I have a MainActivity which holds HomeFragment
HomeFragment has sort button Viewpager which holds 2 fragments
when sort button is clicked in HomeFragment, the value has to be passed to ViewPager Fragmensts
I google where I found communication between Fragments which is placed directly in MainActivity
I tried to solve this by myself with the help of stackoverflow
HomeFragment.kt
private var sort: Int = 0
private var sortListener: SortListener? = null
override fun onActivityCreated(savedInstanceState: Bundle?) {
super.onActivityCreated(savedInstanceState)
val childFragment = adapter?.instantiateItem(viewPager, fragmentPosition) as ChildFragment
setSortListener(childFragment)
}
fun userClickinSort(){
sortListener?.onSorted(HomeConstants.SORT_TYPE_NAME)
}
private fun setSortListener(sortListener: SortListener) {
this.sortListener = sortListener
}
Note: implemented this SortListener in ChildFragment
Related
Hi guys I am trying to preserve the data in an edittext by rotating the phone screen, I know I can do it with the ViewModel class, but no matter how hard I try I have not been able to.
//ViewModel
class UserViewModel: ViewModel() {
lateinit var text:MainFragment
fun data(){
text.textInputUserName.editText.toString()
}
}
//Fragment
class MainFragment : Fragment() {
private lateinit var mUserViewModel: UserViewModel
mUserViewModel = ViewModelProvider(this).get(UserViewModel::class.java)
mUserViewModel.data()
}
You should not pass any lifecycle related components, such as Fragments, into your viewmodel, as they can cause memory leaks.
To preserve the text in an EditText upon rotation, store the EditText's text as a string in the viewmodel. You should update and use it accordingly to make sure the most recent text is preserved even after an orientation change. Example:
ViewModel
class UserViewModel: ViewModel() {
var editTextContent:String = ""
}
Fragment
class MainFragment : Fragment() {
private val mUserViewModel: UserViewModel by viewModels()// could initialize via kotlin delegated property
override fun onCreate(savedInstanceState: Bundle?){
super.onCreate(savedInstanceState)
with(mUserViewModel.editTextContent){
if(isNotEmpty()){
editText.text = text
}
else{
text = editText.text
}
editText.doAfterTextChanged{editable-> if(editable!=null) text = editable.toString()}
}
I think this codelab might be helpful for you.
With Fragment:setRetainInstance(true); the fragment is not re-instantiated on a phones orientation change.
And of course i want my fragments to be kept alive while switching from one fragment to another.
But the Android Studio 4 provides a wizard-template with only
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);
From hours of debugging and searching the net if think it would need to inherent from the class FragmentNavigator so i can overwrite FragmentNavigator:naviagte where a new fragment gets created via final Fragment frag = instantiateFragment(.. and then is added with ft.replace(mContainerId, frag);
So i could find my old fragment and use ftNew.show and ftOld.hide instead.
Of course this is a stupid idea, because this navigate method is full of other internal stuff.
And i have no idea where that FrameNavigator is created.
I can retrieve it in the MainActivity:OnCreate with
NavigatorProvider navProvider = navController.getNavigatorProvider ();
Navigator<NavDestination> navigator = navProvider.getNavigator("fragment");
But at that time i could only replace it with my derived version. And there is no replaceNavigtor method but only a addNavigator method, which is called where ?
And anyways this all will be far to complicated and therefore error prone.
Why is there no simple option to keep my fragments alive :-(
In older Wizard-Templates there was the possibility of
#Override
public void onNavigationDrawerItemSelected(int position) {
Fragment fragment;
switch (position) {
case 1:
fragment = fragment1;
break;
case 2:
fragment = fragment2;
break;
case 3:
fragment = fragment3;
break;
}
FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
if(mCurrentFragment == null) {
ft.add(R.id.container, fragment).commit();
mCurrentFragment = fragment;
} else if(fragment.isAdded()) {
ft.hide(mCurrentFragment).show(fragment).commit();
} else {
ft.hide(mCurrentFragment).add(R.id.container, fragment).commit();
}
mCurrentFragment = fragment;
}
but i have no idea how to do this with the Android 4.0 template where my MainActivity is only derived as:
public class MainActivity extends AppCompatActivity {
private AppBarConfiguration mAppBarConfiguration;
Ideas welcome :'(
Hi there & sorry for my late answer! I had a similar problem with navigation drawers and navigation component. I tried around a little and found a working solution, which might be helpful for others too.
The key is the usage of a custom FragmentFactory in the FragmentManager of the MainActivity. See the code for this below:
public class StaticFragmentFactory extends FragmentFactory {
private myNavHostFragment1 tripNavHostFragment;
private myNavHostFragment2 settingsNavHostFragment;
#NonNull
#Override
public Fragment instantiate(#NonNull ClassLoader classLoader, #NonNull String className) {
if (MyNavHostFragment1.class.getName().equals(className)) {
if (this.myNavHostFragment1 == null) {
this.myNavHostFragment1 = new MyNavHostFragment1();
}
return this.myNavHostFragment1 ;
} else if (MyNavHostFragment2.class.getName().equals(className)) {
if (this.myNavHostFragment2 == null) {
this.myNavHostFragment2 = new MyNavHostFragment2();
}
return this.myNavHostFragment2;
}
return super.instantiate(classLoader, className);
}
}
The FragmentFactory survives the navigation between different fragments using the NavigationComponent of AndroidX. To keep the fragments alive, the FragmentFactory stores an instance of the fragments which should survive and returns this instance if this is not null. You can find a similar pattern when using a singleton pattern in classes.
You have to register the FragmentFactory in the corresponding activity by calling
this.getSupportFragmentManager().setFragmentFactory(new StaticFragmentFactory())
Please note also that I'm using nesten fragments here, so one toplevel fragment (called NavHostFragmen here) contains multiple child fragments. All fragments are using the same FragmentFactory of their parent fragments. The custom FragmentFactory above returns the result of the super class method, when the fragment to be instantiated is not known to keep alive.
I am trying to set up a toolbar in a fragment.
Whilst the Google Developer docs have been updated to include Kotlin code (see this page):
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_my)
// Note that the Toolbar defined in the layout has the id "my_toolbar"
setSupportActionBar(findViewById(R.id.my_toolbar))
it relates to the setup of a toolbar in an activity as opposed to a fragment.
I found this SO post which suggests that you can't just call setSupportActionBar in a fragment. To quote:
Fragments don't have such method setSupportActionBar(). ActionBar is a
property of Activity, so to set your toolbar as the actionBar, your
activity should extend from ActionBarActivity and then you can call in
your Fragment:
...
If you're using AppCompatActivity:
((AppCompatActivity)getActivity()).setSupportActionBar(mToolbar);
However the code given above is in java.
How do I call this in Kotlin?
To access the ActionBar from a Fragment in Kotlin:
if(activity is AppCompatActivity){
(activity as AppCompatActivity).setSupportActionBar(mToolbar)
}
To set an ActionBar title from a Fragment you can do
(activity as AppCompatActivity).supportActionBar?.title = "Title"
or
(activity as AppCompatActivity).supportActionBar?.setTitle(R.string.my_title_string)
There is an implementation in the Navigation codelab from Google that I think will do what I need: enable customisation of the title, menu items and hook into the up navigation for different fragment contexts. Specifically:
The toolbar is included in the main layout xml file (navigation_activity.xml in that codelab) outside of the fragment:
navigation_activity.xml
<LinearLayout>
<android.support.v7.widget.Toolbar/>
<fragment/>
<android.support.design.widget.BottomNavigationView/>
</LinearLayout>
Then setup the toolbar in the main activity file as follows:
MainActivity.kt
class MainActivity : AppCompatActivity() {
private var drawerLayout: DrawerLayout? = null
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.navigation_activity)
val toolbar = findViewById<Toolbar>(R.id.toolbar)
setSupportActionBar(toolbar)
//...
// Set up Action Bar
val navController = host.navController
setupActionBar(navController)
//...
}
private fun setupActionBar(navController: NavController) {
drawerLayout = findViewById(R.id.drawer_layout)
NavigationUI.setupActionBarWithNavController(this, navController, drawerLayout)
}
override fun onCreateOptionsMenu(menu: Menu): Boolean {
val retValue = super.onCreateOptionsMenu(menu)
val navigationView = findViewById<NavigationView>(R.id.nav_view)
// The NavigationView already has these same navigation items, so we only add
// navigation items to the menu here if there isn't a NavigationView
if (navigationView == null) {
menuInflater.inflate(R.menu.menu_overflow, menu)
return true
}
return retValue
}
override fun onOptionsItemSelected(item: MenuItem): Boolean {
// Have the NavHelper look for an action or destination matching the menu
// item id and navigate there if found.
// Otherwise, bubble up to the parent.
return NavigationUI.onNavDestinationSelected(item,
Navigation.findNavController(this, R.id.my_nav_host_fragment))
|| super.onOptionsItemSelected(item)
}
override fun onSupportNavigateUp(): Boolean {
return NavigationUI.navigateUp(drawerLayout,
Navigation.findNavController(this, R.id.my_nav_host_fragment))
}
}
Then in the fragment file you can inflate further menu items. In the codelab, main_menu.xml contains a shopping cart item which is added to the overflow setup in the main activity above.
MainFragment.kt
class MainFragment : Fragment() {
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?): View? {
setHasOptionsMenu(true)
return inflater.inflate(R.layout.main_fragment, container, false)
}
override fun onCreateOptionsMenu(menu: Menu?, inflater: MenuInflater?) {
inflater?.inflate(R.menu.main_menu, menu)
}
}
I'm implementing an MVP app in which the Views are fragments loaded in Activities. Each Activity had 1 fragment to display. I have to change my implementation and add the TabLayout which will now display the fragments. I've tried different ways of passing the fragment to the adapter but all makes my app crash and I can't understand the error. My last try, I'm passing an arraylist of fragments(1 for now) to the adapter. At the base, I'm following google samples MVP todo app, but I need to implement this tab layout. Please, this is for my major project, I looked everywhere and this is my last resort.
public class HomeActivity extends AppCompatActivity implements NavigationView.OnNavigationItemSelectedListener {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_home);
Toolbar mHomeToolbar = (Toolbar) findViewById(R.id.toolbar); // Set to the corresponding Toolbar in the UI.
setSupportActionBar(mHomeToolbar);
mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout); // Set to the corresponding Drawer Layout in the UI.
ActionBarDrawerToggle mToggle = new ActionBarDrawerToggle(this, mDrawerLayout, mHomeToolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
mDrawerLayout.addDrawerListener(mToggle); // Set mToggle as Drawer's toggle button and listen to actions.
mToggle.syncState();
NavigationView mDrawerNavigationView = (NavigationView) findViewById(R.id.nav_view); // Set the corresponding Navigation View in the UI.
mDrawerNavigationView.setNavigationItemSelectedListener(this); // Add listener on Navigation's items.
HomeFragment homeFragment = (HomeFragment) getSupportFragmentManager().findFragmentById(R.id.Quests_Frame); // Set to corresponding Fragment View in the UI.
if (homeFragment == null) {
homeFragment = HomeFragment.newInstance();
FragmentLoader.loadFragmentInActivity(getSupportFragmentManager(), homeFragment, R.id.Quests_Frame); // Display fragment in Activity.
}
repo = QuestsRepository.getInstance(QuestsDataSource.getINSTANCE());
mHomePresenter = new HomePresenter(repo , homeFragment);
TabLayout tabLayout = (TabLayout) findViewById(R.id.tab_layout);
ViewPager viewPager = (ViewPager) findViewById(R.id.pager);
TabPagerAdapter adapter = new TabPagerAdapter(getSupportFragmentManager());
adapter.addFragment(homeFragment);
viewPager.setAdapter(adapter);
}
The adapter class:
public class TabPagerAdapter extends FragmentPagerAdapter {
private final List<Fragment> mFragmentList = new ArrayList<>();
private final int tabCount = 3;
public TabPagerAdapter(FragmentManager fragmentManager) {
super(fragmentManager);
}
#Override
public Fragment getItem(int position) {
switch (position) {
case 0:
mFragmentList.get(position);
default:
return null;
}
}
public void addFragment(Fragment fragment) {
mFragmentList.add(fragment);
}
#Override
public int getCount() {
return tabCount;
}
}
For what you want to achieve, you won't be using the FragmentLoader Class. Remove it (just for the tabs Activities). And the getSupportFragmentManager line.
In Home Activity, how you set up the tabLayout and Viewpager, it's fine.
Remove addFragment line.
Add the following after setAdapter:
mTabLayout.setupWithViewPager(mViewPager);
In the tabPagerAdapter, just create the object presenter and fragment there.
In the getItem method, case 0, you can have:
HomeFragment homeFragment = HomeFragment.newInstance();
homePresenter = new HomePresenter(repo, homeFragment);
return homeFragment;
Oh and in the TabPagerAdapter, you can pass your repo argument there for creating your presenter.
I hope I was clear. Let me know if you have any issues.
I'm using the Android Studio provided class for a tabbed activity that uses Action Bar Tabs with ViewPager. Inside this activity, I'm trying to initialize a RecyclerView with data from a Firebase database.
Problem: On the app's first run, the RecyclerView is empty as shown below.
If I close and reopen the application from within the emulator, my RecyclerView gets populated as it should, as shown below.
Any ideas as to why this might be happening? I have a theory but I haven't been able to find a solution. After trying to read the FragmentPagerAdapter page, I got the impression that the fragments must be static (I don't know what the implications of this might be, so if anyone can shed some light on this it would be appreciated). On the app's first run, it initializes the RecyclerView. It then adds the data from the Firebase database but since the RecyclerView has already been initialized it is empty and is never properly updated. I tried calling the notify... methods to no avail.
StudentFragment's onCreateView method:
private View view;
private Context c;
private RecyclerView mRecyclerView;
private LinearLayoutManager manager;
private Firebase mFirebaseRef;
private FirebaseRecyclerAdapter<Student, ViewHolder> firebaseRecyclerAdapter;
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
view = inflater.inflate(R.layout.fragment_students, container, false);
mFirebaseRef = new Firebase("<your Firebase link here>");
c = getContext();
//Initializes Recycler View and Layout Manager.
mRecyclerView = (RecyclerView) view.findViewById(R.id.studentRecyclerView);
manager = new LinearLayoutManager(c);
mRecyclerView.setHasFixedSize(true);
firebaseRecyclerAdapter =
new FirebaseRecyclerAdapter<Student, ViewHolder>(
Student.class,
R.layout.single_student_recycler,
ViewHolder.class,
mFirebaseRef
) {
#Override
protected void populateViewHolder(ViewHolder viewHolder, Student student, int i) {
viewHolder.vFirst.setText(student.getFirst());
viewHolder.vLast.setText(student.getLast());
viewHolder.vDue.setText(Double.toString(student.getCurrentlyDue()));
viewHolder.vRadio.setButtonTintList(ColorStateList.valueOf(Color.parseColor(student.getColor())));
Log.d(TAG, "populateViewHolder called");
}
};
mRecyclerView.setAdapter(firebaseRecyclerAdapter);
mRecyclerView.setLayoutManager(manager);
return view;
}
ViewHolder:
public static class ViewHolder extends RecyclerView.ViewHolder {
public final TextView vFirst;
public final TextView vLast;
public final TextView vDue;
public final RadioButton vRadio;
public ViewHolder(View itemView) {
super(itemView);
vFirst = (TextView) itemView.findViewById(R.id.recycler_main_text);
vLast = (TextView) itemView.findViewById(R.id.recycler_sub_text);
vRadio = (RadioButton) itemView.findViewById(R.id.recycler_radio_button);
vDue = (TextView) itemView.findViewById(R.id.recycler_due_text);
}
Homescreen's onCreate method:
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_homescreen);
// Create the adapter that will return a fragment for each of the three
// primary sections of the activity.
mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());
// Set up the ViewPager with the sections adapter.
mViewPager = (ViewPager) findViewById(R.id.container);
mViewPager.setAdapter(mSectionsPagerAdapter);
TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs);
tabLayout.setupWithViewPager(mViewPager);
}
Firebase context is set on another application that starts as soon as the Homescreen activity starts. Any help will be appreciated.
Edit: I was digging through the FirebaseUI GitHub page, which is where the problem most likely lies, and found another user with the exact same problem. It seems that onBindViewHolder isn't called after notifyItemInserted in the FirebaseRecyclerAdapter class. Now to fix it...
In my case this was caused by mRecyclerView.setHasFixedSize(true); If you comment out this line of code the list loads properly. I got my solution from this discussion: https://github.com/firebase/FirebaseUI-Android/issues/204
Let me try, as you say on the question title,
RecyclerView not displaying on application start
so, the
Initializes Recycler View and Layout Manager.
should be declared on the onStart
#Override
public void onStart() {
super.onStart();
mFirebaseRef = new Firebase("<your Firebase link here>");
firebaseRecyclerAdapter = ...
//and so on
Hope it helps!
firebaseRecyclerAdapter.registerAdapterDataObserver(new RecyclerView.AdapterDataObserver() {
#Override
public void onItemRangeInserted(int positionStart, int itemCount) {
super.onItemRangeInserted(positionStart, itemCount);
int friendlyMessageCount = firebaseRecyclerAdapter.getItemCount();
int lastVisiblePosition =
linearLayoutManager.findLastCompletelyVisibleItemPosition();
// If the recycler view is initially being loaded or the
// user is at the bottom of the list, scroll to the bottom
// of the list to show the newly added message.
if (lastVisiblePosition == -1 ||
(positionStart >= (friendlyMessageCount - 1) &&
lastVisiblePosition == (positionStart - 1))) {
linearLayoutManager.scrollToPosition(positionStart);
}
}
});
recyclerListIdeas.setAdapter(firebaseRecyclerAdapter);
** Just add Recyclerview.AdapterDataObserver() . worked for me ! hope it helps :)**
i had the same issue, check the documentation:
https://codelabs.developers.google.com/codelabs/firebase-android/#6
fixed it by adding a data observer:
mFirebaseAdapter.registerAdapterDataObserver(new RecyclerView.AdapterDataObserver() {
#Override
public void onItemRangeInserted(int positionStart, int itemCount) {
super.onItemRangeInserted(positionStart, itemCount);
int friendlyMessageCount = mFirebaseAdapter.getItemCount();
int lastVisiblePosition =
mLinearLayoutManager.findLastCompletelyVisibleItemPosition();
// If the recycler view is initially being loaded or the
// user is at the bottom of the list, scroll to the bottom
// of the list to show the newly added message.
if (lastVisiblePosition == -1 ||
(positionStart >= (friendlyMessageCount - 1) &&
lastVisiblePosition == (positionStart - 1))) {
mMessageRecyclerView.scrollToPosition(positionStart);
}
}
});