手势识别

通过touches方法监听view触摸事件，有很明显的几个缺点

1. 必须得自定义view
2. 由于是在view内部的touches方法中监听触摸事件，因此默认情况下，无法让其他外界对象监听view的触摸事件
3. 不容易区分用户的具体手势行为

iOS 3.2之后，苹果推出了手势识别功能（Gesture Recognizer），在触摸事件处理方面，大大简化了开发者的开发难度

UIGestureRecognizer(抽象类)

UIGestureRecognizer是一个抽象类，定义了所有手势的基本行为，使用它的子类才能处理具体的手势

• UITapGestureRecognizer(敲击)
• UIPinchGestureRecognizer(捏合，用于缩放)
• UIPanGestureRecognizer(拖拽)
• UISwipeGestureRecognizer(轻扫)
• UIRotationGestureRecognizer(旋转)
• UILongPressGestureRecognizer(长按)

---

UITapGestureRecognizer(敲击)

- (void)setUpTap
{
    // 创建点按手势 会把手势对象作为参数传到方法中去
    UITapGestureRecognizer *tap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(tap:)];
    
    // numberOfTapsRequired (需要点几次触发手势)
    
    // 设置手势代理
    tap.delegate = self;
    
    // 添加手势
    [self.imageView addGestureRecognizer:tap];
}

- (void)pan:(UIPanGestureRecognizer *)pan
{
    // 获取手势的触摸点
    CGPoint curP = [pan locationInView:self.imageView];
    
    // 移动视图
    // 获取手势的移动，也是相对于最开始的位置
    CGPoint transP = [pan translationInView:self.imageView];
    
    self.imageView.transform = CGAffineTransformTranslate(self.imageView.transform, transP.x, transP.y);
    
    // 复位
    [pan setTranslation:CGPointZero inView:self.imageView];
    
    NSLog(@"%@",NSStringFromCGPoint(curP));
}

---

手势代理方法

// 是否允许开始触发手势
- (BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer *)gestureRecognizer
{
    return NO;
}

// 是否允许同时支持多个手势，默认是不支持多个手势
// 返回yes表示支持多个手势
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer
{
    return YES;
}

// 是否允许接收手指的触摸点
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldReceiveTouch:(UITouch *)touch{
    // 获取当前的触摸点
    CGPoint curP = [touch locationInView:self.imageView];

    if (curP.x < self.imageView.bounds.size.width * 0.5) {
        return NO;
    }else{
        return YES;
    }
}

---

UILongPressGestureRecognizer(长按)

// 默认会触发两次
- (void)setUpLongPress
{
    UILongPressGestureRecognizer *longPress = [[UILongPressGestureRecognizer alloc] initWithTarget:self action:@selector(longPress:)];
    
    [self.imageView addGestureRecognizer:longPress];
}

// 开始长按时会调用一次，长按结束时会调用一次
- (void)longPress:(UILongPressGestureRecognizer *)longPress
{
    
    if (longPress.state == UIGestureRecognizerStateBegan) { // 长按开始时
        
        NSLog(@"%s",__func__);
    }
}

---

UISwipeGestureRecognizer(轻扫)

// 默认轻扫的方向是往右
UISwipeGestureRecognizer *swipe = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:@selector(swipe)];

/* 设置手势方向，

typedef NS_OPTIONS(NSUInteger, UISwipeGestureRecognizerDirection) {
    UISwipeGestureRecognizerDirectionRight = 1 << 0,  默认时往右
    UISwipeGestureRecognizerDirectionLeft  = 1 << 1,  往左
    UISwipeGestureRecognizerDirectionUp    = 1 << 2,  上
    UISwipeGestureRecognizerDirectionDown  = 1 << 3   下
};
 */

swipe.direction = UISwipeGestureRecognizerDirectionUp;

[self.imageView addGestureRecognizer:swipe];

// 如果以后想要一个控件支持多个方向的轻扫，必须创建多个轻扫手势，一个轻扫手势只支持一个方向
// 默认轻扫的方向是往右
UISwipeGestureRecognizer *swipeDown = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:@selector(swipe)];

swipeDown.direction = UISwipeGestureRecognizerDirectionDown;

[self.imageView addGestureRecognizer:swipeDown];

- (void)swipe
{
    NSLog(@"%s",__func__);
}

---

UIRotationGestureRecognizer(旋转)

- (void)setUpRotation
{
    UIRotationGestureRecognizer *rotation = [[UIRotationGestureRecognizer alloc] initWithTarget:self action:@selector(rotation:)];
    rotation.delegate = self;
    [self.imageView addGestureRecognizer:rotation];
}

// 默认传递的旋转的角度都是相对于最开始的位置
- (void)rotation:(UIRotationGestureRecognizer *)rotation
{
    // 获取手势旋转的角度
    NSLog(@"%f",rotation.rotation);
    
    self.imageView.transform = CGAffineTransformRotate(self.imageView.transform, rotation.rotation);
    
    // 复位 ：相当于上一次最后的状态 当做下一次初始状态进行操作
    rotation.rotation = 0;
    
}

---

UIPinchGestureRecognizer(捏合)

- (void)setUpPinch
{
    UIPinchGestureRecognizer *pinch = [[UIPinchGestureRecognizer alloc] initWithTarget:self action:@selector(pinch:)];
    pinch.delegate = self;
    [self.imageView addGestureRecognizer:pinch];
}

- (void)pinch:(UIPinchGestureRecognizer *)pinch
{
    self.imageView.transform = CGAffineTransformScale(self.imageView.transform, pinch.scale, pinch.scale);
    
    // 复位
    
    pinch.scale = 1;
}

---

UIPanGestureRecognizer(拖拽)

- (void)setUpPan
{
    UIPanGestureRecognizer *pan = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(pan:)];
    
    
    [self.imageView addGestureRecognizer:pan];
}

- (void)pan:(UIPanGestureRecognizer *)pan
{
    // 获取手势的触摸点
    CGPoint curP = [pan locationInView:self.imageView];
    
    // 移动视图
    // 获取手势的移动，也是相对于最开始的位置
    CGPoint transP = [pan translationInView:self.imageView];
    
    self.imageView.transform = CGAffineTransformTranslate(self.imageView.transform, transP.x, transP.y);
    
    // 复位
    [pan setTranslation:CGPointZero inView:self.imageView];
    
    NSLog(@"%@",NSStringFromCGPoint(curP));
}

练习：抽屉效果

代码：抽屉效果