监听触摸事件 - 手势识别器(UIGestureRecogniz

• 为了完成手势识别，必须借助于手势识别器----UIGestureRecognizer
• 利用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

UITapGestureRecognizer       //敲击
UIPinchGestureRecognizer     //捏合，用于缩放
UIPanGestureRecognizer       //拖拽
UISwipeGestureRecognizer     //轻扫
UIRotationGestureRecognizer  //旋转
UILongPressGestureRecognizer //长按

• UITapGestureRecognizer
• 每一个手势识别器的用法都差不多，比如UITapGestureRecognizer的使用步骤如下

//创建手势识别器对象
UITapGestureRecognizer *tap = [[UITapGestureRecognizeralloc]init];
//设置手势识别器对象的具体属性
tap.numberOfTapsRequired = 2;        //连续敲击2次
tap.numberOfTouchesRequired = 2;     //需要2根手指一起敲击
//添加手势识别器到对应的view上
[self.iconViewaddGestureRecognizer:tap];
//监听手势的触发
[tapaddTarget:selfaction:@selector(tapIconView:)];

• 手势识别的状态

typedef NS_ENUM(NSInteger, UIGestureRecognizerState) {
    UIGestureRecognizerStatePossible,   //没有触摸事件发生，所有手势识别的默认状态
    UIGestureRecognizerStateBegan,      //一个手势已经开始但尚未改变或者完成时
    UIGestureRecognizerStateChanged,    //手势状态改变
    UIGestureRecognizerStateEnded,      //手势完成
    UIGestureRecognizerStateCancelled,  //手势取消，恢复至Possible状态
    UIGestureRecognizerStateFailed,     //手势失败，恢复至Possible状态
                                        //识别到手势识别
    UIGestureRecognizerStateRecognized = UIGestureRecognizerStateEnded     
};

• 手势识别状态变化示意图