Tag: Graph

Navigation Listener

An example of using a Navigation Listener would be to limit the screens on which your Navigation Drawer will be available. In this instance the drawer is locked on all screens other than the start destination (the opening Fragment):

import ...
class MainActivity : AppCompatActivity() {
    lateinit var drawerLayout: DrawerLayout
    lateinit var navController: NavController
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        @Suppress("UNUSED_VARIABLE")
        val binding = DataBindingUtil.setContentView<ActivityMainBinding>(this, R.layout.activity_main)
        navController = this.findNavController(R.id.myNavHostFragment)
        drawerLayout = binding.drawerLayout
        NavigationUI.setupActionBarWithNavController(this, navController, drawerLayout)

        // Add a listener which will determine if the destination is the start destination. If not, the nav drawer will be locked
        navController.addOnNavigatedListener { nc: NavController, nd: NavDestination -> // This currently doesn't work with Navigation version above 1.0.0-alpha07
            if (nd.id == nc.graph.startDestination) {
                drawerLayout.setDrawerLockMode(DrawerLayout.LOCK_MODE_UNLOCKED)
            } else {
                drawerLayout.setDrawerLockMode(DrawerLayout.LOCK_MODE_LOCKED_CLOSED)
            }
        }

        NavigationUI.setupWithNavController(binding.navView, navController)
    }

    override fun onSupportNavigateUp(): Boolean {
//        return navController.navigateUp()
        return NavigationUI.navigateUp(navController, drawerLayout)
    }
}

 

Adding Navigation to an Android Project

Adding the Navigation component to an Android project in Kotlin

buildscript {
    ext {
        ...
        version_navigation = "1.0.0-beta01" // Update based on version at https://developer.android.com/jetpack/androidx/releases/navigation
    }
    ...
}
dependencies {
    ...
    implementation "android.arch.navigation:navigation-fragment-ktx:$version_navigation"
    implementation "android.arch.navigation:navigation-ui-ktx:$version_navigation"
}
<layout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:orientation="vertical">

                <fragment
                    android:id="@+id/myNavHostFragment" // ID for Navigation fragment
                    android:name="androidx.navigation.fragment.NavHostFragment" // Add this. Don't ask, just do it. This is the host for all the other fragments
                    android:layout_width="match_parent"
                    android:layout_height="match_parent"
                    app:navGraph="@navigation/navigation" // And this. Points to navigation.xml in res/navigation folder which is where the Navigation Graph lives
                    app:defaultNavHost="true" /> // And this. Allows Navigation component to control system back key
        </LinearLayout>

</layout>

Create a new Resource file called navigation.xml in the res/navigation folder and switch to the Design view. You can now pull in Activities and Fragments and link them together. To link the Navigation Graph action (the link between two destinations) to a UI component use the built-in setOnClickListener:

class TitleFragment : Fragment() {
    override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?,
                              savedInstanceState: Bundle?): View? {
        val binding: FragmentTitleBinding = DataBindingUtil.inflate(
                inflater, R.layout.fragment_title, container, false
        )
        binding.playButton.setOnClickListener (
            Navigation.createNavigateOnClickListener(R.id.action_titleFragment_to_gameFragment) // Built-in onClickListener. The resource pointed to here is auto-generated when a link is drawn between the 2 Fragments in the Navigation Graph
        )
        return binding.root
    }
}