VStack

12/5/2021 swiftiosswiftui

# VStack

文档:https://developer.apple.com/documentation/swiftui/vstack (opens new window)

垂直排列子元素的视图。

创建一个垂直排列的静态列表:

VStack (alignment: .center, spacing: 20){
    Text("Hello")
    Divider()
    Text("World")
}

VStack 的定义:

@frozen public struct VStack<Content> : View where Content : View {
    @inlinable public init(alignment: HorizontalAlignment = .center, spacing: CGFloat? = nil, @ViewBuilder content: () -> Content)
    public typealias Body = Never
}

HStack 构造函数的参数说明:

  • spacing: CGFloat?,设置子视图之间垂直间距
  • alignment: HorizontalAlignment, 子视图对齐方式

# HorizontalAlignment

An alignment position along the horizontal axis.

它是个结构体,有以下几个静态属性:

  • leading
  • center
  • trailing

为了更深刻的理解这几种布局差役,首先创建个通用的 VStackCaseItem, 便于代码复用:

struct VStackCaseItem: View {
    let alignment: HorizontalAlignment

    var body: some View {
         VStack(alignment: alignment, spacing: 20){
            Text("A\nB")
                .frame(width: 50)
                .background(Color.yellow)

            Text(alignment.name)
                .foregroundColor(.white)
                .frame(width:150)
                .background(Color.red)


            Text("OldBirds")
                .background(Color.green)
                .foregroundColor(.white)

         }.background(Color.gray)
    }
}

extension HorizontalAlignment {
    var name: String {
        switch self {
        case .leading:
            return "leading"
        case .trailing:
            return "trailing"
        case .center:
            return "center"
        default:
            return "other"
        }
    }
}

然后分别初始化不同的 alignment:


struct ContentView: View {
    var body: some View {
        VStack(spacing: 20) {
            VStackCaseItem(alignment: .leading)
            VStackCaseItem(alignment: .trailing)
            VStackCaseItem(alignment: .center)
        }
    }
}

通过预览效果,可以比较容易发现 alignment 间的差异。

  • .leading: 子视图局左对齐
  • .center: 子视图局中对齐
  • .trailing: 子视图局右对齐

# 使 VStack 填充屏幕的宽度

有这么个案例:

struct ContentView: View {
    var body: some View {
        VStack(alignment: .leading) {
          Text("标题")
            .font(.title)

          Text("内容")
            .lineLimit(nil)
            .font(.body)

          Spacer()
        }
        .background(Color.red)
    }
}

显示效果:

标签/文本组件不需要全宽,如何让 VStack 填充屏幕的宽度?

# 方案一:设置 frame

struct ContentView: View {
    var body: some View {
        VStack(alignment: .leading) {
          Text("标题")
            .font(.title)
            .background(Color.yellow)

          Text("内容")
            .lineLimit(nil)
            .font(.body)
            .background(Color.blue)
        }
        .frame(
          maxWidth: .infinity,
          maxHeight: .infinity,
          alignment: .topLeading
        )
        .background(Color.red)
    }
}

除了通过设置尺寸为 .infinity, 还可以通过 GeometryReader 设置尺寸:

struct ContentView: View {
    var body: some View {
        GeometryReader { geometryProxy in
            VStack(alignment: .leading) {
              Text("标题")
                .font(.title)
                .background(Color.yellow)

              Text("内容")
                .lineLimit(nil)
                .font(.body)
                .background(Color.blue)
            }
            .frame(
                maxWidth: geometryProxy.size.width,
                maxHeight: geometryProxy.size.height,
                alignment: .topLeading
            )
        }
        .background(Color.red)
    }
}

# 方案二:结合 HStack 和 Spacer

struct ContentView: View {

    var body: some View {
        HStack {
            VStack(alignment: .leading) {
              Text("标题")
                .font(.title)
                .background(Color.yellow)

              Text("内容")
                .lineLimit(nil)
                .font(.body)
                .background(Color.blue)

                Spacer()
            }

            Spacer()
        }.background(Color.red)
    }
}

上次更新: 10/20/2022, 5:36:35 AM