Android Jetpack导航，带有Youtube或Instagram的BottomNavigationView像正确的向后导航(向后分段)?

问题描述

Android Jetpack导航，带有BottomNavigationView的自动片段后退按钮位于后退按钮上?

Android Jetpack Navigation, BottomNavigationView with auto fragment back stack on back button click?

我想要的是，在用户一个接一个地选择多个选项卡并且用户单击后退"应用程序之后，必须重定向到他/她打开的最后一页.

What I wanted, after choosing multiple tabs one after another by user and user click on back button app must redirect to the last page he/she opened.

通过将当前选定的项目保存在ArrayList中，我使用Android ViewPager达到了同样的效果. Android Jetpack导航发布后是否有任何自动返回堆栈?我想使用导航图实现

I achieved the same using Android ViewPager, by saving the currently selected item in an ArrayList. Is there any auto back stack after Android Jetpack Navigation Release? I want to achieve it using navigation graph

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout 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/container"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".main.MainActivity">

    <fragment
        android:id="@+id/my_nav_host_fragment"
        android:name="androidx.navigation.fragment.NavHostFragment"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        app:defaultNavHost="true"
        app:layout_constraintBottom_toTopOf="@+id/navigation"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:navGraph="@navigation/nav_graph" />

    <android.support.design.widget.BottomNavigationView
        android:id="@+id/navigation"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="0dp"
        android:layout_marginEnd="0dp"
        android:background="?android:attr/windowBackground"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:menu="@menu/navigation" />

</android.support.constraint.ConstraintLayout>

navigation.xml

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android">

    <item
        android:id="@+id/navigation_home"
        android:icon="@drawable/ic_home"
        android:title="@string/title_home" />

    <item
        android:id="@+id/navigation_people"
        android:icon="@drawable/ic_group"
        android:title="@string/title_people" />

    <item
        android:id="@+id/navigation_organization"
        android:icon="@drawable/ic_organization"
        android:title="@string/title_organization" />

    <item
        android:id="@+id/navigation_business"
        android:icon="@drawable/ic_business"
        android:title="@string/title_business" />

    <item
        android:id="@+id/navigation_tasks"
        android:icon="@drawable/ic_dashboard"
        android:title="@string/title_tasks" />

</menu>

还添加了

bottomNavigation.setupWithNavController(Navigation.findNavController(this, R.id.my_nav_host_fragment))

我从Levi Moreira那里得到一个答案，如下所示

I got one answer from Levi Moreira, as follows

navigation.setOnNavigationItemSelectedListener {item ->

            onNavDestinationSelected(item, Navigation.findNavController(this, R.id.my_nav_host_fragment))

        }

但是这样做只能是最后一个打开的片段的实例再次创建.

But by doing this only happening is that last opened fragment's instance creating again.

为BottomNavigationView提供适当的后退导航

Providing proper Back Navigation for BottomNavigationView

推荐答案

您真的不需要ViewPager即可与BottomNavigation和新的Navigation体系结构组件一起使用.我一直在使用完全使用两者的示例应用程序进行工作，请参见此处.

You don't really need a ViewPager to work with BottomNavigation and the new Navigation architecture component. I have been working in a sample app that uses exactly the two, see here.

基本概念是这样，您具有将承载BottomNavigationView的主要活动，并且这是导航图的导航主机，这是其xml的外观:

The basic concept is this, you have the main activity that will host the BottomNavigationView and that is the Navigation host for your navigation graph, this is how the xml for it look like:

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout 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/container"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".main.MainActivity">

    <fragment
        android:id="@+id/my_nav_host_fragment"
        android:name="androidx.navigation.fragment.NavHostFragment"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        app:defaultNavHost="true"
        app:layout_constraintBottom_toTopOf="@+id/navigation"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:navGraph="@navigation/nav_graph" />

    <android.support.design.widget.BottomNavigationView
        android:id="@+id/navigation"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="0dp"
        android:layout_marginEnd="0dp"
        android:background="?android:attr/windowBackground"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:menu="@menu/navigation" />

</android.support.constraint.ConstraintLayout>

BottomNavigationView的导航菜单(选项卡菜单)如下:

The navigation Menu (tabs menu) for the BottomNavigationView looks like this:

navigation.xml

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android">

    <item
        android:id="@+id/navigation_home"
        android:icon="@drawable/ic_home"
        android:title="@string/title_home" />

    <item
        android:id="@+id/navigation_people"
        android:icon="@drawable/ic_group"
        android:title="@string/title_people" />

    <item
        android:id="@+id/navigation_organization"
        android:icon="@drawable/ic_organization"
        android:title="@string/title_organization" />

    <item
        android:id="@+id/navigation_business"
        android:icon="@drawable/ic_business"
        android:title="@string/title_business" />

    <item
        android:id="@+id/navigation_tasks"
        android:icon="@drawable/ic_dashboard"
        android:title="@string/title_tasks" />

</menu>

所有这些都只是BottomNavigationView设置.现在，要使其与Navigation Arch Component一起使用，您需要进入导航图编辑器，添加所有片段目标(在我的情况下，我有5个目标，每个选项卡一个)，并使用相同的目标ID设置目标ID.名称作为navigation.xml文件中的名称:

All of this is just the BottomNavigationView setup. Now to make it work with the Navigation Arch Component you need to go into the navigation graph editor, add all your fragment destinations (in my case I have 5 of them, one for each tab) and set the id of the destination with the same name as the one in the navigation.xml file:

这将告诉android在选项卡和片段之间建立链接，现在每次用户单击主页"选项卡时，android将负责加载正确的片段.还需要将一段kotlin代码添加到NavHost(主要活动)中，以使用BottomNavigationView进行连接:

This will tell android to make a link between the tab and the fragment, now every time the user clicks the "Home" tab android will take care of loading up the correct fragment.There is also one piece of kotlin code that needs to be added to your NavHost (the main activity) to wire things up with the BottomNavigationView:

您需要添加onCreate:

You need to add in your onCreate:

bottomNavigation.setupWithNavController(Navigation.findNavController(this, R.id.my_nav_host_fragment))

这告诉android在导航架构组件和BottomNavigationView之间进行接线.在 docs 中查看更多内容.

This tells android to do the wiring between the Navigation architecture component and the BottomNavigationView. See more in the docs.

要获得与使用youtube时相同的行为，只需添加以下内容:

To get the same beahvior you have when you use youtube, just add this:

navigation.setOnNavigationItemSelectedListener {item ->

            onNavDestinationSelected(item, Navigation.findNavController(this, R.id.my_nav_host_fragment))

        }

这将使目的地进入后退栈，因此当您单击后退"按钮时，将弹出最后访问的目的地.

This will make destinations go into the backstack so when you hit the back button, the last visited destination will be popped up.

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