手势识别器

手势识别器是对触摸事件做了封装，我们无需自己去判断某个手势是否触发，手势识别器本身起到了识别作用，我们把重心放在识别之后要做什么操作上面。手势识别器是iOS中比较抽象的一个类，用于识别一个手势。
手势识别器有7个子类：轻拍手势、平移手势、轻扫手势、缩放手势、旋转手势、长按手势以及屏幕边界平移手势。一旦指定的手势被识别，我们可以执行我们自己定义好的操作。

UIView *gestureView = [[UIView alloc] initWithFrame:CGRectMake(100, 100, 200, 200)];
gestureView.center = self.window.center;//将当前视图放置在window中间
gestureView.backgroundColor = [UIColor grayColor];//设置背景色
[self.window addSubview:gestureView];//添加到window上```

##UITapGestureRecognizer
轻拍手势识别器，能识别轻拍操作
```//轻拍手势
UITapGestureRecognizer *tapGR = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(tapAction:)];
//给创建好的视图添加手势
[gestureView addGestureRecognizer:tapGR];
[tapGR setNumberOfTapsRequired:2];//设置轻怕次数
tapGR.numberOfTouchesRequired = 1;//设置轻怕次数```
```//轻扫手势的回调方法
- (void)swipeAction: (UISwipeGestureRecognizer *)sender
{
    NSLog(@"123");
    //创建一个警示框
    UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"提示框" message:@"内容" delegate:self cancelButtonTitle:@"取消" otherButtonTitles:@"确定", nil];
    [alertView show];//展示警示框
    
}```

##UILongPressGestureRecognizer
长按手势识别器，能识别长按操作。
```//长按手势
UILongPressGestureRecognizer *longPGR = [[UILongPressGestureRecognizer alloc] initWithTarget:self action:@selector(longAction:)];
[gestureView addGestureRecognizer:longPGR];```
```//长按手势的回调方法
- (void)longAction: (UILongPressGestureRecognizer *)sender
{
    //直接声明，长按手势的回调方法会执行两次，因为长按状态下有开始和结束两种状态，如果不加判断，系统会认为结束也就是另一个长按的开始，所以加一句在长按结束时再执行，开始时不执行
    if (sender.state == UIGestureRecognizerStateEnded) {
        NSLog(@"000");
    }
    else if (sender.state == UIGestureRecognizerStateBegan)
    {
        NSLog(@"123");
    }
}```

##UIPinchGestureRecognizer
捏合手势识别器，能识别捏合操作。
```//捏合手势
UIPinchGestureRecognizer *pinchGR = [[UIPinchGestureRecognizer alloc] initWithTarget:self action:@selector(pinchAction:)];
[gestureView addGestureRecognizer:pinchGR];```
```//捏合手势的回调方法
- (void)pinchAction: (UIPinchGestureRecognizer *)sender
{
    //通过捏合手势得到缩放比率
    float scale = sender.scale;
    //得到该手势得到的视图
    UIView *view = sender.view;
    //2D仿射变换函数的缩放函数来实现视图的放大缩小
    //是在原有基础上来改变当前的视图
    /**
     *  @param t#>  <#t#> description#> 现有的视图的transform
     *  @param sx#> <#sx#> description#> x轴上的缩放比率
     *  @param sy#> <#sy#> description#> y轴上的缩放比率
     *
     */
    view.transform = CGAffineTransformScale(view.transform, scale, scale);
    //是在视图最初的tramsfrom状态上改变，不管执行多少次，都是以该视图最初的transform状态为基础来改变
    //每次捏合动作完毕之后，让此次捏合值复原，使得它每次捏合都是从1倍开始
    sender.scale = 1;
}```

##UIRotationGestureRecognizer
旋转手势识别器，能识别旋转操作。
```//旋转手势
UIRotationGestureRecognizer *rotationGR = [[UIRotationGestureRecognizer alloc] initWithTarget:self action:@selector(rotationAction:)];
[gestureView addGestureRecognizer:rotationGR];

- (void)rotationAction: (UIRotationGestureRecognizer *)sender
{
    //通过手势得到旋转角度
    float rota = sender.rotation;
    //得到该手势作用的视图
    UIView *view = sender.view;
    //通过2D仿射变换函数中的旋转函数来使得当前视图旋转
    view.transform = CGAffineTransformRotate(view.transform, rota);
    //复原
    sender.rotation = 0; 
}```

##UIPanGestureRecognizer
平移手势识别器，能识别拖拽操作。
```//平移手势
UIPanGestureRecognizer *panGP =[[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(panAction:)];
[gestureView addGestureRecognizer:panGP];```
```//平移手势的回调方法
- (void)panAction: (UIPanGestureRecognizer *)sender
{
    //得到手势当前所在视图
    UIImageView *imageView = (UIImageView *)sender.view;
    //得到手势在视图上移动的偏移量
    CGPoint late = [sender translationInView:imageView.superview];
    //通过2D方式变换函数中的平移函数使得当前函数平移
    imageView.transform = CGAffineTransformTranslate(imageView.transform, late.x, late.y);
    [sender setTranslation:CGPointZero inView:imageView.superview];   
}```


##UISwipeGestureRecognizer
轻扫手势识别器，能识别拖拽操作。
```//轻扫手势
UISwipeGestureRecognizer *swipeGR = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:@selector(swipeAction:)];
//设置轻扫的方向，默认值是从左往右，最多同时支持（左右）或者（上下）
swipeGR.direction = UISwipeGestureRecognizerDirectionDown | UISwipeGestureRecognizerDirectionUp;
[gestureView addGestureRecognizer:swipeGR];```
```//轻扫手势的回调方法
- (void)swipeAction: (UISwipeGestureRecognizer *)sender
{
    NSLog(@"实现了轻扫手势");
}```

##UIScreenEdgePanGestureRecognizer
屏幕边缘轻扫识别器，是iOS7中新增的手势。
```//边缘轻扫手势
UIScreenEdgePanGestureRecognizer *screenEdgePanGr = [[UIScreenEdgePanGestureRecognizer alloc] initWithTarget:self action:@selector(edgeAction:)];
screenEdgePanGr.edges = UIRectEdgeAll;
[gestureView addGestureRecognizer:screenEdgePanGr];```
```- (void)edgeAction: (UIScreenEdgePanGestureRecognizer *)sender
{
    NSLog(@"成功触发了屏幕边缘手势");
}```

#使得多个手势可以同时响应的代理方法（必须对手势指定代理）
```- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer
{
    //返回值为yes的时候，当执行一个手势的操作的时候，也可以执行其它手势的操作
    return YES;
}```