Navigation Component

Introduction to the core concepts of Android Navigation | Codemagic Blog

Navigation is one of the core concepts to master if you are working on any Android app that has a complex navigation system.

https://blog.codemagic.io/android-navigation-introduction/

Safeargs library doesnt generate direction class

I use navigation library and safeargs for passing data. I define argument to fragment like that. <fragment android:id="@+id/otherFragment" android:name="com.asd.navigate.OtherFr...

https://stackoverflow.com/questions/50686907/safeargs-library-doesnt-generate-direction-class

• There’s always a starting place: Every Android app should have a fixed start destination. This is the screen the user sees every time they open the app. This is also the last screen they see when they navigate back from other screens within the app by using the Up button.

• A back stack is always maintained: When a user navigates to different Activities or Fragments inside the app, there is a back stack that is always maintained. The back stack helps in navigating the user back to the correct destination from where they came as they go Up or Back. It follows a Last-In-First-Out (LIFO) structure.
• Start Destination is present lower in the stack
• Current Destination is present at the top of the stack
• New Destinations are pushed to the top of the stack
• When going back, the current destination is popped off the stack

• Up versus Back: Both the Up and Back buttons act in a similar way. The difference is that the Up button is only used for navigating inside an app—it will never navigate you out of the app. So, the Up button should never be shown on the first screen of the app. However, the Back button can take you outside of the app to the screen that is present the next level down in the navigation hierarchy.

• Deep linking simulates manual navigation: Whether you use deep linking or manually navigate to a certain screen inside an app, the back stack is populated with the same screens. So, if you have navigated to a certain page using deep linking, when you go back, the same back stack will be used as when navigating to that screen manually.

Key parts of the Navigation component

• Navigation graph: This manages your app’s navigation. It is a resource file that consists of the destinations along with the actions, which are used for navigating to another destination from the current one.

• NavHost: An empty container that displays destinations from your navigation graph.

• NavController: This helps in managing app navigation within a NavHost. It orchestrates the swapping of destination content in the NavHost as users move throughout your app.

Our goal

Set up the Navigation component

dependencies {
    var nav_version = "2.7.7"


// Navigation Component
    implementation ("androidx.navigation:navigation-fragment-ktx:2.7.7")
    implementation ("androidx.navigation:navigation-ui-ktx:2.7.7")
}

Add the Navigation graph

Link the navigation resource file

<!-- activity_main.xml -->

<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">

        <!-- Add the following for linking the navigation resource file -->
        <androidx.fragment.app.FragmentContainerView
            android:id="@+id/myNavHostFragment"
            android:name="androidx.navigation.fragment.NavHostFragment"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            app:defaultNavHost="true"
            app:navGraph="@navigation/navigation" />

    </LinearLayout>

</layout>

Add a fragment to the graph

Navigate to another destination

binding.startButton.setOnClickListener { view: View ->
    view.findNavController().navigate(R.id.action_welcomeFragment_to_triviaFragment)
}

Conditional Navigation

if (correctAnswers < round(0.8 * numQuestions)) {
    view.findNavController().navigate(R.id.action_triviaFragment_to_lostFragment)
} else {
    view.findNavController().navigate(R.id.action_triviaFragment_to_wonFragment)
}

Manipulate the back stack

Using Safe Args

buildscript {
    repositories {
        google()
    }
    dependencies {
    
        val navVersion = "2.7.7"
        classpath("androidx.navigation:navigation-safe-args-gradle-plugin:$navVersion")

    }
}

id("androidx.navigation.safeargs.kotlin")
id("kotlin-kapt")

apply plugin: "androidx.navigation.safeargs"

binding.startButton.setOnClickListener { view: View ->
    view.findNavController().navigate(WelcomeFragmentDirections.actionWelcomeFragmentToTriviaFragment())
}

Pass data between fragments

view.findNavController().navigate(TriviaFragmentDirections.actionTriviaFragmentToWonFragment(numQuestions, correctAnswers))

val args = WonFragmentArgs.fromBundle(requireArguments())

// Setting the values to the TextView(s)
correctAnswersText.text = args.numCorrect.toString()
totalQuestionsText.text = args.numQuestions.toString()

Add support for the Up button

val navHostFragment = supportFragmentManager.findFragmentById(R.id.myNavHostFragment) as NavHostFragment
val navController = navHostFragment.navController
NavigationUI.setupActionBarWithNavController(this, navController)

override fun onSupportNavigateUp(): Boolean {
    val navController = this.findNavController(R.id.myNavHostFragment)
    return navController.navigateUp()
}

Add an overflow menu

<menu xmlns:android="http://schemas.android.com/apk/res/android">
    <item
        android:id="@+id/aboutFragment"
        android:title="@string/about_title" />
</menu>

override fun onCreateView(
    inflater: LayoutInflater, container: ViewGroup?,
    savedInstanceState: Bundle?
): View? {
    // ...

    // Add this line
    setHasOptionsMenu(true)

    return binding.root
}

override fun onCreateOptionsMenu(menu: Menu, inflater: MenuInflater) {
    super.onCreateOptionsMenu(menu, inflater)
    inflater.inflate(R.menu.overflow_menu, menu)
}

override fun onOptionsItemSelected(item: MenuItem): Boolean {
    return NavigationUI.onNavDestinationSelected(
        item,
        requireView().findNavController()
    ) || super.onOptionsItemSelected(item)
}

Add Navigation Drawer

dependencies {
    def material_version = "1.2.1"

    implementation "com.google.android.material:material:$material_version"
}

<menu xmlns:android="http://schemas.android.com/apk/res/android">
    <item
        android:id="@+id/rulesFragment"
        android:icon="@drawable/ic_rules"
        android:title="@string/rules_title" />
    <item
        android:id="@+id/aboutFragment"
        android:icon="@drawable/ic_about"
        android:title="@string/about_title" />
</menu>

<layout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">

    <androidx.drawerlayout.widget.DrawerLayout
        android:id="@+id/drawerLayout"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

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

            <!-- ... -->

        </LinearLayout>

    </androidx.drawerlayout.widget.DrawerLayout>

</layout>

<com.google.android.material.navigation.NavigationView
    android:id="@+id/navView"
    android:layout_width="wrap_content"
    android:layout_height="match_parent"
    android:layout_gravity="start"
    app:menu="@menu/navdrawer_menu" />

• Add two variables:

private lateinit var drawerLayout: DrawerLayout
private lateinit var appBarConfiguration: AppBarConfiguration

• Initialize the DrawerLayout inside onCreate:

drawerLayout = binding.drawerLayout

• Modify to include the drawer:

NavigationUI.setupActionBarWithNavController(this, navController, drawerLayout)

• Create an AppBarConfiguration and hook the NavigationUI up to the navigation view:

appBarConfiguration = AppBarConfiguration(navController.graph, drawerLayout)
NavigationUI.setupWithNavController(binding.navView, navController)

• In the onSupportNavigateUp method, replace the following:

return navController.navigateUp()

with this:

return NavigationUI.navigateUp(navController, drawerLayout)

This helps in replacing the Up button with the menu button when we come to the first screen of the app.

x<com.google.android.material.navigation.NavigationView
    android:id="@+id/navView"
    app:headerLayout="@layout/nav_header"
    app:menu="@menu/navdrawer_menu" />

<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/navHeader"
    android:layout_width="match_parent"
    android:layout_height="192dp"
    android:background="?attr/colorPrimary"
    android:contentDescription="@string/cover_image_desc"
    android:padding="16dp"
    android:theme="@style/ThemeOverlay.AppCompat.Dark">

    <ImageView
        android:id="@+id/imageView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:srcCompat="@drawable/trivia_cover" />

</androidx.constraintlayout.widget.ConstraintLayout>

Listen to navigation changes

navController.addOnDestinationChangedListener { nc: NavController, nd: NavDestination, _: Bundle? ->
    if (nd.id == nc.graph.startDestination) {
        drawerLayout.setDrawerLockMode(DrawerLayout.LOCK_MODE_UNLOCKED)
    } else {
        drawerLayout.setDrawerLockMode(DrawerLayout.LOCK_MODE_LOCKED_CLOSED)
    }
}

Add a share button

• Explicit Intent: For launching Activities within the same app

• Implicit Intent: This helps to provide an abstract description of the action that you want to perform, which is used for launching Activities of other apps on the device

<menu xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">

    <item
        android:id="@+id/share"
        android:enabled="true"
        android:icon="@drawable/ic_share"
        android:title="@string/share_title"
        android:visible="true"
        app:showAsAction="ifRoom" />

</menu>

private fun getShareIntent(): Intent {
    val args = WonFragmentArgs.fromBundle(requireArguments())
    val shareIntent = Intent(Intent.ACTION_SEND)
    shareIntent.setType("text/plain")
        .putExtra(
            Intent.EXTRA_TEXT,
            getString(R.string.share_text, args.numCorrect, args.numQuestions)
        )
    return shareIntent
}

private fun shareSuccess() {
    startActivity(getShareIntent())
}

override fun onCreateOptionsMenu(menu: Menu, inflater: MenuInflater) {
    super.onCreateOptionsMenu(menu, inflater)
    inflater.inflate(R.menu.share_menu, menu)

    if (null == getShareIntent().resolveActivity(requireActivity().packageManager)) {
        menu.findItem(R.id.share)?.isVisible = false
    }
}

override fun onOptionsItemSelected(item: MenuItem): Boolean {
    when (item.itemId) {
        R.id.share -> shareSuccess()
    }

    return super.onOptionsItemSelected(item)
}

Animate navigation

<!-- fade out animation -->
<set xmlns:android="http://schemas.android.com/apk/res/android">
    <alpha
        android:duration="@android:integer/config_mediumAnimTime"
        android:fromAlpha="1.0"
        android:toAlpha="0.0" />
</set>

<!-- slide in left animation -->
<set xmlns:android="http://schemas.android.com/apk/res/android">
    <translate
        android:duration="@android:integer/config_shortAnimTime"
        android:fromXDelta="-100%"
        android:fromYDelta="0%"
        android:toXDelta="0%"
        android:toYDelta="0%" />
</set>

Step 3:

• Design Navigation Graph: The Navigation Component uses a navigation graph to define the app’s navigation flow. It provides a visual representation of the app’s destinations and the connections between them. To create a navigation graph, follow these steps:
1. In the Project window, navigate to the res directory and right-click on the res folder.
2. Select “New” -> “Android resource file” from the context menu.
3. Set the Resource type to “Navigation” and provide a name for the file (e.g., nav_graph).
4. Click “OK” to create the navigation graph file.

• Once the navigation graph is created, it will open in the Navigation Editor. Here, you can add destinations, define connections between them, and configure additional properties.

Step 4:

Step 5:

• Create NavHostFragment: A NavHostFragment acts as a container for displaying different destinations. To create a NavHostFragment, follow these steps:
1. In your activity layout XML file, add a <fragment> tag.
2. Set the android:name attribute to "androidx.navigation.fragment.NavHostFragment".
3. Set the app:navGraph attribute to point to your navigation graph file.
4. Specify an ID for the NavHostFragment.
Here’s an example of how the XML layout file (activity_main.xml) might look like this:

 <androidx.fragment.app.FragmentContainerView
        android:id="@+id/fragment_container"
        android:name="androidx.navigation.fragment.NavHostFragment"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:defaultNavHost="true"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:navGraph="@navigation/nav_graph" />

1. In your activity class, create a private property for the NavController:

private lateinit var navController: NavController

1. In the onCreate() method of your activity, initialize the NavController and set it as the default NavController for your NavHostFragment:

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_main)

// Obtain reference to the NavHostFragment
    val navHostFragment = supportFragmentManager.findFragmentById(R.id.nav_host_fragment) as NavHostFragment
    // Get the NavController
    navController = navHostFragment.navController
    // Set up the ActionBar with the Navigation UI
    setupActionBarWithNavController(navController)
}

1. Override the onSupportNavigateUp() method to handle the navigation when the user presses the back button in the ActionBar. It should call the navigateUp() method on the NavController to perform the appropriate navigation action. If the navigateUp() method returns false, call the superclass's onSupportNavigateUp() method to handle the navigation:

override fun onSupportNavigateUp(): Boolean {
    return navController.navigateUp() || super.onSupportNavigateUp()
}