如何实现呢？
1）监视手势是否结束
2）监视触摸的速度

- (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,self.view.bounds.size.height);

[UIView animateWithDuration:slideFactor*2 delay:0 options:UIViewAnimationOptionCurveEaSEOut animations:^{
recognizer.view.center = finalPoint;
} completion:nil];

}

代码实现解析：
1）计算速度向量的长度（估计大部分都忘了）这些知识了。
2）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
3）基于速度和速度因素计算一个终点
4）确保终点不会跑出父View的边界
5）使用UIView动画使view滑动到终点

运行后，快速拖动图像view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
手势之间是互斥的，如果你想同时触发蛇和龙的view，那么需要实现协议
UIGestureRecognizerDelegate，
@interface ViewController : UIViewController<UIGestureRecognizerDelegate>
@end

并在协议这个方法里返回YES。
-(BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer
{
return YES;
}

把self作为代理设置给手势：
panGestureRecognizer.delegate = self;
pinchGestureRecognizer.delegate = self;
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。
- (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

运行，点一下某个图，就会播放一个咬东西的声音。不过这个点击播放声音有点缺陷，就是在慢慢拖动的时候也会播放。这使得两个手势重合了。怎么解决呢？使用手势的：requireGestureRecognizerToFail方法。

10、手势的依赖性

在viewDidLoad的循环里添加这段代码：
[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
自定义手势继承：UIGestureRecognizer，实现下面的方法：
– touchesBegan:withEvent:
– touchesMoved:withEvent:
– touchesEnded:withEvent:
- touchesCancelled:withEvent:

新建一个类，继承UIGestureRecognizer，代码如下：

.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;

// 确认方向改变了
if (self.lastDirection == DirectionUnknown ||
(self.lastDirection == DirectionLeft && curDirection == DirectionRight) ||
(self.lastDirection == DirectionRight && curDirection == DirectionLeft)) {

// 挠痒次数
self.tickleCount++;
self.curTickleStart = ticklePoint;
self.lastDirection = curDirection;

// 一旦挠痒次数超过指定数，设置手势为结束状态
// 这样回调函数会被调用。
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

调用自定义手势和上面一样，回到这样写：
- (void)handleHappy:(HappyGestureRecognizer *)recognizer{
[self.hehePlayer play];
}

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：
先获取起始坐标：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：http://download.csdn.net/detail/totogo2010/5094059

来源：容芳志的博客