11.UIGestureRecognizer

為沒有繼承UIControl的視圖對象添加響應(yīng)事件

1.1 UIGestureRecognizer類包含UIResponder類中的以下方法：

- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event;
- (void)touchesMoved:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event;
- (void)touchesEnded:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event;
- (void)touchesCancelled:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event;

1.2 手勢狀態(tài)

typedef NS_ENUM(NSInteger, UIGestureRecognizerState) {
    //未知狀態(tài)
    UIGestureRecognizerStatePossible,   // the recognizer has not yet recognized its gesture, but may be evaluating touch events. this is the default state
    //首次識別狀態(tài)，對于連續(xù)手勢永高，例如長按佑吝，有這種狀態(tài)
    UIGestureRecognizerStateBegan,      // the recognizer has received touches recognized as the gesture. the action method will be called at the next turn of the run loop
    //再次識別，當(dāng)手連續(xù)手勢識別之后，再次受到touch事件
    UIGestureRecognizerStateChanged,    // the recognizer has received touches recognized as a change to the gesture. the action method will be called at the next turn of the run loop
    //識別完成，受到touchend 消息之后
    UIGestureRecognizerStateEnded,      // the recognizer has received touches recognized as the end of the gesture. the action method will be called at the next turn of the run loop and the recognizer will be reset to UIGestureRecognizerStatePossible
    //取消識別
    UIGestureRecognizerStateCancelled,  // the recognizer has received touches resulting in the cancellation of the gesture. the action method will be called at the next turn of the run loop. the recognizer will be reset to UIGestureRecognizerStatePossible
    //識別失敗
    UIGestureRecognizerStateFailed,     // the recognizer has received a touch sequence that can not be recognized as the gesture. the action method will not be called and the recognizer will be reset to UIGestureRecognizerStatePossible
    // Discrete Gestures – gesture recognizers that recognize a discrete event but do not report changes (for example, a tap) do not transition through the Began and Changed states and can not fail or be cancelled
    //識別狀態(tài)，與識別結(jié)束一個意思
    UIGestureRecognizerStateRecognized = UIGestureRecognizerStateEnded // the recognizer has received touches recognized as the gesture. the action method will be called at the next turn of the run loop and the recognizer will be reset to UIGestureRecognizerStatePossible
};

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結(jié)合圖我們來看手勢的整個遷移過程壁拉，先明確幾個信息

1）手勢的狀態(tài)遷移，前提是收到Touch message柏靶，才能做狀態(tài)變化處理代碼弃理。
2）手勢分為連續(xù)狀態(tài)手勢、不連續(xù)狀態(tài)手勢宿礁。連續(xù)手勢有長按案铺，慢滑等。不連續(xù)手勢有單擊梆靖，雙擊等等。
3）當(dāng)用戶沒有點擊屏幕笔诵，所有手勢都處于Possiable初始狀態(tài)返吻。
當(dāng)用戶點擊屏幕，手勢會收到Touch Began Message乎婿，手勢的touchBegan方法會被調(diào)用测僵，手勢開始記錄點擊位置和時間，仍處于 Possiable狀態(tài)谢翎。

如果用戶按住不放捍靠，間隔超過一定時間，單擊手勢會變化為Failed狀態(tài)森逮，并在下個一runloop變?yōu)閜ossiable榨婆。

如果時間大于長按手勢設(shè)定時間，長按手勢就會變化為Began狀態(tài)褒侧，當(dāng)用戶移動手指良风，長按手勢的touch move方法被調(diào)用，長按手勢將自己狀態(tài)設(shè)置為Changed狀態(tài)闷供，并且也會回調(diào)處理方法烟央。最后手指離開，系統(tǒng)調(diào)用長按手勢touchEnd方法歪脏，手勢狀態(tài)設(shè)置為 Recognized狀態(tài)疑俭。

1.3 混合手勢處理

1）當(dāng)給UIView添加多個UIGestureRecognizer對象時，默認只有1個生效婿失。如果想全部都生效钞艇，讓協(xié)議中的gestureRecognizer:shouldRecognizeSimultaneouslyWithGestureRecognizer:方法返回YES啄寡。

2）同時添加單擊和雙擊，也均允許生效香璃。問題來了这难，那雙擊屏幕時，默認觸發(fā)1次單擊事件和1次雙擊事件葡秒。但這不是想要的效果姻乓，如何實現(xiàn)雙擊時，只觸發(fā)雙擊手勢呢眯牧，單擊時只觸發(fā)單擊手勢呢蹋岩？解決方案是讓協(xié)議中的gestureRecognizer:shouldRequireFailureOfGestureRecognizer:方法、

gestureRecognizer:shouldBeRequiredToFailByGestureRecognizer:方法都返回YES学少。

1.4 UIGestureRecognizerDelegate協(xié)議

@protocol UIGestureRecognizerDelegate <NSObject>
@optional

// 手勢狀態(tài)是否允許更改剪个，默認為YES。
// 如果實現(xiàn)中返回NO,那么手勢最后都為失敗狀態(tài)版确。
    - (BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer *)gestureRecognizer;

// 允許多個手勢生效扣囊，默認為NO。
// 如果實現(xiàn)中返回YES绒疗，同時添加單擊和雙擊手勢侵歇，雙擊屏幕時，同時產(chǎn)生1次單擊事件和1次雙擊事件
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer;

// 以下2個方法吓蘑，為手勢之間添加依賴惕虑，默認NO。
// 比如單擊和雙擊磨镶，如果雙擊手勢識別失敗溃蔫，轉(zhuǎn)換為識別單擊手勢
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRequireFailureOfGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer NS_AVAILABLE_IOS(7_0);
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldBeRequiredToFailByGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer NS_AVAILABLE_IOS(7_0);

// 手勢是否關(guān)注UITouch、UIPress對象狀態(tài)變化琳猫，和gestureRecognizerShouldBegin:效果類似伟叛，默認為YES。
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldReceiveTouch:(UITouch *)touch;
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldReceivePress:(UIPress *)press;

@end

1.5 蘋果封裝以下幾個手勢

（1）UITapGestureRecognizer

單個或多個塞子沸移。指定數(shù)量的手指必須要承認的姿態(tài)痪伦，挖掘查看指定的次數(shù)。

（2）UIPinchGestureRecognizer

看起來捏的手勢雹锣，涉及兩個接觸网沾。當(dāng)用戶將兩個手指，向?qū)Ψ降膫鹘y(tǒng)意義是縮小;當(dāng)用戶將兩個手指從彼此遠離蕊爵，傳統(tǒng)意義變焦辉哥。

（3）UIRotationGestureRecognizer

看起來輪換涉及兩個觸摸手勢。當(dāng)用戶移動手指對面對方的圓周運動，基本的觀點應(yīng)該在相應(yīng)的方向和速度旋轉(zhuǎn)醋旦。

（4）UISwipeGestureRecognizer

看起來刷卡在一個或多個方向的手勢恒水。抨擊是一個獨立的姿態(tài)，因此饲齐，相關(guān)的操作的消息發(fā)送每個手勢只有一次钉凌。

（5）UIPanGestureRecognizer

看起來平移（拖動）的手勢。用戶必須按查看上一個或更多的手指捂人，而他們平移御雕。實施這個手勢識別動作方法的客戶端可以要求它目前的翻譯和手勢的速度。

（6）UILongPressGestureRecognizer

看起來長按手勢滥搭。用戶必須按下一個或更多的手指行動訊息傳送至少指定期限酸纲。此外，手指可能要承認的姿態(tài)移動唯一指定的距離;如果他們超越這個限制的姿態(tài)失敗瑟匆。