如何使用导航架构组件在另一个 Activity 上显示向上按钮

Question

假设我在父级 ActivityA 上，它有一个 Fab 按钮。单击 Fab 按钮后，它会打开 ActivityB.

ActivityB 包含导航图。所以我设置了导航组件，如：

Toolbar toolbar = findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
if (getSupportActionBar() != null)
    getSupportActionBar().setDisplayHomeAsUpEnabled(true);

NavController navController = Navigation.findNavController(this, R.id.nav_host_fragment);
AppBarConfiguration appBarConfiguration = new AppBarConfiguration.Builder(navController.getGraph())
        .build();
NavigationUI.setupActionBarWithNavController(this, navController, appBarConfiguration);

现在的问题是，我无法显示转到父级的向上按钮 activity。在 AndroidManifext.xml 上，代码是：

<activity
    android:name=".ui.ActivityB"
    android:label="Activity B"
    android:launchMode="singleTop"
    android:parentActivityName=".ui.ActivityA">
    <meta-data
        android:name="android.support.PARENT_ACTIVITY"
        android:value="com.example.ui.ActivityA" />
</activity>

所以，我的问题是如何显示向上按钮？

@ianhanniballake，上面的是你的但不是这个：

Toolbar toolbar = findViewById(R.id.toolbar);

NavController navController = Navigation.findNavController(this, R.id.nav_host_fragment);
AppBarConfiguration appBarConfiguration = new AppBarConfiguration.Builder()
        .build();
NavigationUI.setupWithNavController(toolbar, navController, appBarConfiguration);

或者：

NavigationUI.setupWithNavController(toolbar, navController);

Answer 1

根据 Update UI components with NavigationUI documentation:

By default, the Navigation button is hidden when a user is at a top-level destination of a navigation graph and appears as an Up button in any other destination.

因此，您可以通过传入一组空的顶级目的地，让向上按钮显示在所有个目的地上。当您无法在导航图中向上移动时，将调用您通过 setFallbackOnNavigateUpListener 设置的 OnNavigationUpListener，允许您触发 activity 的向上导航功能：

NavController navController = Navigation.findNavController(this, R.id.nav_host_fragment);
AppBarConfiguration appBarConfiguration = new AppBarConfiguration.Builder()
    .setFallbackOnNavigateUpListener(new AppBarConfiguration.OnNavigateUpListener() {
        @Override
        public boolean onNavigateUp() {
            // Trigger the Activity's navigate up functionality
            return super.onSupportNavigateUp();
        }
    }).build();
NavigationUI.setupActionBarWithNavController(this, navController, appBarConfiguration);

 // Make sure to call NavigationUI.navigateUp(navController, appBarConfiguration);
 // in your Activity's `onSupportNavigateUp()`

Answer 2

下面的方法可以解决你的问题

class SettingsActivity : AppCompatActivity() {

    private lateinit var appBarConfiguration: AppBarConfiguration

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

        val toolbar: Toolbar = findViewById(R.id.toolbar)
        setSupportActionBar(toolbar)

        val navController: NavController = Navigation.findNavController(this, R.id.nav_host_fragment)
        appBarConfiguration = AppBarConfiguration.Builder().build()
        NavigationUI.setupActionBarWithNavController(this, navController, appBarConfiguration)

        fab.setOnClickListener {
            navController.navigate(R.id.action_nav_setting_to_nav_notification)
        }
    }

    override fun onSupportNavigateUp(): Boolean {
        val navController = Navigation.findNavController(this, R.id.nav_host_fragment)
        return NavigationUI.navigateUp(
            navController,
            appBarConfiguration
        ) || super.onSupportNavigateUp()
    }
}

如何使用导航架构组件在另一个 Activity 上显示向上按钮

How to display Up button on another Activity using Navigation Architecture Component

android

android-jetpack

android-architecture-navigation