Let a Tab know the page of another Tab

Hi, I have a Ionic demo Tabs project. On tab 1 I have created a child page (activated by a button). When I switches between the tabs and comes back to tab 1, it does remember if the default page or child page was active before. Perfect so far. This is just the demo project called tabs. But I want tab 3 to know which page is active in tab 1. How to do this?

I have played around with both NavController and ViewController. But they say the Index is 0. I have basically no idea of what I am doing, though I am an educated C-programmer, I have every written Java, Typescript etc. before.

Thanks for any help, Mike

If you don’t get any better answers, I firmly believe this is yet another case of tab abuse. Tabs are supposed to be completely independent sub-worlds in an app, and should not cross-pollinate like this.