使用 navhost 时无法更改工具栏后退图标

Question

我正在尝试（但没有成功）在使用 NavHostFragment 时更改工具栏上的后退箭头图标。我将 NavController 与工具栏一起使用（如您在此处所见）

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_main)
    setSupportActionBar(toolbar)
    val navController = findNavController(R.id.nav_host_fragment)
    appBarConfiguration = AppBarConfiguration(navController.graph)
    setupActionBarWithNavController(navController, appBarConfiguration)
    navigation.setOnNavigationItemSelectedListener(mOnNavigationItemSelectedListener)
    toolbar.setTitleTextColor(resources.getColor(R.color.toolbarTextColor))
    navigation.setupWithNavController(Navigation.findNavController(this, R.id.nav_host_fragment))
}

导航工作正常，但我似乎无法更改后退图标。

我已经尝试过使用自定义主题。 None 个定义的属性到目前为止有效。

    <style name="ToolbarTheme" parent="@style/ThemeOverlay.AppCompat.ActionBar">
        <item name="android:navigationIcon">@drawable/ic_keyboard_arrow_left_black_24dp</item>
        <item name="android:homeAsUpIndicator">@drawable/ic_keyboard_arrow_left_black_24dp</item>
        <item name="collapseIcon">@drawable/ic_keyboard_arrow_left_black_24dp</item>
        <item name="android:closeIcon">@drawable/ic_keyboard_arrow_left_black_24dp</item>
    </style>

尝试使用代码：

toolbar.navigationIcon = resources.getDrawable(R.drawable.ic_keyboard_arrow_left_black_24dp)
toolbar.setNavigationIcon(R.drawable.ic_keyboard_arrow_left_black_24dp)
toolbar.navigationIconResource = R.drawable.ic_keyboard_arrow_left_black_24dp

使用代码时，布局创建后会出现后退按钮，但当我输入另一个片段时，图标会变回默认后退图标。

我该如何更改它？

Answer 1

将来应该添加此功能，目前您可以通过实现 'OnDestinationChangedListener' 并在回调中更改工具栏图标来实现（只需确保在设置后添加 'OnDestinationChangedListener'方法），像这样：

navController.addOnDestinationChangedListener { controller, destination, arguments ->
        toolbar.setNavigationIcon(R.drawable.ic_keyboard_arrow_left_black_24dp) //set it here for all the destinations, or inside the switch statement if you want to change it based on destination
        when(destination.id) {
            R.id.mainFragment -> {
              toolbar.setNavigationIcon(R.drawable.ic_keyboard_arrow_left_black_24dp)
            }
            R.id.detailsFragment -> {
              toolbar.setNavigationIcon(R.drawable.ic_keyboard_arrow_left_black_24dp)
            }
        }
    }

基于这个问题：

https://issuetracker.google.com/issues/121078028

使用 navhost 时无法更改工具栏后退图标

Can't change toolbar back icon while using navhost

android

kotlin

android-toolbar

android-architecture-navigation