👀 Views: 36 💬 Answers: 1 📅 Created: 2025-06-30

android livedata viewmodel navigation Kotlin

I'm trying to debug I'm stuck trying to I'm dealing with I've searched everywhere and can't find a clear answer. I'm stuck on something that should probably be simple... I'm experiencing an issue where changes to LiveData in a nested ViewModel are not triggering UI updates in a Fragment that's part of a Navigation Component graph. I have a MainActivity that initializes a shared ViewModel and then navigates to a DetailFragment, where I instantiate a nested ViewModel specific to that fragment. The nested ViewModel has a MutableLiveData that I update, but the UI does not reflect these changes. Here's a simplified version of my code: ```kotlin class SharedViewModel : ViewModel() { val sharedData: MutableLiveData<String> = MutableLiveData() } class DetailViewModel : ViewModel() { val detailData: MutableLiveData<String> = MutableLiveData() fun updateDetailData(newData: String) { detailData.value = newData } } ``` In my DetailFragment, I'm trying to observe the `detailData` like this: ```kotlin class DetailFragment : Fragment() { private val detailViewModel: DetailViewModel by viewModels() override fun onViewCreated(view: View, savedInstanceState: Bundle?) { super.onViewCreated(view, savedInstanceState) detailViewModel.detailData.observe(viewLifecycleOwner, { data -> // Update UI textView.text = data }) } } ``` I've confirmed that `updateDetailData` is being called correctly (I can log the new data), but the observer in the fragment is not being triggered. I suspect it might be related to the lifecycle of the `ViewModel` or how I'm navigating between fragments. I’ve tried using `viewLifecycleOwner` instead of `this` for observing, but that didn’t change anything. I’m using AndroidX Navigation Component version 2.4.0 and the latest ViewModel dependencies. Has anyone encountered a similar issue, or could there be something I’m overlooking? This is part of a larger CLI tool I'm building. What's the best practice here? My development environment is macOS. What's the best practice here? I'm working on a CLI tool that needs to handle this. What am I doing wrong? This is for a CLI tool running on Ubuntu 22.04. I recently upgraded to Kotlin latest. Any pointers in the right direction?