1. UIGestureRecognizer

1. 父类是NSObject

• 利用手势识别器---UIGestureRecognizer，能轻松识别用户在某个view上面做的一些常见手势
• 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，详见其子类介绍
• 一个手势只能支持一个方向
• 默认只支持一个手势，若要实现多个手势，需要设置手势代理，遵守<UIGestureRecognizerDelegate>，并实现shouldRecognizeSimultaneouslyWithGestureRecognizer，返回YES。

2. 手势识别的状态

3. UIGestureRecognizer属性

// 手势状态
@property(nonatomic,readonly) UIGestureRecognizerState state;

//手势代理
@property(nullable,nonatomic,weak) id <UIGestureRecognizerDelegate> delegate;

// 手势是否可用（默认可用）
// 当前在识别手势时不能修改手势是否可用
@property(nonatomic, getter=isEnabled) BOOL enabled;


// 手势的视图
@property(nullable, nonatomic,readonly) UIView *view;


@property(nonatomic) BOOL cancelsTouchesInView;
@property(nonatomic) BOOL delaysTouchesBegan;
@property(nonatomic) BOOL delaysTouchesEnded;


@property(nonatomic, copy) NSArray<NSNumber *> *allowedTouchTypes
@property(nonatomic, copy) NSArray<NSNumber *> *allowedPressTypes

4. UIGestureRecognizer方法

// 初始化手势，直接用initWithTarget就好，另外两个忽略
//     -(void)handleGesture;
//     -(void)handleGesture:(UIGestureRecognizer*)gestureRecognizer;
- (instancetype)initWithTarget:(nullable id)target action:(nullable SEL)action

// 增加监听和移除监听
- (void)addTarget:(id)target action:(SEL)action;
- (void)removeTarget:(nullable id)target action:(nullable SEL)action; //target为nil，则移除所有相同方法名的方法


// 获取touch的位置
- (CGPoint)locationInView:(nullable UIView*)view;

// 获取locations中的touches的数量
- (NSUInteger)numberOfTouches;


// 获取特定角标的touch的位置
- (CGPoint)locationOfTouch:(NSUInteger)touchIndex inView:(nullable UIView*)view;


- (void)requireGestureRecognizerToFail:(UIGestureRecognizer *)otherGestureRecognizer;
@end

5. UIGestureRecognizer的代理--UIGestureRecognizerDelegate

// 是否允许触发当前手势
- (BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer *)gestureRecognizer;


// Simultaneously:同时  sɪml'teɪnɪəslɪ
// 是否允许同时支持多个手势
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer;

// 是否接收触摸手势
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldReceiveTouch:(UITouch *)touch;

// 是否接收按压手势
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldReceivePress:(UIPress *)press;

- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRequireFailureOfGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer NS_AVAILABLE_IOS(7_0);
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldBeRequiredToFailByGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer NS_AVAILABLE_IOS(7_0);

@end

6. UIGestureRecognizer的子类

6.1. 点按手势

6.2. 捏合手势——用于缩放

6.3. 拖动手势

6.4. 轻扫手势

6.5. 旋转手势

6.6. 长按手势