Question

我想在某个片段上显示导航抽屉图标而不是“后退”按钮。我创建了带有导航图的应用程序。

假设我有2个片段（LoginFragment和DashboardFragment）和一个活动（MainActivity）

MainActivity.kt

class MainActivity : AppCompatActivity() {

    lateinit var drawerLayout: DrawerLayout

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        val binding = DataBindingUtil.setContentView<ActivityMainBinding>(this, R.layout.activity_main)
        drawerLayout = binding.drawerLayout

        val navController = this.findNavController(R.id.myNavHostFragment)

        // prevent nav gesture if not on start destination
        navController.addOnDestinationChangedListener { nc: NavController, nd: NavDestination, args: Bundle? ->
            if (nd.id == nc.graph.startDestination) {
                drawerLayout.setDrawerLockMode(DrawerLayout.LOCK_MODE_UNLOCKED)
            } else {
                drawerLayout.setDrawerLockMode(DrawerLayout.LOCK_MODE_LOCKED_CLOSED)
            }
        }

        NavigationUI.setupActionBarWithNavController(this, navController, drawerLayout)
        NavigationUI.setupWithNavController(binding.navView, navController)

    }


    // Set up the back button on action bar
    override fun onSupportNavigateUp(): Boolean {
        val navController = this.findNavController(R.id.myNavHostFragment)

        return NavigationUI.navigateUp(navController, drawerLayout)
    }
}

LoginFragment.kt

class LoginFragment : Fragment() {

    override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        val binding:FragmentLoginBinding = DataBindingUtil.inflate(inflater,
            R.layout.fragment_login, container, false)

        // Hide the Action bar
        (activity as AppCompatActivity).supportActionBar?.hide()

        binding.loginButton.setOnClickListener {
           //Some unimportant validation
        }


        return binding.root
    }

}

DashboardFragment.kt

class DashboardFragment : Fragment() {

    lateinit var binding : FragmentDashboardBinding

    override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {

        // Binding object for this fragment and the layout
        binding = DataBindingUtil.inflate(inflater,
            R.layout.fragment_dashboard, container, false)

        //Navigate to Product stock fragment when clicked
        binding.productStockButton.setOnClickListener(Navigation.createNavigateOnClickListener(
            R.id.action_dashboardFragment_to_productStockOutletList
        ))

        //Navigate to Switching History fragment when clicked
        binding.switchingHistoryButton.setOnClickListener(Navigation.createNavigateOnClickListener(
            R.id.action_dashboardFragment_to_switchingHistoryFragment
       ))

        //Navigate to Outlet List fragment for Outstanding Product when clicked
        binding.outstandingOrderButton.setOnClickListener(Navigation.createNavigateOnClickListener(
            R.id.action_dashboardFragment_to_outletListFragment
        ))


        // Set action bar title to "Main Dashboard"
        (activity as AppCompatActivity).supportActionBar?.title = "Main Dashboard"

        // Declare that this fragment has menu
        setHasOptionsMenu(true)

        (activity as AppCompatActivity).supportActionBar?.show()
        (activity as AppCompatActivity).supportActionBar?.setDisplayHomeAsUpEnabled(false)


        //Return.... i don't know.
        return binding.root
    }

    override fun onCreateOptionsMenu(menu: Menu, inflater: MenuInflater) {
        super.onCreateOptionsMenu(menu, inflater)
        inflater?.inflate(R.menu.nav_overflow_menu, menu)
    }
}

这是我的导航图（我将LoginFragment设置为主页）

我想在DashboardFragment中而不是LoginFragment中显示导航抽屉。（使用LoginFragment仍然是图形的开始）。我已经隐藏了DashboardFragment的“向上”按钮

This是仪表板的当前外观。如您所见，后退按钮已经消失。

我有什么可以做的吗？如果有不清楚的地方，请通知我。

Answer 1

尝试一下，希望对您有帮助，它将actionBar上的LoginFragment隐藏在graph的startDestination上，否则显示

class MainActivity : AppCompatActivity() {

private lateinit var appBarConfiguration: AppBarConfiguration

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_main)
    val toolbar: Toolbar = findViewById(R.id.toolbar)
    setSupportActionBar(toolbar)

    val drawerLayout: DrawerLayout = findViewById(R.id.drawer_layout)
    val navView: NavigationView = findViewById(R.id.nav_view)
    val navController = findNavController(R.id.nav_host_fragment)



    // prevent nav gesture if not on start destination
    navController.addOnDestinationChangedListener { nc: NavController, nd: NavDestination, args: Bundle? ->
        if (nd.id == nc.graph.startDestination) {
         drawerLayout.setDrawerLockMode(DrawerLayout.LOCK_MODE_LOCKED_CLOSED)
         supportActionBar?.hide()
        } else {
         supportActionBar?.show()
         drawerLayout.setDrawerLockMode(DrawerLayout.LOCK_MODE_UNLOCKED)
        }
    }

     // here this ids are form fragment which should show navigation icon
    appBarConfiguration = AppBarConfiguration(setOf(
            R.id.nav_home,R.id.nav_gallery, R.id.nav_slideshow), drawerLayout)
    setupActionBarWithNavController(navController, appBarConfiguration)
    navView.setupWithNavController(navController)
}

override fun onCreateOptionsMenu(menu: Menu): Boolean {
    // Inflate the menu; this adds items to the action bar if it is present.
    menuInflater.inflate(R.menu.main, menu)
    return true
}

override fun onSupportNavigateUp(): Boolean {
    val navController = findNavController(R.id.nav_host_fragment)
    return navController.navigateUp(appBarConfiguration) || super.onSupportNavigateUp()
 }
}

Android kotlin在某些片段中显示“导航抽屉”图标而不是“后退按钮”

1 个答案: