viewWillEnter is not triggered on App instance when switching between tabs

[stalniy]

Ionic version: (check one with "x")
[ ] 1.x (For Ionic 1.x issues, please use https://github.com/driftyco/ionic-v1)
[x] 2.x
[x] 3.x

I'm submitting a ... (check one with "x")
[x] bug report
[ ] feature request
[ ] support request => Please do not submit support requests here, use one of these channels: https://forum.ionicframework.com/ or http://ionicworldwide.herokuapp.com/

Current behavior:
When switching between tabs in ion-tabs ionic emits value on viewWillEnter observable on App instance only once (when component is created and doesn't emit for subsequent navigations)

Expected behavior:
When switching between tabs in ion-tabs ionic emits viewWillEnter observable on App instance

Steps to reproduce:

1. Create an ionic app with tabs
2. Inject App and subscribe to viewWillEnter
3. Navigate between tabs

Other information:
issue caused by this line https://github.com/driftyco/ionic/blob/master/src/components/tabs/tabs.ts#L383

I think to fix the issue the line should be changed to:

selectedPage && selectedTab._willEnter(selectedPage);

The same should be done for other leave/enter events.
The fix is quite important for properly and easily tracking analytics in the whole application because it allows to track all navigation events through subscription to Apps viewWillEnter observable.
I'm ready to create PR if you think the suggested approach is correct

Ionic info: (run ionic info from a terminal/cmd prompt and paste output below):

Cordova CLI: 7.0.1 
Ionic Framework Version: 2.2.0
Ionic CLI Version: 2.1.18
Ionic App Lib Version: 2.1.9
ios-deploy version: 1.9.0 
ios-sim version: 5.0.8 
OS: OS X El Capitan
Node Version: v6.9.1
Xcode version: Xcode 8.2.1 Build version 8C1002

[jgw96]

Hello, thanks for using Ionic! I am going to close this issue as a duplicate of #11694 and we can continue the discussion on that issue 😃 .

[ionitron-bot]

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