关于ios:iOS图片预览放大缩小

思路

图片预览，优先思考根底控件 UIImageView、UIButton

图片预览中可能需设置不同的 mode，优先思考 UIImageView

typedef NS_ENUM(NSInteger, UIViewContentMode) {
    UIViewContentModeScaleToFill,
    UIViewContentModeScaleAspectFit,      
    UIViewContentModeScaleAspectFill,     
    UIViewContentModeRedraw,             
    UIViewContentModeCenter,              
    UIViewContentModeTop,
    UIViewContentModeBottom,
    UIViewContentModeLeft,
    UIViewContentModeRight,
    UIViewContentModeTopLeft,
    UIViewContentModeTopRight,
    UIViewContentModeBottomLeft,
    UIViewContentModeBottomRight,
}

图片放大、放大的思路：1. 手势 +frame 2.scrollview 的 zoomScale

很欢快的决定抉择 2，不要问为什么，因为我懒，能用零碎提供的，坚定不折腾

上菜

• 设置页面属性

  @property (nonatomic, strong) UIScrollView *mScroll;
  @property (nonatomic, strong) UIImageView *imgInfo;

• 界面初始化

  self.mScroll = [[UIScrollView alloc] initWithFrame:CGRectZero];
  self.mScroll.backgroundColor = [UIColor colorWithHexs:0x3f3f3f];
  self.mScroll.maximumZoomScale = 3.0;
  self.mScroll.minimumZoomScale = 1;
  self.mScroll.delegate = self;
  self.mScroll.showsVerticalScrollIndicator = NO;
  self.mScroll.showsHorizontalScrollIndicator = NO;
  [self.view addSubview:self.mScroll];
  [self.mScroll mas_makeConstraints:^(MASConstraintMaker *make) {make.edges.equalTo(self.preView);
  }];
  
  self.imgInfo = [[UIImageView alloc] initWithFrame:CGRectZero];
  self.imgInfo.clipsToBounds = YES;
  [self.imgInfo setUserInteractionEnabled:YES];
  self.imgInfo.backgroundColor = [UIColor colorWithHexs:0x3f3f3f];
  [self.mScroll addSubview:self.imgInfo];
  [self.imgInfo mas_makeConstraints:^(MASConstraintMaker *make) {make.edges.equalTo(self.mScroll);
      make.width.equalTo(self.mScroll);
  }];

  其中 maximumZoomScale 与 minimumZoomScale 示意可缩放水平

• 顺带加个双击手势，比方双击可放大，再放大，再放大

  UITapGestureRecognizer *tap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(tapHandlerTwice)];
  tap.numberOfTapsRequired = 2;
  [self.imgInfo addGestureRecognizer:tap];

• double click 间接管制缩放

  - (void)tapHandlerTwice {if (self.mScroll.zoomScale < 2) {[self.mScroll setZoomScale:2];
    } else if (self.mScroll.zoomScale < 3) {[self.mScroll setZoomScale:3];
    } else {[self.mScroll setZoomScale:1];
    }
  }

• UIScrollViewDelegate 设置 scrollview 的 Zooming View

  #pragma mark - UIScrollViewDelegate
  - (UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView {return self.imgInfo;