如何为底部导航制作导航图？有没有办法修改返回堆栈的行为？

Question

我是导航架构组件的新手，正在尝试制作 bottom navigation 视图。我真的很困惑我应该如何以正确的方式实现我的导航图。此外，我想让返回堆栈返回到 "home" 片段然后存在而不是导航所有返回堆栈。

我的应用包含三个用于底部导航的片段。我尝试做的是将图中每个可能组合的片段链接起来。结果不是灾难性的，但我仍然不确定这是否是正确的方法。此外，当我使用设备的后退按钮时，应用程序会在退出应用程序之前浏览我浏览过的每个片段。

我想进行导航，以便对于第一个后退按钮，它导航回到第一个片段 - 起点 - 然后对于第二个存在应用程序。

这是导航图的代码

    <?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/nav_graph"
    app:startDestination="@id/bottom_navigation_home">

    <fragment
        android:id="@+id/bottom_navigation_home"
        android:name="com.app.albaladinn.view.ui.HomeFragment"
        android:label="fragment_home"
        tools:layout="@layout/fragment_home" >
        <action
            android:id="@+id/action_homeFragment_to_couponsFragment"
            app:destination="@id/bottom_navigation_coupons" />
        <action
            android:id="@+id/action_homeFragment_to_settingsFragment"
            app:destination="@id/bottom_navigation_settings" />
        <action
            android:id="@+id/action_homeFragment_to_categoriesFragment"
            app:destination="@id/bottom_navigation_categories" />
    </fragment>
    <fragment
        android:id="@+id/bottom_navigation_coupons"
        android:name="com.app.albaladinn.view.ui.CouponsFragment"
        android:label="fragment_coupons"
        tools:layout="@layout/fragment_coupons" >
        <action
            android:id="@+id/action_couponsFragment_to_homeFragment"
            app:destination="@id/bottom_navigation_home" />
        <action
            android:id="@+id/action_couponsFragment_to_settingsFragment"
            app:destination="@id/bottom_navigation_settings" />
        <action
            android:id="@+id/action_couponsFragment_to_categoriesFragment"
            app:destination="@id/bottom_navigation_categories" />
    </fragment>
    <fragment
        android:id="@+id/bottom_navigation_settings"
        android:name="com.app.albaladinn.view.ui.SettingsFragment"
        android:label="fragment_settings"
        tools:layout="@layout/fragment_settings" >
        <action
            android:id="@+id/action_settingsFragment_to_couponsFragment"
            app:destination="@id/bottom_navigation_coupons" />
        <action
            android:id="@+id/action_settingsFragment_to_homeFragment"
            app:destination="@id/bottom_navigation_home" />
        <action
            android:id="@+id/action_settingsFragment_to_categoriesFragment"
            app:destination="@id/bottom_navigation_categories" />
    </fragment>
    <fragment
        android:id="@+id/bottom_navigation_categories"
        android:name="com.app.albaladinn.view.ui.CategoriesFragment"
        android:label="fragment_categories"
        tools:layout="@layout/fragment_categories">
        <action
            android:id="@+id/action_categoriesFragment_to_couponsFragment"
            app:destination="@id/bottom_navigation_coupons" />
        <action
            android:id="@+id/action_categoriesFragment_to_homeFragment"
            app:destination="@id/bottom_navigation_home"
            app:popUpToInclusive="false" />
        <action
            android:id="@+id/action_categoriesFragment_to_settingsFragment"
            app:destination="@id/bottom_navigation_settings" />
    </fragment>
</navigation>

这是主要的 activity

public class MainNavigationActivity extends AppCompatActivity {

    BottomNavigationView mainBottomNavigation;
    MainBottomNavigationControl mainBottomNavigationControl;
    NavController navController;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main_navigation);
        navController = Navigation.findNavController(this, R.id.frame_container);
        mainBottomNavigation = findViewById(R.id.bottom_navigation);
        NavigationUI.setupWithNavController(mainBottomNavigation, navController);
        mainBottomNavigationControl = new MainBottomNavigationControl();
        mainBottomNavigation.setOnNavigationItemSelectedListener(mainBottomNavigationControl);
    }

    class MainBottomNavigationControl implements 
            BottomNavigationView.OnNavigationItemSelectedListener {
        @Override
        public boolean onNavigationItemSelected(@NonNull MenuItem item) {
            switch (item.getItemId()) {
                case R.id.bottom_navigation_home:
                    navController.navigate(R.id.bottom_navigation_home);
                    return true;
                case R.id.bottom_navigation_categories:
                    navController.navigate(R.id.bottom_navigation_categories);
                    return true;
                case R.id.bottom_navigation_coupons:
                    navController.navigate(R.id.bottom_navigation_coupons);
                    return true;
                case R.id.bottom_navigation_settings:
                    navController.navigate(R.id.bottom_navigation_settings);
                    return true;
                default:
                    return false;
            }
        }
    }
}

Answer 1

NavigationUI.setupWithNavController(mainBottomnavigation, navController) 已经为您创建了合适的 OnNavigationItemSelectedListener，所以您应该完全删除您的 MainBottomNavigationControl - 它不需要。

如何为底部导航制作导航图？有没有办法修改返回堆栈的行为？

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