How does an activity manage configuration changes while ensuring the ViewModel instance remains…

<p><em>Question:&nbsp;</em>How does ViewModelProviders know when there is a configuration change vs user explicitly creating a new activity or onDesctory() called?</p> <p><strong>Answer:</strong>&nbsp;</p> <p>The provided code within ComponentActivity monitors lifecycle changes. If onDestroy() is invoked without configuration changes, the ViewModel store is cleared. &nbsp;On the other hand, if onDestroy() is called with configuration changes, the ViewModel instance perseveres.</p> <pre> getLifecycle().addObserver(new LifecycleEventObserver() { @Override public void onStateChanged(@NonNull LifecycleOwner source, @NonNull Lifecycle.Event event) { if (event == Lifecycle.Event.ON_DESTROY) { if (!isChangingConfigurations()) { getViewModelStore().clear(); } } } });</pre> <p><strong>Explanation</strong></p> <ol> <li><strong>Adding a Lifecycle Observer</strong>: It attaches an observer to the current screen&rsquo;s lifecycle. This observer watches for changes in the lifecycle of the screen.</li> <li><strong>Detecting ON_DESTROY Event</strong>: When the screen is about to be destroyed, the code checks if the event is the &ldquo;<strong>ON_DESTROY</strong>&rdquo; event. This event happens when the screen is being removed.</li> <li><strong>Clearing ViewModelStore</strong>: If the screen is truly being destroyed (not just changing configuration), the code clears the ViewModelStore. ViewModelStore is where the app&rsquo;s data is stored during the screen&rsquo;s lifetime otherwise&nbsp;<strong>ViewModel</strong>&nbsp;instance remains alive</li> </ol> <p>This is a prime example of disposing of unnecessary objects when they are no longer required.</p> <p><a href="https://taimurtanveer.medium.com/how-does-an-activity-manage-configuration-changes-while-ensuring-the-viewmodel-instance-remains-8fe3af06da3b">Visit Now</a></p>