从公共中心旋转一组 UIViews [英] Rotate group of UIViews together from common center

问题描述

这是对这个问题的跟进.我有一个类似的设置，有 n 个视图，我想将它们与旋转手势一起旋转.

This is a follow up to this question. I have a similar setup with n number of views, and I want to rotate them together with the rotation gesture.

我知道如何将旋转应用于单个视图，但在这里我想从公共中心而不是它们自己的中心旋转所有视图.

I know how to apply a rotation to a single view, but here I want to rotate all of them from common center instead of their own.

所以我尝试了这个方法

• 计算所有选定视图的公共中心点
• 设置指向这个公共中心的视图转换
• 并旋转视图

这就是我得到的

CGPoint newCenter =CGPointZero;
for(UIView *node in self.selectedNodes){
    newCenter = CGPointMake(newCenter.x + node.center.x, newCenter.y + node.center.y);
}

newCenter = CGPointMake(newCenter.x/self.selectedNodes.count, newCenter.y/self.selectedNodes.count);
for(UIview *node in self.selectedNodes){
     CGAffineTransform newTransform = CGAffineTransformMakeTranslation(groupCenter.x,groupCenter.y);
    newTransform = CGAffineTransformRotate( node.transform,recognizer.rotation);
    newTransform = CGAffineTransformTranslate(newTransform,-groupCenter.x, -groupCenter.y);
     node.transform = newTransform;
}

但这并没有按预期工作.非常感谢任何帮助..

But this isn't working as expected. any help is much appreciated..

推荐答案

又是我.这是我进行轮换的方式:

it's me again. Here's how I did rotation:

let rotation = recognizer.rotation
recognizer.rotation = 0
let center = views.map { $0.center }.reduce(CGPoint.zero, +) / CGFloat(views.count)
views.forEach {
    $0.transform = $0.transform.rotated(by: rotation)
    let distance = $0.center - center
    $0.center = center + CGPoint(
        x: distance.x * cos(rotation) - distance.y * sin(rotation),
        y: distance.y * cos(rotation) + distance.x * sin(rotation)
    )
}

它与比例非常相似，你得到所有视图的中心，对于每个视图你得到到该中心的距离，使用公式旋转它以旋转一个点，并将旋转距离添加到所有视图的中心.

It's very similar to the scale, you get the center of all views, for each view you get the distance to that center, rotate it using the formula to rotate a point, and add that rotated distance to the center of all views.

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