UIPinchGestureRecognizer。放大手指的位置，而不仅仅是中心[重复]

Posted 2023-03-13

【中文标题】UIPinchGestureRecognizer。放大手指的位置，而不仅仅是中心[重复]

【英文标题】：UIPinchGestureRecognizer. Make zoom in location of fingers, not only center [duplicate]

【发布时间】：2014-04-23 13:01:25

【问题描述】：

我可以使用UIPinchGestureRecognizer 来放大UICollectionViewCell 的视图，但是你开始做UIPinch 手势的位置并不重要，缩放总是在中心的看法。例如，我想在视图的左上角区域进行捏合，并且必须在我触摸屏幕的位置创建缩放。但如果我这样做，缩放会在视图的中心创建。

这是我用来进行缩放的代码：

 if([gesture state] == UIGestureRecognizerStateBegan) 
        previousScale = 1.0;

    

    if (
        [gesture state] == UIGestureRecognizerStateChanged) 

        CGFloat currentScale = [[[gesture view].layer valueForKeyPath:@"transform.scale"] floatValue];

        // Constants to adjust the max/min values of zoom
        const CGFloat kMaxScale = 4.0;
        const CGFloat kMinScale = 1.0;

        CGFloat newScale = 1 -  (previousScale - [gesture scale]); // new scale is in the range (0-1)
        newScale = MIN(newScale, kMaxScale / currentScale);
        newScale = MAX(newScale, kMinScale / currentScale);
        scale = newScale;

        CGAffineTransform transform = CGAffineTransformScale([[gesture view] transform], newScale, newScale);

        [gesture view].transform = transform;

        [self.collectionView.collectionViewLayout invalidateLayout];
    

那么如何选择 UIPinchGesture 的位置呢？

谢谢

【参考方案1】：

我做到了，这是我的最终代码：

if([gesture state] == UIGestureRecognizerStateBegan) 
    previousScale = 1.0;
    lastPoint = [gesture locationInView:[gesture view]];


if (
    [gesture state] == UIGestureRecognizerStateChanged) 

    CGFloat currentScale = [[[gesture view].layer valueForKeyPath:@"transform.scale"] floatValue];

    // Constants to adjust the max/min values of zoom
    const CGFloat kMaxScale = 4.0;
    const CGFloat kMinScale = 1.0;

    CGFloat newScale = 1 -  (previousScale - [gesture scale]); // new scale is in the range (0-1)
    newScale = MIN(newScale, kMaxScale / currentScale);
    newScale = MAX(newScale, kMinScale / currentScale);
    scale = newScale;

    CGAffineTransform transform = CGAffineTransformScale([[gesture view] transform], newScale, newScale);

    [gesture view].transform = transform;

    CGPoint point = [gesture locationInView:[gesture view]];
    CGAffineTransform transformTranslate = CGAffineTransformTranslate([[gesture view] transform], point.x-lastPoint.x, point.y-lastPoint.y);

    [gesture view].transform = transformTranslate;