SwiftUI:呈现工作表时防止视图刷新 [英] SwiftUI: prevent View from refreshing when presenting a sheet

问题描述

我注意到添加 sheet 修饰符时，SwiftUI完全刷新了视图.

I have noticed that SwiftUI completely refresh view when adding sheetmodifier.

假设我有一个显示随机数的View.我希望该值是独立的，并且不与工作表逻辑相关(每次打开/关闭工作表时都不会更改)，但是每个工作表显示/关闭的文本都在更改.

Let's say I have View that displays random number. I expect that this value would be independent and not connected to the sheet logic (not changing every time I open/close sheet), but every time sheet presented/dismissed Text is changing.

是否应该这样工作?我是否错误地认为 @Sate 的要点是仅更新已连接的视图，而不是全部视图?呈现模态时，如何防止View刷新自身?

Is it supposed to work so? Am I wrong that main point of @Sateis to update only connected Views but not all stack? How can I prevent my View from refreshing itself when presenting a modal?

struct ContentView: View {

    @State var active = false

    var body: some View {
        VStack {
            Text("Random text: \(Int.random(in: 0...100))")

            Button(action: { self.active.toggle() }) {
                Text("Show pop up")
            }
        }
        .sheet(isPresented: $active) {
            Text("POP UP")
        }
    }
}

P.S.ContentView仅调用 onAppear()/ onDisappear()和 init().

P.S. ContentView calls onAppear()/onDisappear() and init() only ones.

推荐答案

它需要制作独立于条件的独立视图以实现您想要的行为，如下所示

It needs to make separated condition-independent view to achieve behavior as you wish, like below

struct RandomView: View {
    var body: some View {
        Text("Random text: \(Int.random(in: 0...100))")
    }
}

struct ContentView: View {

    @State var active = false

    var body: some View {
        VStack {
            RandomView()

            Button(action: { self.active.toggle() }) {
                Text("Show pop up")
            }
        }
        .sheet(isPresented: $active) {
            Text("POP UP")
        }
    }
}

在这种情况下，不会重建 RandomView ，因为它不依赖于 active 状态.

In this case RandomView is not rebuilt because is not dependent on active state.

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