UIScrollView结合UIImageView实现图片缩放

古城微笑少年丶 2022-03-28 13:52 254阅读 0赞

实现UIImageView的图片缩放功能，需要结合UIScrollView实现。

示例代码

// 定义缩放比例
    CGFloat scaleMini = 1.0;
    CGFloat scaleMax = 3.0;

// 主视图 UIScrollView
    UIScrollView *scrollView = [[UIScrollView alloc] initWithFrame:self.view.bounds];
    [self.view addSubview:scrollView];
    scrollView.pagingEnabled = YES;
    scrollView.backgroundColor = [UIColor redColor];
    scrollView.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;

// 图片视图及子视图UIScrollView
    //
        NSArray *images = @[@"001.jpg", @"002.jpg", @"003.jpg", @"004.jpg"];
        //
        [images enumerateObjectsUsingBlock:^(id  _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
            UIImage *image = [UIImage imageNamed:obj];
            UIImageView *imageView = [[UIImageView alloc] initWithImage:image];
            imageView.contentMode = UIViewContentModeScaleAspectFit;
            imageView.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;
            // 双击实现缩放
            UITapGestureRecognizer *doubleTapGesture = [[UITapGestureRecognizer alloc] initWithTarget:self  action:@selector(handleDoubleTap:)];
            [doubleTapGesture setNumberOfTapsRequired:2];
            imageView.userInteractionEnabled = YES;
            [imageView addGestureRecognizer:doubleTapGesture];
            //
            UIScrollView *subScrollerView = [[UIScrollView alloc] initWithFrame:CGRectMake((idx * scrollView.frame.size.width), 0.0, scrollView.frame.size.width, scrollView.frame.size.height)];
            [scrollView addSubview:subScrollerView];
            subScrollerView.delegate = self;
            [subScrollerView setMinimumZoomScale:scaleMini];
            [subScrollerView setMaximumZoomScale:scaleMax];
            //
            imageView.frame = subScrollerView.bounds;
            [subScrollerView addSubview:imageView];
        }];

// 根据图片数组重置主视图contentSize
    scrollView.contentSize = CGSizeMake((images.count * scrollView.frame.size.width), scrollView.frame.size.height);

// 双击缩放响应
    BOOL isScaleBig = NO;
    - (void)handleDoubleTap:(UITapGestureRecognizer *)recognizer
    {
        UIImageView *imageView = (UIImageView *)recognizer.view;
        UIScrollView *scrollView = (UIScrollView *)imageView.superview;
        
        // 放大缩小
        CGFloat scale = scrollView.zoomScale;
        if (isScaleBig) {
            [scrollView setZoomScale:scale / scaleMini animated:YES];
            isScaleBig = false;
        } else {
            [scrollView setZoomScale:scale * scaleMini animated:YES];
            isScaleBig = true;
        }
    }

// 设置协议UIScrollViewDelegate，并实现协议方法
    - (UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView
    {
        for (UIView *view in scrollView.subviews) {
            if ([view isKindOfClass:[UIImageView class]]) {
                isScaleBig = !isScaleBig;
                return view;
            }
        }
        return nil;
    }
    
    - (void)scrollViewDidZoom:(UIScrollView *)scrollView
    {
        for (UIView *view in scrollView.subviews) {
            if ([view isKindOfClass:[UIImageView class]]) {
                [self showInCenter:scrollView imageView:view];
            }
        }
    }
    
    - (void)scrollViewDidEndZooming:(UIScrollView *)scrollView withView:(UIView *)view atScale:(CGFloat)scale
    {
        // 缩放效果 放大或缩小
        if (scrollView.minimumZoomScale >= scale) {
            [scrollView setZoomScale:scaleMini animated:YES];
        }
        if (scrollView.maximumZoomScale <= scale) {
            [scrollView setZoomScale:scaleMax animated:YES];
        }
    }

// 缩放时居中显示处理
    - (void)showInCenter:(UIScrollView *)scrollView imageView:(UIImageView *)imageView
    {
        // 居中显示
        CGFloat offsetX = (scrollView.bounds.size.width > scrollView.contentSize.width) ? (scrollView.bounds.size.width - scrollView.contentSize.width) * 0.5 : 0.0;
        CGFloat offsetY = (scrollView.bounds.size.height > scrollView.contentSize.height) ?
        (scrollView.bounds.size.height - scrollView.contentSize.height) * 0.5 : 0.0;
        imageView.center = CGPointMake(scrollView.contentSize.width * 0.5 + offsetX, scrollView.contentSize.height * 0.5 + offsetY);
    }