Realize the linkage between bottomnavigationview and navigation

Interface display

Introduce dependencies

// Navigation
implementation "androidx.navigation:navigation-fragment:2.2.2"
implementation "androidx.navigation:navigation-ui:2.2.2"

establish Fragment

establish navigation

<?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" xmlns:tools="http://schemas.android.com/tools" android:id="@+id/navigation" app:startDestination="@id/oneFragment2">
    <fragment android:id="@+id/oneFragment2" android:name="com.example.navigation.OneFragment" android:label="fragment_one" tools:layout="@layout/fragment_one" />
    <fragment android:id="@+id/twoFragment2" android:name="com.example.navigation.TwoFragment" android:label="fragment_two" tools:layout="@layout/fragment_two" />
    <fragment android:id="@+id/threeFragment2" android:name="com.example.navigation.ThreeFragment" android:label="fragment_three" tools:layout="@layout/fragment_three" />
</navigation>

Notice the three here ID

by BottomNavigationView establish menu

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:android="http://schemas.android.com/apk/res/android">

    <item android:id="@+id/oneFragment2" android:icon="@drawable/ic_launcher_background" android:title="Item" />
    <item android:id="@+id/twoFragment2" android:icon="@drawable/ic_launcher_background" android:title="Item" />
    <item android:id="@+id/threeFragment2" android:icon="@drawable/ic_launcher_background" android:title="Item" />
</menu>

Three here ID It must be the same as just now

Main interface layout

<?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" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical" tools:context=".MainActivity" >

    <androidx.fragment.app.FragmentContainerView android:id="@+id/fragmentContainerView" 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" />

    <com.google.android.material.bottomnavigation.BottomNavigationView android:id="@+id/main_bottom_navigation_view" android:layout_width="match_parent" android:layout_height="50dp" app:menu="@menu/menu" />

</LinearLayout>

Realization BottomNavigationView and Navigation linkage

import androidx.appcompat.app.AppCompatActivity;
import androidx.fragment.app.Fragment;
import androidx.navigation.NavController;
import androidx.navigation.Navigation;
import androidx.navigation.fragment.NavHostFragment;
import androidx.navigation.ui.NavigationUI;

import android.os.Bundle;

import com.google.android.material.bottomnavigation.BottomNavigationView;
import com.google.android.material.tabs.TabLayout;

public class MainActivity extends AppCompatActivity {
    

    @Override
    protected void onCreate(Bundle savedInstanceState) {
    
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        NavHostFragment navHostFragment = (NavHostFragment) getSupportFragmentManager()
                .findFragmentById(R.id.fragmentContainerView);
        NavController navController = navHostFragment.getNavController();
        BottomNavigationView bottomNavigationView = findViewById(R.id.main_bottom_navigation_view);
        NavigationUI.setupWithNavController(bottomNavigationView, navController);
    }
}

Mainly three sides and four lines of code

NavHostFragment navHostFragment = (NavHostFragment) getSupportFragmentManager()
                .findFragmentById(R.id.fragmentContainerView);
NavController navController = navHostFragment.getNavController();
BottomNavigationView bottomNavigationView = findViewById(R.id.main_bottom_navigation_view);
NavigationUI.setupWithNavController(bottomNavigationView, navController);