Android JetPack Navigation : How to open a fragment from an activity not associated with it?

Question

scenario :

MainActivity.kt : activity_main.xml contains my_nav_host_fragment

in mobile_navigation.xml first_frag_dest is the startDestination and there is second_frag_dest also, with respective classes FirstFragment.kt and SecondFragment.kt.

I have setup bottom navigation for switch between two fragments using the Android Jetpack Navigation components.

When the Second Fragment is opened for the first time if FirbaseUser is null, A Welcome Activity is launched which is configured for GoogleSignInusing Firebase.

In WelcomeActivity.java I have a function updateUI(user: FirebaseUser) to update the UI.

Now, what code should I write in updateUI function such that I am redirected back to the Second Fragment.

Please tell how to do it using JetPack Navigation components.

Note: Principles of navigation say that only one activity must exist but here I am compelled to use an Activity for GoogleSignIn due to Firebase restrictions.

So your first activity is already on `SecondFragment` and launches your `WelcomeActivity`. And you just want to return to `SecondFragment`? — ianhanniballake, Dec 19 '18 at 19:01

score 2 · Accepted Answer · answered Dec 19 '18 at 19:04

2

If you want to close your WelcomeActivity and return to the activity below it, have your updateUI method call finish():

Call this when your activity is done and should be closed

answered Dec 19 '18 at 19:04

ianhanniballake

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Is there some way to do it using jetpack Navigation? – curiousgeek Dec 19 '18 at 19:09
No, Navigation focuses on a [Single Activity model](https://www.youtube.com/watch?v=2k8x8V77CrU) and has no concept of finishing an activity. – ianhanniballake Dec 19 '18 at 19:13
But in my case I needed to have another activity, so in that case what should I do. – curiousgeek Dec 19 '18 at 19:18
1

Call `finish()`. – ianhanniballake Dec 19 '18 at 19:22
@ianhanniballake wouldn't `ActivityCompat.finishAfterTransition(..)` be more appropriate? – papageorgiouk Jan 11 '19 at 08:10

Android JetPack Navigation : How to open a fragment from an activity not associated with it?

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