这个问题已经被问了几次，但现在是2023年了，有人找到好的可用解决方案了吗？
我希望能够使用底部导航控件进行导航，而不必每次选中时刷新 fragment。这是我目前的代码：
navigation/main.xml:
我希望能够使用底部导航控件进行导航，而不必每次选中时刷新 fragment。这是我目前的代码：
navigation/main.xml:
<?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/main"
app:startDestination="@id/home">
<fragment
android:id="@+id/home"
android:name="com.org.ftech.fragment.HomeFragment"
android:label="@string/app_name"
tools:layout="@layout/fragment_home" />
<fragment
android:id="@+id/news"
android:name="com.org.ftech.fragment.NewsFragment"
android:label="News"
tools:layout="@layout/fragment_news"/>
<fragment
android:id="@+id/markets"
android:name="com.org.ftech.fragment.MarketsFragment"
android:label="Markets"
tools:layout="@layout/fragment_markets"/>
<fragment
android:id="@+id/explore"
android:name="com.org.ftech.ExploreFragment"
android:label="Explore"
tools:layout="@layout/fragment_explore"/>
</navigation>
活动邮件模板文件: activity_mail.xml
<?xml version="1.0" encoding="utf-8"?>
<!-- Use DrawerLayout as root container for activity -->
<androidx.drawerlayout.widget.DrawerLayout
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/drawer_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<androidx.constraintlayout.widget.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<fragment
android:id="@+id/nav_host_fragment"
android:name="androidx.navigation.fragment.NavHostFragment"
android:layout_width="0dp"
android:layout_height="0dp"
app:defaultNavHost="true"
app:layout_constraintBottom_toTopOf="@+id/bottomNavigationView"
app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:navGraph="@navigation/main" />
<com.google.android.material.bottomnavigation.BottomNavigationView
android:id="@+id/bottomNavigationView"
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:itemIconTint="@color/nav"
app:itemTextColor="@color/nav"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintStart_toStartOf="parent"
app:menu="@menu/main">
</com.google.android.material.bottomnavigation.BottomNavigationView>
</androidx.constraintlayout.widget.ConstraintLayout>
<com.google.android.material.navigation.NavigationView
app:menu="@menu/main"
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:id="@+id/navigationView"
android:layout_gravity="start">
</com.google.android.material.navigation.NavigationView>
</androidx.drawerlayout.widget.DrawerLayout>
主活动（MainActivity）.kt：
class MainActivity : AppCompatActivity() {
private var drawerLayout: DrawerLayout? = null
private var navigationView: NavigationView? = null
private var bottomNavigationView: BottomNavigationView? = null
private lateinit var appBarConfiguration: AppBarConfiguration
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
drawerLayout = findViewById(R.id.drawer_layout)
navigationView = findViewById(R.id.navigationView)
bottomNavigationView = findViewById(R.id.bottomNavigationView)
val navController = findNavController(R.id.nav_host_fragment)
appBarConfiguration = AppBarConfiguration(setOf(R.id.markets, R.id.explore, R.id.news, R.id.home), drawerLayout)
setupActionBarWithNavController(navController, appBarConfiguration)
findViewById<NavigationView>(R.id.navigationView)
.setupWithNavController(navController)
findViewById<BottomNavigationView>(R.id.bottomNavigationView)
.setupWithNavController(navController)
}
override fun onSupportNavigateUp(): Boolean {
val navController = findNavController(R.id.nav_host_fragment)
return navController.navigateUp(appBarConfiguration) || super.onSupportNavigateUp()
}
override fun onOptionsItemSelected(item: MenuItem): Boolean {
if (item.itemId == R.id.search) {
startActivity(Intent(applicationContext, SearchableActivity::class.java))
}
return super.onOptionsItemSelected(item)
}
override fun onCreateOptionsMenu(menu: Menu?): Boolean {
menuInflater.inflate(R.menu.options_menu, menu)
return super.onCreateOptionsMenu(menu)
}
}
在这个片段中，我会在onCreateView中调用一些服务来获取数据。当恢复片段时，我认为这些调用将不再执行，并且片段的状态应该得到保留。