and fit the screen, not filling it --> when we rotate, resizes image correctly:
_imageHolder.contentMode = UIViewContentModeScaleAspectFit;


- (void)viewWillAppear:(BOOL)animated 
[super viewWillAppear:animated];

// Set up the minimum & maximum zoom scales
CGRect scrollViewFrame = self.scrollView.frame;
CGFloat scaleWidth = scrollViewFrame.size.width / self.scrollView.contentSize.width;
CGFloat scaleHeight = scrollViewFrame.size.height / self.scrollView.contentSize.height;
CGFloat minScale = MIN(scaleWidth, scaleHeight);
//
self.scrollView.minimumZoomScale = minScale;
self.scrollView.maximumZoomScale = 1.0f;

[self centerScrollViewContents];


- (void)centerScrollViewContents 
CGSize boundsSize = self.scrollView.bounds.size;
CGRect contentsFrame = self.imageHolder.frame;

if (contentsFrame.size.width < boundsSize.width) 
    contentsFrame.origin.x = (boundsSize.width - contentsFrame.size.width) / 2.0f;
 else 
    contentsFrame.origin.x = 0.0f;


if (contentsFrame.size.height < boundsSize.height) 
    contentsFrame.origin.y = (boundsSize.height - contentsFrame.size.height) / 2.0f;
 else 
    contentsFrame.origin.y = 0.0f;


self.imageHolder.frame = contentsFrame;


#pragma mark - UIScrollViewDelegate

- (UIView*)viewForZoomingInScrollView:(UIScrollView *)scrollView 
// Return the view that we want to zoom
return self.imageHolder;
//return self.scrollViewBar;


- (void)scrollViewDidZoom:(UIScrollView *)scrollView 
// The scroll view has zoomed, so we need to re-center the contents
[self centerScrollViewContents];


- (void)didReceiveMemoryWarning

[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.


@end

【参考方案1】：

我没有时间测试它，但我认为问题在于这一行：

self.scrollView.maximumZoomScale = 1.0f;

试着放 2.0f 或更大的东西。

【讨论】：

感谢您的建议。您的建议似乎合乎逻辑，但遗憾的是它仍然无法放大。

嗨，Alois，虽然下面 CodeBySteveZ 的回答为我解决了这个问题，但您的回答也是解决方案的一部分，因为 1.0f 不好。再次感谢。

【参考方案2】：

从快速查看您的代码来看，您似乎在初始化之前在 scrollView 上设置了属性：

self.scrollView.contentSize = self.view.frame.size;

self.scrollView.delegate = self;

self.scrollView.scrollEnabled = YES;

_scrollView = [[UIScrollView alloc]initWithFrame:self.view.frame];

如果您颠倒顺序，它应该可以工作。

【讨论】：

是的！非常感谢。这对我来说非常愚蠢，但我们走了。现在它起作用了。干杯