Android JetPack-Navigation+BottomNavigationView+dataBinding实现底部导航

一，前言：最近看了下JetPack架构，做下笔记。BottomNavigationView+Navigation实现底部菜单。

准备工作：
新建底部menu

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

    <item
        android:id="@+id/homeFragment"
        android:icon="@drawable/ic_home_black_24dp"
        android:title="@string/title_home" />

    <item
        android:id="@+id/notificationsFragment"
        android:icon="@drawable/ic_dashboard_black_24dp"
        android:title="@string/title_dashboard" />

    <item
        android:id="@+id/dashboardFragment"
        android:icon="@drawable/ic_notifications_black_24dp"
        android:title="@string/title_notifications" />

</menu>

新建Fragment

public class HomeFragment extends Fragment {
    FragmentHomeBinding binding;

    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        binding = DataBindingUtil.inflate(inflater, R.layout.fragment_home, container, false);
        View view = binding.getRoot();
        return view;
    }
}

xml

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

    <data></data>
    <LinearLayout android:layout_width="match_parent" android:layout_height="match_parent"
        android:orientation="vertical">
        <TextView
            android:id="@+id/text"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Home页面"
            />
    </LinearLayout>
</layout>

navigation.xml

<?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/homeFragment"
    tools:ignore="UnusedNavigation">

    <fragment
        android:id="@+id/homeFragment"
        android:name="com.cwj.navigation.HomeFragment"
        android:label="fragment_home"
        tools:layout="@layout/fragment_home">

    </fragment>
    <fragment
        android:id="@+id/notificationsFragment"
        android:name="com.cwj.navigation.NotificationsFragment"
        android:label="fragment_notifications"
        tools:layout="@layout/fragment_notifications">


    </fragment>
    <fragment
        android:id="@+id/dashboardFragment"
        android:name="com.cwj.navigation.DashboardFragment"
        android:label="dashboard"
        tools:layout="@layout/dashboard">

    </fragment>
</navigation>

MainActivity

package com.cwj.navigation;

import android.os.Bundle;

import com.cwj.navigation.databinding.ActivityMainBinding;
import com.google.android.material.bottomnavigation.BottomNavigationView;

import androidx.appcompat.app.AppCompatActivity;
import androidx.annotation.NonNull;
import androidx.databinding.DataBindingUtil;
import androidx.fragment.app.FragmentManager;
import androidx.navigation.NavController;
import androidx.navigation.Navigation;
import androidx.navigation.fragment.NavHostFragment;
import androidx.navigation.ui.NavigationUI;

import android.view.MenuItem;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {
    ActivityMainBinding mainBinding;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        mainBinding = DataBindingUtil.  setContentView(this, R.layout.activity_main);
        FragmentManager fragmentManager = getSupportFragmentManager();
        NavHostFragment navHostFragment = (NavHostFragment) fragmentManager.findFragmentById(R.id.fragments);
        NavController navController = navHostFragment.getNavController();
        NavigationUI.setupWithNavController(mainBinding.navView, navController);
    }
    @Override
    public boolean onSupportNavigateUp() {
        return Navigation.findNavController(this,R.id.nav_view).navigateUp();
    }
}

XML

<?xml version="1.0" encoding="utf-8"?>
<layout 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">

    <data>

    </data>

    <androidx.constraintlayout.widget.ConstraintLayout
        android:id="@+id/container"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        tools:context=".MainActivity">

        <fragment
            android:id="@+id/fragments"
            android:name="androidx.navigation.fragment.NavHostFragment"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            app:defaultNavHost="true"
            app:navGraph="@navigation/navigation"
            app:layout_constraintBottom_toTopOf="parent"
            app:layout_constraintLeft_toLeftOf="parent"
            app:layout_constraintRight_toRightOf="parent"
            app:layout_constraintTop_toTopOf="parent" />

        <com.google.android.material.bottomnavigation.BottomNavigationView
            android:id="@+id/nav_view"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_marginStart="0dp"
            android:layout_marginEnd="0dp"
            android:background="?android:attr/windowBackground"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintLeft_toLeftOf="parent"
            app:layout_constraintRight_toRightOf="parent"
            app:menu="@menu/bottom_nav_menu" />
    </androidx.constraintlayout.widget.ConstraintLayout>
</layout>

结尾:这就写完了。代码量少了很多。简洁