SwiftUI 流式布局

引入了类似于 HStack 和 VStack 的 HFlow 和 VFlow。按行排列视图，并在元素超出边界空间时自动换行。

HFlow

struct Colors: View {
    let colors: [Color] = [
        .blue,
        .orange,
        .green,
        .yellow,
        .brown,
        .mint,
        .indigo,
        .cyan,
        .gray,
        .pink
    ]

    var body: some View {
        HFlow {
            ForEach(colors, id: \.description) { color in
                RoundedRectangle(cornerRadius: 10)
                    .fill(color.gradient)
                    .frame(width: .random(in: 40...60), height: 50)
            }
        }
        .frame(maxWidth: 300)
    }
}

HFlow

VFlow

VFlow {
    ForEach(colors, id: \.description) { color in
        RoundedRectangle(cornerRadius: 10)
            .fill(color.gradient)
            .frame(width: 50, height: .random(in: 40...60))
    }
}
.frame(maxHeight: 300)

VFlow

对齐

支持与 HStack 和 VStack 相同的对齐方式。

HFlow(alignment: .top) {
    ForEach(colors, id: \.description) { color in
        RoundedRectangle(cornerRadius: 10)
            .fill(color.gradient)
            .frame(width: 50, height: .random(in: 40...60))
    }
}
.frame(maxWidth: 300)

HFlow

此外，对齐方式可以在两个轴向上指定。非常适合标签。

HFlow(horizontalAlignment: .center, verticalAlignment: .top) {
    ForEach(colors, id: \.description) { color in
        RoundedRectangle(cornerRadius: 10)
            .fill(color.gradient)
            .frame(width: .random(in: 30...60), height: 30)
    }
}
.frame(maxWidth: 300)

HFlow

间距

分别自定义行和项目之间的间距。

HFlow(itemSpacing: 4, rowSpacing: 20) {
    ForEach(colors, id: \.description) { color in
        RoundedRectangle(cornerRadius: 10)
            .fill(color.gradient)
            .frame(width: 50, height: 50)
    }
}
.frame(maxWidth: 300)

HFlow

分布项目

通过最小化每行剩余的空白空间来均匀分布项目。实现 Knuth-Plass 断行算法。

HFlow(distributeItemsEvenly: true) {
    ForEach(colors, id: \.description) { color in
        RoundedRectangle(cornerRadius: 10)
            .fill(color.gradient)
            .frame(width: 65, height: 50)
    }
}
.frame(width: 300, alignment: .leading)

HFlow

两端对齐

HFlow(justified: true) {
    ForEach(colors, id: \.description) { color in
        RoundedRectangle(cornerRadius: 10)
            .fill(color.gradient)
            .frame(width: 50, height: 50)
    }
}
.frame(width: 300)

HFlow

灵活性

HFlow { // distributes flexible items proportionally
    RoundedRectangle(cornerRadius: 10)
        .fill(.red)
        .frame(minWidth: 50, maxWidth: .infinity)
        .frame(height: 50)
        .flexibility(.minimum) // takes as little space as possible, rigid
    RoundedRectangle(cornerRadius: 10)
        .fill(.green)
        .frame(minWidth: 50, maxWidth: .infinity)
        .frame(height: 50)
        .flexibility(.natural) // expands
    RoundedRectangle(cornerRadius: 10)
        .fill(.blue)
        .frame(minWidth: 50, maxWidth: .infinity)
        .frame(height: 50)
        .flexibility(.natural) // expands
    RoundedRectangle(cornerRadius: 10)
        .fill(.yellow)
        .frame(minWidth: 50, maxWidth: .infinity)
        .frame(height: 50) // takes as much space as possible
        .flexibility(.maximum)
}
.frame(width: 300)

HFlow

换行

HFlow {
    RoundedRectangle(cornerRadius: 10)
        .fill(.red)
        .frame(width: 50, height: 50)
    RoundedRectangle(cornerRadius: 10)
        .fill(.green)
        .frame(width: 50, height: 50)
    RoundedRectangle(cornerRadius: 10)
        .fill(.blue)
        .frame(width: 50, height: 50)
    LineBreak()
    RoundedRectangle(cornerRadius: 10)
        .fill(.yellow)
        .frame(width: 50, height: 50)
}
.frame(width: 300)

HFlow

HFlow {
    RoundedRectangle(cornerRadius: 10)
        .fill(.red)
        .frame(width: 50, height: 50)
    RoundedRectangle(cornerRadius: 10)
        .fill(.green)
        .frame(width: 50, height: 50)
        .startInNewLine()
    RoundedRectangle(cornerRadius: 10)
        .fill(.blue)
        .frame(width: 50, height: 50)
    RoundedRectangle(cornerRadius: 10)
        .fill(.yellow)
        .frame(width: 50, height: 50)
}
.frame(width: 300)

HFlow

RTL

也适配从左到右和从右到左的环境。

HFlow {
    ForEach(colors, id: \.description) { color in
        RoundedRectangle(cornerRadius: 10)
            .fill(color.gradient)
            .frame(width: .random(in: 40...60), height: 50)
    }
}
.frame(maxWidth: 300)
.environment(\.layoutDirection, .rightToLeft)

HFlow