在 SwiftUI 中,我们List
表示可重用的项目。就像UIKit
UITableView
一样.
静态列表构建如下:
List {
Text("cell")
Text("cell")
Text("cell")
Text("cell")
}
但似乎它根本不可重复使用
如何拥有一些对象的数组并根据数组及其动态大小(计数(填充列表?
单元格被重用。请参阅 SwiftUI 中的列表是否重用类似于 UITableView 的单元格?
对于静态列表,限制为 10 个项目。这与ViewBuilder
实现有关。
extension ViewBuilder {
public static func buildBlock<C0, C1>(_ c0: C0, _ c1: C1) -> TupleView<(C0, C1)> where C0 : View, C1 : View
}
…
extension ViewBuilder {
public static func buildBlock<C0, C1, C2, C3, C4, C5, C6, C7, C8, C9>(_ c0: C0, _ c1: C1, _ c2: C2, _ c3: C3, _ c4: C4, _ c5: C5, _ c6: C6, _ c7: C7, _ c8: C8, _ c9: C9) -> TupleView<(C0, C1, C2, C3, C4, C5, C6, C7, C8, C9)> where C0 : View, C1 : View, C2 : View, C3 : View, C4 : View, C5 : View, C6 : View, C7 : View, C8 : View, C9 : View
}
要使用数组,您可以使用以下 API:
let array = [1,2,3,4]
let listView = List(array) { value in
Text(value.description)
}
extension List {
extension List {
/// Creates a List that computes its rows on demand from an underlying
/// collection of identified data.
@available(watchOS, unavailable)
public init<Data, RowContent>(_ data: Data, selection: Binding<Selection>?, rowContent: @escaping (Data.Element.IdentifiedValue) -> RowContent) where Content == ForEach<Data, HStack<RowContent>>, Data : RandomAccessCollection, RowContent : View, Data.Element : Identifiable
…
通常由动态数据生成的动态视图。因此,您应该考虑为重复视图使用数据结构,然后基于如下数据构建列表:
struct Student: Identifiable {
let name: String
let id: Int
}
struct ContentView : View {
// Could be `@State Var` instead
let students = [
Student(name: "AAAAA", id: 1),
Student(name: "BBBBB", id: 2),
Student(name: "CCCCC", id: 3), // Notice that trailing comma is not problem here?
]
var body: some View {
List(students) { student in
Text(student.name)
}
}
}
数组应包含Identifiable
对象(推荐(
或者,如果您不喜欢遵守Identifiable
协议,则可以像这样使用它:
struct Book {
let anyPropertyName: String
let title: String
}
struct ContentView : View {
// Could be `@State Var` instead
let books = [
Book(anyPropertyName: "AAAA", title: "1111"),
Book(anyPropertyName: "BBBB", title: "2222"),
Book(anyPropertyName: "CCCC", title: "3333")
]
var body: some View {
List(books.identified(by: .anyPropertyName)) { book in
Text(book.title)
}
}
}
请注意,数据源可以@State var
,并且能够在任何@State var
更改时更新 UI。
最后,虽然看起来不是重用,但实际上确实如此!10 个静态项的限制与重用无关。