Navigation的主要元素：

1、Navigation Graph：
一种新的XML资源文件,包含应用程序所有的页面，以及页面间的关系。

<?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/my_nav_graph"app:startDestination="@id/homeFragment"><fragmentandroid:id="@+id/homeFragment"android:name="com.example.navigation.HomeFragment"android:label="fragment_home"tools:layout="@layout/fragment_home" ><actionandroid:id="@+id/action_homeFragment_to_detailFragment"app:destination="@id/detailFragment" /></fragment><fragmentandroid:id="@+id/detailFragment"android:name="com.example.navigation.DetailFragment"android:label="fragment_detail"tools:layout="@layout/fragment_detail" ><actionandroid:id="@+id/action_detailFragment_to_homeFragment"app:destination="@id/homeFragment" /></fragment>
</navigation>

2、NavHostFragment：
一个特殊的Fragment，可以将它看作是其他Fragment的容器，Navigation Graph中的Fragment正是通过NavHostFragment进行展示的。

<?xml version="1.0" encoding="utf-8"?>
<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:layout_width="match_parent"android:layout_height="match_parent"tools:context=".MainActivity"><androidx.fragment.app.FragmentContainerViewandroid:id="@+id/fragmentContainerView"android:name="androidx.navigation.fragment.NavHostFragment"android:layout_width="409dp"android:layout_height="729dp"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/my_nav_graph" />
</androidx.constraintlayout.widget.ConstraintLayout>

3、NavController：
用于在代码中完成Navigation Graph中具体的页面切换工作。

MainActivity.java
public class MainActivity extends AppCompatActivity {NavController navController;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);// 这样写会报错// NavController navController = Navigation.findNavController(this, R.id.fragmentContainerView);// 需要先通过id获取到对应的NavHostFragment容器NavHostFragment navHostFragment = (NavHostFragment) getSupportFragmentManager().findFragmentById(R.id.fragmentContainerView);if (navHostFragment != null) {// 如果不为空，再获取到的容器对应的NavControllernavController = navHostFragment.getNavController();} else {throw new RuntimeException("NavHostFragment not found");}// 该代码的主要目的是将 ActionBar（或 Toolbar）与 NavController 关联起来，以便在使用 Android 导航组件时，ActionBar 可以自动更新其显示内容NavigationUI.setupActionBarWithNavController(this, navController);}@Overridepublic boolean onSupportNavigateUp() {// header上返回按键好用return navController.navigateUp();}
}
HomeFragment.java
@Overridepublic void onActivityCreated(@Nullable Bundle savedInstanceState) {super.onActivityCreated(savedInstanceState);Button button = getView().findViewById(R.id.button);button.setOnClickListener(view -> {// 由于最外层设置了NavController，所以这里可以通过容器中的view找到NavControllerNavController navController = Navigation.findNavController(view);// 通过NavController进行导航，确定目的地navController.navigate(R.id.action_homeFragment_to_detailFragment);});}
DetailFragment.java
@Overridepublic void onActivityCreated(@Nullable Bundle savedInstanceState) {super.onActivityCreated(savedInstanceState);Button button = getView().findViewById(R.id.button2);button.setOnClickListener((v)->{// 由于最外层设置了NavController，所以这里可以通过容器中的view找到NavControllerNavController navController = Navigation.findNavController(v);// 通过NavController进行导航，确定目的地navController.navigate(R.id.action_detailFragment_to_homeFragment);});}

三者之间的关系
当你想切换Fragment时，使用NavController对象,告诉它你想要去Nlavigation Graph中的哪个Fragment，NavController会将你想去的Fragment展示NavHostFragment中
实现顺序
1.创建Fragment
2.创建navgation_graph，指定fragment切换逻辑
3.在Activity的页面中添加navHostFragmrnt容器进行界面显示
4.在Activity中通过navHostFragmrnt获取到navController，并设置bar和fragment的对应关系，以及bar上返回按键生效
5.在需要触发fragment切换的位置通过获取navController进行导航，设置对应的action，确认触发后目的地
添加页面切换动画

页面之间参数传递
方法一：直接传递bundle对象（接收数据时需要知道对应key值以及value类型，并且需要判空）

        Bundle bundle = new Bundle();bundle.putString("user_name", "Jay");NavController navController = Navigation.findNavController(view);navController.navigate(R.id.action_homeFragment_to_detailFragment, bundle);

接收bundle对象

		Bundle arguments = getArguments();String userName = null;if (arguments != null) {userName = arguments.getString("user_name");Log.d("userName", "" + userName);}

方法二：引入arg插件

		dependencies {// 添加 safe-arg 插件依赖classpath("androidx.navigation:navigation-safe-args-gradle-plugin:2.4.0")}plugins {id 'androidx.navigation.safeargs'}

        Bundle bundle = new HomeFragmentArgs.Builder().setUserName("Jay").setAge(20).build().toBundle();HomeFragmentArgs args = HomeFragmentArgs.fromBundle(getArguments());String username = args.getUserName();int age = args.getAge();Log.d("Test", "userName = " + userName + "age = " +　age);

NavigationUI的使用场景
Fragment切换时，设计到AppBar上的内容显示，为了方便统一管理引入NavigationUI

public class MainActivity extends AppCompatActivity {private NavController navController;private AppBarConfiguration appBarConfiguration;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);NavHostFragment navHostFragment = (NavHostFragment) getSupportFragmentManager().findFragmentById(R.id.fragmentContainerView);if (navHostFragment != null) {navController = navHostFragment.getNavController();}appBarConfiguration = new AppBarConfiguration.Builder(navController.getGraph()).build();// 将Appbar与Navigation建立联系NavigationUI.setupActionBarWithNavController(this, navController, appBarConfiguration);}@Overridepublic boolean onCreateOptionsMenu(Menu menu) {super.onCreateOptionsMenu(menu);getMenuInflater().inflate(R.menu.menu_settings, menu);return true;}// 响应Meun的点击事件@Overridepublic boolean onOptionsItemSelected(@NonNull MenuItem item) {return NavigationUI.onNavDestinationSelected(item, navController) || super.onOptionsItemSelected(item);}// 响应AppBar的返回按键@Overridepublic boolean onSupportNavigateUp() {return NavigationUI.navigateUp(navController, appBarConfiguration) || super.onSupportNavigateUp();}
}

跳转后的假面不显示meun

    public View onCreateView(LayoutInflater inflater, ViewGroup container,Bundle savedInstanceState) {setHasOptionsMenu(true);return inflater.inflate(R.layout.fragment_setting, container, false);}@Overridepublic void onCreateOptionsMenu(@NonNull Menu menu, @NonNull MenuInflater inflater) {menu.clear();super.onCreateOptionsMenu(menu, inflater);}

监听页面切换完成的回调

        // 监听界面切换完成navController.addOnDestinationChangedListener(new NavController.OnDestinationChangedListener() {@Overridepublic void onDestinationChanged(@NonNull NavController navController, @NonNull NavDestination navDestination, @Nullable Bundle bundle) {Log.d("test","onDestinationChanged");}});

深层链接DeepLink之PendingIntent

private void sendNotifycation() {if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {NotificationChannel myChannel = new NotificationChannel(getActivity().getPackageName(), "MyChannel", NotificationManager.IMPORTANCE_DEFAULT);myChannel.setDescription("My NotificationChannel");NotificationManager notificationManager = getActivity().getSystemService(NotificationManager.class);notificationManager.createNotificationChannel(myChannel);}NotificationCompat.Builder builder = new NotificationCompat.Builder(getActivity(), getActivity().getPackageName()).setSmallIcon(R.drawable.ic_launcher_background).setContentTitle("Deep Link").setContentText("点我").setPriority(NotificationManager.IMPORTANCE_DEFAULT).setContentIntent(getPendingIntent());// 发送通知NotificationManagerCompat notificationManager = NotificationManagerCompat.from(getActivity());if (ActivityCompat.checkSelfPermission(getActivity(), android.Manifest.permission.POST_NOTIFICATIONS) != PackageManager.PERMISSION_GRANTED) {// TODO: Consider calling//    ActivityCompat#requestPermissions// here to request the missing permissions, and then overriding//   public void onRequestPermissionsResult(int requestCode, String[] permissions,//                                          int[] grantResults)// to handle the case where the user grants the permission. See the documentation// for ActivityCompat#requestPermissions for more details.return;}notificationManager.notify(notifyId++, builder.build());}private PendingIntent getPendingIntent() {Bundle bundle = new Bundle();bundle.putString("name","Jay");return Navigation.findNavController(getActivity(),R.id.button).createDeepLink().setGraph(R.navigation.my_nav_graph).setDestination(R.id.detailFragment).setArguments(bundle).createPendingIntent();}

深层链接DeepLink之Url