(导航组件)返回首页片段时如何在活动上显示后退箭头? [英] (Navigation component) How to display back arrow on the activity when back to the home fragment?

问题描述

我必须对折扣片段进行分段，并在编辑服务"活动上显示编辑服务片段.当我返回以编辑服务片段时，折扣片段上显示的后退箭头消失了，我想显示它以导航来自编辑服务活动的上一个活动.

I have to fragments discount fragment and edit service fragment displayed on Edit Service activity. the back arrow displayed on discount fragment when i back to edit service fragment the arrow disappear i want to display it to navigate the previous activity from edit service activity.

活动布局..........................................................

activity layout .........................................................

<?xml version="1.0" encoding="utf-8"?>
<androidx.coordinatorlayout.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <androidx.constraintlayout.widget.ConstraintLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent">
        <androidx.appcompat.widget.Toolbar

            android:id="@+id/toolbar_hesham"
            android:theme="@style/ThemeOverlay.AppCompat.ActionBar"
            app:popupTheme="@style/ThemeOverlay.AppCompat.Light"
            app:title="@string/edit_service"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:background="@color/colorPrimary"
            android:minHeight="?attr/actionBarSize"
            app:layout_constraintTop_toTopOf="parent" />

        <fragment
            android:id="@+id/nav_host_edit_service"
            android:name="androidx.navigation.fragment.NavHostFragment"
            android:layout_width="match_parent"
            android:layout_height="0dp"
            app:layout_constraintTop_toBottomOf="@+id/toolbar_hesham"
            app:layout_constraintBottom_toBottomOf="parent"
            app:defaultNavHost="true"
            app:navGraph="@navigation/edit_service_nav" />
    </androidx.constraintlayout.widget.ConstraintLayout>


    <include layout="@layout/confirm_request_bottom_sheet"/>
</androidx.coordinatorlayout.widget.CoordinatorLayout>

活动代码........................................................

activity code .............................................................

public class EditServicesActivity extends BaseActivity<MainViewModel> {


    public Toolbar toolbar;
    public NavController navController;

    @Override
    protected void initActivityComponent() {
        component = ProServeTechApp.getComponent(this)
                .plus(new ActivityModule(this));
        component.inject(this);
    }

    @Override
    protected int getLayout() {
        return R.layout.activity_edit_services;
    }

    @Override
    protected Class<MainViewModel> getViewModelClass() {
        return MainViewModel.class;
    }

    @Override
    protected void initActivity() {
        viewModel.getRequestDetails(getIntent().getExtras().getString("requestId"), String.valueOf(0));
        viewModel.getIssues(getIntent().getStringExtra("requestId"));

        toolbar = findViewById(R.id.toolbar_hesham);
        setSupportActionBar(toolbar);

        navController = Navigation.findNavController(this, R.id.nav_host_edit_service);
        NavigationUI.setupWithNavController(toolbar, navController );

    }



}

导航........................................

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/edit_service_nav"
    app:startDestination="@id/edi_service_fragment">

    <fragment
        android:id="@+id/edi_service_fragment"
        android:name="com.unicomg.proservetech.ui.requestdetails.edit.service.fragments.EditServiceFragment"
        android:label="@string/edit_service"
        tools:layout="@layout/edit_service_fragment">

        <action
            android:id="@+id/action_edi_service_fragment_to_discount_fragment"
            app:destination="@id/discount_fragment"
            app:enterAnim="@anim/slide_up"
            app:exitAnim="@anim/slide_bottom"
            app:popEnterAnim="@anim/slide_up"
            app:popExitAnim="@anim/slide_bottom" />
    </fragment>

    <fragment
        android:id="@+id/discount_fragment"
        android:name="com.unicomg.proservetech.ui.requestdetails.edit.service.fragments.DiscountFragment"
        android:label="@string/add_discount"
        tools:layout="@layout/discount_fragment">


    </fragment>

</navigation>

推荐答案

按照

导航图的起始目标被认为是唯一的顶级目标.在所有其他目标上，工具栏将显示向上"按钮.

The start destination of your navigation graph is considered the only top level destination. On all other destinations, the Toolbar will show the Up button.

如果您还想在开始目的地上显示向上"按钮(即转到上一个活动)，则需要使用带有 AppBarConfiguration 的版本.

If you want to also show the Up button on your start destination (i.e., to go to the previous activity), you'd want to use the version that takes an AppBarConfiguration.

按照在AppBarConfiguration上更新UI组件文档，<通过code> AppBarConfiguration ，您可以准确地将所需的目的地设置为顶级目的地.要使向上"按钮显示在每个目的地上，请使用一组空的顶级目的地:

As per the Update UI components documentation on AppBarConfiguration, AppBarConfiguration allows you to set exactly what destinations you want as top level destinations. To get the Up button to show on every destination, you'd use an empty set of top level destinations:

AppBarConfiguration appBarConfiguration =
    new AppBarConfiguration.Builder().build();

请注意，由于您使用的是 setSUpportActionBar()，因此应遵循操作栏文档，并使用 setupActionBarWithNavController()方法而不是 Toolbar 版本.您还必须覆盖 onSupportNavigateUp()来处理向上按钮.

Note that since you're using setSUpportActionBar(), you should follow the Action Bar documentation and use the setupActionBarWithNavController() method rather than the Toolbar version. You must also override onSupportNavigateUp() to handle the up button.

因此，您的完整代码如下:

Therefore your complete code would look like:

public class EditServicesActivity extends BaseActivity<MainViewModel> {


    public Toolbar toolbar;
    public AppBarConfiguation appBarConfiguation;
    public NavController navController;

    @Override
    protected void initActivityComponent() {
        component = ProServeTechApp.getComponent(this)
                .plus(new ActivityModule(this));
        component.inject(this);
    }

    @Override
    protected int getLayout() {
        return R.layout.activity_edit_services;
    }

    @Override
    protected Class<MainViewModel> getViewModelClass() {
        return MainViewModel.class;
    }

    @Override
    protected void initActivity() {
        viewModel.getRequestDetails(getIntent().getExtras().getString("requestId"), String.valueOf(0));
        viewModel.getIssues(getIntent().getStringExtra("requestId"));

        toolbar = findViewById(R.id.toolbar_hesham);
        setSupportActionBar(toolbar);

        navController = Navigation.findNavController(this, R.id.nav_host_edit_service);
        appBarConfiguration = new AppBarConfiguration.Builder().build();
        NavigationUI.setupActionBarWithNavController(this, navController,
            appBarConfiguration);
    }

    @Override
    public boolean onSupportNavigateUp() {
        return NavigationUI.navigateUp(navController, appBarConfiguration)
                || super.onSupportNavigateUp();
    }
}

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