viewWillAppear/DidAppear called twice when changing rootViewController with an Animation - swift

Question

Here is the code of my animation/transition :
if let window = self.window where animated {
window.rootViewController?.dismissViewControllerAnimated(true, completion: {
UIView.transitionFromView(window.rootViewController!.view, toView: tabBarController.view, duration: 0.8, options: .TransitionFlipFromLeft, completion: { _ in
window.rootViewController = tabBarController
})
})
}
Without the animation code, (just setting the rootViewControlller), the problem does not appear.
Any idea why it makes the view appear twice and how I could fix this ?

Answer 1

using UIViewController.transitionFromViewController1 ,instead of your UIView.transitionFromView.act like it :
//
// AppDelegate.swift
// helloapp
//
// Created by quota on 2/18/16.
// Copyright © 2016 liu. All rights reserved.
//
import UIKit
class ViewController1: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
view.backgroundColor = UIColor.greenColor()
let button = UIButton()
button.setTitle("transit", forState: .Normal)
button.frame = CGRectMake(20, 20, 100,20)
button.addTarget(self, action: "click:", forControlEvents: .TouchDown)
view.addSubview(button)
}
func click(sender:UIButton!){
let appDelegate = UIApplication.sharedApplication().delegate as! AppDelegate
if let window = appDelegate.window {
// let v2 = ViewController2()
if let r = window.rootViewController{
r.transitionFromViewController(
appDelegate.v1!
,toViewController:appDelegate.v2!,duration:0.8,options: .TransitionFlipFromLeft,animations:nil){_ in }
}
}
}
}
class ViewController2: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
view.backgroundColor = UIColor.blueColor()
}
override func viewWillAppear(animated: Bool) {
print(animated)
}
}
class ViewController3: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
view.backgroundColor = UIColor.redColor()
}
}
#UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
var window: UIWindow?
var v1 : ViewController1?
var v2 : ViewController2?
func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
self.window = UIWindow(frame: UIScreen.mainScreen().bounds)
self.window!.rootViewController = ViewController3()
v1 = ViewController1()
v2 = ViewController2()
v1!.view.frame = self.window!.frame
self.window!.rootViewController?.addChildViewController(v1!)
self.window!.rootViewController?.view.addSubview(v1!.view)
self.window!.rootViewController?.addChildViewController(v2!)
self.window?.makeKeyAndVisible()
return true
}
}