获得视图

Question

我正在使用“ rectgetter”来获取 view 的 cgrect 。

这样：

Text("Hello")
    .background(RectGetter(rect: self.$rect))


struct RectGetter: View {
    @Binding var rect: CGRect

    var body: some View {
        GeometryReader { proxy in
            self.createView(proxy: proxy)
        }
    }

    func createView(proxy: GeometryProxy) -> some View {
        DispatchQueue.main.async {
            self.rect = proxy.frame(in: .global) // crash here
        }

        return Rectangle().fill(Color.clear)
    }
}

但是有时在设置rect时会崩溃。

Thread 0 name:
Thread 0 Crashed:
0   libsystem_kernel.dylib          0x00000001a1ec5ec4 __pthread_kill + 8
1   libsystem_pthread.dylib         0x00000001a1de5724 pthread_kill$VARIANT$armv81 + 216 (pthread.c:1458)
2   libsystem_c.dylib               0x00000001a1d358c0 __abort + 112 (abort.c:147)
3   libsystem_c.dylib               0x00000001a1d35850 abort + 112 (abort.c:118)
4   AttributeGraph                  0x00000001cce56548 0x1cce25000 + 202056
5   AttributeGraph                  0x00000001cce2b980 0x1cce25000 + 27008
6   SwiftUI                         0x00000001d89ce9b4 $s7SwiftUI27_PositionAwareLayoutContextV10dimensionsSo6CGSizeVvg + 56 (<compiler-generated>:0)
7   SwiftUI                         0x00000001d8a43584 $sSo6CGSizeVIgd_ABIegr_TRTA + 24 (<compiler-generated>:0)
8   SwiftUI                         0x00000001d8a43a54 $s7SwiftUI13GeometryProxyV4sync33_4C4BAC551E328ACCA9CD3748EDC0CC3ALLyxSgxyXElFxAA9ViewGraphCXEfU_... + 92 (GeometryReader.swift:126)
9   SwiftUI                         0x00000001d8a43f20 $s7SwiftUI13GeometryProxyV4sync33_4C4BAC551E328ACCA9CD3748EDC0CC3ALLyxSgxyXElFxAA9ViewGraphCXEfU_... + 20 (<compiler-generated>:0)
10  SwiftUI                         0x00000001d8c4842c $s7SwiftUI16ViewRendererHostPAAE06updateC5Graph4bodyqd__qd__AA0cG0CXE_tlF + 80 (ViewRendererHost.swift:64)
11  SwiftUI                         0x00000001d8a438d4 $s7SwiftUI13GeometryProxyV5frame2inSo6CGRectVAA15CoordinateSpaceO_tF + 196 (GeometryReader.swift:125)
12  MyApp                           0x0000000102cf5c54 closure #1 in RectGetter.createView(proxy:) + 128 (RectGetter.swift:22)

是否有一些更可靠的方法（不崩溃）来获取 view 的 cgrect ？

Answer 1

更新：改进并简化了一种可能的解决方案，可以通过辅助扩展程序读取任何坐标空间中任何视图的rect。自Xcode 11.1以来的工作，用Xcode 13.3重新测试。

主要部分：

func rectReader(_ binding: Binding<CGRect>, _ space: CoordinateSpace = .global) -> some View {
    GeometryReader { (geometry) -> Color in
        let rect = geometry.frame(in: space)
        DispatchQueue.main.async {
            binding.wrappedValue = rect
        }
        return .clear
    }
}

用法相同

Text("Test").background(rectReader($rect))

或使用新扩展

Text("Test").reading(rect: $rect)

完成

Answer 2

另一种方法是使用偏好键，如下所示。

总而言之，您可以设置一个修饰符：

struct SizePreferenceKey: PreferenceKey {
    static var defaultValue: CGRect = .zero

    static func reduce(value: inout CGRect, nextValue: () -> CGRect) {
        value = nextValue()
    }
}

struct SizeModifier: ViewModifier {
    private var sizeView: some View {
        GeometryReader { geometry in
            Color.clear.preference(key: SizePreferenceKey.self, value: geometry.frame(in: .global))
        }
    }

    func body(content: Content) -> some View {
        content.background(sizeView)
    }
}

然后使用该修饰符：

SomeView()
   .modifier(SizeModifier())
   .onPreferenceChange(SizePreferenceKey.self) { print("My rect is: \($0)") }