Android-抽屉布局只显示后箭头

Question

我正试图在我的Android(Kotlin)应用程序中构建一个汉堡包菜单。我以为我遵循了所有的步骤，但只显示了后箭头，这没有任何作用。但是，我可以从左边滑动菜单。

然后我启动了一个新的应用程序，并尝试从头开始，得到了同样的结果。再次显示状态栏，只显示后退箭头。

我似乎找不到自己做错了什么。

这是我的代码

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<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"
android:fitsSystemWindows="true"
tools:openDrawer="start">
<include
layout="@layout/app_bar_main"
android:layout_width="match_parent"
android:layout_height="match_parent" />
<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="match_parent"
android:layout_height="match_parent"
app:defaultNavHost="true"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:navGraph="@navigation/nav_graph" />
</androidx.constraintlayout.widget.ConstraintLayout>
<com.google.android.material.navigation.NavigationView
android:id="@+id/nav_view"
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:layout_gravity="start"
android:fitsSystemWindows="true"
app:headerLayout="@layout/nav_header_main"
app:menu="@menu/drawer_menu" />
</androidx.drawerlayout.widget.DrawerLayout>

mainActivity.kt

package com.wensline.myapplication
import android.os.Bundle
import androidx.appcompat.app.AppCompatActivity
import androidx.appcompat.widget.Toolbar
import androidx.drawerlayout.widget.DrawerLayout
import androidx.navigation.findNavController
import androidx.navigation.fragment.NavHostFragment.findNavController
import androidx.navigation.ui.AppBarConfiguration
import androidx.navigation.ui.navigateUp
import androidx.navigation.ui.setupActionBarWithNavController
import androidx.navigation.ui.setupWithNavController
import com.google.android.material.navigation.NavigationView
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)
// Passing each menu ID as a set of Ids because each
// menu should be considered as top level destinations.
appBarConfiguration = AppBarConfiguration(setOf(
R.id.nav_home, R.id.nav_gallery, R.id.nav_slideshow), drawerLayout)
setupActionBarWithNavController(navController, appBarConfiguration)
navView.setupWithNavController(navController)
}

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

app_bar_main.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.coordinatorlayout.widget.CoordinatorLayout 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:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<com.google.android.material.appbar.AppBarLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:theme="@style/Theme.AppCompat.Light.DarkActionBar">
<androidx.appcompat.widget.Toolbar
android:id="@+id/toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:background="?attr/colorPrimary"
app:popupTheme="@style/AppTheme" />
</com.google.android.material.appbar.AppBarLayout>
</androidx.coordinatorlayout.widget.CoordinatorLayout>

Answer 1

更改这行代码

setupActionBarWithNavController(navController, appBarConfiguration)

到此

toolbar.setupWithNavController(navController, appBarConfiguration)

Answer 2

您需要设置ActionBarDrawerToggle来实现这一点-

private lateinit var drawerToggle: ActionBarDrawerToggle 

在onCreate方法中，您需要初始化drawerToggle，如下所示-

drawerToggle = ActionBarDrawerToggle(this, drawer, toolbar, 
R.string.navigation_drawer_open, R.string.navigation_drawer_close)
drawer.addDrawerListener(toggle)
toggle.setDrawerIndicatorEnabled(true)
toggle.syncState()

Answer 3

感谢您的建议。@KakyireLastBorn的回答给了我一个想法。我换了

setupActionBarWithNavController(navController, appBarConfiguration)

至

toolbar.setupWithNavController(navController, drawerLayout)

这解决了问题！