在 iPhone 或 iPad 的开发中，除了用 touchesBegan / touchesMoved / touchesEnded 这组方法来控制使用者的手指触控外，也可以用 UIGestureRecognizer 的衍生类別来进行判断。用 UIGestureRecognizer 的好处在于有现成的手势，开发者不用自己计算手指移动轨迹。UIGestureRecognizer的衍生类別有以下几种：
UITapGestureRecognizer
UIPinchGestureRecognizer
UIRotationGestureRecognizer
UISwipeGestureRecognizer
UIPanGestureRecognizer
UILongPressGestureRecognizer
从命名上不难了解這些类別所对应代表的手势，分別是 Tap（点一下）、Pinch（二指往內或往外拨动）、Rotation（旋转）、Swipe（滑动，快速移动）、Pan （拖移，慢速移动）以及 LongPress（长按）。這些手势別在使用上也很简单，只要在使用前定义并添加到对应的视图上即可。
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// 定义一个 recognizer, 并加到需要偵測该手势的 UIView 元件上
- (void)viewDidLoad {
UISwipeGestureRecognizer* recognizer;
// handleSwipeFrom 是偵測到手势，所要呼叫的方法
recognizer = [[UISwipeGestureRecognizer alloc] initWithTarget:selfaction:@selector(handleSwipeFrom)];
// 不同的 Recognizer 有不同的实体变数
// 例如 SwipeGesture 可以指定方向
// 而 TapGesture 則可以指定次數
recognizer.direction = UISwipeGestureRecognizerDirectionUp
[self.view addGestureRecognizer:recognizer];
[recognizer release];
}
- (void)handleSwipeFrom:(UISwipeGestureRecognizer*)recognizer {
// 触发手勢事件后，在这里作些事情
// 底下是刪除手势的方法
[self.view removeGestureRecognizer:recognizer];
}
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问题來了。有些手势其实是互相关联的，例如 Tap 与 LongPress、Swipe与 Pan，或是 Tap 一次与Tap 兩次。当一個 UIView 同时添加兩个相关联的手势时，到底我这一下手指头按的要算是 Tap 还是 LongPress？如果照預设作法来看，只要「先滿足条件」的就会跳出并呼叫对应方法，举例来说，如果同时注册了 Pan 和 Swipe，只要手指头一移动就会触发 Pan 然后跳出，因而永远都不會发生 Swipe；单点与双点的情形也是一样，永远都只会触发单点，不會有双点。
那么这个问题有解吗？答案是肯定的，UIGestureRecognizer 有个方法叫做requireGestureRecognizerToFail，他可以指定某一个 recognizer，即便自己已经滿足條件了，也不會立刻触发，会等到该指定的 recognizer 确定失败之后才触发。以同时支持单点与双点的手势为例，代码如下：
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- (void)viewDidLoad {
// 单击的 Recognizer
UITapGestureRecognizer* singleRecognizer;
singleRecognizer = [[UITapGestureRecognizer alloc] initWithTarget:selfaction:@selector(handleSingleTapFrom)];
singleTapRecognizer.numberOfTapsRequired = 1; // 单击
[self.view addGestureRecognizer:singleRecognizer];
// 双击的 Recognizer
UITapGestureRecognizer* double;
doubleRecognizer = [[UITapGestureRecognizer alloc] initWithTarget:selfaction:@selector(handleDoubleTapFrom)];
doubleTapRecognizer.numberOfTapsRequired = 2; // 双击
[self.view addGestureRecognizer:doubleRecognizer];
// 关键在这一行，如果双击确定偵測失败才會触发单击
[singleRecognizer requireGestureRecognizerToFail:doubleRecognizer];
[singleRecognizer release];
[doubleRecognizer release];
}
Demo
首先新建一个基于Sigle view Application的项目，名为GestureTest;我的项目结构如下：
往viewController.xib文件里拖动一个imageView,并使覆盖整个屏幕，改动属性为：
viewController.h文件：
1. #import <UIKit/UIKit.h>
2.
3. @interface ViewController : UIViewController{
4. IBOutlet UIImageView *imageView;
5. }
6. @property (nonatomic,retain)IBOutlet UIImageView *imageView;
7. @end
并使xib文件里的imageView与之连接；
然后是viewController.m文件的实现部分：
1. @synthesize imageView;
2.
3. CGFloat lastScaleFactor=1;//放大、缩小
4. CGFloat netRotation;//旋转
5. CGPoint netTranslation;//平衡
6. NSArray *images;//图片数组
7. int imageIndex=0;//数组下标
8.
9. - (void)viewDidLoad
10. {
11. //1、创建手势实例，并连接方法handleTapGesture,点击手势
12. UITapGestureRecognizer *tapGesture=[[UITapGestureRecognizer alloc]initWithTarget:self action:@selector(handleTapGesture:)];
13. //设置手势点击数,双击：点2下
14. tapGesture.numberOfTapsRequired=2;
15. // imageView添加手势识别
16. [imageView addGestureRecognizer:tapGesture];
17. //释放内存
18. [tapGesture release];
19.
20. //2、手势为捏的姿势:按住option按钮配合鼠标来做这个动作在虚拟器上
21. UIPinchGestureRecognizer *pinchGesture=[[UIPinchGestureRecognizer alloc]initWithTarget:self action:@selector(handlePinchGesture:)];
22. [imageView addGestureRecognizer:pinchGesture];//imageView添加手势识别
23. [pinchGesture release];
24.
25. //3、旋转手势:按住option按钮配合鼠标来做这个动作在虚拟器上
26. UIRotationGestureRecognizer *rotateGesture=[[UIRotationGestureRecognizer alloc]initWithTarget:self action:@selector(handleRotateGesture:)];
27. [imageView addGestureRecognizer:rotateGesture];
28. [rotateGesture release];
29.
30. //4、拖手势
31. UIPanGestureRecognizer *panGesture=[[UIPanGestureRecognizer alloc]initWithTarget:self action:@selector(handlePanGesture:)];
32. // [imageView addGestureRecognizer:panGesture];
33. [panGesture release];
34.
35. //5、划动手势
36. images=[[NSArray alloc]initWithObjects:@"cell.jpg",@"heihua.jpg",@"xuanyi.jpg", nil];
37. //右划
38. UISwipeGestureRecognizer *swipeGesture=[[UISwipeGestureRecognizer alloc]initWithTarget:self action:@selector(handleSwipeGesture:)];
39. [imageView addGestureRecognizer:swipeGesture];
40. [swipeGesture release];
41. //左划
42. UISwipeGestureRecognizer *swipeLeftGesture=[[UISwipeGestureRecognizer alloc]initWithTarget:self action:@selector(handleSwipeGesture:)];
43. swipeGesture.direction=UISwipeGestureRecognizerDirectionLeft;//不设置黑夜是右
44. [imageView addGestureRecognizer:swipeLeftGesture];
45. [swipeLeftGesture release];
46.
47. //6、长按手势
48. UILongPressGestureRecognizer *longpressGesutre=[[UILongPressGestureRecognizer alloc]initWithTarget:self action:@selector(handleLongpressGesture:)];
49. //长按时间为1秒
50. longpressGesutre.minimumPressDuration=1;
51. //允许15秒中运动
52. longpressGesutre.allowableMovement=15;
53. //所需触摸1次
54. longpressGesutre.numberOfTouchesRequired=1;
55. [imageView addGestureRecognizer:longpressGesutre];
56. [longpressGesutre release];
57.
58. [super viewDidLoad];
59. // Do any additional setup after loading the view, typically from a nib.
60. }
61. //双击屏幕时会调用此方法,放大和缩小图片
62. -(IBAction)handleTapGesture:(UIGestureRecognizer*)sender{
63. //判断imageView的内容模式是否是UIViewContentModeScaleAspectFit,该模式是原比例，按照图片原时比例显示大小
64. if(sender.view.contentMode==UIViewContentModeScaleAspectFit){
65. //把imageView模式改成UIViewContentModeCenter，按照图片原先的大小显示中心的一部分在imageView
66. sender.view.contentMode=UIViewContentModeCenter;
67. }else{
68. sender.view.contentMode=UIViewContentModeScaleAspectFit;
69. }
70. }
71. //捏的手势，使图片放大和缩小，捏的动作是一个连续的动作
72. -(IBAction)handlePinchGesture:(UIGestureRecognizer*)sender{
73. //得到sender捏手势的大小
74. CGFloat factor=[(UIPinchGestureRecognizer*)sender scale];
75. if(factor>1){
76. //图片放大
77. sender.view.transform=CGAffineTransformMakeScale(lastScaleFactor+(factor-1), (lastScaleFactor+(factor-1)));
78.
79. }else{
80. //缩小
81. sender.view.transform=CGAffineTransformMakeScale(lastScaleFactor*factor, lastScaleFactor*factor);
82.
83. }
84. //状态是否结束，如果结束保存数据
85. if(sender.state==UIGestureRecognizerStateEnded){
86. if(factor>1){
87. lastScaleFactor+=(factor-1);
88. }else{
89. lastScaleFactor*=factor;
90. }
91. }
92. }
93. //旋转手势
94. -(IBAction)handleRotateGesture:(UIGestureRecognizer*)sender{
95. //浮点类型，得到sender的旋转度数
96. CGFloat rotation=[(UIRotationGestureRecognizer*)sender rotation];
97. //旋转角度CGAffineTransformMakeRotation
98. CGAffineTransform transform=CGAffineTransformMakeRotation(rotation+netRotation);
99. //改变图像角度
100. sender.view.transform=transform;
101. //状态结束，保存数据
102. if(sender.state==UIGestureRecognizerStateEnded){
103. netRotation+=rotation;
104. }
105.
106. }
107. //拖手势
108. -(IBAction)handlePanGesture:(UIGestureRecognizer*)sender{
109. //得到拖的过程中的xy坐标
110. CGPoint translation=[(UIPanGestureRecognizer*)sender translationInView:imageView];
111. //平移图片CGAffineTransformMakeTranslation
112. sender.view.transform=CGAffineTransformMakeTranslation(netTranslation.x+translation.x, netTranslation.y+translation.y);
113. //状态结束，保存数据
114. if(sender.state==UIGestureRecognizerStateEnded){
115. netTranslation.x+=translation.x;
116. netTranslation.y+=translation.y;
117. }
118.
119. }
120. //划动手势
121. -(IBAction)handleSwipeGesture:(UIGestureRecognizer*)sender{
122. //划动的方向
123. UISwipeGestureRecognizerDirection direction=[(UISwipeGestureRecognizer*) sender direction];
124. //判断是上下左右
125. switch (direction) {
126. case UISwipeGestureRecognizerDirectionUp:
127. NSLog(@"up");
128. break;
129. case UISwipeGestureRecognizerDirectionDown:
130. NSLog(@"down");
131. break;
132. case UISwipeGestureRecognizerDirectionLeft:
133. NSLog(@"left");
134. imageIndex++;//下标++
135. break;
136. case UISwipeGestureRecognizerDirectionRight:
137. NSLog(@"right");
138. imageIndex--;//下标--
139. break;
140. default:
141. break;
142. }
143. //得到不越界不<0的下标
144. imageIndex=(imageIndex<0)?([images count]-1):imageIndex%[images count];
145. //imageView显示图片
146. imageView.image=[UIImage imageNamed:[images objectAtIndex:imageIndex]];
147.
148. }
149. //长按手势
150. -(IBAction)handleLongpressGesture:(UIGestureRecognizer*)sender{
151. //创建警告
152. UIActionSheet *actionSheet=[[UIActionSheet alloc]initWithTitle:@"Image options" delegate:self cancelButtonTitle:nil destructiveButtonTitle:nil otherButtonTitles:@"Save Image",@"Copy", nil];
153. //当前view显示警告
154. [actionSheet showInView:self.view];
155. [actionSheet release];
156. }
157. -(void)dealloc{
158. [images release];
159. [imageView release];
160. [super dealloc];
161. }