阻止BottomNavigationView 重新创建片段

Question

每次导航时，带有导航组件的底部导航视图都会重新创建片段。我想要一个 Singletop，我该怎么做？

我跟着这个教程：https : //proandroiddev.com/android-navigation-arch-component-a-curious-investigation-3e56e24126e1

class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        setupNavigation()
    }

    private fun setupNavigation() {
        val navController = findNavController(R.id.mainNavigationFragment)
        setupActionBarWithNavController(navController)
        bottomNavigationView.setupWithNavController(navController)
    }

    override fun onSupportNavigateUp() =
            findNavController(R.id.mainNavigationFragment).navigateUp()
}