1、UIGestureRecognizer介紹
手勢識別在iOS上非常重要，手勢操作移動裝置的重要特徵，極大的增加了移動裝置使用便捷性。
iOS系統在3.2以後，為方便開發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，開發這可以直接使用這些手勢識別。
- UITapGestureRecognizer
- UIPinchGestureRecognizer
- UIRotationGestureRecognizer
- UISwipeGestureRecognizer
- UIPanGestureRecognizer
- UILongPressGestureRecognizer
上面的手勢對應的操作是：
- Tap（點一下）
- Pinch（二指往內或往外撥動，平時經常用到的縮放）
- Rotation（旋轉）
- Swipe（滑動，快速移動）
- Pan （拖移，慢速移動）
- LongPress（長按）
UIGestureRecognizer的繼承關係如下：
2、使用手勢的步驟
使用手勢很簡單，分為兩步：
- 建立手勢例項。當建立手勢時，指定一個回撥方法，當手勢開始，改變、或結束時，回撥方法被呼叫。
- 新增到需要識別的View中。每個手勢只對應一個View，當螢幕觸控在View的邊界內時，如果手勢和預定的一樣，那就會回撥方法。
ps：一個手勢只能對應一個View，但是一個View可以有多個手勢。
建議在真機上執行這些手勢,模擬器操作不太方便，可能導致你認為手勢失效。
3、Pan 拖動手勢：
|
1 2 3 4 5 6 7 8 |
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，然後新增手勢
回撥方法：
|
1 2 3 4 5 6 7 8 |
- (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
|
1 2 3 |
UIPinchGestureRecognizer *pinchGestureRecognizer = [[UIPinchGestureRecognizer alloc] initWithTarget:self action:@selector(handlePinch:)];<p class="p1">[<span class="s1">snakeImageView</span> <span class="s2">addGestureRecognizer</span>:pinchGestureRecognizer];</p> |
|
1 2 3 4 5 |
- (void) handlePinch:(UIPinchGestureRecognizer*) recognizer { recognizer.view.transform = CGAffineTransformScale(recognizer.view.transform, recognizer.scale, recognizer.scale); recognizer.scale = 1; } |
5、Rotation旋轉手勢
|
1 2 3 4 |
UIRotationGestureRecognizer *rotateRecognizer = [[UIRotationGestureRecognizer alloc] initWithTarget:self action:@selector(handleRotate:)]; [snakeImageView addGestureRecognizer:rotateRecognizer]; |
|
1 2 3 4 5 |
- (void) handleRotate:(UIRotationGestureRecognizer*) recognizer { recognizer.view.transform = CGAffineTransformRotate(recognizer.view.transform, recognizer.rotation); recognizer.rotation = 0; } |
新增了這幾個手勢後，執行看效果，程式中的imageView放了一個
/^\/^\
_|__| O|
\/ /~ \_/ \
\____|__________/ \
\_______ \
`\ \ \
| | \
/ / \
/ / \\
/ / \ \
/ / \ \
/ / _—-_ \ \
/ / _-~ ~-_ | |
( ( _-~ _–_ ~-_ _/ |
\ ~-____-~ _-~ ~-_ ~-_-~ /
~-_ _-~ ~-_ _-~
~–______-~ ~-___-~
的圖片，在模擬器上拖動是沒問題的。縮放和旋轉有點問題，估計是因為在模擬器上的模擬的兩個接觸點距離在imageView的邊界外了，所以操作無效果。
建議在真機上執行這個手勢。
在模擬器上縮放和選擇的操作技巧：
可以把imageView的frame值設定大一點，按住alt鍵，按下觸控板(不按下不行)，這樣就可以旋轉和縮放了。
6、新增第二個ImagView並新增手勢
記住：一個手勢只能新增到一個View，兩個View當然要有兩個手勢的例項了
|
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 |
- (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]]; } |
多新增了一條龍的view，兩個view都能接收上面的三種手勢。執行效果如下：
7、拖動(pan手勢)速度(以較快的速度拖放後view有滑行的效果)
如何實現呢？
- 監視手勢是否結束
- 監視觸控的速度
|
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 |
- (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]; } |
程式碼實現解析：
- 計算速度向量的長度（估計大部分都忘了）這些知識了。
- 如果速度向量小於200，那就會得到一個小於的小數，那麼滑行會很短
- 基於速度和速度因素計算一個終點
- 確保終點不會跑出父View的邊界
- 使用UIView動畫使view滑動到終點
執行後，快速拖動影像view放開會看到view還會在原來的方向滑行一段路。
8、同時觸發兩個view的手勢
手勢之間是互斥的，如果你想同時觸發蛇和龍的view，那麼需要實現協議UIGestureRecognizerDelegate，
|
1 2 |
@interface ViewController : UIViewController<UIGestureRecognizerDelegate> @end |
並在協議這個方法裡返回YES。
|
1 2 3 4 |
-(BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer { return YES; } |
把self作為代理設定給手勢：
|
1 2 3 |
panGestureRecognizer.delegate = self; pinchGestureRecognizer.delegate = self; rotateRecognizer.delegate = self; |
這樣可以同時拖動或旋轉縮放兩個view了。
9、tap點選手勢
這裡為了方便看到tap的效果，當點選一下螢幕時，播放一個聲音。
為了播放聲音，我們加入AVFoundation.framework這個框架。
|
1 2 3 4 5 6 7 8 9 10 11 |
- (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; } |
我會在最後例子程式碼給出完整程式碼，新增手勢的步驟和前面一樣的。
|
1 2 3 4 5 6 7 8 |
#import <UIKit/UIKit.h> #import <AVFoundation/AVFoundation.h> @interface ViewController : UIViewController<UIGestureRecognizerDelegate> @property (strong) AVAudioPlayer * chompPlayer; @property (strong) AVAudioPlayer * hehePlayer; @end |
|
1 2 3 |
- (void)handleTap:(UITapGestureRecognizer *)recognizer { [self.chompPlayer play]; } |
執行，點一下某個圖，就會播放一個咬東西的聲音。
不過這個點選播放聲音有點缺陷，就是在慢慢拖動的時候也會播放。這使得兩個手勢重合了。怎麼解決呢？使用手勢的：requireGestureRecognizerToFail方法。
10、手勢的依賴性
在viewDidLoad的迴圈裡新增這段程式碼：
|
1 |
[tapRecognizer requireGestureRecognizerToFail:panGestureRecognizer]; |
意思就是，當如果pan手勢失敗，就是沒發生拖動，才會出發tap手勢。這樣如果你有輕微的拖動，那就是pan手勢發生了。tap的聲音就不會發出來了。
11、自定義手勢
自定義手勢繼承：UIGestureRecognizer，實現下面的方法：
|
1 2 3 4 |
– touchesBegan:withEvent: – touchesMoved:withEvent: – touchesEnded:withEvent: - touchesCancelled:withEvent: |
新建一個類，繼承UIGestureRecognizer，程式碼如下：
.h檔案
|
1 2 3 4 5 6 7 8 9 10 11 12 13 |
#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檔案
|
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 |
#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; // 確認方向改變了 if (self.lastDirection == DirectionUnknown || (self.lastDirection == DirectionLeft && curDirection == DirectionRight) || (self.lastDirection == DirectionRight && curDirection == DirectionLeft)) { // 撓癢次數 self.tickleCount++; self.curTickleStart = ticklePoint; self.lastDirection = curDirection; // 一旦撓癢次數超過指定數，設定手勢為結束狀態 // 這樣回撥函式會被呼叫。 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 |
呼叫自定義手勢和上面一樣，回到這樣寫：
|
1 2 3 |
- (void)handleHappy:(HappyGestureRecognizer *)recognizer{ [self.hehePlayer play]; } |
手勢成功後播放呵呵笑的聲音。
在真機上執行，按住某個view，快速左右拖動，就會發出笑的聲音了。
程式碼解析：
先獲取起始座標：curTickleStart
通過和ticklePoint的x值對比，得出當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，如果是則手勢結束，回撥。
參考：http://www.raywenderlich.com/6567/uigesturerecognizer-tutorial-in-ios-5-pinches-pans-and-more