手勢識別在iOS上非常重要,手勢操作移動設(shè)備的重要特征,極大的增加了移動設(shè)備使用便捷性。
1、UIGestureRecognizer介紹
手勢識別在iOS上非常重要，手勢操作移動設(shè)備的重要特征，極大的增加了移動設(shè)備使用便捷性。
iOS系統(tǒng)在3.2以后，為方便開發(fā)這使用一些常用的手勢，提供了UIGestureRecognizer類。手勢識別UIGestureRecognizer類是個抽象類，下面的子類是具體的手勢，開發(fā)這可以直接使用這些手勢識別。
上面的手勢對應(yīng)的操作是：
UIGestureRecognizer的繼承關(guān)系如下：
2、使用手勢的步驟
使用手勢很簡單，分為兩步：
創(chuàng)建手勢實(shí)例。當(dāng)創(chuàng)建手勢時，指定一個回調(diào)方法，當(dāng)手勢開始，改變、或結(jié)束時，回調(diào)方法被調(diào)用。
添加到需要識別的View中。每個手勢只對應(yīng)一個View，當(dāng)屏幕觸摸在View的邊界內(nèi)時，如果手勢和預(yù)定的一樣，那就會回調(diào)方法。
ps：一個手勢只能對應(yīng)一個View，但是一個View可以有多個手勢。
建議在真機(jī)上運(yùn)行這些手勢,模擬器操作不太方便，可能導(dǎo)致你認(rèn)為手勢失效。
3、Pan 拖動手勢：
UIImageView *snakeImageView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"snake.png"]]; snakeImageView.frame = CGRectMake(50, 50, 100, 160); UIPanGestureRecognizer *panGestureRecognizer = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(handlePan:)]; [snakeImageView addGestureRecognizer:panGestureRecognizer]; [self.view setBackgroundColor:[UIColor whiteColor]]; [self.view addSubview:snakeImageView];
新建一個ImageView，然后添加手勢
回調(diào)方法：
- (void) handlePan:(UIPanGestureRecognizer*) recognizer { CGPoint translation = [recognizer translationInView:self.view]; recognizer.view.center = CGPointMake(recognizer.view.center.x + translation.x, recognizer.view.center.y + translation.y); [recognizer setTranslation:CGPointZero inView:self.view]; } 4、Pinch縮放手勢
UIPinchGestureRecognizer *pinchGestureRecognizer = [[UIPinchGestureRecognizer alloc] initWithTarget:self action:@selector(handlePinch:)];<p class="p1">[<span class="s1">snakeImageView</span> <span class="s2">addGestureRecognizer</span>:pinchGestureRecognizer];</p>
- (void) handlePinch:(UIPinchGestureRecognizer*) recognizer { recognizer.view.transform = CGAffineTransformScale(recognizer.view.transform, recognizer.scale, recognizer.scale); recognizer.scale = 1; } 5、Rotation旋轉(zhuǎn)手勢
UIRotationGestureRecognizer *rotateRecognizer = [[UIRotationGestureRecognizer alloc] initWithTarget:self action:@selector(handleRotate:)]; [snakeImageView addGestureRecognizer:rotateRecognizer];
- (void) handleRotate:(UIRotationGestureRecognizer*) recognizer { recognizer.view.transform = CGAffineTransformRotate(recognizer.view.transform, recognizer.rotation); recognizer.rotation = 0; } 
添加了這幾個手勢后，運(yùn)行看效果，程序中的imageView放了一個
/^//^/
_|__| O|
// /~ /_/ /
/____|__________/ /
/_______ /
`/ / /
| | /
/ / /
/ / //
/ / / /
/ / / /
/ / _----_ / /
/ / _-~ ~-_ | |
( ( _-~ _--_ ~-_ _/ |
/ ~-____-~ _-~ ~-_ ~-_-~ /
~-_ _-~ ~-_ _-~
~--______-~ ~-___-~
的圖片，在模擬器上拖動是沒問題的。縮放和旋轉(zhuǎn)有點(diǎn)問題，估計(jì)是因?yàn)樵谀M器上的模擬的兩個接觸點(diǎn)距離在imageView的邊界外了，所以操作無效果。
建議在真機(jī)上運(yùn)行這個手勢。
在模擬器上縮放和選擇的操作技巧：
可以把imageView的frame值設(shè)置大一點(diǎn)，按住alt鍵，按下觸摸板(不按下不行)，這樣就可以旋轉(zhuǎn)和縮放了。
6、添加第二個ImagView并添加手勢
記住：一個手勢只能添加到一個View，兩個View當(dāng)然要有兩個手勢的實(shí)例了
- (void)viewDidLoad { [super viewDidLoad]; UIImageView *snakeImageView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"snake.png"]]; UIImageView *dragonImageView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"dragon.png"]]; snakeImageView.frame = CGRectMake(120, 120, 100, 160); dragonImageView.frame = CGRectMake(50, 50, 100, 160); [self.view addSubview:snakeImageView]; [self.view addSubview:dragonImageView]; for (UIView *view in self.view.subviews) { UIPanGestureRecognizer *panGestureRecognizer = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(handlePan:)]; UIPinchGestureRecognizer *pinchGestureRecognizer = [[UIPinchGestureRecognizer alloc] initWithTarget:self action:@selector(handlePinch:)]; UIRotationGestureRecognizer *rotateRecognizer = [[UIRotationGestureRecognizer alloc] initWithTarget:self action:@selector(handleRotate:)]; [view addGestureRecognizer:panGestureRecognizer]; [view addGestureRecognizer:pinchGestureRecognizer]; [view addGestureRecognizer:rotateRecognizer]; [view setUserInteractionEnabled:YES]; } [self.view setBackgroundColor:[UIColor whiteColor]]; } 多添加了一條龍的view，兩個view都能接收上面的三種手勢。運(yùn)行效果如下：
7、拖動(pan手勢)速度(以較快的速度拖放后view有滑行的效果)
如何實(shí)現(xiàn)呢？
- (void) handlePan:(UIPanGestureRecognizer*) recognizer { CGPoint translation = [recognizer translationInView:self.view]; recognizer.view.center = CGPointMake(recognizer.view.center.x + translation.x, recognizer.view.center.y + translation.y); [recognizer setTranslation:CGPointZero inView:self.view]; if (recognizer.state == UIGestureRecognizerStateEnded) { CGPoint velocity = [recognizer velocityInView:self.view]; CGFloat magnitude = sqrtf((velocity.x * velocity.x) + (velocity.y * velocity.y)); CGFloat slideMult = magnitude / 200; NSLog(@"magnitude: %f, slideMult: %f", magnitude, slideMult); float slideFactor = 0.1 * slideMult; // Increase for more of a slide CGPoint finalPoint = CGPointMake(recognizer.view.center.x + (velocity.x * slideFactor), recognizer.view.center.y + (velocity.y * slideFactor)); finalPoint.x = MIN(MAX(finalPoint.x, 0), self.view.bounds.size.width); finalPoint.y = MIN(MAX(finalPoint.y, 0), self.view.bounds.size.height); [UIView animateWithDuration:slideFactor*2 delay:0 options:UIViewAnimationOptionCurveEaseOut animations:^{ recognizer.view.center = finalPoint; } completion:nil]; } 代碼實(shí)現(xiàn)解析：
運(yùn)行后，快速拖動圖像view放開會看到view還會在原來的方向滑行一段路。
8、同時觸發(fā)兩個view的手勢
手勢之間是互斥的，如果你想同時觸發(fā)蛇和龍的view，那么需要實(shí)現(xiàn)協(xié)議
UIGestureRecognizerDelegate，
@interface ViewController : UIViewController<UIGestureRecognizerDelegate> @end
并在協(xié)議這個方法里返回YES。
-(BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer { return YES; } 把self作為代理設(shè)置給手勢：
panGestureRecognizer.delegate = self; pinchGestureRecognizer.delegate = self; rotateRecognizer.delegate = self;
這樣可以同時拖動或旋轉(zhuǎn)縮放兩個view了。
9、tap點(diǎn)擊手勢
這里為了方便看到tap的效果，當(dāng)點(diǎn)擊一下屏幕時，播放一個聲音。
為了播放聲音，我們加入AVFoundation.framework這個框架。
- (AVAudioPlayer *)loadWav:(NSString *)filename { NSURL * url = [[NSBundle mainBundle] URLForResource:filename withExtension:@"wav"]; NSError * error; AVAudioPlayer * player = [[AVAudioPlayer alloc] initWithContentsOfURL:url error:&error]; if (!player) { NSLog(@"Error loading %@: %@", url, error.localizedDescription); } else { [player prepareToPlay]; } return player; } 我會在最后例子代碼給出完整代碼，添加手勢的步驟和前面一樣的。
#import <UIKit/UIKit.h> #import <AVFoundation/AVFoundation.h> @interface ViewController : UIViewController<UIGestureRecognizerDelegate> @property (strong) AVAudioPlayer * chompPlayer; @property (strong) AVAudioPlayer * hehePlayer; @end - (void)handleTap:(UITapGestureRecognizer *)recognizer { [self.chompPlayer play]; } 運(yùn)行，點(diǎn)一下某個圖，就會播放一個咬東西的聲音。
不過這個點(diǎn)擊播放聲音有點(diǎn)缺陷，就是在慢慢拖動的時候也會播放。這使得兩個手勢重合了。怎么解決呢？使用手勢的：
requireGestureRecognizerToFail方法。
10、手勢的依賴性
在viewDidLoad的循環(huán)里添加這段代碼：
[tapRecognizer requireGestureRecognizerToFail:panGestureRecognizer];
意思就是，當(dāng)如果pan手勢失敗，就是沒發(fā)生拖動，才會出發(fā)tap手勢。這樣如果你有輕微的拖動，那就是pan手勢發(fā)生了。tap的聲音就不會發(fā)出來了。
11、自定義手勢
自定義手勢繼承：UIGestureRecognizer，實(shí)現(xiàn)下面的方法：
– touchesBegan:withEvent: – touchesMoved:withEvent: – touchesEnded:withEvent: - touchesCancelled:withEvent:
新建一個類，繼承UIGestureRecognizer，代碼如下：
.h文件
#import <UIKit/UIKit.h> typedef enum { DirectionUnknown = 0, DirectionLeft, DirectionRight } Direction; @interface HappyGestureRecognizer : UIGestureRecognizer @property (assign) int tickleCount; @property (assign) CGPoint curTickleStart; @property (assign) Direction lastDirection; @end .m文件
#import "HappyGestureRecognizer.h" #import <UIKit/UIGestureRecognizerSubclass.h> #define REQUIRED_TICKLES 2 #define MOVE_AMT_PER_TICKLE 25 @implementation HappyGestureRecognizer - (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event { UITouch * touch = [touches anyObject]; self.curTickleStart = [touch locationInView:self.view]; } - (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event { // Make sure we've moved a minimum amount since curTickleStart UITouch * touch = [touches anyObject]; CGPoint ticklePoint = [touch locationInView:self.view]; CGFloat moveAmt = ticklePoint.x - self.curTickleStart.x; Direction curDirection; if (moveAmt < 0) { curDirection = DirectionLeft; } else { curDirection = DirectionRight; } if (ABS(moveAmt) < MOVE_AMT_PER_TICKLE) return; // 確認(rèn)方向改變了 if (self.lastDirection == DirectionUnknown || (self.lastDirection == DirectionLeft && curDirection == DirectionRight) || (self.lastDirection == DirectionRight && curDirection == DirectionLeft)) { // 撓癢次數(shù) self.tickleCount++; self.curTickleStart = ticklePoint; self.lastDirection = curDirection; // 一旦撓癢次數(shù)超過指定數(shù)，設(shè)置手勢為結(jié)束狀態(tài) // 這樣回調(diào)函數(shù)會被調(diào)用。 if (self.state == UIGestureRecognizerStatePossible && self.tickleCount > REQUIRED_TICKLES) { [self setState:UIGestureRecognizerStateEnded]; } } } - (void)reset { self.tickleCount = 0; self.curTickleStart = CGPointZero; self.lastDirection = DirectionUnknown; if (self.state == UIGestureRecognizerStatePossible) { [self setState:UIGestureRecognizerStateFailed]; } } - (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event { [self reset]; } - (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event { [self reset]; } @end 調(diào)用自定義手勢和上面一樣，回到這樣寫：
- (void)handleHappy:(HappyGestureRecognizer *)recognizer{ [self.hehePlayer play]; } 手勢成功后播放呵呵笑的聲音。
在真機(jī)上運(yùn)行，按住某個view，快速左右拖動，就會發(fā)出笑的聲音了。
代碼解析：
先獲取起始坐標(biāo)：curTickleStart
通過和ticklePoint的x值對比，得出當(dāng)前的放下是向左還是向右。再算出移動的x的值是否比MOVE_AMT_PER_TICKLE距離大，如果太則返回。
再判斷是否有三次是不同方向的動作，如果是則手勢結(jié)束，回調(diào)。
源代碼：源代碼下載。
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