iOS图片预览、放大缩小

• 思路

  图片预览，优先考虑基础控件UIImageView、UIButton

  图片预览中可能需设置不同的mode，优先考虑UIImageView

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

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

  很愉快的决定选择2，不要问为什么，因为我懒，能用系统提供的，坚决不折腾

• 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表示可缩放程度- 顺带加个双击手势，比如双击可放大，再放大，再缩小

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

- double click直接控制缩放

• (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;
  }