typedef NS_ENUM(NSInteger, UIGestureRecognizerState) {
    UIGestureRecognizerStatePossible,   // 默认的状态，这个时候的手势并没有具体的情形状态
    UIGestureRecognizerStateBegan,      // 手势开始被识别的状态
    UIGestureRecognizerStateChanged,    // 手势识别发生改变的状态
    UIGestureRecognizerStateEnded,      // 手势识别结束，将会执行触发的方法
    UIGestureRecognizerStateCancelled,  // 手势识别取消
    UIGestureRecognizerStateFailed,     // 识别失败，方法将不会被调用
    UIGestureRecognizerStateRecognized = UIGestureRecognizerStateEnded 
};