在 Swiftui 中没有一种简单的方法可以通过捏来放大图像吗? [英] Isn't there an easy way to pinch to zoom in an image in Swiftui?

问题描述

我希望能够在 SwiftUI 中调整大小和移动图像(就像地图一样)，同时捏合缩放和拖动它.

I want to be able to resize and move an image in SwiftUI (like if it were a map) with pinch to zoom and drag it around.

我使用 UIKit 将图像嵌入到 UIScrollView 中并处理它，但我不知道如何在 SwiftUI 中执行此操作.我尝试使用 MagnificationGesture 但我无法让它顺利工作.

With UIKit I embedded the image into a UIScrollView and it took care of it, but I don't know how to do it in SwiftUI. I tried using MagnificationGesture but I cannot get it to work smoothly.

我一直在寻找这个，有没有人知道是否有更简单的方法?

I've been searching about this for a while, does anyone know if there's an easier way?

推荐答案

SwiftUI API 在这里非常没有帮助:onChanged 给出了相对于当前缩放手势的开始的数字，并且在回调中没有明显的方法来获取初始值.还有一个 onEnded 回调，但很容易错过/忘记.

The SwiftUI API is pretty unhelpful here: the onChanged gives number relative to start of current zoom gesture and no obvious way within a callback to get the initial value. And there is an onEnded callback but easy to miss/forget.

解决方法，添加:

@State var lastScaleValue: CGFloat = 1.0

然后在回调中:

.gesture(MagnificationGesture().onChanged { val in
            let delta = val / self.lastScaleValue
            self.lastScaleValue = val
            let newScale = self.scale * delta

//... anything else e.g. clamping the newScale
}.onEnded { val in
  // without this the next gesture will be broken
  self.lastScaleValue = 1.0
}

其中 newScale 是您自己的比例跟踪(可能是状态或绑定).如果你直接设置你的比例，它会变得一团糟，因为在每个刻度上，数量将相对于之前的数量.

where newScale is your own tracking of scale (perhaps state or a binding). If you set your scale directly it will get messed up as on each tick the amount will be relative to previous amount.

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