Kuidas sa rakendaksid navigatsiooni nuppude abil, et…

Navigation Architecture Component kasutamine:

NavGraph'i loomine: Määrake Destinations (fragmentid või Activity) ja Actions (üleminekud nende vahel) XML-resurssides:

<?xml version="1.0" encoding="utf-8"?>
<navigation xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/nav_graph"
    app:startDestination="@id/fragmentA">

    <fragment
        android:id="@+id/fragmentA"
        android:name="com.example.FragmentA"
        android:label="FragmentA" >
        <action
            android:id="@+id/action_fragmentA_to_fragmentB"
            app:destination="@id/fragmentB" />
    </fragment>
    <fragment
        android:id="@+id/fragmentB"
        android:name="com.example.FragmentB"
        android:label="FragmentB" >
        <action
            android:id="@+id/action_fragmentB_to_fragmentC"
            app:destination="@id/fragmentC" />
    </fragment>
    <fragment
        android:id="@+id/fragmentC"
        android:name="com.example.FragmentC"
        android:label="FragmentC" />
</navigation>

NavHost'i seadistamine: Lisage NavHost (näiteks, NavHostFragment) tegevuse paigutusse, mis on seotud NavGraph'iga:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <androidx.fragment.app.FragmentContainerView
        android:id="@+id/nav_host_fragment"
        android:name="androidx.navigation.fragment.NavHostFragment"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1"
        app:defaultNavHost="true"
        app:navGraph="@navigation/nav_graph" />

    <!-- Siin võivad olla navigeerimisnupud -->
</LinearLayout>

Lisage navigeerimisnupud: Kasutage BottomNavigationView või eraldi nuppe ning siduge need NavController-iga:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <androidx.fragment.app.FragmentContainerView
        android:id="@+id/nav_host_fragment"
        android:name="androidx.navigation.fragment.NavHostFragment"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1"
        app:defaultNavHost="true"
        app:navGraph="@navigation/nav_graph" />

    <Button
        android:id="@+id/button_go_to_b"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Mine B" />

    <Button
        android:id="@+id/button_go_to_c"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Mine C" />
</LinearLayout>

Koodis käsitlege nuppude vajutusi: Saage NavController ja kutsuge navigate() nuppu vajutamisel. NavController haldab automaatselt back stack-i, säilitades eelnevad Destination'id:

// Activity või Fragment
import androidx.navigation.findNavController

override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
    super.onViewCreated(view, savedInstanceState)

    val navController = findNavController(R.id.nav_host_fragment)

    view.findViewById<Button>(R.id.button_go_to_b).setOnClickListener {
        navController.navigate(R.id.action_fragmentA_to_fragmentB)
    }

    view.findViewById<Button>(R.id.button_go_to_c).setOnClickListener {
        navController.navigate(R.id.fragmentC)
    }
}

Kui on vaja keerulisemat navigeerimist mitmel vahelehel (BottomNavigationView, DrawerLayout), kasutage setupWithNavController():

// Activity, kus on BottomNavigationView
import androidx.navigation.ui.setupWithNavController
import com.google.android.material.bottomnavigation.BottomNavigationView

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

    val navController = findNavController(R.id.nav_host_fragment)
    val bottomNavView = findViewById<BottomNavigationView>(R.id.bottom_nav_view)
    bottomNavView.setupWithNavController(navController)
}

Navigation Component haldab vaikimisi back stack-i. Kui vajutate "Tagasi" nuppu, kasutaja naaseb eelmise Destination juurde. navigate()-i käigus back stack-i juhtimiseks saate kasutada NavOptions ja popUpTo.

Kuidas sa rakendaksid navigatsiooni nuppude abil, et see säilitaks virna?