导航组件:找不到 NavController [英] Navigation Component: Cannot find NavController
问题描述
我正在使用导航组件在我的应用程序中导航.它在片段内工作正常,但无法在包含实际导航主机的活动中找到导航主机.
I am using Navigation Component for navigating in my app. It works fine inside fragments but it fails to find the nav host in the activity that holds the actual navigation host.
当用户单击 FAB 时,我试图打开一个新片段,我将它包含在 Main 活动的 XML 中.当我调用 findNavController() 时,它找不到控制器.导航主机控制器位于 XML 布局中.我不明白为什么它找不到它.
I am trying to open a new fragment when the user clicks on FAB, which I included in Main activity's XML. When I call findNavController() it fails to find the controller. The nav host controller is in the XML layout. I can't understand why it fails to find it.
主活动
class MainActivity : AppCompatActivity(), OnActivityComponentRequest {
override fun getTabLayout(): TabLayout {
return this.tabLayout
}
override fun getFap(): FloatingActionButton {
return this.floatingActionButton
}
private lateinit var tabLayout: TabLayout
private lateinit var floatingActionButton: FloatingActionButton
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
setSupportActionBar(toolbar)
this.tabLayout = tabs
this.floatingActionButton = fab
fab.setOnClickListener {
it.findNavController().navigate(R.id.addNewWorkoutFragment)
}
}
}
活动主 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=".domain.MainActivity"
android:animateLayoutChanges="true">
<com.google.android.material.appbar.AppBarLayout
android:layout_height="wrap_content"
android:layout_width="match_parent"
android:theme="@style/AppTheme.AppBarOverlay">
<androidx.appcompat.widget.Toolbar
android:id="@+id/toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:background="?attr/colorPrimary"
app:layout_scrollFlags="scroll|enterAlways"
app:popupTheme="@style/AppTheme.PopupOverlay"/>
<com.google.android.material.tabs.TabLayout
android:id="@+id/tabs"
android:layout_width="match_parent"
android:layout_height="wrap_content">
<com.google.android.material.tabs.TabItem
android:text="Test 1"
android:layout_height="match_parent"
android:layout_width="match_parent"/>
<com.google.android.material.tabs.TabItem
android:text="Test 2"
android:layout_height="match_parent"
android:layout_width="match_parent"/>
</com.google.android.material.tabs.TabLayout>
</com.google.android.material.appbar.AppBarLayout>
<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:navGraph="@navigation/main_navigation" />
<com.google.android.material.bottomappbar.BottomAppBar
android:id="@+id/bar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_gravity="bottom"/>
<com.google.android.material.floatingactionbutton.FloatingActionButton
android:id="@+id/fab"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
app:layout_anchorGravity="right|top"
app:layout_anchor="@+id/bar"
android:src="@drawable/ic_add_black_24dp"/>
</androidx.coordinatorlayout.widget.CoordinatorLayout>
推荐答案
尝试在Activity的onStart
中设置Fab按钮的onClickListener,如onCreate
Activity只是在膨胀View 并没有设置 NavHostController
.因此,如果您在活动的 onStart 中设置 onClickListener
将按预期工作.
Try setting up onClickListener of Fab button in onStart
of the Activity as in onCreate
Activity is just inflating the View and haven't set the NavHostController
. So if you setup onClickListener
in onStart of activity is will work as expected.
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
setSupportActionBar(toolbar)
this.tabLayout = tabs
this.floatingActionButton = fab
}
override fun onStart() {
super.onStart()
floatingActionButton.setOnClickListener {
it.findNavController().navigate(R.id.addNewWorkoutFragment)
}
}
这篇关于导航组件:找不到 NavController的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!