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Preserve nav state across MainActivity recreation #251

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Merged
merged 1 commit into from
Sep 19, 2025
Merged

Preserve nav state across MainActivity recreation #251

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83 changes: 70 additions & 13 deletions app/src/main/java/com/d4rk/androidtutorials/java/ui/screens/main/MainActivity.java
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Original file line number Diff line number Diff line change
Expand Up @@ -62,6 +62,8 @@
public class MainActivity extends AppCompatActivity {

private static final long BACK_PRESS_INTERVAL = 2000;
private static final String STATE_NAV_GRAPH_INITIALIZED = "state_nav_graph_initialized";
private static final String STATE_LAST_PREFERRED_DESTINATION = "state_last_preferred_destination";
private ActivityResultLauncher<IntentSenderRequest> updateActivityResultLauncher;
private final SparseIntArray navOrder = new SparseIntArray();
private ActivityMainBinding mBinding;
Expand All @@ -84,6 +86,8 @@ public void onResume(@NonNull LifecycleOwner owner) {
private MainViewModel mainViewModel;
private NavController navController;
private int currentNavIndex;
private boolean navGraphInitialized;
private int lastPreferredStartDestination;
private AppUpdateManager appUpdateManager;
private InstallStateUpdatedListener installStateUpdatedListener;
private long backPressedTime;
Expand All @@ -93,6 +97,11 @@ protected void onCreate(Bundle savedInstanceState) {
SplashScreen.installSplashScreen(this);
super.onCreate(savedInstanceState);

if (savedInstanceState != null) {
navGraphInitialized = savedInstanceState.getBoolean(STATE_NAV_GRAPH_INITIALIZED, true);
lastPreferredStartDestination = savedInstanceState.getInt(STATE_LAST_PREFERRED_DESTINATION, 0);
}

updateActivityResultLauncher = registerForActivityResult(
new ActivityResultContracts.StartIntentSenderForResult(),
result -> {
Expand Down Expand Up @@ -222,16 +231,24 @@ private void observeViewModel() {
getSupportFragmentManager().findFragmentById(R.id.nav_host_fragment_activity_main);
if (navHostFragment != null) {
navController = navHostFragment.getNavController();
NavGraph navGraph = navController.getNavInflater().inflate(R.navigation.mobile_navigation);
navGraph.setStartDestination(uiState.defaultNavDestination());
navController.setGraph(navGraph);

navOrder.put(R.id.navigation_home, 0);
navOrder.put(R.id.navigation_android_studio, 1);
navOrder.put(R.id.navigation_about, 2);
androidx.navigation.NavDestination destination = navController.getCurrentDestination();
if (destination != null) {
currentNavIndex = navOrder.get(destination.getId());

int preferredStartDestination = uiState.defaultNavDestination();
if (!navGraphInitialized) {
NavGraph navGraph = navController.getNavInflater().inflate(R.navigation.mobile_navigation);
navGraph.setStartDestination(preferredStartDestination);
navController.setGraph(navGraph);
navGraphInitialized = true;
lastPreferredStartDestination = preferredStartDestination;
} else {
if (lastPreferredStartDestination == 0) {
lastPreferredStartDestination = preferredStartDestination;
} else if (preferredStartDestination != lastPreferredStartDestination) {
navigateToPreferredDestination(preferredStartDestination);
}
}

NavOptions forwardOptions = new NavOptions.Builder()
Expand All @@ -248,11 +265,17 @@ private void observeViewModel() {
.setPopExitAnim(R.anim.fragment_spring_exit)
.build();

androidx.navigation.NavDestination destination = navController.getCurrentDestination();
if (destination != null) {
currentNavIndex = navOrder.get(destination.getId(), currentNavIndex);
}

if (useRail) {
if (mBinding.navRail != null) {
NavigationUI.setupWithNavController(mBinding.navRail, navController);
mBinding.navRail.setOnItemSelectedListener(item -> {
if (item.getItemId() == navController.getCurrentDestination().getId()) {
if (binding.navRail != null) {
NavigationUI.setupWithNavController(binding.navRail, navController);
binding.navRail.setOnItemSelectedListener(item -> {
androidx.navigation.NavDestination currentDestination = navController.getCurrentDestination();
if (currentDestination != null && item.getItemId() == currentDestination.getId()) {
return true;
}
int newIndex = navOrder.get(item.getItemId());
Expand All @@ -265,7 +288,8 @@ private void observeViewModel() {
} else {
NavigationUI.setupWithNavController(navBarView, navController);
navBarView.setOnItemSelectedListener(item -> {
if (item.getItemId() == navController.getCurrentDestination().getId()) {
androidx.navigation.NavDestination currentDestination = navController.getCurrentDestination();
if (currentDestination != null && item.getItemId() == currentDestination.getId()) {
return true;
}
int newIndex = navOrder.get(item.getItemId());
Expand All @@ -276,9 +300,9 @@ private void observeViewModel() {
});
}

setSupportActionBar(mBinding.toolbar);
setSupportActionBar(binding.toolbar);

mBinding.toolbar.setNavigationOnClickListener(v -> {
binding.toolbar.setNavigationOnClickListener(v -> {
BottomSheetMenuFragment bottomSheet = new BottomSheetMenuFragment();
bottomSheet.show(getSupportFragmentManager(), bottomSheet.getTag());
});
Expand All @@ -297,6 +321,32 @@ private void observeViewModel() {
}


private void navigateToPreferredDestination(int preferredDestination) {
if (navController == null) {
return;
}
NavGraph graph = navController.getGraph();
if (graph != null) {
graph.setStartDestination(preferredDestination);
}
androidx.navigation.NavDestination currentDestination = navController.getCurrentDestination();
if (currentDestination != null && currentDestination.getId() == preferredDestination) {
lastPreferredStartDestination = preferredDestination;
return;
}
if (graph == null) {
lastPreferredStartDestination = preferredDestination;
return;
}
NavOptions options = new NavOptions.Builder()
.setPopUpTo(graph.getStartDestinationId(), true)
.setLaunchSingleTop(true)
.build();
navController.navigate(preferredDestination, null, options);
lastPreferredStartDestination = preferredDestination;
}


@Override
public boolean onCreateOptionsMenu(android.view.Menu menu) {
getMenuInflater().inflate(R.menu.menu_main, menu);
Expand Down Expand Up @@ -390,6 +440,13 @@ private void popupSnackbarForCompleteUpdate() {
.show();
}

@Override
protected void onSaveInstanceState(@NonNull Bundle outState) {
super.onSaveInstanceState(outState);
outState.putBoolean(STATE_NAV_GRAPH_INITIALIZED, navGraphInitialized);
outState.putInt(STATE_LAST_PREFERRED_DESTINATION, lastPreferredStartDestination);
}

@Override
protected void onDestroy() {
if (installStateUpdatedListener != null && appUpdateManager != null) {
Expand Down