你真的了解UIGestureRecognizer吗？

一：首先查看一下关于UIGestureRecognizer的定义

//当前手势状态
typedef NS_ENUM(NSInteger, UIGestureRecognizerState) {
    //尚未识别是何种手势操作（但可能已经触发了触摸事件），默认状态
    UIGestureRecognizerStatePossible,   
    //手势已经开始，此时已经被识别，但是这个过程中可能发生变化，手势操作尚未完成
    UIGestureRecognizerStateBegan,     
    //手势状态发生改变
    UIGestureRecognizerStateChanged, 
    // 手势识别操作完成（此时已经松开手指）  
    UIGestureRecognizerStateEnded, 
    //手势被取消，恢复到默认状态   
    UIGestureRecognizerStateCancelled, 
    //手势识别失败，恢复到默认状态
    UIGestureRecognizerStateFailed,    
    //手势识别完成，同end
    UIGestureRecognizerStateRecognized = UIGestureRecognizerStateEnded 
};

NS_CLASS_AVAILABLE_IOS(3_2) @interface UIGestureRecognizer : NSObject

//创建一个手势对象并添加触发事件
- (instancetype)initWithTarget:(nullable id)target action:(nullable SEL)action NS_DESIGNATED_INITIALIZER; 
//给一个手势对象添加监听事件
- (void)addTarget:(id)target action:(SEL)action;   
//移除一个手势的监听事件
- (void)removeTarget:(nullable id)target action:(nullable SEL)action; 
//获取当前手势状态
@property(nonatomic,readonly) UIGestureRecognizerState state;  
//委托
@property(nullable,nonatomic,weak) id <UIGestureRecognizerDelegate> delegate; 
//手势识别是否可用
@property(nonatomic, getter=isEnabled) BOOL enabled;  
//获取手势触摸的View视图 只读
@property(nullable, nonatomic,readonly) UIView *view;         
//是否取消触摸控件的响应
默认为YES，这种情况下当手势识别器识别到触摸之后，会发送touchesCancelled给触摸到的控件以取消控件view对touch的响应，这个时候只有手势识别器响应touch，当设置成NO时，手势识别器识别到触摸之后不会发送touchesCancelled给控件，这个时候手势识别器和控件view均响应touch。
注意：手势识别和触摸事件是同时存在的，只是因为touchesCancelled导致触摸事件失效、
@property(nonatomic) BOOL cancelsTouchesInView; 
      
//是否延迟发送触摸事件给触摸到的控件
默认是NO，这种情况下当发生一个触摸时，手势识别器先捕捉到到触摸，然后发给触摸到的控件，两者各自做出响应。如果设置为YES，手势识别器在识别的过程中（注意是识别过程），不会将触摸发给触摸到的控件，即控件不会有任何触摸事件。只有在识别失败之后才会将触摸事件发给触摸到的控件，这种情况下控件view的响应会延迟约0.15ms。
@property(nonatomic) BOOL delaysTouchesBegan;     
  
//如果触摸识别失败是否立即结束本次手势识别的触摸事件
@property(nonatomic) BOOL delaysTouchesEnded;        

//指定一个手势需要另一个手势执行失败才会执行，同时触发多个手势使用其中一个手势的解决办法
有时手势是相关联的，如单机和双击，点击和长按，点下去瞬间可能只会识别到单击无法识别其他，该方法可以指定某一个 手势，即便自己已经满足条件了，也不会立刻触发，会等到该指定的手势确定失败之后才触发
- (void)requireGestureRecognizerToFail:(UIGestureRecognizer *)otherGestureRecognizer;

//获取当前触摸在指定视图上的点
- (CGPoint)locationInView:(nullable UIView*)view;                               

//获取触摸手指数
- (NSUInteger)numberOfTouches;                                         

//多指触摸的触摸点相对于指定视图的位置
- (CGPoint)locationOfTouch:(NSUInteger)touchIndex inView:(nullable UIView*)view; 

@end

UIGestureRecognizer是一个抽象类，定义了所有手势的基本行为，使用它的子类才能处理具体的手势

知识点1：关于UIGestureRecognizer的子类如下（下面这些才是我们平常会直接运用到的类）：

UITapGestureRecognizer（轻触，点按）
UILongPressGestureRecognizer（长按）
UISwipeGestureRecognizer（轻扫手势）
UIRotationGestureRecognizer（旋转手势）
UIPanGestureRecognizer（拖拽手势）
UIPinchGestureRecognizer（捏合手势，缩放用）

实例如下：

//拖拽手势
UIPanGestureRecognizer *pan = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(pan:)];
[tagButton addGestureRecognizer:pan];


- (void)pan:(UIPanGestureRecognizer *)pan
{
             
｝

//给视图增加点击动作

UITapGestureRecognizer *tap = [[UITapGestureRecognizer alloc]initWithTarget:self action:@selector(tapHandle:)];
[self.view addGestureRecognizer:tap];


-(void)tapHandle:(UITapGestureRecognizer*)tap
{
    
}

二：关于UIGestureRecognizerDelegate代理的内容

@protocol UIGestureRecognizerDelegate <NSObject>
@optional

//开始进行手势识别时调用的方法，返回NO则结束识别，不再触发手势，用处：可以在控件指定的位置使用手势识别
- (BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer *)gestureRecognizer;

//是否支持多手势触发，返回YES，则可以多个手势一起触发方法，返回NO则为互斥
是否允许多个手势识别器共同识别，一个控件的手势识别后是否阻断手势识别继续向下传播，默认返回NO；如果为YES，响应者链上层对象触发手势识别后，如果下层对象也添加了手势并成功识别也会继续执行，否则上层对象识别后则不再继续传播
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer;

// 这个方法返回YES，第一个手势和第二个互斥时，第一个会失效
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRequireFailureOfGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer NS_AVAILABLE_IOS(7_0);

//这个方法返回YES，第一个和第二个互斥时，第二个会失效
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldBeRequiredToFailByGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer NS_AVAILABLE_IOS(7_0);

//手指触摸屏幕后回调的方法，返回NO则不再进行手势识别，方法触发等
此方法在window对象在有触摸事件发生时，调用gesture recognizer的touchesBegan:withEvent:方法之前调用，如果返回NO,则gesture recognizer不会看到此触摸事件。(默认情况下为YES)
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldReceiveTouch:(UITouch *)touch;

@end

知识点1：

//是否同时支持多种手势
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer{
  return YES;
}

//是否允许开始点击
- (BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer *)gestureRecognizer{
return YES;
}
//设置点击的范围
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldReceiveTouch:(UITouch *)touch{
//获取当前的触摸点
  CGPoint curp = [touch locationInView:self.imageView];
  if (curp.x <= self.imageView.bounds.size.width*0.5) {
      return NO;
  }else{

      return YES;
  }
}

知识点2：UITapGestureRecognizer和UIButton的点击事件冲突的解决办法

- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldReceiveTouch:(UITouch *)touch{    
if ([touch.view isKindOfClass:[UIButton class]])    { 
       return NO;    }   
       return YES;
}

三：关于UIGestureRecognizer的子类知识

1:UITapGestureRecognizer（轻触，点按）

NS_CLASS_AVAILABLE_IOS(3_2) @interface UITapGestureRecognizer : UIGestureRecognizer

//设置能识别到手势的最少的轻触次数（默认为1）
@property (nonatomic) NSUInteger  numberOfTapsRequired;     
//设置能识别到手势的最少的手指的个数（默认为1） 
@property (nonatomic) NSUInteger  numberOfTouchesRequired;  
@end

知识点1：实例代码如下

// 创建一个手势对象
UITapGestureRecognizer *tap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(tapAction:)];
// 设置能识别到手势的最少的轻触次数
tap.numberOfTapsRequired = 3;
// 设置能识别到手势的最少的手指的个数
tap.numberOfTouchesRequired = 2;
//把手势对象添加到对应的控件中
[self.imgView addGestureRecognizer:tap];

2：UILongPressGestureRecognizer（长按手势）

NS_CLASS_AVAILABLE_IOS(3_2) @interface UILongPressGestureRecognizer : UIGestureRecognizer
//设置能识别到手势的最少的轻触次数（默认为1）
@property (nonatomic) NSUInteger numberOfTapsRequired;     
//设置能识别到手势的最少的手指的个数（默认为1） 
@property (nonatomic) NSUInteger numberOfTouchesRequired;   
//设置能识别到长按手势的最短的长按时间，单位：秒，默认为0.5
@property (nonatomic) CFTimeInterval minimumPressDuration; 
//设置长按时允许移动的最大距离，单位：像素，默认为10像素
@property (nonatomic) CGFloat allowableMovement;           

@end

知识点1：实例代码如下

UILongPressGestureRecognizer *longPress = [[UILongPressGestureRecognizer alloc] initWithTarget:self action:@selector(longPressAction:)];
// 设置能识别到长按手势的最小的长按时间
longPress.minimumPressDuration = 0.5;
// "容错的范围"
longPress.allowableMovement  = 10;
// 把长按手势添加到对应的控件中
[self.imgView addGestureRecognizer:longPress];

3：UISwipeGestureRecognizer（轻扫手势）

typedef NS_OPTIONS(NSUInteger, UISwipeGestureRecognizerDirection) {
    UISwipeGestureRecognizerDirectionRight = 1 << 0,  //向右滑
    UISwipeGestureRecognizerDirectionLeft  = 1 << 1,  //向左滑
    UISwipeGestureRecognizerDirectionUp    = 1 << 2,  //向上滑
    UISwipeGestureRecognizerDirectionDown  = 1 << 3  //向下滑
};

NS_CLASS_AVAILABLE_IOS(3_2) @interface UISwipeGestureRecognizer : UIGestureRecognizer 
//最少触摸手指个数，默认为1
@property(nonatomic) NSUInteger                        numberOfTouchesRequired; 
//设置轻扫手势支持的方向，默认为向右滑
@property(nonatomic) UISwipeGestureRecognizerDirection direction;               

@end

知识点1：实例代码如下

UISwipeGestureRecognizer *swipeLeft = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:@selector(swipeAction:)];
swipeLeft.direction = UISwipeGestureRecognizerDirectionLeft;
[self.imgView addGestureRecognizer:swipeLeft];

4：UIRotationGestureRecognizer（旋转手势）

NS_CLASS_AVAILABLE_IOS(3_2) @interface UIRotationGestureRecognizer : UIGestureRecognizer
//旋转的角度
@property (nonatomic)          CGFloat rotation;  
//旋转速度，单位：度/秒、         
@property (nonatomic,readonly) CGFloat velocity;           

@end

知识点1：实例代码如下

//为图片框添加一个旋转手势
UIRotationGestureRecognizer *rotation = [[UIRotationGestureRecognizer alloc] initWithTarget:self action:@selector(rotateAction:)];rotation.delegate = self;
[self.imgView addGestureRecognizer:rotation];


// 旋转手势的监听方法
- (void)rotateAction:(UIRotationGestureRecognizer *)recognizer {
// 在原来的基础上, 累加多少度
recognizer.view.transform = CGAffineTransformRotate(recognizer.view.transform, recognizer.rotation);
// 每次旋转完毕后将rotation的值, 恢复到0的位置.recognizer.rotation = 0;
}

5：UIPanGestureRecognizer（拖拽手势）

NS_CLASS_AVAILABLE_IOS(3_2) @interface UIPanGestureRecognizer : UIGestureRecognizer 
//设置触发拖拽最少手指数，默认为1
@property (nonatomic)          NSUInteger minimumNumberOfTouches;   
//设置触发拖拽最多手指数，默认为 UINT_MAX 无限大
@property (nonatomic)          NSUInteger maximumNumberOfTouches;   
//获取当前拖拽位置
- (CGPoint)translationInView:(nullable UIView *)view;                        
//设置当前拖拽位置
- (void)setTranslation:(CGPoint)translation inView:(nullable UIView *)view;
//设置拖拽速度，单位：像素/秒
- (CGPoint)velocityInView:(nullable UIView *)view;                          

@end

知识点1：实例代码

UIPanGestureRecognizer *pan = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(panAction:)];
[self.imgView addGestureRecognizer:pan];


// 拖拽手势的监听方法
- (void)panAction:(UIPanGestureRecognizer *)recognizer {
// 1. 获取手指拖拽的时候, 平移的值
CGPoint translation = [recognizer translationInView:recognizer.view];
// 2. 让当前控件做响应的平移
recognizer.view.transform = CGAffineTransformTranslate(recognizer.view.transform, translation.x, translation.y);
// 3. 每次平移手势识别完毕后, 让平移的值不要累加
[recognizer setTranslation:CGPointZero inView:recognizer.view];
}

6：UIPinchGestureRecognizer（捏合手势，缩放用）

NS_CLASS_AVAILABLE_IOS(3_2) @interface UIPinchGestureRecognizer : UIGestureRecognizer 

//设置缩放比例
@property (nonatomic)          CGFloat scale;     
//获取捏合速度，单位：缩放比/秒         
@property (nonatomic,readonly) CGFloat velocity;            

@end

知识点1：实例代码

UIPinchGestureRecognizer *pinch = [[UIPinchGestureRecognizer alloc] initWithTarget:self action:@selector(pinchAction:)];
pinch.delegate = self;
[self.imgView addGestureRecognizer:pinch];



// 捏合手势监听方法
- (void)pinchAction:(UIPinchGestureRecognizer *)recognizer {
recognizer.view.transform = CGAffineTransformScale(recognizer.view.transform, recognizer.scale, recognizer.scale);
recognizer.scale = 1.0;
}