Center Item Inside Horizontal Stack

问题

If I have 3 items inside a Horizontal Stack, I thought I could do something like this:

HStack{

      Text("test")

      Spacer()

      item2()

      Spacer()

      Text("test")
}

to center item2() in between the two Text views. However, the problem with this is that item2() isn't necessarily always centered, because, lets say Text("test") changes to Text("a") or something. This causes problems, and the second item isn't always centered on the screen.

How can I make it so item2() is always centered?

Thanks

回答1:

I would propose the following start point (simplest case... read below why)

As it's seen it really gives centred w/o frame shift with correctly aligned side elements, but ... there is drawback - it will work in such simplest variant only if it is known in advance that those three text elements should never overlap in user run-time. If it is the case (really there are such) then this approach just goes. However if left/right text might grow in run-time, then more calculations will be needed to limit their width by .frame(maxWidth:) depending on the width of centred element... that variant is more complicated, but it is feasible.

var body: some View {
        ZStack {
            HStack {
                Text("Longer side")
                Spacer()
                Text("One")
            }
            item2()
        }
    }

private func item2() -> some View {
    Text("CENTER")
        .background(Color.yellow)
        .border(Color.red)
}

Update: here is possible approach to limit one of the side to not overlap centred one (contains async updates, so should be tested in Live Preview or Simulator)

So... if left text is dynamic and the requirement to cut trailing symbols, here is how it could go ...

and it automatically fit well on device orientation change

struct TestHorizontalPinCenter: View {

    @State var centerFrame: CGRect = .zero

    private let kSpacing: CGFloat = 4.0
    var body: some View {
            ZStack {
                HStack {
                    Text("Longer side very long text to fit")
                        .lineLimit(1)
                        .frame(maxWidth: (centerFrame == .zero ? .infinity : centerFrame.minX - kSpacing), alignment: .leading)

                    Spacer()

                    Text("One")
                }
                item2()
                    .background(rectReader($centerFrame))
            }
        }

    private func item2() -> some View {
        Text("CENTER")
            .background(Color.yellow)
            .border(Color.red)
    }

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

And if it is needed to wrap left side, then .lineLimit(nil) and additional layout will be needed, and solution growth, but the idea is the same. Hope this will be helpful for someone.

回答2:

You may need to add some customized Alignment components.

                       extension HorizontalAlignment{
                    private enum MyHAlignment: AlignmentID {
                        static func defaultValue(in d: ViewDimensions) -> CGFloat {
                            return d[HorizontalAlignment.center]
                        }
                    }
                     static let myhAlignment = HorizontalAlignment(MyHAlignment.self)
                }







         HStack{
                Spacer()
                  Text("jjjjjjjjjj")
                 Spacer()
                  Image("image").alignmentGuide(.myhAlignment) { (ViewDimensions) -> CGFloat in
                      return ViewDimensions[HorizontalAlignment.center]
                  }
                Spacer()

                  Text("test")

              }.frame(alignment: Alignment(horizontal: .myhAlignment, vertical: .center))

回答3:

To center views you can use a ZStack:

ZStack {
    item2()

    HStack {
        Text("test")
        Spacer()
        Text("test")
    }
}

来源：https://stackoverflow.com/questions/59517327/center-item-inside-horizontal-stack

标签

swift

swiftui

centering

vstack

hstack