问题描述
我正在尝试应用我所看到的关于带有 Fragment 和 MVVM“新组件”的导航抽屉活动的课程，在这个简单的应用程序中，我尝试使用三个 Fragment 在它们之间导航
navController.addOnDestinationChangedListener
并显示吐司消息，但似乎代码不起作用，我不知道原因
这是我的代码
public class MainActivity extends AppCompatActivity {
private AppBarConfiguration mAppBarConfiguration;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
FloatingActionButton fab = findViewById(R.id.fab);
FragmentManager fragmentManager = getSupportFragmentManager();
FragmentTransaction fragmentTransaction =
fragmentManager.beginTransaction();
fab.setonClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Snackbar.make(view,"Replace with your own action",Snackbar.LENGTH_LONG)
.setAction("Action",null).show();
}
});
DrawerLayout drawer = findViewById(R.id.drawer_layout);
NavigationView navigationView = findViewById(R.id.nav_view);
// Passing each menu ID as a set of Ids because each
// menu should be considered as top level destinations.
mAppBarConfiguration = new AppBarConfiguration.Builder(
R.id.nav_home,R.id.nav_gallery,R.id.nav_slideshow)
.setDrawerLayout(drawer)
.build();
NavController navController = Navigation.findNavController(this,R.id.nav_host_fragment);
NavigationUI.setupActionBarWithNavController(this,navController,mAppBarConfiguration);
NavigationUI.setupWithNavController(navigationView,navController);
navController.addOnDestinationChangedListener(new NavController.OnDestinationChangedListener() {
@Override
public void onDestinationChanged(@NonNull NavController controller,@NonNull NavDestination destination,@Nullable Bundle arguments) {
int menuId = destination.getId();
switch (menuId){
case R.id.nav_gallery:
fab.hide();
Toast.makeText(getApplicationContext(),"gallery",Toast.LENGTH_LONG).show();
fragmentTransaction.replace(R.id.homeFragment,new galleryFragment());
fragmentTransaction.addToBackStack(null);
fragmentTransaction.commit();
NavGraph navGraph = new NavGraph()
// controller.getGraph().clear();
// controller.navigate(R.id.nav_gallery);
break;
case R.id.nav_slideshow:
fab.hide();
Toast.makeText(getApplicationContext(),"Slideshow",Toast.LENGTH_LONG).show();
break;
}
}
});
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main,menu);
return true;
}
@Override
public boolean onSupportNavigateUp() {
NavController navController = Navigation.findNavController(this,R.id.nav_host_fragment);
return NavigationUI.navigateUp(navController,mAppBarConfiguration)
|| super.onSupportNavigateUp();
}
}
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">
<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/activity_main_drawer" />
<include
layout="@layout/app_bar_main"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</androidx.drawerlayout.widget.DrawerLayout>
content.main.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 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"
app:layout_behavior="@string/appbar_scrolling_view_behavior"
tools:showIn="@layout/app_bar_main">
<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/mobile_navigation" />
</androidx.constraintlayout.widget.ConstraintLayout>
mobile_navigation.xml
<?xml version="1.0" encoding="utf-8"?>
<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/mobile_navigation"
app:startDestination="@+id/nav_home">
<fragment
android:id="@+id/nav_home"
android:name="com.test.dummyappv3.ui.home.HomeFragment"
android:label="@string/menu_home"
tools:layout="@layout/fragment_home" />
<fragment
android:id="@+id/nav_gallery"
android:name="com.test.dummyappv3.ui.gallery.galleryFragment"
android:label="@string/menu_gallery"
tools:layout="@layout/fragment_gallery" />
<fragment
android:id="@+id/nav_slideshow"
android:name="com.test.dummyappv3.ui.slideshow.SlideshowFragment"
android:label="@string/menu_slideshow"
tools:layout="@layout/fragment_slideshow" />
</navigation>
在寻找解决方案时，我发现了这个 answer，并尝试像这样使用控制器
controller.getGraph().clear();
controller.navigate(R.id.nav_gallery);
而不是使用片段事务，但它也不起作用
解决方法
问题在这里
<include
layout="@layout/app_bar_main"
android:layout_width="match_parent"
android:layout_height="match_parent" />
将这个包含从这里移到 NavigationView 的顶部
<?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" />
<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/activity_main_drawer" />
</androidx.drawerlayout.widget.DrawerLayout>
然后一切都会好的
,好的，你需要了解两件事。
-
NavigationController 与 FragmentManager 没有任何共同之处，只是它也可以交换 Fragment。
-
应用您的课程，您需要决定使用 FragmentManager 还是 NavigationController。
同时使用两者不仅会使您感到困惑，而且可能会使应用程序本身崩溃。