后退箭頭未轉換為漢堡包圖標

Question

我將Kotlin與Android Studio 3.1.4配合使用。 我選擇了NavigationDrawer模板創建了一個新項目。 我加了兩個片段MainFragment和SecondFragment到Mainactivity 。 當activity開始時，將顯示MainFragment ，然后單擊NavigationDrawer Camera項來調用SecondFragment 。 當我按下后退按鈕時，它轉到MainFragment，但ActionBar仍顯示后退箭頭而不是漢堡包。 以前，我使用android.support.v4.widget.DrawerLayout開發了一個項目，並且一切正常。

以下是我的MainActiviy代碼：

import android.os.Bundle
import android.support.design.widget.NavigationView
import android.support.v4.view.GravityCompat
import android.support.v7.app.ActionBarDrawerToggle
import android.support.v7.app.AppCompatActivity
import android.view.Menu
import android.view.MenuItem
import kotlinx.android.synthetic.main.activity_main.*
import kotlinx.android.synthetic.main.app_bar_main.*


class MainActivity : AppCompatActivity(), NavigationView.OnNavigationItemSelectedListener {

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

        showMainFragment()

        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)
    }


    override fun onBackPressed() {
        if (drawer_layout.isDrawerOpen(GravityCompat.START)) {
            drawer_layout.closeDrawer(GravityCompat.START)
        } else if (supportFragmentManager.backStackEntryCount > 0) {
            supportFragmentManager.popBackStack()
        } else {
            super.onBackPressed()
        }
    }

    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 onOptionsItemSelected(item: MenuItem): Boolean {

    val itemId = item.itemId
        if (itemId == android.R.id.home) {
            onBackPressed()
        }

        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.
        when (item.itemId) {
            R.id.nav_camera -> {
                // Handle the camera action
                val fragment = SecondFragment()
                val fragmentTransaction = supportFragmentManager.beginTransaction()
                fragmentTransaction.replace(R.id.fragment_container, fragment, "OK")
                fragmentTransaction.addToBackStack(null)
                fragmentTransaction.commit()
            }
            R.id.nav_gallery -> {

            }
            R.id.nav_slideshow -> {

            }
            R.id.nav_manage -> {

            }
            R.id.nav_share -> {

            }
            R.id.nav_send -> {

            }
        }

        drawer_layout.closeDrawer(GravityCompat.START)
        return true
    }


    private fun showMainFragment(){
        val fragment = MainFragment()
        val fragmentTransaction = supportFragmentManager.beginTransaction()
        fragmentTransaction.replace(R.id.fragment_container, fragment)        
        fragmentTransaction.commit()
    }
}

MainFragment代碼：

import android.os.Bundle
import android.support.v4.app.Fragment
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.support.v7.app.AppCompatActivity
import kotlinx.android.synthetic.main.app_bar_main.*


// TODO: Rename parameter arguments, choose names that match
// the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
private const val ARG_PARAM1 = "param1"
private const val ARG_PARAM2 = "param2"

/**
 * A simple [Fragment] subclass.
 *
 */
class MainFragment : Fragment() {

    override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
        // Inflate the layout for this fragment
        var view : View = inflater.inflate(R.layout.fragment_main, container, false)


        return view
    }

SecondFragment代碼：

import android.os.Bundle
import android.support.v4.app.Fragment
import android.support.v7.app.AppCompatActivity
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup

// TODO: Rename parameter arguments, choose names that match
// the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
private const val ARG_PARAM1 = "param1"
private const val ARG_PARAM2 = "param2"

class SecondFragment : Fragment() {

    override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
        // Inflate the layout for this fragment
        val view : View = inflater!!.inflate(R.layout.fragment_surah, container, false)

        (activity as AppCompatActivity).supportActionBar!!.setDisplayHomeAsUpEnabled(true)
        val toolbar = activity!!.findViewById<android.support.v7.widget.Toolbar>(R.id.toolbar)
        (activity as AppCompatActivity).setSupportActionBar(toolbar)
        toolbar.setNavigationIcon(R.drawable.abc_ic_ab_back_material)

        return view
    }

}

Answer 1

在SecondFragment的onDestroy上設置此行

(activity as AppCompatActivity).supportActionBar!!.setDisplayHomeAsUpEnabled(false)

Answer 2

您永遠不會將NavigationIcon退回到漢堡包。

也許嘗試：

toolbar.setNavigationIcon(R.drawable.hamburger)

在您的MainFragment中？

Answer 3

因此，漢堡沒有顯示-

val工具欄=活動!!。findViewById（R.id.toolbar）（活動為AppCompatActivity）.setSupportActionBar（工具欄）toolbar.setNavigationIcon（R.drawable.abc_ic_ab_back_material）

要同時處理后退按鈕和漢堡包，請在活動中添加以下代碼。

supportFragmentManager.addOnBackStackChangedListener(android.support.v4.app.FragmentManager.OnBackStackChangedListener {

        if (supportFragmentManager.getBackStackEntryCount() > 0) {
                supportActionBar?.setDisplayHomeAsUpEnabled(true); // show back button
                toolbar?.setNavigationOnClickListener(View.OnClickListener { onBackPressed() })
            } else {
                //show hamburger
                supportActionBar?.setDisplayHomeAsUpEnabled(false);
                toogle.syncState();
                toolbar?.setNavigationOnClickListener(View.OnClickListener {
                    drawer.openDrawer(GravityCompat.START);
                })
                setTitle(resources.getString(R.string.app_name))
            }
    })

並從第二個片段中刪除以下代碼-

(activity as AppCompatActivity).supportActionBar!!.setDisplayHomeAsUpEnabled(true)
    val toolbar = activity!!.findViewById<android.support.v7.widget.Toolbar>(R.id.toolbar)
    (activity as AppCompatActivity).setSupportActionBar(toolbar)
    toolbar.setNavigationIcon(R.drawable.abc_ic_ab_back_material)