The Navigation Component 2.0 Laurence de Villers @L_de_V

Laurence de Villers Mobile dev at Transit Lead organizer of GDG Montreal Women Techmakers Lead Canada Regional Mentor @L_de_V

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Navigation Component ● Simplified setup for commun navigation patterns ○ Handles backstack ○ Automates fragment transaction ● Type safe argument passing ● Handles transition animations ● Simplified deep link

Simplified setup for commun navigation patterns

Challenges of standard navigation: FragmentManager FragmentManager Fragment FragmentTransaction Activity Fragments Back Stack

Challenges of standard navigation: Pop Inclusive Home Category Item Size ● Need to add dynamically code to pop Inclusive some screen with the fragmentManager Remove fragments

Principal of view navigation ● Up button vs Back button ○ You need to make sure that both work together and follow Android Developer Guide override fun onOptionsItemSelected(item: MenuItem): Boolean { return when (item.itemId) { android.R.id.home -> { onBackPressed() //or finish() true } else -> super.onOptionsItemSelected(item) } } Or @Override public boolean onSupportNavigateUp() { onBackPressed(); return true; }

Up button ● The Up button is used to navigate with an app based on the hierarchical relationship between screen. Back button ● The system Back button is used to navigate, in reverse chronological order, through the history of screens the user has recently worked with. VS

First principle of Navigation There’s Always a starting point

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Navigation component take care of BackStack Fragmentmanager DeepLink

How to get started?

Gradle dependencies { def nav_version = "2.1.0" // Java implementation "androidx.navigation:navigation-fragment:$nav_version" implementation "androidx.navigation:navigation-ui:$nav_version" // Kotlin implementation "androidx.navigation:navigation-fragment-ktx:$nav_version" implementation "androidx.navigation:navigation-ui-ktx:$nav_version" }

Add the navigation graph New → Android resource file

Create your graph By default, android studio will find all the fragment that you have in your application

Nested Graph If you have too much screen you can separate graph into groups Move to Nested Graph > New Graph

Add a Navigation Host Fragment in your main activity ... You need to specify if this navHost is the default. You can have multiple NavHost is you have more than one activity

How it works ? A NavHostFragment swaps different destinations in and out as you navigate through the navigation graph.

Navigate between fragments NavController is a special class that triggers the fragment swaps in the NavHostFragment You can call methods like navigate() or popBackStack() The NavController will translates these commands into the appropriate framework operations based on the type of destination you are navigating to or from If you call navigate() with an activity destination, the NavController calls startActivity() on your behalf

Navigate between fragments talkViewHolder.itemView.setOnClickListener(v -> { Navigation.findNavController(v).navigate(R.id.action_nav_program_to_talkFragment); } You need to use the same id that was generated in your action on the graph

Up button ● You need to setup the action bar with the NavController Back button ● The back button is handle by the navigation graph automatically VS

Setup the up button navigation private fun setupNavigation() { val host: NavHostFragment = supportFragmentManager .findFragmentById(R.id.mainNavigationFragment) as NavHostFragment? ?: return val navController = host.navController val topLevelDestinations = HashSet() topLevelDestinations.add(R.id.nav_program) ... topLevelDestinations.add(R.id.nav_twitter) appBarConfiguration = AppBarConfiguration.Builder(topLevelDestinations) .setDrawerLayout(drawer_layout).build() setupActionBarWithNavController(this, navController, appBarConfiguration) }

Navigate using drawers and navigation view On the activity_main.xml

Auto setup NavigationView with the navigation graph Use the same ID in your NavigationView menu and on your graph. ...

Code that is not needed anymore override fun onNavigationItemSelected(item: MenuItem): Boolean { val id = item.itemId var fragment: Fragment when(id) { R.id.nav_program -> { fragment = ProgramFragment.newInstance() setActionBarName(getString(R.string.program)) } ... R.id.nav_twitter -> { fragment = TwitterFragment.newInstance() setActionBarName(getString(R.string.twitter)) } else -> { fragment = ProgramFragment.newInstance() setActionBarName(getString(R.string.program)) } } val drawer = findViewById(R.id.drawer_layout) as DrawerLayout drawer.closeDrawer(GravityCompat.START) FragmentManager fragmentManager = activity.getFragmentManager(); fragmentManager.beginTransaction().replace(R.id.container, fragment).commit(); return true } val toggle = ActionBarDrawerToggle(this, drawer, toolbar, string.navigation_drawer_open, string.navigation_drawer_close) drawer.addDrawerListener(toggle) toggle.syncState()

Navigate using drawers and navigation view private fun setupNavigationView() { val host: NavHostFragment = supportFragmentManager .findFragmentById(R.id.my_nav_host_fragment) as NavHostFragment? ?: return val navController = host.navController NavigationUI.setupWithNavController(findViewById(R.id.nav_view), navController) } On the MainActivity.kt override fun onSupportNavigateUp(): Boolean { // Allows NavigationUI to support proper up navigation or the drawer layout // drawer menu, depending on the situation return NavigationUI.navigateUp(findNavController(this, R.id.mainNavigationFragment), appBarConfiguration) }

Wait, how to pass an argument with the new Navigation Component?

Passing Bundle talkViewHolder.itemView.setOnClickListener(v -> { Bundle bundle = new Bundle(); bundle.putParcelable(EXTRA_TALK, talk); Navigation.findNavController(v).navigate(R.id.action_nav_program_to_talkFragment, bundle); }

Type Safe argument passing

Safe Args Safe Arg is a plugin that generates simple object and builder classes for type-safe access to arguments specified for destinations and actions. val username = arguments?.getString("usernameKey") Is replace by val username = args.username

Safe Args Gradle Build.gradle dependencies { classpath "android.arch.navigation:navigation-safe-args-gradle-plugin:$navigationVersion" //... } app/build.gradle apply plugin: 'kotlin-android' apply plugin: 'androidx.navigation.safeargs'

Safe Arg in NavGraph

Passing Safe Args The plugin will generate a class {currentFragment}Directions with a function action{currentFragment}To{NextFragment)({Object specified } obj) talkViewHolder.itemView.setOnClickListener(v -> { Bundle bundle = new Bundle(); bundle.putParcelable(EXTRA_TALK, talk); Navigation.findNavController(v).navigate(R.id.action_nav_program_to_talkFragment, bundle); } talkViewHolder.itemView.setOnClickListener(v -> { ProgramFragmentDirections.ActionNavProgramToTalkFragment action; action = ProgramFragmentDirections.actionNavProgramToTalkFragment(talk); Navigation.findNavController(v).navigate(action); }

Receiving the Safe Args @Override public View onCreateView(@NonNull LayoutInflater inflater, @androidx.annotation.Nullable ViewGroup container, @androidx.annotation.Nullable Bundle savedInstanceState) { ... this.talk = TalkFragmentArgs.fromBundle(getArguments()).getTalk(); ... } The plugin will generate a class {FragmentWithArgs}Args

Pros and cons of SafeArgs Pros ● You know easily what are the parameter you need to pass for a destination. ● You don’t need to cast serializable and parcelable. (You can specify directly a child of those classes) ● You can pass Enum Cons ● Proguard ○ You need to prevent all your safe Args (Parcelable, Serializable and Enum class) to be obfuscated

Handles transition animations

Animations Handle via XML animations on an Action

Animations ● You can still overwrite onCreateAnimator @Override public Animator onCreateAnimator(int transit, boolean enter, int nextAnim) { … } ● You can shared Element for transition FragmentNavigator.Extras navigatorExtras = new FragmentNavigator.Extras.Builder() .addSharedElement(image, "imageName").build(); Navigation.findNavController(v).navigate(action, navigatorExtras); ● And it easy to add animations for transition between screens

Simplified deep link

Challenges of Deep Links Home Category Item gdg://item For deeplink those screen need to be recreated and added to the back sack

Deep Linking with Navigation Component There is two type of Deeplink with the Navigation Component ● Explicite ○ Will recreate all the stack following your graph to the destination of your deeplink. ○ Is for Notification, Widget, App Shortcut ● Implicite ○ If FLAG_ACTIVITY_NEW_TASK is not set, will open the fragment on top of your current navigation

Explicite DeepLink You need to use NavDeepLinkBuilder to create your pendingIntent val args = Bundle() args.putString("myarg", "From Widget"); val pendingIntent = NavDeepLinkBuilder(context) .setGraph(R.navigation.mobile_navigation) .setDestination(R.id.deeplink_dest) .setArguments(args) .createPendingIntent() remoteViews.setOnClickPendingIntent(R.id.deep_link_button, pendingIntent) You can also use navController to create the deeplink Navigation.findNavController(v).createDeepLink() .setGraph(R.navigation.mobile_navigation) .setDestination(R.id.deeplink_dest).createPendingIntent();

Implicite DeepLink To enable implicit deep linking, you need to add the Nav-graph in the Manifest ... ... When building your projet, all elements will be generated by the nav-graph

2.0.0

Change from 1.0.0 to 2.0.0 // Allows NavigationUI to support proper up navigation or the drawer layout // drawer menu, depending on the situation override fun onSupportNavigateUp(): Boolean { return findNavController(R.id.my_nav_host_fragment).navigateUp(appBarConfiguration) } Everything function that hooks navigation drawer, bottom nav bar with the NavController is now on the class NavigationUI override fun onSupportNavigateUp(): Boolean { return NavigationUI.navigateUp(findNavController(this, R.id.mainNavigationFragment), appBarConfiguration) } 2.0.0

Change from 1.0.0 to 2.0.0 2.0.0 private fun setupNavigation() { ... val topLevelDestinations = HashSet() topLevelDestinations.add(R.id.nav_program) ... topLevelDestinations.add(R.id.nav_twitter) appBarConfiguration = AppBarConfiguration.Builder(topLevelDestinations) .setDrawerLayout(drawer_layout).build() setupActionBarWithNavController(this, navController, appBarConfiguration) } 1.0.0 private fun setupNavigation() { val appBarConfiguration = AppBarConfiguration(navController.graph, drawerLayout) setupActionBarWithNavController(this, navController, appBarConfiguration) }

New in 2.0.0 New Method Navigation.createNavigateOnClickListener(NavDirections) New features ● You can create ViewModels that are scoped at a navigation graph ● You can call navigation on Uri and deeplink ● You can create destinations

THE END! Questions? Laurence de Villers @L_de_V