正确使用 iOS 开发中的六大操作手势

在 iOS 的开发过程中，我们一般使用 touches 方法来监听 view 的触摸事件，但是这样使用会有一些弊端：

1. 必须得自定义 view, 在自定义的 View 当中去实现 touches 方法
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. 不容易区分用户具体的手势行为

鉴于这些问题，在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 手势识别器

• 利用 UIGestureRecognizer，能轻松识别用户在某个 view 上面做的一些常见手势
• 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
  1. 点按手势 UITapGestureRecognizer
  2. 长按手势 UILongPressGestureRecognizer
  3. 平移（拖拽）手势 UIPanGestureRecognizer
  4. 轻扫手势 UISwipeGestureRecognizer
  5. 旋转手势 UIRotationGestureRecognizer
  6. 捏合手势 UIPinchGestureRecognizer
• 手势的使用方法
  1. 创建手势
  2. 添加手势
  3. 实现手势方法
  4. 补充（手势也可以设置代理）

1. UITapGestureRecognizer 点按手势

点按手势效果图

- (void)topGes {
    //创建点按手势
    UITapGestureRecognizer *tapGes = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(tap)];
    //手势也可以设置代理
    tapGes.delegate = self;
    //添加手势
    [self.imageView addGestureRecognizer:tapGes];
}

- (void)tap {
    NSLog(@"现在是点按手势");
}

• 实现代理方法

//代理方法：是否允许接收手指
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldReceiveTouch:(UITouch *)touch {
    //让图片左边可以点击，右边不能点击
    //获取当前手指所在的点进行判断
    CGPoint curP = [touch locationInView:self.imageView];
    if (curP.x > self.imageView.bounds.size.width * 0.5) {
        return NO;
    }else {
        return YES;
    }
}

2. UILongPressGestureRecognizer 长按手势

长按手势效果图

- (void)longPGes {
    UILongPressGestureRecognizer *longPGes = [[UILongPressGestureRecognizer alloc]initWithTarget:self action:@selector(longP:)];
    [self.imageView addGestureRecognizer:longPGes];
}

//当长按并移动时，会多次调用这个方法
- (void)longP:(UILongPressGestureRecognizer *)longP {
    //判断长按时的状态
    if (longP.state == UIGestureRecognizerStateBegan) {
        NSLog(@"开始长按");
    }else if (longP.state == UIGestureRecognizerStateChanged) {
        NSLog(@"- - - 长按时手指移动了 - - -");
    }else if (longP.state == UIGestureRecognizerStateEnded) {
        NSLog(@"长按结束");
    }
}

3. UIPanGestureRecognizer 平移（拖拽）手势

平移（拖拽）手势效果图

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

- (void)pan:(UIPanGestureRecognizer *)pan {
    //获取偏移量
    CGPoint transP = [pan translationInView:self.imageView];
    NSLog(@"transP = %@", NSStringFromCGPoint(transP));
    
    //移动图片
    self.imageView.transform = CGAffineTransformTranslate(self.imageView.transform, transP.x, transP.y);
    //清零,不要累加
    [pan setTranslation:CGPointZero inView:self.imageView];
}

4. UISwipeGestureRecognizer 轻扫手势

轻扫手势效果图

• 一个手势只能对应一个方向，若要支持多个方向，可以添加多个手势
• 轻扫手势的方向默认是向右
• 可以通过修改手势的 direction 属性修改手势的方向

- (void)swipeGes {
    //一个手势只能对应一个方向，若要支持多个方向，可以添加多个手势
    UISwipeGestureRecognizer *swipeGes1 = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:@selector(swipe:)];
    //轻扫手势的方向默认是向右
    [self.imageView addGestureRecognizer:swipeGes1];
    
    UISwipeGestureRecognizer *swipeGes2 = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:@selector(swipe:)];
    //可以修改手势的方向，向上
    swipeGes2.direction = UISwipeGestureRecognizerDirectionUp;
    [self.imageView addGestureRecognizer:swipeGes2];
    
    UISwipeGestureRecognizer *swipeGes3 = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:@selector(swipe:)];
    //手势的方向，向左
    swipeGes3.direction =  UISwipeGestureRecognizerDirectionLeft;
    [self.imageView addGestureRecognizer:swipeGes3];
    
    UISwipeGestureRecognizer *swipeGes4 = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:@selector(swipe:)];
    //手势的方向，向下
    swipeGes4.direction = UISwipeGestureRecognizerDirectionDown;
    [self.imageView addGestureRecognizer:swipeGes4];
}

- (void)swipe:(UISwipeGestureRecognizer *)swipe {
    if (swipe.direction == UISwipeGestureRecognizerDirectionLeft) {
        NSLog(@"向左轻扫 --- left");
    }else if (swipe.direction == UISwipeGestureRecognizerDirectionRight){
        NSLog(@"向右轻扫 --- right");
    }else if (swipe.direction == UISwipeGestureRecognizerDirectionUp){
        NSLog(@"向上轻扫 --- up");
    } else if (swipe.direction == UISwipeGestureRecognizerDirectionDown) {
        NSLog(@"向下轻扫 --- down");
    }
}

5. UIRotationGestureRecognizer 旋转手势

旋转手势效果图

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

- (void)rotation:(UIRotationGestureRecognizer *)rotationGes {
    //获取旋转的度数
    CGFloat angle = rotationGes.rotation;
    //旋转图片
    self.imageView.transform = CGAffineTransformRotate(self.imageView.transform, angle);
    //清零
    [rotationGes setRotation:0];
}

6. UIPinchGestureRecognizer 捏合手势

捏合手势效果图

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

- (void)pinch:(UIPinchGestureRecognizer *)pinchGes {
    //获取缩放比例
    CGFloat scale = pinchGes.scale;
    NSLog(@"scale = %f", scale);
    //缩放图片
    self.imageView.transform = CGAffineTransformScale(self.imageView.transform, scale, scale);
    //初始化大小
    [pinchGes setScale:1];
}

补充：手势的混合使用

• 默认情况下只能同时支持一种手势
• 若要同时支持多种手势，可以给要支持的手势设置代理，并实现以下代理方法

//是否允许同时支持多个手势
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer  shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer {

    return YES;
}

旋转与捏合混合手势使用效果图

至此，iOS 开发中的 6 种手势操作已经介绍完毕了，大家可以通过设置多种手势混合使用来达到一定的效果，希望大家都能更上一层楼！