How could I simply have a View transition to SwiftUI View? - ios

Question

I'd like to implement a simple view transition through SwiftUI and Timer.
I have a primary View, it's content View. If I call func FireTimer() from in the View, the function fires timer. Then after 5 seconds, I would have a View transition.
I tried NavigationLink, but it has a button. Timer can't push the button so now I'm confused.
I'll show my code below.
TimerFire.swift
import Foundation
import UIKit
import SwiftUI
let TIME_MOVENEXT = 5
var timerCount : Int = 0
class TimerFire : ObservableObject{
var workingTimer = Timer()
#objc func FireTimer() {
print("FireTimer")
workingTimer = Timer.scheduledTimer(timeInterval: 1,
target: self,
selector: #selector(TimerFire.timerUpdate),
userInfo: nil,
repeats: true)
}
#objc func timerUpdate(timeCount: Int) {
timerCount += 1
let timerText = "timerCount:\(timerCount)"
print(timerText)
if timerCount == TIME_MOVENEXT {
print("timerCount == TIME_MOVENEXT")
workingTimer.invalidate()
print("workingTimer.invalidate()")
timerCount = 0
//
//want to have a transition to SecondView here
//
}
}
}
ContentView.swift
import SwiftUI
struct ContentView: View {
var body: some View {
Button(action: {
// What to perform
let timerFire = TimerFire()
timerFire.FireTimer()
}) {
// How the button looks like
Text("Fire timer")
}
}
}
SecondView.swift
import Foundation
import SwiftUI
struct SecondView: View {
var body: some View {
Text("Second World")
}
}
How could I simply show this SecondView?

Answer 1

Ok, if you want to do this w/o NavigationView on first screen (for any reason) here is a possible approach based on transition between two views.
Note: Preview has limited support for transitions, so please test on Simulator & real device
Here is a demo how it looks (initial white screen is just Simulator launch)
Here is single testing module:
import SwiftUI
import UIKit
let TIME_MOVENEXT = 5
var timerCount : Int = 0
class TimerFire : ObservableObject{
var workingTimer = Timer()
#Published var completed = false
#objc func FireTimer() {
print("FireTimer")
workingTimer = Timer.scheduledTimer(timeInterval: 1,
target: self,
selector: #selector(TimerFire.timerUpdate),
userInfo: nil,
repeats: true)
}
#objc func timerUpdate(timeCount: Int) {
timerCount += 1
let timerText = "timerCount:\(timerCount)"
print(timerText)
if timerCount == TIME_MOVENEXT {
print("timerCount == TIME_MOVENEXT")
workingTimer.invalidate()
print("workingTimer.invalidate()")
timerCount = 0
//
//want to have a transition to SecondView here
//
self.completed = true
}
}
}
struct SecondView: View {
var body: some View {
Text("Second World")
}
}
struct TestTransitionByTimer: View {
#ObservedObject var timer = TimerFire()
#State var showDefault = true
var body: some View {
ZStack {
Rectangle().fill(Color.clear) // << to make ZStack full-screen
if showDefault {
Rectangle().fill(Color.blue) // << just for demo
.overlay(Text("Hello, World!"))
.transition(.move(edge: .leading))
}
if !showDefault {
Rectangle().fill(Color.red) // << just for demo
.overlay(SecondView())
.transition(.move(edge: .trailing))
}
}
.onAppear {
self.timer.FireTimer()
}
.onReceive(timer.$completed, perform: { completed in
withAnimation {
self.showDefault = !completed
}
})
}
}
struct TestTransitionByTimer_Previews: PreviewProvider {
static var previews: some View {
TestTransitionByTimer()
}
}

Answer 2

There is no code snippet for ContentView, so I tried to build simple example by myself. You can use NavigationLink(destination: _, isActive: Binding<Bool>, label: () -> _) in your case. Change some State var while receiving changes from Timer.publish and you'll go to SecondView immediately:
struct TransitionWithTimer: View {
#State var goToSecondWorld = false
let timer = Timer.publish(every: 5, on: .main, in: .common).autoconnect()
var body: some View {
NavigationView {
VStack {
NavigationLink(destination: SecondWorld(), isActive: self.$goToSecondWorld) {
Text("First World")
.onReceive(timer) { _ in
self.goToSecondWorld = true
}
}
}
}
}
}
// you can use ZStack and opacity/offset of view's:
struct TransitionWithTimerAndOffset: View {
#State var goToSecondWorld = false
let timer = Timer.publish(every: 3, on: .main, in: .common).autoconnect()
var body: some View {
ZStack {
Text("First world") // here can be your first View
.opacity(self.goToSecondWorld ? 0 : 1)
.offset(x: goToSecondWorld ? 1000 : 0)
Text("Second world") // and here second world View
.opacity(self.goToSecondWorld ? 1 : 0)
.offset(x: goToSecondWorld ? 0 : -1000)
}
.onReceive(timer) { _ in
withAnimation(.spring()) {
self.goToSecondWorld = true
}
}
}
}
struct SecondWorld: View {
var body: some View {
Text("Second World")
}
}