将 SwiftUI 视图渲染为 UIImage

Question

我正在尝试将 SwiftUI 视图呈现为 UIImage，然后让用户选择保存到相机胶卷或通过电子邮件发送给其他人。

例如，我想将 50 行的列表呈现到 UIImage 中。

struct MyList: View {
    var body: some View {
        List {
            ForEach(0 ..< 50, id:\.self) {
                Text("row \($0)")
            }
        }
    }
}

过去几周在互联网上搜索仍然没有运气。我尝试了 2 种不同的方法。

1. UIHostingController（来源在这里）

let hosting = UIHostingController(rootView: Text("TEST"))
hosting.view.frame = // Calculate the content size here //
let snapshot = hosting.view.snapshot        // output: an empty snapshot of the size
print(hosting.view.subviews.count)          // output: 0

我试过layoutSubviews(), setNeedsLayout(), layoutIfNeeded(), loadView()，但结果仍然是 0 个子视图。

2. UIWindow.rootViewController（来源在这里）

var vc = UIApplication.shared.windows[0].rootViewController
vc = vc.visibleController          // loop through the view controller stack to find the top most view controller
let snapshot = vc.view.snapshot    // output: a snapshot of the top most view controller

这几乎产生了我想要的输出。然而，我得到的快照实际上是一个屏幕截图，即带有导航栏、标签栏和固定大小（与屏幕大小相同）。我需要捕获的只是没有这些条的视图内容，有时可能比屏幕大（我的视图在这个例子中是一个很长的列表）。

试图查询vc.view.subviews以查找我想要的表视图，但返回一个无用的[<_TtGC7SwiftUI16PlatformViewHostGVS_42PlatformViewControllerRepresentableAdaptorGVS_16BridgedSplitViewVVS_22_VariadicView_Children7ElementGVS_5GroupGVS_19_ConditionalContentS4_GVS_17_UnaryViewAdaptorVS_9EmptyView______: 0x7fb061cc4770; frame = (0 0; 414 842); anchorPoint = (0, 0); tintColor = UIExtendedSRGBColorSpace 0 0.478431 1 1; layer = <CALayer: 0x600002d8caa0>>].

任何帮助深表感谢。

Answer 1

Would something like this work for you?

import SwiftUI

extension UIView {
    func takeScreenshot() -> UIImage {
        // Begin context
        UIGraphicsBeginImageContextWithOptions(self.bounds.size, false, UIScreen.main.scale)
        // Draw view in that context
        drawHierarchy(in: self.bounds, afterScreenUpdates: true)
        // And finally, get image
        let image = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()

        if (image != nil) {
            UIImageWriteToSavedPhotosAlbum(image!, nil, nil, nil);
            return image!
        }

        return UIImage()
    }
}

struct ContentView: UIViewRepresentable {
    func makeUIView(context: Context) -> UIView {
        let someView = UIView(frame: UIScreen.main.bounds)
        _ = someView.takeScreenshot()
        return someView
    }

    func updateUIView(_ view: UIView, context: Context) {

    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}