如何在 SwiftUI 的列表中启用选择 [英] How does one enable selections in SwiftUI's List
问题描述
我正在尝试使用 SwiftUI 创建一个简单的多选列表.我无法让它工作.
I am trying to create a simple multiple selection List with SwiftUI. I am unable to make it work.
List 接受第二个参数,它是一个 SelectionManager,所以我尝试创建一个的具体实现.但是,它永远不会被调用,行也不会突出显示.
List takes a second argument which is a SelectionManager, so I tried creating a concrete implementation of one. But, it never gets called and the rows never highlight.
import SwiftUI
var demoData = ["Phil Swanson", "Karen Gibbons", "Grant Kilman", "Wanda Green"]
struct SelectKeeper : SelectionManager{
var selections = Set<UUID>()
mutating func select(_ value: UUID) {
selections.insert(value)
}
mutating func deselect(_ value: UUID) {
selections.remove(value)
}
func isSelected(_ value: UUID) -> Bool {
return selections.contains(value)
}
typealias SelectionValue = UUID
}
struct SelectionDemo : View {
@State var selectKeeper = SelectKeeper()
var body: some View {
NavigationView {
List(demoData.identified(by: .self)){ name in
Text(name)
}
.navigationBarTitle(Text("Selection Demo"))
}
}
}
#if DEBUG
struct SelectionDemo_Previews : PreviewProvider {
static var previews: some View {
SelectionDemo()
}
}
#endif
代码运行良好,但行没有突出显示,并且从不调用 SelectionManager 代码.
Code runs fine but rows don't highlight and the SelectionManager code is never called.
推荐答案
根据您的需求,有两种方法可以做到这一点:
Depending on what you want, there are two ways to do this:
您必须启用编辑模式";在选择之前的名单上很重要.从 List
的界面:
You must enable "Edit mode" on the list before a selection matters. From the interface for List
:
/// Creates an instance.
///
/// - Parameter selection: A selection manager that identifies the selected row(s).
///
/// - See Also: `View.selectionValue` which gives an identifier to the rows.
///
/// - Note: On iOS and tvOS, you must explicitly put the `List` into Edit
/// Mode for the selection to apply.
@available(watchOS, unavailable)
public init(selection: Binding<Selection>?, content: () -> Content)
您可以通过将 EditButton
添加到您的视图中的某处来实现.之后,你只需要为实现 SelectionManager
的东西绑定一个 var(你不需要在这里滚动你自己的:D)
You do that by adding an EditButton
to your view somewhere. After that, you just need to bind a var for something that implements SelectionManager
(you don't need to roll your own here :D)
var demoData = ["Phil Swanson", "Karen Gibbons", "Grant Kilman", "Wanda Green"]
struct SelectionDemo : View {
@State var selectKeeper = Set<String>()
var body: some View {
NavigationView {
List(demoData.identified(by: .self), selection: $selectKeeper){ name in
Text(name)
}
.navigationBarItems(trailing: EditButton())
.navigationBarTitle(Text("Selection Demo (selectKeeper.count)"))
}
}
}
这种方法看起来像这样:
This approach looks like this:
此时,我们将不得不推出自己的产品.注意:这个实现有一个错误,这意味着只有 Text
会导致选择发生.使用 Button
可以做到这一点,但由于 Beta 2 中删除了 borderlessButtonStyle()
的更改,它看起来很傻,我还没有想出解决方法.
At this point, we're going to have to roll our own.
Note: this implementation has a bug which means that only the Text
will cause a selection to occur. It is possible to do this with Button
but because of the change in Beta 2 that removed borderlessButtonStyle()
it looks goofy, and I haven't figured out a workaround yet.
struct Person: Identifiable, Hashable {
let id = UUID()
let name: String
}
var demoData = [Person(name: "Phil Swanson"), Person(name: "Karen Gibbons"), Person(name: "Grant Kilman"), Person(name: "Wanda Green")]
struct SelectKeeper : SelectionManager{
var selections = Set<UUID>()
mutating func select(_ value: UUID) {
selections.insert(value)
}
mutating func deselect(_ value: UUID) {
selections.remove(value)
}
func isSelected(_ value: UUID) -> Bool {
return selections.contains(value)
}
typealias SelectionValue = UUID
}
struct SelectionDemo : View {
@State var selectKeeper = Set<UUID>()
var body: some View {
NavigationView {
List(demoData) { person in
SelectableRow(person: person, selectedItems: self.$selectKeeper)
}
.navigationBarTitle(Text("Selection Demo (selectKeeper.count)"))
}
}
}
struct SelectableRow: View {
var person: Person
@Binding var selectedItems: Set<UUID>
var isSelected: Bool {
selectedItems.contains(person.id)
}
var body: some View {
GeometryReader { geo in
HStack {
Text(self.person.name).frame(width: geo.size.width, height: geo.size.height, alignment: .leading)
}.background(self.isSelected ? Color.gray : Color.clear)
.tapAction {
if self.isSelected {
self.selectedItems.remove(self.person.id)
} else {
self.selectedItems.insert(self.person.id)
}
}
}
}
}
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