如何解决BottomNavigationView NavHostFragment我不想每次选择选项卡时都从数据服务器读取片段
当从“帖子”选项卡单击“个人资料”选项卡单击服务器时,我不想从服务器调用该信息,而我又返回到“帖子”选项卡,并且我不想再次进行刷新。
>如果我再次处于“发帖”标签中,则我不想刷新该信息。 我不希望在“帖子”选项卡中,选择“个人资料”选项卡并返回“帖子”选项卡时刷新页面 当我从服务器收到新信息时,我想秘密更新帖子列表 像WhatsApp一样,每个片段中的信息都是实时的
此代码与名为Fragment_Posts的Fragment Post选项卡有关,该选项卡从服务器接收帖子并在recyclerview中显示它们
public class Fragment_Posts extends Fragment {
public FragmentPostsBinding binding;
public viewmodel_Posts vm_psots;
Adapter_posts adapter_posts;
@Override
public void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
@Nullable
@Override
public View onCreateView(@NonNull LayoutInflater inflater,@Nullable ViewGroup container,@Nullable Bundle savedInstanceState) {
Log.e(TAG,"onCreateView: posts");
binding = DataBindingUtil.inflate(inflater,R.layout.fragment_posts,container,false);
vm_psots = new viewmodelProvider(this).get(viewmodel_Posts.class);
vm_psots.Post();
vm_psots.listmutablelivedata_posts.observe(requireActivity(),new Observer<List<Model_Post>>() {
@Override
public void onChanged(List<Model_Post> model_posts) {
binding.recycleviewFrgposts.setLayoutManager(new linearlayoutmanager(requireActivity()));
adapter_posts = new Adapter_posts(model_posts);
binding.recycleviewFrgposts.setAdapter(adapter_posts);
}
});
return binding.getRoot();
}
}
public class MainActivity extends AppCompatActivity implements BottomNavigationView.OnNavigationItemSelectedListener {
private static final String TAG = "MainActivity";
ActivityMainBinding binding;
NavHostFragment navHostFragment;
NavController navController;
AppBarConfiguration appBarConfiguration;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//getSupportActionBar().hide();
binding = DataBindingUtil.setContentView(this,R.layout.activity_main);
appBarConfiguration = new AppBarConfiguration.Builder(R.navigation.navigation).build();
navHostFragment = (NavHostFragment) getSupportFragmentManager().findFragmentById(R.id.fragment_main);
//If the inequality is null,run the line
assert navHostFragment != null;
navController = navHostFragment.getNavController();
binding.botnavMain.setonNavigationItemSelectedListener(this);
}
//That we can work with our fragment stack
@Override
public boolean onSupportNavigateUp() {
return NavigationUI.navigateUp(navController,appBarConfiguration);
}
@Override
public boolean onNavigationItemSelected(@NonNull MenuItem menuItem) {
switch (menuItem.getItemId()) {
case R.id.menu_home:
navController.navigate(R.id.fragment_Posts);
break;
case R.id.menu_cart:
navController.navigate(R.id.fragment_Cart);
break;
case R.id.menu_profile:
navController.navigate(R.id.fragment_Profile);
break;
}
return false;
}
}
<?xml version="1.0" encoding="utf-8"?>
<layout 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">
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<!--If the user presses the back button,do not leave the app
app:defaultNavHost="true"-->
<fragment
android:id="@+id/fragment_main"
android:name="androidx.navigation.fragment.NavHostFragment"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:defaultNavHost="true"
android:layout_above="@+id/botnav_main"
app:navGraph="@navigation/navigation" />
<com.google.android.material.bottomnavigation.BottomNavigationView
android:id="@+id/botnav_main"
android:layout_alignParentBottom="true"
android:layout_width="match_parent"
android:layout_height="60dp"
app:menu="@menu/menu"
app:itemTextColor="?colorAccent"
app:itemIconTint="?colorAccent"
/>
</RelativeLayout>
</layout>
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