我正在创建一个垂直布局,其中包含可滚动的水平
LazyHGrid
。问题在于LazyHGrid
中的视图可能具有不同的高度(主要是由于动态文本行),但网格始终根据网格中的第一个元素计算其自身的高度:
我想要的是根据可见项更改浅红色矩形的大小,因此当有较小的可见项时,它应该看起来像这样:
当有更大的项目时,它应该看起来像这样:
这是导致第一张图片状态的代码:struct TestView: PreviewProvider {
static var previews: some View {
ScrollView {
VStack {
Color.blue
.frame(height: 100)
ScrollView(.horizontal) {
LazyHGrid(
rows: [GridItem()],
alignment: .top,
spacing: 16
) {
Color.red
.frame(width: 64, height: 24)
ForEach(Array(0...10), id: \.self) { value in
Color.red
.frame(width: 64, height: CGFloat.random(in: 32...92))
}
}.padding()
}.background(Color.red.opacity(0.3))
Color.green
.frame(height: 100)
}
}
}
}
我想要的类似的东西可以通过以下方式实现:
extension View {
func readSize(edgesIgnoringSafeArea: Edge.Set = [], onChange: @escaping (CGSize) -> Void) -> some View {
background(
GeometryReader { geometryProxy in
SwiftUI.Color.clear
.preference(key: ReadSizePreferenceKey.self, value: geometryProxy.size)
}.edgesIgnoringSafeArea(edgesIgnoringSafeArea)
)
.onPreferenceChange(ReadSizePreferenceKey.self) { size in
DispatchQueue.main.async { onChange(size) }
}
}
}
struct ReadSizePreferenceKey: PreferenceKey {
static var defaultValue: CGSize = .zero
static func reduce(value: inout CGSize, nextValue: () -> CGSize) {}
}
struct Size: Equatable {
var height: CGFloat
var isValid: Bool
}
struct TestView: View {
@State private var sizes = [Int: Size]()
@State private var height: CGFloat = 32
static let values: [(Int, CGFloat)] =
(0...3).map { ($0, CGFloat(32)) }
+ (4...10).map { ($0, CGFloat(92)) }
var body: some View {
ScrollView {
VStack {
Color.blue
.frame(height: 100)
ScrollView(.horizontal) {
LazyHGrid(
rows: [GridItem(.fixed(height))],
alignment: .top,
spacing: 16
) {
ForEach(Array(Self.values), id: \.0) { value in
Color.red
.frame(width: 300, height: value.1)
.readSize { sizes[value.0]?.height = $0.height }
.onAppear {
if sizes[value.0] == nil {
sizes[value.0] = Size(height: .zero, isValid: true)
} else {
sizes[value.0]?.isValid = true
}
}
.onDisappear { sizes[value.0]?.isValid = false }
}
}.padding()
}.background(Color.red.opacity(0.3))
Color.green
.frame(height: 100)
}
}.onChange(of: sizes) { sizes in
height = sizes.filter { $0.1.isValid }.map { $0.1.height }.max() ?? 32
}
}
}
...但是你会发现它有点卡顿且有点复杂,难道没有更好的解决方案吗?谢谢大家!