我使用的活动布局是afragment
和aBottomNavigationView
:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<fragment
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1"
android:id="@+id/fragment"
android:name="androidx.navigation.fragment.NavHostFragment"
app:navGraph="@navigation/navigation_bottom"
app:defaultNavHost="true"/>
<com.google.android.material.bottomnavigation.BottomNavigationView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="@+id/bottom_navigation_view"
app:menu="@menu/bottom_navigation_menu"/>
</LinearLayout>
并在我的导航布局中定义了三个片段:
<navigation
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/navigation_bottom"
app:startDestination="@id/firstFragment">
<fragment
android:id="@+id/firstFragment"
android:name="fragments.FirstFragment"
android:label="fragment_first"
tools:layout="@layout/fragment_first" />
//The other two fragments
</navigation>
在我的活动中,我使用以下代码:
navController = Navigation.findNavController(this, R.id.fragment);
BottomNavigationView bnw = findViewById(R.id.bottom_navigation_view);
NavigationUI.setupWithNavController(bnw, navController);
NavigationUI.setupActionBarWithNavController(this, navController);
我的方法是:
@Override
public boolean onSupportNavigateUp() {
return Navigation.findNavController(this, R.id.fragment).navigateUp();
}
但当我按下第二个图标(片段)时,什么也没有发生。如何解决这个问题?谢谢!
最佳答案
解决方案1:
在菜单(底部导航菜单)项中,设置与导航图生成的片段ID相同的ID,如下所示:
<menu xmlns:android="http://schemas.android.com. /apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto">
<item
android:id="@+id/firstFragment"
android:title="First fragment" />
<item
android:id="@+id/secondFragment"
android:title="Second fragmnet" />
<item
android:id="@+id/thirdFragment"
android:title="Third fragment" />
</menu>
你不需要按专业语法设置,因为
NavigationUI.setupWithNavController(bnw, navController);
方法将完成此工作。
解决方案2:不建议和不必要
但如果你想在语法上更专业一些,请按以下步骤做:
private lateinit var navController: NavController
private val onNavigationItemSelectedListener = BottomNavigationView.OnNavigationItemSelectedListener { item ->
when (item.itemId) {
R.id.navigation_home -> {
navController.navigate(R.id.firstFragment)
return@OnNavigationItemSelectedListener true
}
R.id.navigation_dashboard -> {
navController.navigate(R.id.secondFragment)
return@OnNavigationItemSelectedListener true
}
R.id.navigation_notifications -> {
Toast.makeText(this,R.string.title_notifications,Toast.LENGTH_SHORT).show()
navController.navigate(R.id.thirdFragment)
return@OnNavigationItemSelectedListener true
}
}
false
}
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
navController = findNavController(R.id.nav_controller_fragment)
navView.setOnNavigationItemSelectedListener(onNavigationItemSelectedListener)
}