• 為了完成手勢識別，必須借助于手勢識別器----UIGestureRecognizer
• 利用UIGestureRecognizer，能輕松識別用戶在某個view上面做的一些常見手勢
• UIGestureRecognizer是一個抽象類，定義了所有手勢的基本行為，使用它的子類才能處理具體的手勢

UITapGestureRecognizer       //敲擊
UIPinchGestureRecognizer     //捏合，用于縮放
UIPanGestureRecognizer       //拖拽
UISwipeGestureRecognizer     //輕掃
UIRotationGestureRecognizer  //旋轉(zhuǎn)
UILongPressGestureRecognizer //長按

• UITapGestureRecognizer
• 每一個手勢識別器的用法都差不多，比如UITapGestureRecognizer的使用步驟如下

//創(chuàng)建手勢識別器對象
UITapGestureRecognizer *tap = [[UITapGestureRecognizeralloc]init];
//設(shè)置手勢識別器對象的具體屬性
tap.numberOfTapsRequired = 2;        //連續(xù)敲擊2次
tap.numberOfTouchesRequired = 2;     //需要2根手指一起敲擊
//添加手勢識別器到對應(yīng)的view上
[self.iconViewaddGestureRecognizer:tap];
//監(jiān)聽手勢的觸發(fā)
[tapaddTarget:selfaction:@selector(tapIconView:)];

• 手勢識別的狀態(tài)

typedef NS_ENUM(NSInteger, UIGestureRecognizerState) {
    UIGestureRecognizerStatePossible,   //沒有觸摸事件發(fā)生，所有手勢識別的默認(rèn)狀態(tài)
    UIGestureRecognizerStateBegan,      //一個手勢已經(jīng)開始但尚未改變或者完成時
    UIGestureRecognizerStateChanged,    //手勢狀態(tài)改變
    UIGestureRecognizerStateEnded,      //手勢完成
    UIGestureRecognizerStateCancelled,  //手勢取消，恢復(fù)至Possible狀態(tài)
    UIGestureRecognizerStateFailed,     //手勢失敗，恢復(fù)至Possible狀態(tài)
                                        //識別到手勢識別
    UIGestureRecognizerStateRecognized = UIGestureRecognizerStateEnded     
};

• 手勢識別狀態(tài)變化示意圖