iOS 7缩放在使用AutoLayout的ScrollView中无效,但在iOS8/9中工作

Question

我用缩放图像做了一个演示UIScrollView.我ViewController只包含一张图片.问题是图像无法放大iO7(我已经测试过iPhone4S-iOS7)但在iOS8/中完美地工作iOS9.
关于如何修复它的任何想法？

这是我的代码

#import "ViewController.h"

@interface ViewController ()<UIScrollViewDelegate>
@property (weak, nonatomic) IBOutlet UIScrollView *scrollview;
@property (weak, nonatomic) IBOutlet UIView *contentview;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
        float minimumScale = [_contentview frame].size.width /[_scrollview frame].size.width;
        _scrollview.maximumZoomScale = 5;  //Change as per you need
        _scrollview.minimumZoomScale = minimumScale;  //Change as you need
        _scrollview.zoomScale = minimumScale;
        _scrollview.delegate =self;
        _scrollview.clipsToBounds = YES;
}

- (UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView{
    return self.contentview;
}

@end

这是布局结构

Screen.png约束 ContentView约束

ScrollView约束

这是我的演示项目

https://drive.google.com/file/d/0B679aXO0SBmMeUVHTUdOcmxJSXM/view

Answer 1

iOS 7 中的高度和宽度constraints导致了这种情况。解决方法是删除constraintsiOS 7 的高度和宽度并minimumScale手动计算。在 iOS 8 及更高版本中，请勿更改任何内容。

- (void)viewDidLoad {
    [super viewDidLoad];

    float minimumScale = 1;

    if (floor(NSFoundationVersionNumber) < NSFoundationVersionNumber_iOS_8_0) {
        [self.view removeConstraints:self.heightWidthConstraints];
        minimumScale = self.scrollview.frame.size.width / self.imageView.image.size.width;
    }

    _scrollview.maximumZoomScale = 5;  //Change as per you need
    _scrollview.minimumZoomScale = minimumScale;  //Change as you need
    //_scrollview.zoomScale = minimumScale;
    _scrollview.delegate = self;
    //_scrollview.clipsToBounds = YES;

    [self.scrollview setZoomScale:minimumScale animated:YES];
}