Provide an easy way to access currently displayed fragment [119800853]

Fixed

Feature Request

Status Update

No update yet.

Description

[Deleted User]

created issue #1

Nov 20, 2018 05:00PM

Component used: Navigation
Version used: 1.0.0-alpha07

It would be great if we can have an easy way to access the currently displayed fragment. As far as I know today the only way to get it is to access to primaryNavigationFragment from the navigation fragment's childFragmentManager.

A common use case is when you have a bottom navigation and on item resselected you want to scroll on top of your list. Youtube and many apps using bottom navigation implement a scrollToTop function.

Code required to do it with primaryNavigationFragment isn't complex or ugly, but there is no documentation neither about that on

https://developer.android.com/topic/libraries/architecture/navigation/

I'm afraid this "hack" could stop working after a navigation component lib update.

So if it's not relevant in an api perspective to have a method for that, could we have a status/documentation about the primaryNavigationFragment usage ?

Comments

il...@google.com <il...@google.com> Nov 30, 2018 06:36AM

Assigned to il...@google.com.

il...@google.com <il...@google.com> Feb 1, 2019 10:26PM

Accepted by il...@google.com.

ap...@google.com <ap...@google.com> #2Feb 2, 2019 12:30AM

Project: platform/frameworks/support
Branch: androidx-master-dev

commit 88fc53038eb76bea8e2b040f84d14919f02941d7
Author: Ian Lake <ilake@google.com>
Date: Fri Feb 01 14:25:13 2019

Add documentation around FragmentNavigation + primary nav

Provide more clear guidance and documentation around
the interactions between FragmentNavigator behavior and
the FragmentManager's primary navigation Fragment,
specifically calling out that the currently displayed
Fragment should be available through the
getPrimaryNavigationFragment() API, but that operations
can (and will, by default) be asynchronous.

Test: docs only
BUG: 119800853
Change-Id: I594461ae5c7203f3f47b2278ea611688a93e9c74

M navigation/fragment/src/main/java/androidx/navigation/fragment/FragmentNavigator.java

https://android-review.googlesource.com/892740

https://goto.google.com/android-sha1/88fc53038eb76bea8e2b040f84d14919f02941d7

il...@google.com <il...@google.com> #3Feb 2, 2019 12:36AM

Marked as fixed.

We've decided to be more explicit in our documentation that getting the current Fragment from getPrimaryNavigationFragment() is indeed the supported pattern, rather than offer an explicit API for this functionality as part of Navigation.

[Deleted User] <[Deleted User]> #4Feb 2, 2019 07:35AM

Great ! Thanks for that !

dd...@gmail.com <dd...@gmail.com> #5Oct 20, 2020 02:14PM

Hi,
Where i can find this info?
any links?
Thanks

[Deleted User] <[Deleted User]> #6Oct 20, 2020 02:23PM

https://stackoverflow.com/questions/51385067/android-navigation-architecture-component-get-current-visible-fragment/53396780#53396780

il...@google.com <il...@google.com> #7Oct 20, 2020 04:04PM

As per the documentation:

The current Fragment from FragmentNavigator's perspective can be retrieved by calling FragmentManager.getPrimaryNavigationFragment() with the FragmentManager passed to this FragmentNavigator.

Note that the default implementation does Fragment transactions asynchronously, so the current Fragment will not be available immediately (i.e., in callbacks to NavController.OnDestinationChangedListener).

mr...@gmail.com <mr...@gmail.com> #8Jun 22, 2021 12:53AM

It doesn't work when used in navController.addOnDestinationChangedListener....
Being able to set a simple tag in nav graph, or just some api call to get the current fragment and some kind of name, tag is knowere to be found.

Also you should keep in mind obfuscation.

co...@gmail.com <co...@gmail.com> #9Aug 30, 2022 12:24AM

Isn't it a bit overreaching to expect that whatever Fragment the "current Fragment" is has a List in it that can be scrolled to the top? Wouldn't a scrollToTop mechanism that necessitates a certain type of Fragment to be (previously) focused be better delivered with an Activity callback or eventbus pattern?

What is the "current Fragment" if not the primaryNavigationFragment when multiple Fragments exist on the screen at the same time? What if I want to navigate within a nested Fragment? So at the very least if a change is to be made here it would need to "provide an easy way to access currently displayed fragments" (plural fragments)

Also if there are problems with the state of the Fragment when using getPrimaryNavigationFragment, using FragmentManager.FragmentLifecycleCallbacks would seem a better fit, no?