深度编程 SwiftUI NavigationView 导航 [英] Deep programmatic SwiftUI NavigationView navigation
问题描述
我正在尝试按顺序获得一个深层嵌套的程序化导航堆栈.当手动完成导航(即:按下链接)时,以下代码按预期工作.当您按下 Set Nav
按钮时,导航堆栈确实发生了变化 - 但不像预期的那样 - 并且您最终会得到一个损坏的堆栈 [start ->;b->bbb]
视图之间有很多翻转
I'm trying to get a deep nested programmatic navigation stack in order. The following code works as expected when navigation is done by hand (ie: pressing the links). When you press the Set Nav
button the navigation stack does change - but not as expected - and you end up with a broken stack [start -> b -> bbb]
with much flipping between views
class NavState: ObservableObject {
@Published var firstLevel: String? = nil
@Published var secondLevel: String? = nil
@Published var thirdLevel: String? = nil
}
struct LandingPageView: View {
@ObservedObject var navigationState: NavState
func resetNav() {
self.navigationState.firstLevel = "b"
self.navigationState.secondLevel = "ba"
self.navigationState.thirdLevel = "bbb"
}
var body: some View {
return NavigationView {
List {
NavigationLink(
destination: Place(
text: "a",
childValues: [ ("aa", [ "aaa"]) ],
navigationState: self.navigationState
).navigationBarTitle("a"),
tag: "a",
selection: self.$navigationState.firstLevel
) {
Text("a")
}
NavigationLink(
destination: Place(
text: "b",
childValues: [ ("bb", [ "bbb"]), ("ba", [ "baa", "bbb" ]) ],
navigationState: self.navigationState
).navigationBarTitle("b"),
tag: "b",
selection: self.$navigationState.firstLevel
) {
Text("b")
}
Button(action: self.resetNav) {
Text("Set Nav")
}
}
.navigationBarTitle("Start")
}
.navigationViewStyle(StackNavigationViewStyle())
}
}
struct Place: View {
var text: String
var childValues: [ (String, [String]) ]
@ObservedObject var navigationState: NavState
var body: some View {
List(childValues, id: \.self.0) { childValue in
NavigationLink(
destination: NextPlace(
text: childValue.0,
childValues: childValue.1,
navigationState: self.navigationState
).navigationBarTitle(childValue.0),
tag: childValue.0,
selection: self.$navigationState.secondLevel
) {
Text(childValue.0)
}
}
}
}
struct NextPlace: View {
var text: String
var childValues: [String]
@ObservedObject var navigationState: NavState
var body: some View {
List(childValues, id: \.self) { childValue in
NavigationLink(
destination: FinalPlace(
text: childValue,
navigationState: self.navigationState
).navigationBarTitle(childValue),
tag: childValue,
selection: self.$navigationState.thirdLevel
) {
Text(childValue)
}
}
}
}
struct FinalPlace: View {
var text: String
@ObservedObject var navigationState: NavState
var body: some View {
let concat: String = "\(navigationState.firstLevel)/\(navigationState.secondLevel))/\(navigationState.thirdLevel)/"
return VStack {
Text(text)
Text(concat)
}
}
}
我最初尝试将导航过渡动画作为问题源来解决 - 但 如何禁用 NavigationView 推送和弹出动画 暗示这是不可配置的
I originally attempted to tackle navigation transition animations as a problem source - but How to disable NavigationView push and pop animations is suggesting that this is not configurable
是否有任何关于 >1 级程序化导航的合理示例?
Are there any sane examples of >1 level programmatic navigation working out there?
我希望在这里获得的部分内容也是用于导航正常工作的初始状态 - 如果我从具有我希望反映的导航状态的外部上下文进来(即:从带有一些应用内上下文的通知,或从保存到磁盘编码状态开始)然后我希望能够加载顶部 View
导航正确指向右子视图.本质上 - 用实际值替换 NavState
中的 nil
s.Qt 的 QML 和 ReactRouter 都可以声明性地做到这一点——SwiftUI 也应该能够做到.
Part of what I am looking to get here is also initial state for navigation working correctly - if I come in from an external context with a navigation state I wish to reflect (ie: from a notification with some in-app context to start from, or from a saved-to-disk-encoded-state) then I would expect to be able to load up the top View
with navigation correctly pointing to the right child view. Essentially - replace the nil
s in the NavState
with real values. Qt's QML and ReactRouter can both do this declaratively - SwiftUI should be able to as well.
推荐答案
将我自己的解决方案放在此处作为一个选项,以防有人遇到 NavigationView
似乎没有的导航要求能够实现.在我的书中 - 功能比图形元素和动画更难修复.灵感来自 https://medium.com/swlh/swiftui-custom-navigation-view-for-your-applications-7f6effa7dbcf
Putting my own solution up here as a option in the case that someone is hitting the same requirements for navigation that NavigationView
does not seem to be able fulfill. In my book - functionality is a lot harder to fix than graphical elements and animation. Inspired by https://medium.com/swlh/swiftui-custom-navigation-view-for-your-applications-7f6effa7dbcf
它的工作原理是根级的单个声明变量决定导航堆栈 - 当从 a
链跳转到 b 等操作时,绑定到单个变量似乎很奇怪
需要在我上面演示中的链或从特定位置开始
It works off the idea of a single declarative variable at the root level determines the navigation stack - binding to individual variables seems odd when an operation like jumping from the a
chain to the b
chain in my above demo or starting at a particular position is required
我使用了像 URI 这样的字符串化路径的概念作为变量概念 - 这可能会被一个更具表现力的模型(如 enum
s 的向量)替换
I've used the concept of a stringified path like a URI as the variable concept - this could probably be replaced with a more expressive model (like a vector of enum
s)
重要的警告 - 它非常粗糙,没有动画,根本看起来不像原生,使用 AnyView
,你不能多次使用相同的节点名称,只反映一个 StackNavigationViewStyle
等 - 如果我把它变成更漂亮、更理智和更通用的东西,我会把它放在 Gist 中.
Big ol caveats - its very rough, has no animations, doesn't look native at all, uses AnyView
, you can't have the same node name more than once, only reflects a StackNavigationViewStyle
, etc - if I make this into something more pretty, sane and generic I'll put that up in Gist.
struct NavigationElement {
var tag: String
var title: String
var viewBuilder: () -> AnyView
}
class NavigationState: ObservableObject {
let objectWillChange = ObservableObjectPublisher()
var stackPath: [String] {
willSet {
if rectifyRootElement(path: newValue) {
_stackPath = newValue
rectifyStack(path: newValue, elements: _stackElements)
}
}
}
/// Temporary storage for the most current stack path during transition periods
private var _stackPath: [String] = []
@Published var stack: [NavigationElement] = []
var stackElements: [String : NavigationElement] = [:] {
willSet {
_stackElements = newValue
rectifyStack(path: _stackPath, elements: newValue)
}
}
/// Temporary storage for the most current stack elements during transition periods
private var _stackElements: [String : NavigationElement] = [:]
init(initialPath: [String] = []) {
self.stackPath = initialPath
rectifyRootElement(path: initialPath)
_stackPath = self.stackPath
}
@discardableResult func rectifyRootElement(path: [String]) -> Bool {
// Rectify root state if set from outside
if path.first != "" {
stackPath = [ "" ] + path
return false
}
return true
}
private func rectifyStack(path: [String], elements: [String : NavigationElement]) {
var newStack: [NavigationElement] = []
for tag in path {
if let elem = elements[tag] {
newStack.append(elem)
}
else {
print("Path has a tag '\(tag)' which cannot be represented - truncating at last usable element")
break
}
}
stack = newStack
}
}
struct NavigationStack<Content: View>: View {
@ObservedObject var navState: NavigationState
@State private var trigger: String = "humperdoo" //HUMPERDOO! Chose something that would not conflict with empty root state - could probably do better with an enum
init(_ navState: NavigationState, title: String, builder: @escaping () -> Content) {
self.navState = navState
self.navState.stackElements[""] = NavigationElement(tag: "", title: title, viewBuilder: { AnyView(builder()) })
}
var backButton: some View {
Button(action: { self.navState.stackPath.removeLast() }) {
Text("Back")
}
}
var navigationHeader: some View {
HStack {
ViewBuilder.buildIf( navState.stack.count > 1 ? backButton : nil )
Spacer()
ViewBuilder.buildIf( navState.stack.last?.title != nil ? Text(navState.stack.last!.title) : nil )
Spacer()
}
.frame(height: 40)
.background(Color(.systemGray))
}
var currentNavElement: some View {
return navState.stack.last!.viewBuilder()
}
var body: some View {
VStack {
// This is an effectively invisible element which primarily serves to force refreshes of the tree
Text(trigger)
.frame(width: 0, height: 0)
.onReceive(navState.$stack, perform: { stack in
self.trigger = stack.reduce("") { tag, elem in
return tag + "/" + elem.tag
}
})
navigationHeader
ViewBuilder.buildBlock(
navState.stack.last != nil
? ViewBuilder.buildEither(first: currentNavElement)
: ViewBuilder.buildEither(second: Text("The navigation stack is empty - this is odd"))
)
}
}
}
struct NavigationDestination<Label: View, Destination: View>: View {
@ObservedObject var navState: NavigationState
var tag: String
var label: () -> Label
init(_ navState: NavigationState, tag: String, title: String, destination: @escaping () -> Destination, label: @escaping () -> Label) {
self.navState = navState
self.tag = tag
self.label = label
self.navState.stackElements[tag] = NavigationElement(tag: tag, title: title, viewBuilder: { AnyView(destination()) })
}
var body: some View {
label()
.onTapGesture {
self.navState.stackPath.append(self.tag)
}
}
}
以及一些基本的使用代码
And some basic usage code
struct LandingPageView: View {
@ObservedObject var navState: NavigationState
var destinationA: some View {
List {
NavigationDestination(self.navState, tag: "aa", title: "AA", destination: { Text("AA") }) {
Text("Go to AA")
}
NavigationDestination(self.navState, tag: "ab", title: "AB", destination: { Text("AB") }) {
Text("Go to AB")
}
}
}
var destinationB: some View {
List {
NavigationDestination(self.navState, tag: "ba", title: "BA", destination: { Text("BA") }) {
Text("Go to BA")
}
Button(action: { self.navState.stackPath = [ "a", "ab" ] }) {
Text("Jump to AB")
}
}
}
var body: some View {
NavigationStack(navState, title: "Start") {
List {
NavigationDestination(self.navState, tag: "a", title: "A", destination: { self.destinationA }) {
Text("Go to A")
}
NavigationDestination(self.navState, tag: "b", title: "B", destination: { self.destinationB }) {
Text("Go to B")
}
}
}
}
}
这篇关于深度编程 SwiftUI NavigationView 导航的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!