<p>公司产品需要实现点击个人主页头像可以放大头像、缩放头像、保存头像效果（和点击微信个人头像类似），故找个时间实现一下，记录下来，供自己查看，也给大家做个参考。</p>    <p>实现效果（GIF）：</p>    <p style="text-align:center"><img src="https://simg.open-open.com/show/9cdf1ea93f87e96dc684fcad305bb8d1.gif"></p>    <p>实现思路：</p>    <p>直接自定义 UIView（CYPhotoPreviewer），为了实现双击缩放，可以实现 UIScrollViewDelegate 对应的方法。如果需要模糊背景，可以在自定义的 UIView 中先添加模糊背景，再添加 UIScrollView，继而在 UIScrollView 中添加图片容器，这个容器就是要显示的图片的 superView，代码一目了然：</p>    <pre>  <code class="language-objectivec">- (void)setup {         self.frame = [UIScreenmainScreen].bounds;      self.backgroundColor = [UIColorclearColor];       UITapGestureRecognizer *singleTap = [[UITapGestureRecognizeralloc] initWithTarget:selfaction:@selector(singleTap:)];      [self addGestureRecognizer:singleTap];         UITapGestureRecognizer *doubleTap = [[UITapGestureRecognizeralloc] initWithTarget:selfaction:@selector(doubleTap:)];      doubleTap.numberOfTapsRequired = 2;      [singleTaprequireGestureRecognizerToFail:doubleTap];      [self addGestureRecognizer:doubleTap];         UILongPressGestureRecognizer *longPress = [[UILongPressGestureRecognizeralloc] initWithTarget:selfaction:@selector(longPress:)];      [self addGestureRecognizer:longPress];         // 设置模糊背景      self.blurBackground = [[UIVisualEffectViewalloc] initWithEffect:[UIBlurEffecteffectWithStyle:UIBlurEffectStyleExtraLight]];      self.blurBackground.frame = self.frame;      [self addSubview:self.blurBackground];         // 设置 UIScrollView 相关属性      self.scrollView = [[UIScrollViewalloc] initWithFrame:[UIScreenmainScreen].bounds];      self.scrollView.delegate = self;      self.scrollView.bouncesZoom = YES;      self.scrollView.maximumZoomScale = 3.0;      self.scrollView.multipleTouchEnabled = YES;      self.scrollView.alwaysBounceVertical = NO;      self.scrollView.showsVerticalScrollIndicator = NO;      self.scrollView.showsHorizontalScrollIndicator = NO;      [self addSubview:self.scrollView];         // containerView      self.containerView = [[UIViewalloc] init];      [self.scrollViewaddSubview:self.containerView];         // imageView      self.imageView = [[UIImageViewalloc] init];      self.imageView.clipsToBounds = YES;      self.imageView.backgroundColor = [UIColorcolorWithWhite:1.0 alpha:0.5];      [self.containerViewaddSubview:self.imageView];  }  </code></pre>    <p>可以看到，我们给设置了模糊背景，给这个 CYPhotoPreviewer 添加了单击手势（关闭 PhotoPreviewer）、双击手势（缩放图片）、长按手势（使用 UIAlertController 菜单，比如保存图片等）。</p>    <p>好，确定了这个 CYPhotoPreviewer 中的显示内容，那么我们该如何显示这个 CYPhotoPreviewer 呢？</p>    <ul>     <li>直接将这个 CYPhotoPreviewer 添加到 keyWindow 上</li>     <li>将这个 CYPhotoPreviewer 添加到控制器的 self.view 上</li>    </ul>    <p>这两种方式的实现都差不多，不过如果使用第一种方式的话，会导致将 CYPhotoPreviewer 添加到 keyWindow 上之后，再长按继续将 UIAlertController 显示就比较麻烦了，因此，这里打算采用将 CYPhotoPreviewer 添加到控制器的 self.view 上，继而就可以很方便的显示 UIAlertController 了：</p>    <pre>  <code class="language-objectivec">- (void)previewFromImageView:(UIImageView *)fromImageViewinContainer:(UIView *)container {      _fromImageView = fromImageView;      fromImageView.hidden = YES;      [containeraddSubview:self]; // 将 CYPhotoPreviewer 添加到 container 上         self.containerView.origin = CGPointZero;      self.containerView.width = self.width; // containerView 的宽度是屏幕的宽度         UIImage *image = fromImageView.image;         // 计算 containerView 的高度      if (image.size.height / image.size.height > self.height / self.width) {          self.containerView.height = floor(image.size.height / (image.size.width / self.width));      } else {          CGFloatheight = image.size.height / image.size.width * self.width;          if (height  self.height && self.containerView.height - self.height  </code></pre>    <p>可以看到，我们将外面的图片 fromImageView 传递进来，是为了显示更好的动画效果；将控制器的 container（self.view）传递进来，是为了将 CYPhotoPreviewer 添加到 container 的细节不需要在调用处处理，即初始化 CYPhotoPreviewer 之后，CYPhotoPreviewer 就直接被 container 添加为 subview 了。动画很简单不再细说。</p>    <p>显示的效果已经做好，单击关闭 CYPhotoPreviewer 也比较好实现，只需要从父类移除 CYPhotoPreviewer 即可：</p>    <pre>  <code class="language-objectivec">- (void)dismiss {      [UIViewanimateWithDuration:0.18 delay:0.0 options:UIViewAnimationOptionCurveEaseInOutanimations:^{          CGRectfromRect = [self.fromImageViewconvertRect:self.fromImageView.boundstoView:self.containerView];          self.imageView.contentMode = self.fromImageView.contentMode;          self.imageView.frame = fromRect;          self.blurBackground.alpha = 0.01;      } completion:^(BOOL finished) {          [UIViewanimateWithDuration:0.10 delay:0 options:UIViewAnimationOptionCurveEaseInOutanimations:^{              self.fromImageView.hidden = NO;              self.alpha = 0;          } completion:^(BOOL finished) {              [self removeFromSuperview];          }];      }];  }  </code></pre>    <p>好了，显示和关闭 CYPhotoPreviewer 都实现了，如果需要双击缩放图片效果，就得实现 UIScrollViewDelegate 的两个方法以及 CYPhotoPreviewer 的双击手势：</p>    <pre>  <code class="language-objectivec">- (UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView{      return self.containerView;  }     - (void)scrollViewDidZoom:(UIScrollView *)scrollView {      UIView *subView = self.containerView;         CGFloatoffsetX = (scrollView.bounds.size.width > scrollView.contentSize.width)?      (scrollView.bounds.size.width - scrollView.contentSize.width) * 0.5 : 0.0;         CGFloatoffsetY = (scrollView.bounds.size.height > scrollView.contentSize.height)?      (scrollView.bounds.size.height - scrollView.contentSize.height) * 0.5 : 0.0;         subView.center = CGPointMake(scrollView.contentSize.width * 0.5 + offsetX,                                  scrollView.contentSize.height * 0.5 + offsetY);  }     - (void)doubleTap:(UITapGestureRecognizer *)recognizer {      if (self.scrollView.zoomScale > 1.0) {          [self.scrollViewsetZoomScale:1.0 animated:YES];      } else {          CGPointtouchPoint = [recognizerlocationInView:self.imageView];          CGFloatnewZoomScale = self.scrollView.maximumZoomScale;          CGFloatxSize = self.width / newZoomScale;          CGFloatySize = self.height / newZoomScale;          [self.scrollViewzoomToRect:CGRectMake(touchPoint.x - xSize / 2, touchPoint.y - ySize / 2, xSize, ySize) animated:YES];      }  }  </code></pre>    <p>最后一个就是长按弹出菜单（UIAlertController）了：</p>    <pre>  <code class="language-objectivec">- (void)longPress:(UILongPressGestureRecognizer *)recognizer {         // 为了避免弹警告：Warning: Attempt to present   on  which is already presenting ，最好加入状态判断      if (recognizer.state == UIGestureRecognizerStateBegan) {          UIAlertController *alertController = [UIAlertControlleralertControllerWithTitle:@"QuoraDots" message:nilpreferredStyle:UIAlertControllerStyleActionSheet];             [alertControlleraddAction:[UIAlertActionactionWithTitle:@"保存" style:UIAlertActionStyleDefaulthandler:nil]];          [alertControlleraddAction:[UIAlertActionactionWithTitle:@"取消" style:UIAlertActionStyleCancelhandler:nil]];             UIViewController *vc = self.viewController;          [vcpresentViewController:alertControlleranimated:YEScompletion:nil];      }  }  </code></pre>    <p>注意一点， longPress: 这个方法会调用很频繁，因此，为了避免 Attempt to present xxx on xxx which is already presenting xxx 这个警告，我们需要判断手势的状态。</p>    <p>后话：</p>    <p>这个只是显示单张图片的大图，如果需要显示多张图片类似微信微博的九宫格图片的大图显示，则需要将这个 CYPhotoPreviewer 搞成 UICollectionView 的 item 即可，大家可以尝试尝试。</p>    <p> </p>    <p> </p>    <p> </p>