IOS开发基础：手势事件(UiGestureRecognizer)

在介绍之前，咱们首先要知道为什么要用手势。比如我们需要添加一些触屏、滑屏事件，比如捏合图片、双击屏幕、下拉视图等等，就会用到手势

一、手势（UIGestureRecognizer）的种类

其实UIGestureRecognizer这一类并不复杂,简单来说这就是一个特殊的触摸事件,UIGestureRecognizer是一个父类,而实际操作中我们要使用它的子类,、大概有以下几种:

子类名称	名称
UITapGestureRecognizer	轻拍手势
UISwipeGestureRecognizer	轻扫手势
UILongPressGestureRecognizer	长按手势
UIPanGestureRecognizer	平移手势
UIPinchGestureRecognizer	捏合（缩放）手势
UIRotationGestureRecognizer	旋转手势
UIScreenEdgePanGestureRecognizer	屏幕边缘平移
UISharkGestureRecognizer	晃动

二、创建手势

手势的创建的方法大同小异

• UITapGestureRecognizer(轻拍手势)

//创建手势 使用initWithTarget:action:的方法创建
    UITapGestureRecognizer *tap = [[UITapGestureRecognizer alloc]initWithTarget:self action:@selector(tapView:)];
    
    //设置属性
    //tap 手势一共两个属性，一个是设置轻拍次数，一个是设置点击手指个数
    //设置轻拍次数
    tap.numberOfTapsRequired = 2;
    //设置手指字数
    tap.numberOfTouchesRequired = 2;
    
    //别忘了添加到testView上
    [self.view addGestureRecognizer:tap];

-(void)tapView:(UITapGestureRecognizer *)sender{
    //设置轻拍事件改变testView的颜色
    _testView.backgroundColor = [UIColor colorWithRed:arc4random()%256/255.0 green:arc4random()%256/255.0 blue:arc4random()%256/255.0 alpha:1];
}

• UISwipeGestureRecognizer (轻扫手势)

//创建手势
UISwipeGestureRecognizer *swipe = [[UISwipeGestureRecognizer alloc]initWithTarget:self action:@selector(swipeView:)];
//设置属性，swipe也是有两种属性设置手指个数及轻扫方向
swipe.numberOfTouchesRequired = 2;
    //设置轻扫方向(默认是从左往右)
    //direction是一个枚举值有四个选项，我们可以设置从左往右，从右往左，从下往上以及从上往下
  //设置轻扫方向(默认是从左往右)
swipe.direction = UISwipeGestureRecognizerDirectionLeft;
[self.view addGestureRecognizer:swipe];


- (void)swipeView:(UISwipeGestureRecognizer *)sender {
    self.view.backgroundColor = [UIColor colorWithRed:arc4random()%256/255.0 green:arc4random()%256/255.0 blue:arc4random()%256/255.0 alpha:1];
   //可在这里获取手势位置
}

• UILongPressGestureRecognizer(长按手势)

UILongPressGestureRecognizer *longPress = [[UILongPressGestureRecognizer alloc]initWithTarget:self action:@selector(longPress:)];
    //属性设置
    //最小长按时间
    longPress.minimumPressDuration = 2;
        [self.view addGestureRecognizer:longPress];

-(void)longPress:(UILongPressGestureRecognizer *)sender{
    //进行判断,在什么时候触发事件
    if (sender.state == UIGestureRecognizerStateBegan) {
        NSLog(@"长按状态");
    //改变testView颜色
        self.view.backgroundColor = [UIColor colorWithRed:arc4random()%256/255.0 green:arc4random()%256/255.0 blue:arc4random()%256/255.0 alpha:1];
    }
}

• UIPanGestureRecognizer(拖拽手势)

UIPanGestureRecognizer *pan = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(pan:)];
    [self.imageV addGestureRecognizer:pan];

当手指拖动时调用
- (void)pan:(UIPanGestureRecognizer *)pan{
   
    拖动手势也有状态 
    if(pan.state == UIGestureRecognizerStateBegan){
          开始拖动  
    }else if(pan.state == UIGestureRecognizerStateChanged){
        注意:获取偏移量是相对于最原始的点 
        CGPoint transP = [pan translationInView:self.imageV];
        self.imageV.transform = CGAffineTransformTranslate(self.imageV.transform, transP.x, transP.y);

        复位,让它相对于上一次. 
        [pan setTranslation:CGPointZero inView:self.imageV];
    }else if(pan.state == UIGestureRecognizerStateEnded){
        结束拖动       
    }
}

• UIPinchGestureRecognizer(捏合手势，用于缩放)
• UIRotationGestureRecognizer(旋转手势)

//现在视图上添加图片 对图片进行操作
//添加捏合手势
UIPinchGestureRecognizer *pinGes = [[UIPinchGestureRecognizer alloc] initWithTarget:self action:@selector(pinGes:)];
[self.imageView addGestureRecognizer:pinGes];


旋转时调用
- (void)pinGes:(UIPinchGestureRecognizer *)pin{
    self.imageView.transform = CGAffineTransformScale(self.imageV.transform, pin.scale, pin.scale);
    复位 
    [pin setScale:1];
   
}

添加旋转手势
 UIRotationGestureRecognizer *rotation = [[UIRotationGestureRecognizer alloc] initWithTarget:self action:@selector(rotation:)];
 设置代理使其能够同时支持多个手势(捏合的时候同时支持旋转)
 rotation.delegate = self;
 [self.imageView addGestureRecognizer:rotation];


当手指开始旋转时调用.
- (void)rotation:(UIRotationGestureRecognizer *)rotation{ 
    self.imageView.transform = CGAffineTransformRotate(self.imageV.transform, rotation.rotation);
    复位. 
    [rotation setRotation:0]; 
}

三、手势的一些代理函数（UIGestureRecognizerDelegate）

// 是否允许开始触发手势
- (BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer *)gestureRecognizer;

//手指触摸屏幕后回调的方法，返回NO则不再进行手势识别，方法触发等
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldReceiveTouch:(UITouch *)touch;

//开始进行手势识别时调用的方法，返回NO则结束，不再触发手势
- (BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer *)gestureRecognizer;

//是否支持多时候触发，返回YES，则可以多个手势一起触发方法，返回NO则为互斥
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer;

//下面这个两个方法也是用来控制手势的互斥执行的
//这个方法返回YES，第一个手势和第二个互斥时，第一个会失效
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRequireFailureOfGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer NS_AVAILABLE_IOS(7_0);

//这个方法返回YES，第一个和第二个互斥时，第二个会失效
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldBeRequiredToFailByGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer NS_AVAILABLE_IOS(7_0);

四、手势冲突处理

一般在含有UIScrollView或者UIScrollView的子类的视图上添加自己的手势就会有冲突；利用UIGestureRecognizerDelegate中的代理方法可以解决相应的冲突；
因为在UIScrollView上有手势，利用

- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer;
//设置为YES就可以一直传递下去

同时手势与事件触摸有优先级的关系，使用手势时应该多注意