前言
在iOS中，你可以使用系統(tǒng)內(nèi)置的手勢識別(GestureRecognizer)，也可以創(chuàng)建自己的手勢.GestureRecognizer將低級別的轉(zhuǎn)換為高級別的執(zhí)行行為，是你綁定到view的對象，當(dāng)發(fā)生手勢，綁定到的view對象會響應(yīng)，它確定這個動作是否對應(yīng)一個特定的手勢(swipe，pinch，pan,rotation).如果它能識別這個手勢，那么就會向綁定它的view發(fā)送消息，如下圖
UIKit框架提供了一些預(yù)定義的GestureRecognizer.包含下列手勢
如果你想讓你的應(yīng)用程序來識別一個獨(dú)特的手勢,如選擇目錄或糾結(jié)的運(yùn)動,你可以創(chuàng)建自己的自定義GestureRecognizer，將在下篇介紹
將特定的手勢和view相關(guān)聯(lián)
每一個特定的手勢必須關(guān)聯(lián)到view對象中才會有作用，一個view對象可以關(guān)聯(lián)多個不同的特定手勢，但是每一個特定的手勢只能與一個view相關(guān)聯(lián)。當(dāng)用戶觸摸了view，這個GestureRecognizer就會接受到消息，它可以響應(yīng)特定的觸摸事件。
與特定view關(guān)聯(lián)
可以使用removeGestureRecognizer: 來移除手勢。
_panGestureRecognizer = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(handlerPanGesture:)]; _panGestureRecognizer.delegate = self; _panGestureRecognizer.maximumNumberOfTouches = 2; _panGestureRecognizer.minimumNumberOfTouches = 2; [self.view addGestureRecognizer:_panGestureRecognizer];- (void)handlerPanGesture:(UIPanGestureRecognizer *)recognizer{ if ((recognizer.state == UIGestureRecognizerStateBegan) || (recognizer.state == UIGestureRecognizerStateChanged)) { CGPoint offset = [recognizer translationInView:self.view]; CGRect frame = self.rightViewController.view.frame; frame.origin.x += offset.x; if (frame.origin.x >= 0 && frame.origin.x <= kScreenWidth) { self.rightViewController.view.frame = frame; } [recognizer setTranslation:CGPointZero inView:self.view]; } else if (recognizer.state == UIGestureRecognizerStateEnded) { BOOL isVisible = self.rightViewController.view.frame.origin.x < kScreenWidth / 2; [self showRightView:isVisible]; }} 手勢識別狀態(tài)
Gesture recognizers從一個狀態(tài)轉(zhuǎn)到另一狀態(tài)(state)。對于每個狀態(tài)，根據(jù)它們是否符合特定條件來決定時候可以移動到下一個狀態(tài)。它們分析多點(diǎn)觸摸。是否識別失敗。未能識別手勢意味著state 轉(zhuǎn)換失敗。UIGestureRecognizerStateFailed。詳見UIGestureRecognizerState枚舉
typedef NS_ENUM(NSInteger, UIGestureRecognizerState) { UIGestureRecognizerStatePossible, // the recognizer has not yet recognized its gesture, but may be evaluating touch events. this is the default state UIGestureRecognizerStateBegan, // the recognizer has received touches recognized as the gesture. the action method will be called at the next turn of the run loop 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 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 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 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 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};為view添加多個手勢
當(dāng)一個view添加多個手勢時，在缺省情況下，沒有為優(yōu)先執(zhí)行哪個手勢做排序，每次發(fā)生不同。不過你可以覆蓋默認(rèn)的行為（使用類方法、委托方法、和子類化覆蓋這些）
指定一個Gesture recognizers應(yīng)該在另一個前捕捉。
requireGestureRecognizerToFail: 這個方法就是在作為參數(shù)的Gesture recognizer失敗以后接受者才發(fā)生，否則從不會發(fā)生。
[self.panRecognizer requireGestureRecognizerToFail:self.swipeRecognizer];
允許2個手勢同時操作
gestureRecognizer:shouldRecognizeSimultaneouslyWithGestureRecognizer:
禁止在某一點(diǎn)發(fā)生Gesture recognizers
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldReceiveTouch:(UITouch *)touch{ if ([touch.view isKindOfClass:[UIControl class]]) { return NO; } return YES;}指定一個單向關(guān)系兩個手勢識別器
想控制兩個識別器相互作用，但你需要指定一個單向關(guān)系,您可以重寫或canPreventGestureRecognizer:或canBePreventedByGestureRecognizer:子類方法。return yes。例如,如果你想要一個旋轉(zhuǎn)的姿態(tài)來防止捏動作,但你不想夾手勢防止旋轉(zhuǎn)的姿態(tài)。例如，你想一個旋轉(zhuǎn)手勢阻止一個縮放手勢，但你不想一個縮放手勢阻止旋轉(zhuǎn)手勢，就加入下面代碼
[rotationGestureRecognizer canPreventGestureRecognizer:pinchGestureRecognizer];
以上就是本文的全部內(nèi)容，希望對大家的學(xué)習(xí)有所幫助，也希望大家多多支持VEVB武林網(wǎng)。
新聞熱點(diǎn)
疑難解答
圖片精選
