使用Navigation结合底部导航栏实现fragment切换

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简介

关于通过google官方提供的Navigation实现fragment切换,之前已经写了一篇《使用Navigation简化fragment切换》。本文继续深入,结合底部导航栏实现fragment切换.

使用方法

1. build.gradle中添加依赖

implementation "android.arch.navigation:navigation-common-ktx:1.0.0"
implementation "android.arch.navigation:navigation-fragment-ktx:1.0.0"
implementation "android.arch.navigation:navigation-runtime-ktx:1.0.0"
implementation "android.arch.navigation:navigation-ui-ktx:1.0.0"

2. 添加navigation文件
   下面仅提供样例,完整代码请直接下载demo源代码

<?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/home"
   app:startDestination="@+id/titleScreen">

   <fragment
       android:id="@+id/titleScreen"
       android:name="com.cxyzy.myapplication.FirstFragment"
       android:label="@string/first_page"
       tools:layout="@layout/fragment_first" />
</navigation>

3. 添加menu文件bottom_nav.xml

<menu xmlns:android="http://schemas.android.com/apk/res/android">
    <item
        android:id="@+id/home"
        android:icon="@drawable/ic_first"
        android:contentDescription="@string/first_page"
        android:title="@string/first_page" />
    <item
        android:icon="@drawable/ic_second"
        android:contentDescription="@string/second_page"
        android:title="@string/second_page" />
</menu>

4. MainActivity

class MainActivity : AppCompatActivity() {

    private var currentNavController: LiveData<NavController>? = null

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        if (savedInstanceState == null) {
            setupBottomNavigationBar()
        }
    }

    override fun onRestoreInstanceState(savedInstanceState: Bundle?) {
        super.onRestoreInstanceState(savedInstanceState)
        setupBottomNavigationBar()
    }

    private fun setupBottomNavigationBar() {
        val bottomNavigationView = findViewById<BottomNavigationView>(R.id.bottom_nav)

        val navGraphIds = listOf(R.navigation.navi_first, R.navigation.navi_second)

        // Setup the bottom navigation view with a list of navigation graphs
        val controller = bottomNavigationView.setupWithNavController(
                navGraphIds = navGraphIds,
                fragmentManager = supportFragmentManager,
                containerId = R.id.nav_host_container,
                intent = intent
        )

        // Whenever the selected controller changes, setup the action bar.
        controller.observe(this, Observer { navController ->
            setupActionBarWithNavController(navController)
        })
        currentNavController = controller
    }

    override fun onSupportNavigateUp(): Boolean {
        return currentNavController?.value?.navigateUp() ?: false
    }

    /**
     * Overriding popBackStack is necessary in this case if the app is started from the deep link.
     */
    override fun onBackPressed() {
        if (currentNavController?.value?.popBackStack() != true) {
            super.onBackPressed()
        }
    }
}

5. 实现效果
   

源代码

https://gitee.com/cxyzy1/navigationDemo/tree/master/bottomNavigationView

附录

navigation官方介绍文档：https://codelabs.developers.google.com/codelabs/android-navigation/#0

另外一种在navigation中实现fragment复用的方法：
https://github.com/STAR-ZERO/navigation-keep-fragment-sample.git

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