iOS17中使用PhaseAnimator时Dismiss视图致App崩溃求助

问题说明 #

使用 iOS 17 新增的 PhaseAnimator 实现动画效果时，若在动画运行期间 dismiss 包含该动画的视图，App 会触发并发访问崩溃。已通过小型项目复现问题，并向苹果提交反馈（编号 FB13655444）。

复现代码 #

struct ContentView: View {
    @State var isPresenting = false

    var body: some View {
        Button("Present", action: {
            isPresenting = true
        })
        .sheet(isPresented: $isPresenting, content: {
            AnimatedView()
        })
    }
}

struct AnimatedView: View {
    @Environment(\.dismiss) var dismiss

    var body: some View {
        VStack {
            Text("Hello")
                .phaseAnimator([1, 1.3]) { content, phase in
                    content.scaleEffect(
                        CGSize(width: phase, height: phase),
                        anchor: .center
                    )
                }

            Button("Dismiss", action: {
                dismiss()
            })
        }
    }
}

崩溃栈信息 #

Simultaneous accesses to 0x102b079c0, but modification requires exclusive access.
Previous access (a modification) started at SwiftUI`OUTLINED_FUNCTION_0 + 8352 (0x1c571eb30).
Current access (a read) started at:
0    libswiftCore.dylib                 0x0000000192c95ec8 swift::runtime::AccessSet::insert(swift::runtime::Access*, void*, void*, swift::ExclusivityFlags) + 428
1    libswiftCore.dylib                 0x0000000192c960dc swift_beginAccess + 72
2    SwiftUI                            0x00000001c571ca90 OUTLINED_FUNCTION_0 + 10144
3    SwiftUI                            0x00000001c583a898 OUTLINED_FUNCTION_21 + 11580
4    SwiftUI                            0x00000001c4cccec4 OUTLINED_FUNCTION_31 + 7832
5    SwiftUI                            0x00000001c4cccec4 OUTLINED_FUNCTION_31 + 7556
6    SwiftUI                            0x00000001c59814f8 OUTLINED_FUNCTION_31 + 1452
7    SwiftUI                            0x00000001c57ab900 OUTLINED_FUNCTION_83 + 84188
8    SwiftUI                            0x00000001c57ab900 OUTLINED_FUNCTION_83 + 79588
9    SwiftUI                            0x00000001c57ab900 OUTLINED_FUNCTION_83 + 79548
10   SwiftUI                            0x00000001c57ab900 OUTLINED_FUNCTION_83 + 79680
11   AttributeGraph                     0x00000001b2c03748 __swift_instantiateConcreteTypeFromMangledName + 4000
12   AttributeGraph                     0x00000001b2bf2930 AG::Node::destroy(AG::Graph&) + 188
13   AttributeGraph                     0x00000001b2be87b0 AG::Subgraph::invalidate_now(AG::Graph&) + 1184
14   AttributeGraph                     0x00000001b2be8678 AG::Graph::invalidate_subgraphs() + 192
15   AttributeGraph                     0x00000001b2be13c8 AG::Graph::Context::~Context() + 348
16   AttributeGraph                     0x00000001b2bfa740 AGGraphInvalidate + 32
17   SwiftUI                            0x00000001c571ca90 OUTLINED_FUNCTION_0 + 8400
18   SwiftUI                            0x00000001c583a898 OUTLINED_FUNCTION_21 + 32348
19   SwiftUI                            0x00000001c583a898 OUTLINED_FUNCTION_21 + 32124
20   SwiftUI                            0x00000001c583a898 OUTLINED_FUNCTION_21 + 32392
21   libobjc.A.dylib                    0x0000000180083080 AutoreleasePoolPage::releaseUntil(objc_object**) + 200
22   libobjc.A.dylib                    0x0000000180082f18 objc_autoreleasePoolPop + 256
23   CoreFoundation                     0x00000001804a62b4 _CFAutoreleasePoolPop + 28
24   CoreFoundation                     0x00000001803f0ecc __CFRunLoopPerCalloutARPEnd + 44
25   CoreFoundation                     0x00000001803eb9b8 __CFRunLoopRun + 1976
26   CoreFoundation                     0x00000001803eb368 CFRunLoopRunSpecific + 572
27   GraphicsServices                   0x000000018e9fba44 GSEventRunModal + 160
28   UIKitCore                          0x00000001852eff80 -[UIApplication _run] + 868
29   UIKitCore                          0x00000001852f3ee0 UIApplicationMain + 124
30   SwiftUI                            0x00000001c51fbfbc OUTLINED_FUNCTION_70 + 500
31   SwiftUI                            0x00000001c51fbfbc OUTLINED_FUNCTION_70 + 148
32   SwiftUI                            0x00000001c4f02f48 OUTLINED_FUNCTION_2 + 92
33   SimultaneousAccessesCrash          0x0000000102632f18 static SimultaneousAccessesCrashApp.$main() + 40
34   SimultaneousAccessesCrash          0x0000000102632fe4 main + 12

临时方案 #

放弃使用 PhaseAnimator，通过 .onAppear 配合一系列 withAnimation 调用实现多状态切换动画，后续动画用 DispatchQueue.main.async(after: ...) 延迟触发。该方案可行但代码不够优雅。

可靠解决方案 #

利用 PhaseAnimator 的 isActive 参数手动控制动画启停，在 dismiss 视图前先停止动画，避免并发访问冲突：

struct AnimatedView: View {
    @Environment(\.dismiss) var dismiss
    @State private var isAnimating = true

    var body: some View {
        VStack {
            Text("Hello")
                .phaseAnimator([1, 1.3], isActive: $isAnimating) { content, phase in
                    content.scaleEffect(
                        CGSize(width: phase, height: phase),
                        anchor: .center
                    )
                }

            Button("Dismiss", action: {
                // 先停止动画
                isAnimating = false
                // 立即dismiss即可，动画停止后不会再触发并发访问
                dismiss()
            })
        }
        // 视图消失时确保动画停止，防止意外场景触发崩溃
        .onDisappear {
            isAnimating = false
        }
    }
}

原理说明 #

崩溃原因是视图销毁时，PhaseAnimator 的动画仍在运行，导致对内部状态的并发读写冲突。通过 isActive 参数主动停止动画后，视图销毁时动画逻辑已终止，不会再触发访问冲突。

内容的提问来源于stack exchange，提问作者vrutberg