导航组件无法弹出以退出应用程序

Question

Using Android's Navigation Component , I have 3 fragments hosted by a single Activity. The launch fragment is a splash screen fragment (A), if the user is not logged in, I launch the login fragment (B), if they are logged in, I launch a list fragment (C).

So launch routes are either A->B->C or A->C.

When you land on B or C, pressing back should kill the app. The NavigationController though is instead backs up to A (I think, A's onActivityCreated is certainly called at which point it crashes which is probably unrelated).

Pop behaviors in the graph editor for A -> B seem to allow me to pop to different fragments but there doesn't seem to be an option to just kill the app.

Do I really need to override onBackPressed for this behavior and just kill the activity? Because this is easier without the NavigationController, usually I would just finish an activity as I start a new one.

Answer 1

Open text tab in Graph Editor to view xml code, find your two actions A -> B and A -> C and put tag: app:clearTask="true" , it's should kill you app when user press back button.

Example:

 <fragment
        android:id="@+id/launcher_fragment"
        android:name="com.example.LauncherFragment"
        android:label="launcher_fragment">
        <action
            android:id="@+id/action_launcher_to_login"
            app:destination="@id/login_fragment"
            app:clearTask="true"/>
        <action
            android:id="@+id/action_launcher_to_list"
            app:destination="@id/list_fragment"
            app:clearTask="true" />
    </fragment>