UIGestureRecognizer介绍

1、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：

1）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。
2）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]; 

新建一个ImageView，然后添加手势
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.                                                        action:@selector(handlePinch:)];

[snakeImageView addGestureRecognizer:pinchGestureRecognizer];

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放了一个这样的图片
                    /^\/^\
                  _|__|  O|
         \/     /~     \_/ \
          \____|__________/  \
                 \_______      \
                         `\     \                 \
                           |     |                  \
                          /      /                    \
                         /     /                       \\
                       /      /                         \ \
                      /     /                            \  \
                    /     /             _----_            \   \
                   /     /           _-~      ~-_         |   |
                  (      (        _-~    _--_    ~-_     _/   |
                   \      ~-____-~    _-~    ~-_    ~-_-~    /
                     ~-_           _-~          ~-_       _-~   
                        ~--______-~                ~-___-~
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。

- (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？
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, 0), 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  
@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    
2.#import    
3.  
4.@interface ViewController : UIViewController  
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 
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    
#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