android – 导航组件,控制何时显示汉堡包或后退图标

class MainActivity : AppCompatActivity() {

private lateinit var drawerLayout: androidx.drawerlayout.widget.DrawerLayout

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceStatE)
    setContentView(R.layout.main_activity)

    drawerLayout = drawer_layout

    val navController = Navigation.findNavController(this,R.id.fragment_main_navHost)

    setSupportActionBar(toolbar)

    NavigationUI.setupActionBarWithNavController(this,navController,drawerLayout)
    navView_main.setupWithNavController(navController)
}

override fun onSupportNavigateUp(): Boolean {
    return NavigationUI.navigateUp(drawerLayout,Navigation.findNavController(this,R.id.fragment_main_navHost))
}

override fun onBACkPressed() {
    if (drawerLayout.isDrawerOpen(GravityCompat.START)) {
        drawerLayout.closeDrawer(GravityCompat.START)
    } else {
        super.onBACkPressed()
    }
}

按照以下步骤操作

1.绑定你的NavigationView with NavigationUI

NavigationUI.setupWithNavController(nav_view,hostFragment.navController)

2.绑定ActionBar With NavController

NavigationUI.setupActionBarWithNavController(this@NavActivity,hostFragment.navController)

3.绑定ActionBar and DrawerLayout With NavController

NavigationUI.setupActionBarWithNavController(this@NavActivity,hostFragment.navController,drawer_layout)

4.覆盖您活动中的onSupportNavigateUp()

override fun onSupportNavigateUp(): Boolean {
    return NavigationUI.navigateUp(drawer_layout,hostFragment.navController) 
              || super.onSupportNavigateUp()
}

样品：

class NavActivity : AppCompatActivity(),NavigationView.onNavigationItemSELEctedListener {

    lateinit var hostFragment: NavHostFragment

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceStatE)
        setContentView(R.layout.activity_nav)
        setSupportActionBar(toolbar)

        fab.setOnClickListener { view ->
            Snackbar.make(view,"replace with your own action",Snackbar.LENGTH_LONG)
                    .setAction("Action",null).show()
        }

        val toggle = ActionBarDrawerToggle(
                this,drawer_layout,toolbar,R.String.navigation_drawer_open,R.String.navigation_drawer_closE)
        drawer_layout.addDrawerListener(togglE)
        toggle.syncState()

        nav_view.setNavigationItemSELEctedListener(this)

        hostFragment = supportFragmentManager.findFragmentById(R.id.my_nav_host_fragment) as NavHostFragment    
        NavigationUI.setupWithNavController(nav_view,hostFragment.navController)    
        NavigationUI.setupActionBarWithNavController(this@NavActivity,drawer_layout)    
    }

    override fun onBACkPressed() {
        if (drawer_layout.isDrawerOpen(GravityCompat.START)) {
            drawer_layout.closeDrawer(GravityCompat.START)
        } else {
            super.onBACkPressed()
        }
    }

    override fun onSupportNavigateUp(): Boolean {
        return NavigationUI.navigateUp(drawer_layout,hostFragment.navController) || super.onSupportNavigateUp()
    }

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

    override fun onOptionsItemSELEcted(item: MenuItem): Boolean {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button,so long
        // as you specify a parent activity in AndroidManifest.xml.
        when (item.itemId) {
            R.id.action_setTings -> return true
            else -> return super.onOptionsItemSELEcted(item)
        }
    }

    override fun onNavigationItemSELEcted(item: MenuItem): Boolean {
        // Handle navigation view item clicks here.
        drawer_layout.closeDrawer(GravityCompat.START)
        return true
    }
}

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