IssueTracker

Project: platform/frameworks/support
Branch: androidx-main

commit b17204359581a71c427d7519a6cfc1825141ed72
Author: Jeremy Woods <jbwoods@google.com>
Date:   Fri Mar 17 21:47:24 2023

    Prevent crash when adding unmanaged fragment in nav
   
    Currently, if you attempt to add a fragment to the fragment manager
    associated with the FragmentNavigator, navigation crashes as it cannot
    find an entry associated with fragment.
   
    While it is strongly recommended to only use navigation APIs to
    manipulate the fragment manager, if the back stack is not affected, then
    we should not crash.
   
    RelNote: "Adding fragments to the `FragmentNavigator`'s
    `FragmentManager` without using navigation will no longer crash."
    Test: Added FragmentNavigatorTest
    Bug: 274167493
   
    Change-Id: I47d4c75ca46ee7f8282b2a7b97d28d71edd9a07b

M       navigation/navigation-fragment/src/androidTest/java/androidx/navigation/fragment/FragmentNavigatorTest.kt
M       navigation/navigation-fragment/src/main/java/androidx/navigation/fragment/FragmentNavigator.kt

https://android-review.googlesource.com/2496343

popUpTo will be able to do that: https://stackoverflow.com/questions/50336112/how-to-disable-up-in-navigation-for-some-fragment-with-the-new-navigation-archit

At current now，there is two ways to do the above。

One：
In the NavHostFragment's Activity, override the onBackPress() method,adn if the current NavDestination is MainFragment then just finish the Activity.

@Override
    public void onBackPressed() {
       NavDestination navDestination = mNavController.getCurrentDestination();
        if (navDestination != null
                && navDestination.getId() == R.id.mainFragment) {
            finish();
            return;
        }
        super.onBackPressed();
    }

Two:
Set the to MainFragment action in Navigation_graph app:popUpTo="@id/nav_graph" and app:popUpToInclusive="true"

<?xml version="1.0" encoding="utf-8"?>
<navigation
    android:id="@+id/nav_graph"
    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"
    app:startDestination="@id/splashFragment">

    <fragment
        android:id="@+id/splashFragment"
        android:name="com.ihuman.storydemo.fragment.splash.SplashFragment"
        android:label="fragment_splash"
        tools:layout="@layout/fragment_splash">
        <action
            android:id="@+id/action_splashFragment_to_mainFragment"
            app:destination="@id/mainFragment"
            app:enterAnim="@anim/anim_right_in"
            app:exitAnim="@anim/anim_left_out"
            app:popEnterAnim="@anim/anim_left_in"
            app:popExitAnim="@anim/anim_right_out"
            app:popUpTo="@id/nav_graph"
            app:popUpToInclusive="true"/>
        <action
            android:id="@+id/action_splashFragment_to_guideFragment"
            app:destination="@id/guideFragment"
            app:enterAnim="@anim/anim_right_in"
            app:exitAnim="@anim/anim_left_out"
            app:popEnterAnim="@anim/anim_left_in"
            app:popExitAnim="@anim/anim_right_out"
            app:popUpTo="@id/nav_graph"
            app:popUpToInclusive="true"/>
    </fragment>
       
        <fragment
        android:id="@+id/guideFragment"
        android:name="com.ihuman.storydemo.fragment.guide.GuideFragment"
        android:label="GuideFragment"
        tools:layout="@layout/fragment_guide">
        <action
            android:id="@+id/action_guideFragment_to_mainFragment"
            app:destination="@id/mainFragment"
            app:enterAnim="@anim/anim_right_in"
            app:exitAnim="@anim/anim_left_out"
            app:popEnterAnim="@anim/anim_left_in"
            app:popExitAnim="@anim/anim_right_out"
            app:popUpTo="@id/nav_graph"
            app:popUpToInclusive="true"/>
    </fragment>

    <fragment
        android:id="@+id/mainFragment"
        android:name="com.ihuman.storydemo.fragment.main.MainFragment"
        android:label="fragment_main"
        tools:layout="@layout/fragment_main">
       
    </fragment>
       
</navigation>

Wish for help!