如何降低捏缩放 UIGestureRecognizer 的速度

Posted 2023-02-19

【中文标题】如何降低捏缩放 UIGestureRecognizer 的速度

【英文标题】：How to reduce velocity of pinch-zoom UIGestureRecognizer

【发布时间】：2014-04-07 03:31:16

【问题描述】：

我创建了一个UIGestureRecognizer，很像 this one：

- (void)handlePinchGesture:(UIPinchGestureRecognizer *)gestureRecognizer 

    if([gestureRecognizer state] == UIGestureRecognizerStateBegan) 
        // Reset the last scale, necessary if there are multiple objects with different scales
        lastScale = [gestureRecognizer scale];
    

    if ([gestureRecognizer state] == UIGestureRecognizerStateBegan || 
        [gestureRecognizer state] == UIGestureRecognizerStateChanged) 

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

        // Constants to adjust the max/min values of zoom
        const CGFloat kMaxScale = 2.0;
        const CGFloat kMinScale = 1.0;

        CGFloat newScale = 1 -  (lastScale - [gestureRecognizer scale]); 
        newScale = MIN(newScale, kMaxScale / currentScale);   
        newScale = MAX(newScale, kMinScale / currentScale);
        CGAffineTransform transform = CGAffineTransformScale([[gestureRecognizer view] transform], newScale, newScale);
        [gestureRecognizer view].transform = transform;

        lastScale = [gestureRecognizer scale];  // Store the previous scale factor for the next pinch gesture call  
    

这可以按预期工作，但是我的客户希望它对触摸不敏感。如何降低捏合的速度（向内和向外），使其以默认速度的 80% 左右缩放？

【问题讨论】：

您是否尝试手动设置您的scrollView 的zoomScale ？

@NicolasBonnet 不幸的是，这个特定的没有包裹在滚动视图中，所以这样做是不可行的：|

【参考方案1】：

你有没有试过把scale当前值调到80%。

if ([gestureRecognizer state] == UIGestureRecognizerStateBegan || 
        [gestureRecognizer state] == UIGestureRecognizerStateChanged) 

    CGFloat maxScale = 2.0;
    CGFloat currentScale = [gestureRecognizer scale];
    currentScale = 0.8 * currentScale;   //80% of scaling

    if(currentScale < 0.8)
        currentScale = 0.8;

    if(currentScale > maxScale)
        currentScale = maxScale;

    [gestureRecognizer view].transform = CGAffineTransformScale([[gestureRecognizer view] transform], currentScale, currentScale);

【讨论】：

我相信这也可以，但是为什么要裁剪您的比例值，我认为没有必要这样做。

裁剪 Scale 值，因为它会限制您的缩放属性。

好的，抱歉，我已经快速阅读了原始代码并错过了那部分。

不，这根本不起作用 - 有一些非常奇怪的相反效果：|

【参考方案2】：

试试这个。

- (void)handlePinching:(UIPinchGestureRecognizer *)gestureRecognizer 

    if([gestureRecognizer state] == UIGestureRecognizerStateBegan) 
        if (CGRectIsEmpty(self.initalFrame)) 
            self.initalFrame = gestureRecognizer.view.frame;
            // store view's original frame and never change it
        

        if (self.preScale == 0.f) 
            self.preScale = 1.f; 
        

        gestureRecognizer.scale = self.preScale;
        // gestureRecognizer and view should share the same scale state at the beginning
    

    if ([gestureRecognizer state] == UIGestureRecognizerStateBegan ||
        [gestureRecognizer state] == UIGestureRecognizerStateChanged) 

        const CGFloat kMaxScale = 2.0;
        const CGFloat kMinScale = 1.0;

        CGFloat newScale = gestureRecognizer.scale;

        newScale = (newScale - self.preScale) * 0.8 + self.preScale;

        newScale = MIN(newScale, kMaxScale);
        newScale = MAX(newScale, kMinScale);


        CGRect newFrame = self.initalFrame;
        newFrame.size.height *= newScale;
        newFrame.size.width *= newScale;
        gestureRecognizer.view.frame = newFrame;
        self.preScale = newScale;
    

点是

使用框架实现缩放。 将比例变量更改为慢/速缩放。

【讨论】：

尝试了很多次，但似乎没有任何效果。

【参考方案3】：

事实证明，缩放速度过快实际上是链接答案代码中的一个错误。遗憾的是，这实际上并没有回答我的实际问题（我仍然想要一个答案！），但它确实可以解决我客户的问题。

注意底部添加的将gestureRecognizer重置为1的行：

- (void)handlePinchGesture:(UIPinchGestureRecognizer *)gestureRecognizer 

        ...

        lastScale = [gestureRecognizer scale];  // Store the previous scale factor for the next pinch gesture call  

        gestureRecognizer.scale = 1;
        // ^ added this line
    

【讨论】：

哦，是的，我的代码中没有添加那行，我的错误。

@HimanshuJoshi 人力资源部。现在你让我想到了——也许你的建议会在这行之后起作用。打算试试看。