手势识别

#pragma mark - 点按手势
- (void)tap:(UITapGestureRecognizer *)recognizer
{
    // 双击放大图片
    UIImageView *imageView = (UIImageView *)recognizer.view;

    [UIView animateWithDuration:0.8f animations:^{
        [imageView setTransform:CGAffineTransformScale(imageView.transform, 2.0, 2.0)];
    } completion:^(BOOL finished) {
        [UIView animateWithDuration:0.5f animations:^{
            [imageView setTransform:CGAffineTransformScale(imageView.transform, 0.5, 0.5)];
        }];
    }];
}

#pragma mark - 捏合
- (void)pinch:(UIPinchGestureRecognizer *)recognizer
{
    // 调整图像的显示比例
    if (UIGestureRecognizerStateChanged == recognizer.state) {
        
        // 等比例缩放
        [recognizer.view setTransform:CGAffineTransformScale(recognizer.view.transform, recognizer.scale, recognizer.scale)];
        
        // 在设置累加形变参数时，需要重置手势的缩放比例
        recognizer.scale = 1.0f;
    }
}

#pragma mark - 拖动
- (void)pan:(UIPanGestureRecognizer *)recognizer
{
    CGPoint translation = [recognizer translationInView:self.view];
    
    // 让图像根据手指移动
    if (UIGestureRecognizerStateChanged == recognizer.state) {
        // 形变参数，有Make的时候，是相对初始位置计算的
        // 没有Make是递增修改形变的
        [recognizer.view setTransform:CGAffineTransformTranslate(recognizer.view.transform, translation.x, translation.y)];
        
        // 拖动手指中的平移距离是相对于初始位置，如果使用CGAffineTransformTranslate累加形变方法
        // 需要在每次位移之后，重置recognizer的位移量，就是将位移量清零
        [recognizer setTranslation:CGPointZero inView:recognizer.view];
    }
}

#pragma mark - 旋转
- (void)rotate:(UIRotationGestureRecognizer *)recognizer
{
    if (UIGestureRecognizerStateChanged == recognizer.state) {
        recognizer.view.transform = CGAffineTransformRotate(recognizer.view.transform, recognizer.rotation);
        
        // 重置旋转量
        recognizer.rotation = 0.0f;
    }
}

#pragma mark - 长按手势
- (void)longPress:(UILongPressGestureRecognizer *)recognizer
{
    NSLog(@"长按");
    // 长按旋转图片
    // 开始长按
    // 在形变时，iOS采取就近原则旋转，如果不能按照希望的方向旋转，可以增加一些修正值，例如0.01
    // 直接通过形变属性，要实现一次性转一圈，比较困难，可以分两次进行
    if (UIGestureRecognizerStateBegan == recognizer.state) {
        [UIView animateWithDuration:0.8f animations:^{
            [recognizer.view setTransform:CGAffineTransformRotate(recognizer.view.transform, M_PI - 0.01)];
        }];
    } else if (UIGestureRecognizerStateEnded == recognizer.state) {
        [UIView animateWithDuration:0.8f animations:^{
            [recognizer.view setTransform:CGAffineTransformRotate(recognizer.view.transform, M_PI - 0.01)];
        } completion:^(BOOL finished) {
            // 清除所有的形变属性
            [recognizer.view setTransform:CGAffineTransformIdentity];
        }];
    }
}