我最近一直在使用SwiftUI,并且我已经设法在ContentView.swift中编写了作为我的根View,包括2个按钮来改变到应用程序中的其他 "页面 "或 "屏幕"。目前,我的代码中能够在两个视图之间移动。我在每个 "屏幕 "swift文件中使用了ObservableObjects(viewRouter : ViewRouter)。我决定写第三个屏幕弹出供用户查看。在包含了相同的结构和方法来带出那个视图后 : 第三个视图的Button的Action没有被运行。编译时没有错误,应用程序会构建! 但是,当点击FirstScreen里面的按钮时,ThirdScreen是不可见的。
这里是主视图ContentView。
import SwiftUI
struct ContentView: View {
@State var screen: String = "FirstScreen" //Declares the first state
@EnvironmentObject var viewRouter : ViewRouter //References our other swift file.
var body : some View {
VStack {
if viewRouter.currentScreen == "FirstScreen" {
FirstScreen()
} else if viewRouter.currentScreen == "SecondScreen" {
SecondScreen()
.transition(.slide)
} else if viewRouter.currentScreen == "ThirdScreen" {
ThirdScreen()
.transition(.opacity)
}
struct ContentView_Previews: PreviewProvider { //Looks fine, its the previews
static var previews: some View {
ContentView().environmentObject(ViewRouter())}}
这是FirstScreen文件,结构如下。
import Foundation
import UIKit
import SwiftUI
struct FirstScreen : View {
@EnvironmentObject var viewRouter : ViewRouter
var body : some View {
VStack {
Button(action: {
print("The info button has been clicked.")
self.viewRouter.currentScreen = "SecondScreen" //Heres an action
}) {
Image(systemName: "info")
.padding()
.background(Color.green)
.font(.largeTitle)
.foregroundColor(Color.orange)
.frame(width: 300, height: 600)
}
Button(action: {
print("You have erased it.")
self.viewRouter.currentScreen = "ThirdScreen" //This action does not happen.
}) {
Image(systemName: "trash")
.padding()
.background(Color.red)
.font(.largeTitle)
.foregroundColor(Color.white)
.frame(width: 426, height: 620)
}}}}
struct FirstScreen_previews : PreviewProvider {
static var previews: some View {
FirstScreen().environmentObject(ViewRouter())
}
}
这里是我的ThirdScreen的代码,它应该从ViewRouter加载进来,以及从FirstScreen的Swift文件中点击按钮的变化。
import Foundation
import UIKit
import SwiftUI
struct ThirdScreen : View {
@EnvironmentObject var viewRouter : ViewRouter
var body : some View {
VStack {
Text("You step a bit off balance")
.font(.largeTitle)
.foregroundColor(Color.red)
Text("You stand up, shaking, under a pass")
.font(.callout)
Text("It looks to be a wrong step. Maybe you head back?")
.font(.caption)
.foregroundColor(Color.gray)
Button(action :{self.viewRouter.currentScreen = "FirstScreen"}){
Image(systemName: "capslock" )
.frame(width: 209, height: 308)
.foregroundColor(Color.green)
}}}}
struct Third_preview : PreviewProvider {
static var previews: some View {
ThirdScreen().environmentObject(ViewRouter())
}
}
这里是ViewRouter.swift,它可以很好地管理屏幕。
import Foundation
import Combine
import SwiftUI
class ViewRouter: ObservableObject {
let objectWillChange = PassthroughSubject<ViewRouter, Never>()
var currentScreen : String = "FirstScreen" {
didSet {
withAnimation(){
objectWillChange.send(self)
}
}
}
}
最后是我正确工作的SecondScreen.swift。这个文件可能是多余的,但我把它包括在内,因为万一这个文件里面有好的东西在工作。因为里面的按钮可以改变视图。
import Foundation
import UIKit
import SwiftUI
struct SecondScreen : View {
@EnvironmentObject var viewRouter : ViewRouter
var body : some View {
VStack {
Button(action: {self.viewRouter.currentScreen = "FirstScreen"}) {
Image(systemName: "arrowshape.turn.up.left" )
.padding()
.cornerRadius(18)
.frame(width: 180, height: 400)
}}}}
struct SecondScreen_previews : PreviewProvider{
static var previews : some View {
SecondScreen().environmentObject(ViewRouter())
}
}
非常感谢你在这里帮助我。我很想继续制作屏幕文件,因为它们在下面,我只是想知道为什么我的第三个屏幕没有拉起来。我将在继续排除故障的同时迅速回复。谢谢您!我一直在使用SwiftUI。
!!!解决了 对代码进行了一些测试,使用其他动作类型的按钮,并能够查看下一个屏幕。