实现BottomNavigationView和Navigation联动

界面展示

引入依赖

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

创建Fragment

创建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>

注意这里的三个ID

为BottomNavigationView创建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>

这里的三个ID必须和刚才一样

主界面布局

<?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>

实现BottomNavigationView和Navigation联动

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);
    }
}

主要是三面四行代码

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);