1、UIGestureRecognizer 介绍
手势识别在 iOS 中非常重要，他极大地提高了移动设备的使用便捷性。
iOS 系统在 3.2 以后，他提供了一些常用的手势（UIGestureRecognizer 的子类），开发者可以直接使用他们进行手势操作。
UIPanGestureRecognizer（拖动）
UIPinchGestureRecognizer（捏合）
UIRotationGestureRecognizer（旋转）
UITapGestureRecognizer（点按）
UILongPressGestureRecognizer（长按）
UISwipeGestureRecognizer（轻扫）
另外，可以通过继承 UIGestureRecognizer 类，实现自定义手势（手势识别器类）。
PS：自定义手势时，需要 #import <UIKit/UIGestureRecognizerSubclass.h>，一般需实现如下方法：
1 - (void)reset;
2
3 - (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event;
4 - (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event;
5 - (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event;
6 - (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event;
7 //以上方法在分类 UIGestureRecognizer (UIGestureRecognizerProtected) 中声明，更多方法声明请自行查看
UIGestureRecognizer 的继承关系如下：
2、手势状态
在六种手势识别中，只有一种手势是离散型手势，他就是 UITapGestureRecognizer。
离散型手势的特点就是：一旦识别就无法取消，而且只会调用一次手势操作事件（初始化手势时指定的回调方法）。
换句话说其他五种手势是连续型手势，而连续型手势的特点就是：会多次调用手势操作事件，而且在连续手势识别后可以取消手势。从下图可以看出两者调用操作事件的次数是不同的：
手势状态枚举如下：
1 typedef NS_ENUM(NSInteger, UIGestureRecognizerState) {
2 UIGestureRecognizerStatePossible, // 尚未识别是何种手势操作（但可能已经触发了触摸事件），默认状态
3 UIGestureRecognizerStateBegan, // 手势已经开始，此时已经被识别，但是这个过程中可能发生变化，手势操作尚未完成
4 UIGestureRecognizerStateChanged, // 手势状态发生转变
5 UIGestureRecognizerStateEnded, // 手势识别操作完成（此时已经松开手指）
6 UIGestureRecognizerStateCancelled, // 手势被取消，恢复到默认状态
7 UIGestureRecognizerStateFailed, // 手势识别失败，恢复到默认状态
8 UIGestureRecognizerStateRecognized = UIGestureRecognizerStateEnded // 手势识别完成，同UIGestureRecognizerStateEnded
9 };
- 对于离散型手势 UITapGestureRecgnizer 要么被识别，要么失败，点按（假设点按次数设置为1，并且没有添加长按手势）下去一次不松开则此时什么也不会发生，松开手指立即识别并调用操作事件，并且状态为3（已完成）。
但是连续型手势要复杂一些，就拿旋转手势来说，如果两个手指点下去不做任何操作，此时并不能识别手势（因为我们还没旋转）但是其实已经触发了触摸开始事件，此时处于状态0；如果此时旋转会被识别，也就会调用对应的操作事件，同时状态变成1（手势开始），但是状态1只有一瞬间；紧接着状态变为2（因为我们的旋转需要持续一会），并且重复调用操作事件（如果在事件中打印状态会重复打印2）；松开手指，此时状态变为3，并调用1次操作事件。
3、使用手势的步骤
使用手势很简单，分为三步：
创建手势识别器对象实例。创建时，指定一个回调方法，当手势开始，改变、或结束时，执行回调方法。
设置手势识别器对象实例的相关属性（可选部分）
添加到需要识别的 View 中。每个手势只对应一个 View，当屏幕触摸在 View 的边界内时，如果手势和预定的一样，那就会执行回调方法。
PS：一个手势只能对应一个 View，但是一个 View 可以有多个手势。建议在真机上测试这些手势，模拟器操作不太方便，可能导致认为手势失效的情况。（模拟器测试捏合和旋转手势时，按住 option 键，再用触摸板或鼠标操作）
4、举例说明
功能描述：
附加到两个图片视图 UIImageView 的有『拖动』、『捏合』、『旋转』、『点按』；
而『轻扫』和『自定义手势 KMGestureRecognizer』附加在根视图 UIView 中。
拖动：进行当前图片视图位置移动
捏合：进行当前图片视图缩放
旋转：进行当前图片视图角度旋转
点按：双击恢复当前图片视图的缩放、角度旋转、不透明度
长按：设置当前图片视图的不透明度为0.7
轻扫：左右轻扫设置两个图片视图为居中，同时以垂直居中的特定偏移量定位
自定义手势：挠痒功能，左右扫动共3次或以上，设置两个图片视图为居中，同时以水平居中的特定偏移量定位
效果如下：
KMGestureRecognizer.h
1 #import <UIKit/UIKit.h>
2
3 typedef NS_ENUM(NSUInteger, Direction) {
4 DirectionUnknown,
5 DirectionLeft,
6 DirectionRight
7 };
8
9 @interface KMGestureRecognizer : UIGestureRecognizer
10 @property (assign, nonatomic) NSUInteger tickleCount; //挠痒次数
11 @property (assign, nonatomic) CGPoint currentTickleStart; //当前挠痒开始坐标位置
12 @property (assign, nonatomic) Direction lastDirection; //最后一次挠痒方向
13
14 @end
KMGestureRecognizer.m
1 #import "KMGestureRecognizer.h"
2 #import <UIKit/UIGestureRecognizerSubclass.h>
3
4 @implementation KMGestureRecognizer
5 #define kMinTickleSpacing 20.0
6 #define kMaxTickleCount 3
7
8 - (void)reset {
9 _tickleCount = 0;
10 _currentTickleStart = CGPointZero;
11 _lastDirection = DirectionUnknown;
12
13 if (self.state == UIGestureRecognizerStatePossible) {
14 self.state = UIGestureRecognizerStateFailed;
15 }
16 }
17
18 - (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
19 UITouch *touch = [touches anyObject];
20 _currentTickleStart = [touch locationInView:self.view]; //设置当前挠痒开始坐标位置
21 }
22
23 - (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
24 //『当前挠痒开始坐标位置』和『移动后坐标位置』进行 X 轴值比较，得到是向左还是向右移动
25 UITouch *touch = [touches anyObject];
26 CGPoint tickleEnd = [touch locationInView:self.view];
27 CGFloat tickleSpacing = tickleEnd.x - _currentTickleStart.x;
28 Direction currentDirection = tickleSpacing < 0 ? DirectionLeft : DirectionRight;
29
30 //移动的 X 轴间距值是否符合要求，足够大
31 if (ABS(tickleSpacing) >= kMinTickleSpacing) {
32 //判断是否有三次不同方向的动作，如果有则手势结束，将执行回调方法
33 if (_lastDirection == DirectionUnknown ||
34 (_lastDirection == DirectionLeft && currentDirection == DirectionRight) ||
35 (_lastDirection == DirectionRight && currentDirection == DirectionLeft)) {
36 _tickleCount++;
37 _currentTickleStart = tickleEnd;
38 _lastDirection = currentDirection;
39
40 if (_tickleCount >= kMaxTickleCount && self.state == UIGestureRecognizerStatePossible) {
41 self.state = UIGestureRecognizerStateEnded;
42 //NSLog(@"自定义手势成功，将执行回调方法");
43 }
44 }
45 }
46 }
47
48 - (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
49 [self reset];
50 }
51
52 - (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event {
53 [self reset];
54 }
55
56 @end
ViewController.h
1 #import <UIKit/UIKit.h>
2 #import "KMGestureRecognizer.h"
3
4 @interface ViewController : UIViewController
5 @property (strong, nonatomic) UIImageView *imgV;
6 @property (strong, nonatomic) UIImageView *imgV2;
7 @property (strong, nonatomic) KMGestureRecognizer *customGestureRecognizer;
8
9 @end
ViewController.m
1 #import "ViewController.h"
2
3 @interface ViewController ()
4 - (void)handlePan:(UIPanGestureRecognizer *)recognizer;
5 - (void)handlePinch:(UIPinchGestureRecognizer *)recognizer;
6 - (void)handleRotation:(UIRotationGestureRecognizer *)recognizer;
7 - (void)handleTap:(UITapGestureRecognizer *)recognizer;
8 - (void)handleLongPress:(UILongPressGestureRecognizer *)recognizer;
9 - (void)handleSwipe:(UISwipeGestureRecognizer *)recognizer;
10 - (void)handleCustomGestureRecognizer:(KMGestureRecognizer *)recognizer;
11
12 - (void)bindPan:(UIImageView *)imgVCustom;
13 - (void)bindPinch:(UIImageView *)imgVCustom;
14 - (void)bindRotation:(UIImageView *)imgVCustom;
15 - (void)bindTap:(UIImageView *)imgVCustom;
16 - (void)bindLongPress:(UIImageView *)imgVCustom;
17 - (void)bindSwipe;
18 - (void)bingCustomGestureRecognizer;
19 - (void)layoutUI;
20 @end
21
22 @implementation ViewController
23
24 - (void)viewDidLoad {
25 [super viewDidLoad];
26
27 [self layoutUI];
28 }
29
30 - (void)didReceiveMemoryWarning {
31 [super didReceiveMemoryWarning];
32 // Dispose of any resources that can be recreated.
33 }
34
35 #pragma mark - 处理手势操作
36 /**
37 * 处理拖动手势
38 *
39 * @param recognizer 拖动手势识别器对象实例
40 */
41 - (void)handlePan:(UIPanGestureRecognizer *)recognizer {
42 //视图前置操作
43 [recognizer.view.superview bringSubviewToFront:recognizer.view];
44
45 CGPoint center = recognizer.view.center;
46 CGFloat cornerRadius = recognizer.view.frame.size.width / 2;
47 CGPoint translation = [recognizer translationInView:self.view];
48 //NSLog(@"%@", NSStringFromCGPoint(translation));
49 recognizer.view.center = CGPointMake(center.x + translation.x, center.y + translation.y);
50 [recognizer setTranslation:CGPointZero inView:self.view];
51
52 if (recognizer.state == UIGestureRecognizerStateEnded) {
53 //计算速度向量的长度，当他小于200时，滑行会很短
54 CGPoint velocity = [recognizer velocityInView:self.view];
55 CGFloat magnitude = sqrtf((velocity.x * velocity.x) + (velocity.y * velocity.y));
56 CGFloat slideMult = magnitude / 200;
57 //NSLog(@"magnitude: %f, slideMult: %f", magnitude, slideMult); //e.g. 397.973175, slideMult: 1.989866
58
59 //基于速度和速度因素计算一个终点
60 float slideFactor = 0.1 * slideMult;
61 CGPoint finalPoint = CGPointMake(center.x + (velocity.x * slideFactor),
62 center.y + (velocity.y * slideFactor));
63 //限制最小［cornerRadius］和最大边界值［self.view.bounds.size.width - cornerRadius］，以免拖动出屏幕界限
64 finalPoint.x = MIN(MAX(finalPoint.x, cornerRadius),
65 self.view.bounds.size.width - cornerRadius);
66 finalPoint.y = MIN(MAX(finalPoint.y, cornerRadius),
67 self.view.bounds.size.height - cornerRadius);
68
69 //使用 UIView 动画使 view 滑行到终点
70 [UIView animateWithDuration:slideFactor*2
71 delay:0
72 options:UIViewAnimationOptionCurveEaseOut
73 animations:^{
74 recognizer.view.center = finalPoint;
75 }
76 completion:nil];
77 }
78 }
79
80 /**
81 * 处理捏合手势
82 *
83 * @param recognizer 捏合手势识别器对象实例
84 */
85 - (void)handlePinch:(UIPinchGestureRecognizer *)recognizer {
86 CGFloat scale = recognizer.scale;
87 recognizer.view.transform = CGAffineTransformScale(recognizer.view.transform, scale, scale); //在已缩放大小基础下进行累加变化；区别于：使用 CGAffineTransformMakeScale 方法就是在原大小基础下进行变化
88 recognizer.scale = 1.0;
89 }
90
91 /**
92 * 处理旋转手势
93 *
94 * @param recognizer 旋转手势识别器对象实例
95 */
96 - (void)handleRotation:(UIRotationGestureRecognizer *)recognizer {
97 recognizer.view.transform = CGAffineTransformRotate(recognizer.view.transform, recognizer.rotation);
98 recognizer.rotation = 0.0;
99 }
100
101 /**
102 * 处理点按手势
103 *
104 * @param recognizer 点按手势识别器对象实例
105 */
106 - (void)handleTap:(UITapGestureRecognizer *)recognizer {
107 UIView *view = recognizer.view;
108 view.transform = CGAffineTransformMakeScale(1.0, 1.0);
109 view.transform = CGAffineTransformMakeRotation(0.0);
110 view.alpha = 1.0;
111 }
112
113 /**
114 * 处理长按手势
115 *
116 * @param recognizer 点按手势识别器对象实例
117 */
118 - (void)handleLongPress:(UILongPressGestureRecognizer *)recognizer {
119 //长按的时候，设置不透明度为0.7
120 recognizer.view.alpha = 0.7;
121 }
122
123 /**
124 * 处理轻扫手势
125 *
126 * @param recognizer 轻扫手势识别器对象实例
127 */
128 - (void)handleSwipe:(UISwipeGestureRecognizer *)recognizer {
129 //代码块方式封装操作方法
130 void (^positionOperation)() = ^() {
131 CGPoint newPoint = recognizer.view.center;
132 newPoint.y -= 20.0;
133 _imgV.center = newPoint;
134
135 newPoint.y += 40.0;
136 _imgV2.center = newPoint;
137 };
138
139 //根据轻扫方向，进行不同控制
140 switch (recognizer.direction) {
141 case UISwipeGestureRecognizerDirectionRight: {
142 positionOperation();
143 break;
144 }
145 case UISwipeGestureRecognizerDirectionLeft: {
146 positionOperation();
147 break;
148 }
149 case UISwipeGestureRecognizerDirectionUp: {
150 break;
151 }
152 case UISwipeGestureRecognizerDirectionDown: {
153 break;
154 }
155 }
156 }
157
158 /**
159 * 处理自定义手势
160 *
161 * @param recognizer 自定义手势识别器对象实例
162 */
163 - (void)handleCustomGestureRecognizer:(KMGestureRecognizer *)recognizer {
164 //代码块方式封装操作方法
165 void (^positionOperation)() = ^() {
166 CGPoint newPoint = recognizer.view.center;
167 newPoint.x -= 20.0;
168 _imgV.center = newPoint;
169
170 newPoint.x += 40.0;
171 _imgV2.center = newPoint;
172 };
173
174 positionOperation();
175 }
176
177
178 #pragma mark - 绑定手势操作
179 /**
180 * 绑定拖动手势
181 *
182 * @param imgVCustom 绑定到图片视图对象实例
183 */
184 - (void)bindPan:(UIImageView *)imgVCustom {
185 UIPanGestureRecognizer *recognizer = [[UIPanGestureRecognizer alloc] initWithTarget:self
186 action:@selector(handlePan:)];
187 [imgVCustom addGestureRecognizer:recognizer];
188 }
189
190 /**
191 * 绑定捏合手势
192 *
193 * @param imgVCustom 绑定到图片视图对象实例
194 */
195 - (void)bindPinch:(UIImageView *)imgVCustom {
196 UIPinchGestureRecognizer *recognizer = [[UIPinchGestureRecognizer alloc] initWithTarget:self
197 action:@selector(handlePinch:)];
198 [imgVCustom addGestureRecognizer:recognizer];
199 //[recognizer requireGestureRecognizerToFail:imgVCustom.gestureRecognizers.firstObject];
200 }
201
202 /**
203 * 绑定旋转手势
204 *
205 * @param imgVCustom 绑定到图片视图对象实例
206 */
207 - (void)bindRotation:(UIImageView *)imgVCustom {
208 UIRotationGestureRecognizer *recognizer = [[UIRotationGestureRecognizer alloc] initWithTarget:self
209 action:@selector(handleRotation:)];
210 [imgVCustom addGestureRecognizer:recognizer];
211 }
212
213 /**
214 * 绑定点按手势
215 *
216 * @param imgVCustom 绑定到图片视图对象实例
217 */
218 - (void)bindTap:(UIImageView *)imgVCustom {
219 UITapGestureRecognizer *recognizer = [[UITapGestureRecognizer alloc] initWithTarget:self
220 action:@selector(handleTap:)];
221 //使用一根手指双击时，才触发点按手势识别器
222 recognizer.numberOfTapsRequired = 2;
223 recognizer.numberOfTouchesRequired = 1;
224 [imgVCustom addGestureRecognizer:recognizer];
225 }
226
227 /**
228 * 绑定长按手势
229 *
230 * @param imgVCustom 绑定到图片视图对象实例
231 */
232 - (void)bindLongPress:(UIImageView *)imgVCustom {
233 UILongPressGestureRecognizer *recognizer = [[UILongPressGestureRecognizer alloc] initWithTarget:self action:@selector(handleLongPress:)];
234 recognizer.minimumPressDuration = 0.5; //设置最小长按时间；默认为0.5秒
235 [imgVCustom addGestureRecognizer:recognizer];
236 }
237
238 /**
239 * 绑定轻扫手势；支持四个方向的轻扫，但是不同的方向要分别定义轻扫手势
240 */
241 - (void)bindSwipe {
242 //向右轻扫手势
243 UISwipeGestureRecognizer *recognizer = [[UISwipeGestureRecognizer alloc] initWithTarget:self
244 action:@selector(handleSwipe:)];
245 recognizer.direction = UISwipeGestureRecognizerDirectionRight; //设置轻扫方向；默认是 UISwipeGestureRecognizerDirectionRight，即向右轻扫
246 [self.view addGestureRecognizer:recognizer];
247 [recognizer requireGestureRecognizerToFail:_customGestureRecognizer]; //设置以自定义挠痒手势优先识别
248
249 //向左轻扫手势
250 recognizer = [[UISwipeGestureRecognizer alloc] initWithTarget:self
251 action:@selector(handleSwipe:)];
252 recognizer.direction = UISwipeGestureRecognizerDirectionLeft;
253 [self.view addGestureRecognizer:recognizer];
254 [recognizer requireGestureRecognizerToFail:_customGestureRecognizer]; //设置以自定义挠痒手势优先识别
255 }
256
257 /**
258 * 绑定自定义挠痒手势；判断是否有三次不同方向的动作，如果有则手势结束，将执行回调方法
259 */
260 - (void)bingCustomGestureRecognizer {
261 //当 recognizer.state 为 UIGestureRecognizerStateEnded 时，才执行回调方法 handleCustomGestureRecognizer:
262
263 //_customGestureRecognizer = [KMGestureRecognizer new];
264 _customGestureRecognizer = [[KMGestureRecognizer alloc] initWithTarget:self
265 action:@selector(handleCustomGestureRecognizer:)];
266 [self.view addGestureRecognizer:_customGestureRecognizer];
267 }
268
269 - (void)layoutUI {
270 //图片视图 _imgV
271 UIImage *img = [UIImage imageNamed:@"Emoticon_tusiji_icon"];
272 CGFloat cornerRadius = img.size.width;
273 _imgV = [[UIImageView alloc] initWithImage:img];
274 _imgV.frame = CGRectMake(20.0, 20.0,
275 cornerRadius * 2, cornerRadius * 2);
276 _imgV.userInteractionEnabled = YES;
277 _imgV.layer.masksToBounds = YES;
278 _imgV.layer.cornerRadius = cornerRadius;
279 _imgV.layer.borderWidth = 2.0;
280 _imgV.layer.borderColor = [UIColor grayColor].CGColor;
281 [self.view addSubview:_imgV];
282
283 //图片视图 _imgV2
284 img = [UIImage imageNamed:@"Emoticon_tusiji_icon2"];
285 cornerRadius = img.size.width;
286 _imgV2 = [[UIImageView alloc] initWithImage:img];
287 _imgV2.frame = CGRectMake(20.0, 40.0 + _imgV.frame.size.height,
288 cornerRadius * 2, cornerRadius * 2);
289 _imgV2.userInteractionEnabled = YES;
290 _imgV2.layer.masksToBounds = YES;
291 _imgV2.layer.cornerRadius = cornerRadius;
292 _imgV2.layer.borderWidth = 2.0;
293 _imgV2.layer.borderColor = [UIColor orangeColor].CGColor;
294 [self.view addSubview:_imgV2];
295
296
297 [self bindPan:_imgV];
298 [self bindPinch:_imgV];
299 [self bindRotation:_imgV];
300 [self bindTap:_imgV];
301 [self bindLongPress:_imgV];
302
303 [self bindPan:_imgV2];
304 [self bindPinch:_imgV2];
305 [self bindRotation:_imgV2];
306 [self bindTap:_imgV2];
307 [self bindLongPress:_imgV2];
308
309 //为了处理手势识别优先级的问题，这里需先绑定自定义挠痒手势
310 [self bingCustomGestureRecognizer];
311 [self bindSwipe];
312 }
313
314 @end