UIGestureRecognizer介绍
手势识别在iOS上非常重要，手势操作移动设备的重要特征，极大的增加了移动设备使用便捷性。
iOS系统在3.2以后，为方便开发这使用一些常用的手势，提供了UIGestureRecognizer类。手势识别UIGestureRecognizer类是个抽象类，下面的子类是具体的手势，开发这可以直接使用这些手势识别。
- UITapGestureRecognizer
- UIPinchGestureRecognizer
- UIRotationGestureRecognizer
- UISwipeGestureRecognizer
- UIPanGestureRecognizer
- UILongPressGestureRecognizer
上面的手势对应的操作是：
- Tap（点一下）
- Pinch（二指往內或往外拨动，平时经常用到的缩放）
- Rotation（旋转）
- Swipe（滑动，快速移动）
- Pan （拖移，慢速移动）
- LongPress（长按）
UIGestureRecognizer的继承关系如下：
2、使用手势的步骤
使用手势很简单，分为两步：
- 创建手势实例。当创建手势时，指定一个回调方法，当手势开始，改变、或结束时，回调方法被调用。
- 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。
建议在真机上运行这些手势,模拟器操作不太方便，可能导致你认为手势失效。
3、Pan 拖动手势：
1. UIImageView *snakeImageView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"snake.png"]];
2. snakeImageView.frame = CGRectMake(50, 50, 100, 160);
3. UIPanGestureRecognizer *panGestureRecognizer = [[UIPanGestureRecognizer alloc]
4. initWithTarget:self
5. action:@selector(handlePan:)];
6. [snakeImageView addGestureRecognizer:panGestureRecognizer];
7. [self.view setBackgroundColor:[UIColor whiteColor]];
8. [self.view addSubview:snakeImageView];
回调方法：
1. - (void) handlePan:(UIPanGestureRecognizer*) recognizer
2. {
3. CGPoint translation = [recognizer translationInView:self.view];
4. recognizer.view.center = CGPointMake(recognizer.view.center.x + translation.x,
5. recognizer.view.center.y + translation.y);
6. [recognizer setTranslation:CGPointZero inView:self.view];
7.
8. }
4、Pinch缩放手势
1. UIPinchGestureRecognizer *pinchGestureRecognizer = [[UIPinchGestureRecognizer alloc]
2. initWithTarget:self
3. class="p1">[<span class="s1">snakeImageView</span> <span class="s2">addGestureRecognizer</span>:pinchGestureRecognizer];</p>
1. - (void) handlePinch:(UIPinchGestureRecognizer*) recognizer
2. {
3. recognizer.view.transform = CGAffineTransformScale(recognizer.view.transform, recognizer.scale, recognizer.scale);
4. recognizer.scale = 1;
5. }
5、Rotation旋转手势
1. UIRotationGestureRecognizer *rotateRecognizer = [[UIRotationGestureRecognizer alloc]
2. initWithTarget:self
3. action:@selector(handleRotate:)];
4. [snakeImageView addGestureRecognizer:rotateRecognizer];
1. - (void) handleRotate:(UIRotationGestureRecognizer*) recognizer
2. {
3. recognizer.view.transform = CGAffineTransformRotate(recognizer.view.transform, recognizer.rotation);
4. recognizer.rotation = 0;
5. }
添加了这几个手势后，运行看效果，程序中的imageView放了一个
/^\/^\
_|__| O|
\/ /~ \_/ \
\____|__________/ \
\_______ \
`\ \ \
| | \
/ / \
/ / \\
/ / \ \
/ / \ \
/ / _----_ \ \
/ / _-~ ~-_ | |
( ( _-~ _--_ ~-_ _/ |
\ ~-____-~ _-~ ~-_ ~-_-~ /
~-_ _-~ ~-_ _-~
~--______-~ ~-___-~
的图片，在模拟器上拖动是没问题的。缩放和旋转有点问题，估计是因为在模拟器上的模拟的两个接触点距离在imageView的边界外了，所以操作无效果。
建议在真机上运行这个手势。
在模拟器上缩放和选择的操作技巧：
可以把imageView的frame值设置大一点，按住alt键，按下触摸板(不按下不行)，这样就可以旋转和缩放了。
6、添加第二个ImagView并添加手势
记住：一个手势只能添加到一个View，两个View当然要有两个手势的实例了
1. - (void)viewDidLoad
2. {
3. [super viewDidLoad];
4.
5. "snake.png"]];
6. "dragon.png"]];
7. snakeImageView.frame = CGRectMake(120, 120, 100, 160);
8. dragonImageView.frame = CGRectMake(50, 50, 100, 160);
9. [self.view addSubview:snakeImageView];
10. [self.view addSubview:dragonImageView];
11.
12. for (UIView *view in self.view.subviews) {
13. UIPanGestureRecognizer *panGestureRecognizer = [[UIPanGestureRecognizer alloc]
14. initWithTarget:self
15. action:@selector(handlePan:)];
16.
17. UIPinchGestureRecognizer *pinchGestureRecognizer = [[UIPinchGestureRecognizer alloc]
18. initWithTarget:self
19. action:@selector(handlePinch:)];
20.
21. UIRotationGestureRecognizer *rotateRecognizer = [[UIRotationGestureRecognizer alloc]
22. initWithTarget:self
23. action:@selector(handleRotate:)];
24.
25. [view addGestureRecognizer:panGestureRecognizer];
26. [view addGestureRecognizer:pinchGestureRecognizer];
27. [view addGestureRecognizer:rotateRecognizer];
28. [view setUserInteractionEnabled:YES];
29. }
30. [self.view setBackgroundColor:[UIColor whiteColor]];
31. }
多添加了一条龙的view，两个view都能接收上面的三种手势。运行效果如下：
7、拖动(pan手势)速度(以较快的速度拖放后view有滑行的效果)
如何实现呢？
- 监视手势是否结束
- 监视触摸的速度
1. - (void) handlePan:(UIPanGestureRecognizer*) recognizer
2. {
3. CGPoint translation = [recognizer translationInView:self.view];
4. recognizer.view.center = CGPointMake(recognizer.view.center.x + translation.x,
5. recognizer.view.center.y + translation.y);
6. [recognizer setTranslation:CGPointZero inView:self.view];
7.
8. if (recognizer.state == UIGestureRecognizerStateEnded) {
9.
10. CGPoint velocity = [recognizer velocityInView:self.view];
11. CGFloat magnitude = sqrtf((velocity.x * velocity.x) + (velocity.y * velocity.y));
12. CGFloat slideMult = magnitude / 200;
13. "magnitude: %f, slideMult: %f", magnitude, slideMult);
14.
15. float slideFactor = 0.1 * slideMult; // Increase for more of a slide
16. CGPoint finalPoint = CGPointMake(recognizer.view.center.x + (velocity.x * slideFactor),
17. recognizer.view.center.y + (velocity.y * slideFactor));
18. finalPoint.x = MIN(MAX(finalPoint.x, 0), self.view.bounds.size.width);
19. finalPoint.y = MIN(MAX(finalPoint.y, 0), self.view.bounds.size.height);
20.
21. [UIView animateWithDuration:slideFactor*2 delay:0 options:UIViewAnimationOptionCurveEaseOut animations:^{
22. recognizer.view.center = finalPoint;
23. } completion:nil];
24.
25. }
26.
- 计算速度向量的长度（估计大部分都忘了）这些知识了。
- 如果速度向量小于200，那就会得到一个小于的小数，那么滑行会很短
- 基于速度和速度因素计算一个终点
- 确保终点不会跑出父View的边界
- 使用UIView动画使view滑动到终点
放开会看到view还会在原来的方向滑行一段路。
8、同时触发两个view的手势
UIGestureRecognizerDelegate，
1. @interface ViewController : UIViewController<UIGestureRecognizerDelegate>
2. @end 并在协议这个方法里返回YES。
1. -(BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer
2. {
3. return YES;
4. } 把self作为代理设置给手势：
1. panGestureRecognizer.delegate = self;
2. pinchGestureRecognizer.delegate = self;
3. rotateRecognizer.delegate = self; 这样可以同时拖动或旋转缩放两个view了。
9、tap点击手势
这里为了方便看到tap的效果，当点击一下屏幕时，播放一个声音。
为了播放声音，我们加入AVFoundation.framework这个框架。
1. - (AVAudioPlayer *)loadWav:(NSString *)filename {
2. "wav"];
3. NSError * error;
4. AVAudioPlayer * player = [[AVAudioPlayer alloc] initWithContentsOfURL:url error:&error];
5. if (!player) {
6. "Error loading %@: %@", url, error.localizedDescription);
7. else {
8. [player prepareToPlay];
9. }
10. return player;
11. } 我会在最后例子代码给出完整代码，添加手势的步骤和前面一样的。
1. #import <UIKit/UIKit.h>
2. #import <AVFoundation/AVFoundation.h>
3.
4. @interface ViewController : UIViewController<UIGestureRecognizerDelegate>
5. @property (strong) AVAudioPlayer * chompPlayer;
6. @property (strong) AVAudioPlayer * hehePlayer;
7.
8. @end
1. - (void)handleTap:(UITapGestureRecognizer *)recognizer {
2. [self.chompPlayer play];
3. }
运行，点一下某个图，就会播放一个咬东西的声音。
requireGestureRecognizerToFail方法。
10、手势的依赖性
在viewDidLoad的循环里添加这段代码：
1. [tapRecognizer requireGestureRecognizerToFail:panGestureRecognizer]; 意思就是，当如果pan手势失败，就是没发生拖动，才会出发tap手势。这样如果你有轻微的拖动，那就是pan手势发生了。tap的声音就不会发出来了。
11、自定义手势
UIGestureRecognizer，实现下面的方法：
1. – touchesBegan:withEvent:
2. – touchesMoved:withEvent:
3. – touchesEnded:withEvent:
4. - touchesCancelled:withEvent:
新建一个类，继承UIGestureRecognizer，代码如下：
.h文件
#import <UIKit/UIKit.h>
1. typedef enum {
2. DirectionUnknown = 0,
3. DirectionLeft,
4. DirectionRight
5. } Direction;
6.
7. @interface HappyGestureRecognizer : UIGestureRecognizer
8. @property (assign) int tickleCount;
9. @property (assign) CGPoint curTickleStart;
10. @property (assign) Direction lastDirection;
11.
12. @end .m文件
1. #import "HappyGestureRecognizer.h"
2. #import <UIKit/UIGestureRecognizerSubclass.h>
3. #define REQUIRED_TICKLES 2
4. #define MOVE_AMT_PER_TICKLE 25
5.
6. @implementation HappyGestureRecognizer
7.
8. - (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
9. UITouch * touch = [touches anyObject];
10. self.curTickleStart = [touch locationInView:self.view];
11. }
12.
13. - (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
14.
15. // Make sure we've moved a minimum amount since curTickleStart
16. UITouch * touch = [touches anyObject];
17. CGPoint ticklePoint = [touch locationInView:self.view];
18. CGFloat moveAmt = ticklePoint.x - self.curTickleStart.x;
19. Direction curDirection;
20. if (moveAmt < 0) {
21. curDirection = DirectionLeft;
22. else {
23. curDirection = DirectionRight;
24. }
25. if (ABS(moveAmt) < MOVE_AMT_PER_TICKLE) return;
26.
27. // 确认方向改变了
28. if (self.lastDirection == DirectionUnknown ||
29. (self.lastDirection == DirectionLeft && curDirection == DirectionRight) ||
30. (self.lastDirection == DirectionRight && curDirection == DirectionLeft)) {
31.
32. // 挠痒次数
33. self.tickleCount++;
34. self.curTickleStart = ticklePoint;
35. self.lastDirection = curDirection;
36.
37. // 一旦挠痒次数超过指定数，设置手势为结束状态
38. // 这样回调函数会被调用。
39. if (self.state == UIGestureRecognizerStatePossible && self.tickleCount > REQUIRED_TICKLES) {
40. [self setState:UIGestureRecognizerStateEnded];
41. }
42. }
43.
44. }
45.
46. - (void)reset {
47. self.tickleCount = 0;
48. self.curTickleStart = CGPointZero;
49. self.lastDirection = DirectionUnknown;
50. if (self.state == UIGestureRecognizerStatePossible) {
51. [self setState:UIGestureRecognizerStateFailed];
52. }
53. }
54.
55. - (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
56. {
57. [self reset];
58. }
59.
60. - (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event
61. {
62. [self reset];
63. }
64.
65. @end
调用自定义手势和上面一样，回到这样写：
1. - (void)handleHappy:(HappyGestureRecognizer *)recognizer{
2. [self.hehePlayer play];
3. } 手势成功后播放呵呵笑的声音。
在真机上运行，按住某个view，快速左右拖动，就会发出笑的声音了。
代码解析：
curTickleStart
通过和 ticklePoint的x值对比，得出当前的放下是向左还是向右。再算出移动的x的值是否比 MOVE_AMT_PER_TICKLE距离大，如果太则返回。
再判断是否有三次是不同方向的动作，如果是则手势结束，回调。
参考：http://www.raywenderlich.com/6567/uigesturerecognizer-tutorial-in-ios-5-pinches-pans-and-more
例子代码：
