是否可以使用 Android 导航架构组件(Android Jetpack)有条件地设置 startDestination? [英] Is it possible to set startDestination conditionally using Android Navigation Architecture Component(Android Jetpack)?

问题描述

我正在使用 Navigation 来自 Android Jetpack 在屏幕之间导航.现在我想动态设置 startDestination.

I am using Navigation from Android Jetpack to navigate between screens. Now I want to set startDestination dynamically.

我有一个名为 MainActivity 的活动还有两个 Fragment，FragmentA &片段B.

I have an Activity named MainActivity And two Fragments, FragmentA & FragmentB.

var isAllSetUp : Boolean = // It is dynamic and I’m getting this from Preferences.

    If(isAllSetUp)
    {
     // show FragmentA
    }
    else
    {
     //show FragmentB
    }

我想使用导航架构组件设置上述流程.目前我使用 startDestionation 如下，但它不能满足我的要求.

I want to set above flow using Navigation Architecture Component. Currently I have used startDestionation as below but it’s not fulfilling my requirement.

<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/lrf_navigation"
   app:startDestination="@id/fragmentA">

   <fragment
       android:id="@+id/fragmentA"
       android:name="com.mindinventory.FragmentA"
       android:label="fragment_a"
       tools:layout="@layout/fragment_a" />
</navigation>

是否可以使用 Android 导航架构组件有条件地设置 startDestination?

Is it possible to set startDestination conditionally using Android Navigation Architecture Component?

推荐答案

最后，我得到了一个解决方案...

Finally, I got a solution to my query...

将下面的代码放在Activity的onCreate()方法中.

Put below code in onCreate() method of Activity.

Kotlin 代码

val navHostFragment = (supportFragmentManager.findFragmentById(R.id.home_nav_fragment) as NavHostFragment)
val inflater = navHostFragment.navController.navInflater
val graph = inflater.inflate(R.navigation.nav_main)
//graph.addArgument("argument", NavArgument)
graph.startDestination = R.id.fragment1
//or
//graph.startDestination = R.id.fragment2

navHostFragment.navController.graph = graph

Java 代码

NavHostFragment navHostFragment = (NavHostFragment) getSupportFragmentManager().findFragmentById(R.id.home_nav_fragment);  // Hostfragment
NavInflater inflater = navHostFragment.getNavController().getNavInflater();
NavGraph graph = inflater.inflate(R.navigation.nav_main);
//graph.addArgument("argument", NavArgument)
graph.setStartDestination(R.id.fragment1);

navHostFragment.getNavController().setGraph(graph);
navHostFragment.getNavController().getGraph().setDefaultArguments(getIntent().getExtras());


NavigationView navigationView = findViewById(R.id.navigationView);
NavigationUI.setupWithNavController(navigationView, navHostFragment.getNavController());

附加信息

按照@artnest 的建议，从布局中删除 app:navGraph 属性.删除后看起来像这样

As @artnest suggested, remove the app:navGraph attribute from the layout. It would look something like this after removal

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

    <androidx.fragment.app.FragmentContainerView
        android:id="@+id/home_nav_fragment"
        android:name="androidx.navigation.fragment.NavHostFragment"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:defaultNavHost="true" />

</FrameLayout>

在使用 fragment 标签代替 FragmentContainerView 的情况下，上述更改保持不变

In the case of a fragment tag used instead of FragmentContainerView, the above changes remain the same

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