UIPinchGestureRecognizer和UIImageView的问题

Question

我试图通过UIPinchGestureRecognizer压缩图像，但问题是我的代码不能正常工作，实际上它不能缩放我的图像

-(void) pinching: (UIPinchGestureRecognizer *) sender {

    CGAffineTransform myTransformation =
    CGAffineTransformMakeScale(sender.scale, sender.scale);
    sender.view.transform = myTransformation;
}


- (void)viewDidLoad
{
  UIPinchGestureRecognizer *pinch =
    [[UIPinchGestureRecognizer alloc]
     initWithTarget:self
     action:@selector(pinching:)];

    pinch.delegate = self;

    [imageBG addGestureRecognizer:pinch];

    [imageBG setUserInteractionEnabled:YES];
    [imageBG setMultipleTouchEnabled:YES];
}

Answer 1

尝试使用UIScrollView。

要执行此操作，请创建它

self.scrollView = [[UIScrollView alloc] initWithFrame:...];
self.scrollView.delegate = self;
self.scrollView.maximumZoomScale = 2.0; // adjust as you need
self.scrollView.minimumZoomScale = 0.5; // adjust as you need
[self.scrollView addSubview:self.imageView];

并添加委托方法：

- (UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView {
    return self.imageView;
}

Answer 2

只需在.h文件中获取一个变量，如下图所示。

CGFloat lastScale;

并使用这种类型的代码。

在viewWillAppear:方法中，只需添加它..

- (void)viewWillAppear:(BOOL)animated
{
     UIPinchGestureRecognizer *pinchRecognizer = [[UIPinchGestureRecognizer alloc] initWithTarget:self action:@selector(scale:)];
        [pinchRecognizer setDelegate:self];
        [yourImageView addGestureRecognizer:pinchRecognizer];
}

-(void)scale:(id)sender {
    if([(UIPinchGestureRecognizer*)sender state] == UIGestureRecognizerStateEnded) {

            lastScale = 1.0;
            return;
        }

        CGFloat scale = 1.0 - (lastScale - [(UIPinchGestureRecognizer*)sender scale]);

        CGAffineTransform currentTransform = [(UIPinchGestureRecognizer*)sender view].transform;
        CGAffineTransform newTransform = CGAffineTransformScale(currentTransform, scale, scale);

        [[(UIPinchGestureRecognizer*)sender view] setTransform:newTransform];
        yourImageView.transform = newTransform

        lastScale = [(UIPinchGestureRecognizer*)sender scale];
}

也可以试试这段代码。

Answer 3

您需要添加scrollView才能启用缩放。添加您的imageView作为滚动视图的subView。将UIScrollViewDelegate的代理设置为self。实现委托方法。

- (UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView

{
    //return the imageview here
    return self.imageView;

}

在此处缩放您的图像视图：

- (CGRect)zoomRectForScrollView:(UIScrollView *)scrollView withScale:(float)scale withCenter:(CGPoint)center

你可以参考这个example from Apple。