The application has a BottomNavigationView on the MainActivity which deals with the navigation between Fragments. One of the Fragments has a RecyclerView in it and the items of the RecyclerView have a button.
I am trying to make the RecyclerView Items' button navigate to another Fragment and pass a value along with it but I keep receiving a null object reference with passing the data.
I created an interface to get the click to the MainActivity for the Fragment switch and created a Bundle to communicate the received value to the required Fragment
// The interface
public interface OnItemClickListener {
void onItemClick();
The Adapter class
//Define interface
OnItemClickListener listener;
//Create constructor for interface
public LocationsAdapter(Activity activity) {
listener = (MainActivity)activity;
...
#Override
public void onBindViewHolder(#NonNull LocationsViewHolder holder, int position) {
//A click listener for the button
holder.showMarkerButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
//Create instance of MapFragment to pass data as Bundle
MapFragment mapFragment = new MapFragment();
LatLng latLng = new LatLng(markerObject.getLatitude(),markerObject.getLongitude());
//Create Bundle and add data
Bundle bundle = new Bundle();
bundle.putString("latitude",markerObject.getLatitude().toString());
bundle.putString("longitude",markerObject.getLongitude().toString());
listener.onItemClick(bundle);
}
});
}
Then in the MainActivity I implemented the interface to switch the View of the BottomNavigation.
public class MainActivity extends AppCompatActivity implements OnItemClickListener {
BottomNavigationView navView;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
navView = findViewById(R.id.nav_view);
// Passing each menu ID as a set of Ids because each
// menu should be considered as top level destinations.
AppBarConfiguration appBarConfiguration = new AppBarConfiguration.Builder(
R.id.navigation_home,R.id.navigation_map, R.id.navigation_locations, R.id.navigation_profile)
.build();
NavController navController = Navigation.findNavController(this, R.id.nav_host_fragment);
NavigationUI.setupActionBarWithNavController(this, navController, appBarConfiguration);
NavigationUI.setupWithNavController(navView, navController);
}
#Override
public void onItemClick() {
navView.setSelectedItemId(R.id.navigation_map);
}
}
As a final step I called on the Bundle I made in the first step but that's where the null object reference comes up.
//MapFragment
private void setCam(){
Bundle bundle = getArguments();
if (getArguments() != null ){
String SLatitude = bundle.getString("latitude");
String SLongitude = bundle.getString("longitude");
Double latitude = Double.parseDouble(SLatitude);
Double longitude = Double.parseDouble(SLongitude);
LatLng latLng = new LatLng(latitude,longitude);
mMap.moveCamera(CameraUpdateFactory.newLatLngZoom(latLng, 20));
Toast.makeText(getActivity(), latLng.toString(), Toast.LENGTH_SHORT).show();
}
else{
Toast.makeText(getActivity(), "error present", Toast.LENGTH_SHORT).show();
}
}
Thanks in advance.
MapFragment mapFragment = new MapFragment();
LatLng latLng = new LatLng(markerObject.getLatitude(),markerObject.getLongitude());
//Create Bundle and add data
Bundle bundle = new Bundle();
bundle.putString("position",latLng.toString());
mapFragment.setArguments(bundle);
Here the mapFragment is just a created object that is not used in the navigation graph. i.e. it's a standalone object that is independent of the navigation, so it is not involved in the navigation as it's not the same as the current mapFragment fragment in the navGraph.
Solution:
In order to solve this, you need to pass the argument whenever you switch among fragments of the BottomNavigationView, and registering OnNavigationItemSelectedListener is a good place for that:
First allow the adapter to send the arguments back to the activity through the listener callback
So, modify the listener callback to accept a parameter
interface OnItemClickListener listener {
void onItemClick(Bundle args);
}
Apply that on adapter
#Override
public void onBindViewHolder(#NonNull LocationsViewHolder holder, int position) {
//A click listener for the button
holder.showMarkerButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
LatLng latLng = new LatLng(markerObject.getLatitude(),markerObject.getLongitude());
//Create Bundle and add data
Bundle bundle = new Bundle();
bundle.putString("position",latLng.toString());
//Interface to transport the click event to the MainActivity to switch Fragment in the BottomNavigationView
listener.onItemClick(bundle);
}
});
}
And finally, register OnNavigationItemSelectedListener to the navView and modify the callback to accept the Bundle in activity:
public class MainActivity extends AppCompatActivity implements OnItemClickListener {
BottomNavigationView navView;
private Bundle mapArgs;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
navView = findViewById(R.id.nav_view);
// Passing each menu ID as a set of Ids because each
// menu should be considered as top level destinations.
AppBarConfiguration appBarConfiguration = new AppBarConfiguration.Builder(
R.id.navigation_home,R.id.navigation_map, R.id.navigation_locations, R.id.navigation_profile)
.build();
NavController navController = Navigation.findNavController(this, R.id.nav_host_fragment);
NavigationUI.setupActionBarWithNavController(this, navController, appBarConfiguration);
NavigationUI.setupWithNavController(navView, navController);
navView.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener() {
#Override
public boolean onNavigationItemSelected(#NonNull MenuItem item) {
navController.navigate(item.getItemId(), mapArgs);
return true;
}
});
}
#Override
public void onItemClick(Bundle args) {
navView.setSelectedItemId(R.id.navigation_map);
mapArgs = args;
}
}
When using the navigation controller, you pass in data with parameters. Go to your navigation component XML file and make the following changes;
1.Inside the navigation action, you need to add an argument.
<action
android:id="#+id/action_id"
app:destination="#id/destinationFragment">
<argument
android:name="paramterName"
app:argType="string" />
</action>
2.Add the same argument to the destination fragment
<fragment
android:id="#+id/coursesNavFragment"
android:name="com.example.example.DestinationFragment"
android:label="destination_fragment"
tools:layout="#layout/destination_fragment" >
<argument
android:name="parameterName"
app:argType="string" />
</fragment>
You can easily do this using the design view as well.
Now the function you call to navigate to the destination fragment expects you to pass it a parameter.
navigationController.navigate(actionSourceFragmentToDestinationFragment("text123"))
Then you can extract the bundle in the destination fragment.
val parameter = DestinationFragmentArgs.fromBundle(requireArguments()).parameterName
// parameter has the value of "text123"
Since the navigation component uses safeargs, you can pass any type of parameter that inherits from Parcellable.
Related
I am working on an application where I am using bottom navigation on Home where i have three fragments on the second fragment called Post Ad I have a button called enter fragment zone through that i enter into another fragment now when I enter inside another fragment now I don't want there to show the bottom navigation so to hide it I am using a method inside my main activity called "setBottomNavigationVisibility" where I am writing code to set the visibility of bottom nav. but the problem is that it is throwing the null pointer exception in the mainactivty's method saying that
"void com.google.android.material.bottomnavigation.BottomNavigationView.setVisibility(int)' on a null object reference" on the method's line where i am setting the visibility
code of MainActivity
public class MainActivity extends AppCompatActivity {
NavController navController;
BottomNavigationView bottomNavigationView;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
navController = Navigation.findNavController(this, R.id.fragmentContainerView);
bottomNavigationView = findViewById(R.id.activity_main_bottom_navigation_view);
NavigationUI.setupWithNavController(bottomNavigationView, navController);
}
public void setBottomNavigationVisibility(int visibility) {
bottomNavigationView.setVisibility(visibility);
}}
On the above method when i am trying to setting the visibility on the line bottomNavigationView.setVisibility(visibility); that's where it is thrwoing the exception
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
binding = FragmentSecondBinding.inflate(inflater, container, false);
// Inflate the layout for this fragment
View view = binding.getRoot();
viewModel = new ViewModelProvider(requireActivity()).get(PageViewModel.class);
((MainActivity) requireActivity()).setBottomNavigationVisibility(View.GONE);
binding.toolbar.setNavigationOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
Navigation.findNavController(view).navigate(R.id.action_secondFragment2_to_postad);
}
});
No Please guide me how can i solve this error.
do something like this, define interface
interface DashboardActivityDelegate {
void hideBottomBar();
void showBottomBar();
}
your activity must implement this interface
and in your fragment in which you want to hide bottom nav view do this:
declare global variable
private DashboardActivityDelegate dashboardActivityDelegate;
#Override
public void onAttach(Context context) {
super.onAttach(context);
if (context instanceof DashboardActivityDelegate) {
dashboardActivityDelegate = (DashboardActivityDelegate)context;
}
}
#Override
public void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (dashboardActivityDelegate != null) {
dashboardActivityDelegate.hideBottomBar();
}
}
#Override
public void onDestroy() {
super.onDestroy();
if (dashboardActivityDelegate != null) {
dashboardActivityDelegate.showBottomBar();
}
}
in fragment you want hide bottom bar, just call this line in onViewCreated
getActivity().findViewById(R.id.activity_main_bottom_navigation_view).setVisibility(View.GONE);
and when you leave fragment, call this line in onDestroy or onStop to visible bottom nav for another fragment:
getActivity().findViewById(R.id.activity_main_bottom_navigation_view).setVisibility(View.VISIBLE)
I have an Android app (Java) which uses the Navigation Component to set up a Bottom Navigation. The app consists of a single Activity (Main), everything else is loaded in fragments.
The idea is for the Splash Screen to launch and check if the user is logged in or not. If the user is logged in, then the home screen loads and the bottom navigation (previously hidden) becomes visible.
The bottom navigation consists of 3 tabs.
However, when the user signs in, it can be one of two types of users. If he's a subscriber he will get access to all sections of the app. However if the user is a visitor, he will get access to only two sections. In this case I want to have a different bottom navigation menu to be visible with only 2 tabs.
How can I replace the bottom navigation depending on the user type if the main bottom navigation has already been assigned in the main activity?
This is the code in the MainActivity:
Toolbar toolbar = findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
FragmentManager supportFragmentManager = getSupportFragmentManager();
NavHostFragment navHostFragment = (NavHostFragment) supportFragmentManager.findFragmentById(R.id.nav_host_fragment);
NavController navController = navHostFragment.getNavController();
AppBarConfiguration appBarConfiguration = new AppBarConfiguration.Builder(R.id.homeFragment, R.id.libraryFragment, R.id.searchFragment, R.id.myStuffFragment).build();
NavigationUI.setupWithNavController(toolbar, navController, appBarConfiguration);
BottomNavigationView bottomNav = findViewById(R.id.bottom_nav);
NavigationUI.setupWithNavController(bottomNav, navController);
navController.addOnDestinationChangedListener(new NavController.OnDestinationChangedListener() {
#Override
public void onDestinationChanged(#NonNull NavController controller, #NonNull NavDestination destination, #Nullable Bundle arguments) {
if (destination.getId() == R.id.splashScreenFragment || destination.getId() == R.id.welcomeFragment || destination.getId() == R.id.signInFragment) {
toolbar.setVisibility(View.GONE);
bottomNav.setVisibility(View.GONE);
} else if (destination.getId() == R.id.audioPlayerFragment) {
bottomNav.setVisibility(View.GONE);
} else {
toolbar.setVisibility(View.VISIBLE);
bottomNav.setVisibility(View.VISIBLE);
}
}
});
This is the code in the SplashScreenFragment (this is the startDestination in the nav_graph):
public class SplashScreenFragment extends Fragment {
private static final String TAG = "SplashScreenFragment";
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.fragment_splash_screen, container, false);
return v;
}
#Override
public void onViewCreated(#NonNull View view, #Nullable Bundle savedInstanceState) {
SharedPreferences getSharedData = this.getActivity().getSharedPreferences("AppTitle", Context.MODE_PRIVATE);
Boolean loggedIn = getSharedData.getBoolean("isUserLoggedIn", false);
new Handler().postDelayed(new Runnable() {
#Override
public void run() {
if (!loggedIn) {
Navigation.findNavController(view).navigate(R.id.action_splashScreenFragment_to_welcomeFragment);
} else {
Navigation.findNavController(view).navigate(R.id.action_splashScreenFragment_to_homeFragment);
}
}
}, 2000);
}
You can have the full menu items by default in the BottomNavigationView, so when a subscribed user logged in, then no change in the menu is required.
And if the user is not subscribed, then you can remove the needed items from the menu programmatically using removeItem()
So, in MainActivity add a condition :
if (notSubscribedUser) {
if (bottomNav.getMenu().findItem(R.id.my_item_id) != null)
bottomNavigationView.getMenu().removeItem(R.id.my_item_id);
}
And do the same for all menu item ids that you want to remove
MainActivity class:
/* all necessary imports */
public class MainActivity extends AppCompatActivity
implements NavigationView.OnNavigationItemSelectedListener {
/* Other variable initialized here... */
FragOne fo;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
fo.setTextViewText("This is added from Activity");
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
drawer.addDrawerListener(toggle);
toggle.syncState();
NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
navigationView.setNavigationItemSelectedListener(this);
viewPager = (ViewPager) findViewById(R.id.viewpager);
setupViewPager(viewPager);
tabLayout = (TabLayout) findViewById(R.id.tabs);
tabLayout.setupWithViewPager(viewPager);
}
private void setupViewPager(ViewPager viewPager) {
ViewPagerAdapter adapter = new ViewPagerAdapter(getSupportFragmentManager());
adapter.addFragment(new FragOne(), "My Tracker");
adapter.addFragment(new FragTwo(), "Team Tracker");
viewPager.setAdapter(adapter);
}
class ViewPagerAdapter extends FragmentPagerAdapter {
private final List<Fragment> mFragmentList = new ArrayList<>();
private final List<String> mFragmentTitleList = new ArrayList<>();
public ViewPagerAdapter(FragmentManager manager) {
super(manager);
}
#Override
public Fragment getItem(int position) {
return mFragmentList.get(position);
}
#Override
public int getCount() {
return mFragmentList.size();
}
public void addFragment(Fragment fragment, String title) {
mFragmentList.add(fragment);
mFragmentTitleList.add(title);
}
#Override
public CharSequence getPageTitle(int position) {
return mFragmentTitleList.get(position);
}
}
#Override
public void onBackPressed() {
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
if (drawer.isDrawerOpen(GravityCompat.START)) {
drawer.closeDrawer(GravityCompat.START);
} else {
super.onBackPressed();
}
}
#SuppressWarnings("StatementWithEmptyBody")
#Override
public boolean onNavigationItemSelected(MenuItem item) {
// Handle navigation view item clicks here.
int id = item.getItemId();
if (id == R.id.nav_manage) {
} else if (id == R.id.nav_share) {
} else if (id == R.id.nav_send) {
}
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
drawer.closeDrawer(GravityCompat.START);
return true;
}
}
Fragment class:
/* all necessary imports */
public class FragOne extends Fragment {
TextView tvCName;
public FragOne() {
// Required empty public constructor
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View view = inflater.inflate(R.layout.fragment_frag_one, container, false);
return view;
//return inflater.inflate(R.layout.fragment_frag_one, container, false);
}
#Override
public void onViewCreated(View view , Bundle savedInstanceState) {
tvCName = (TextView) view.findViewById(R.id.tvctq);
}
public void setTextViewText(String value){
tvCName.setText(value);
}
}
Fragment XML Layout:
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.mytip.FragOne">
<TextView
android:text="TextView"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="#+id/tvctq" />
</FrameLayout>
I am trying to access the TextView inside the Fragment from MainActivity like this:
FragOne fo;
fo.setTextViewText("This is added from Activity");
I keep getting a NullPointerExceptionError. I looked at all the articles to see how to access, however none of them helped me.
Can someone please let me know what am I doing wrong and how to fix it?
I also plan on adding other Views inside my Fragment that I would need to access in the future.
Because fo hasn't been initialized in the following code snippet:
FragOne fo;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
fo.setTextViewText("This is added from Activity");
...
}
fo.setTextViewText() reasonably throws NPE.
You have to pay attention to the Activity lifecycle - you seem to be setting everything up correctly, but making a few mistakes accessing the correct instance of the fragment at the time it's actually ready. Things you should do
Get proper instance of the fragment from your ViewPager, like #ginomempin suggested;
Only try to set your text no earlier then your activities onStart method has been called - I usually do it onResume method (you can override it if you haven't already). Doing it in onResume method in the activity makes sure your Fragment has already gone through it's lifecycle up till onResume as well, and data will refresh if it has been brought to the background previously.
Here's a lifecycle diagram for your reference:
You need to use your Fragment factory method when creating your Fragment in your activity. Please see below:
**
Back Stack
**
The transaction in which fragments are modified can be placed on an internal back-stack of the owning activity. When the user presses back in the activity, any transactions on the back stack are popped off before the activity itself is finished.
For example, consider this simple fragment that is instantiated with an integer argument and displays that in a TextView in its UI:
public static class CountingFragment extends Fragment {
int mNum;
/**
* Create a new instance of CountingFragment, providing "num"
* as an argument.
*/
static CountingFragment newInstance(int num) {
CountingFragment f = new CountingFragment();
// Supply num input as an argument.
Bundle args = new Bundle();
args.putInt("num", num);
f.setArguments(args);
return f;
}
/**
* When creating, retrieve this instance's number from its arguments.
*/
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mNum = getArguments() != null ? getArguments().getInt("num") : 1;
}
/**
* The Fragment's UI is just a simple text view showing its
* instance number.
*/
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.hello_world, container, false);
View tv = v.findViewById(R.id.text);
((TextView)tv).setText("Fragment #" + mNum);
tv.setBackgroundDrawable(getResources().getDrawable(android.R.drawable.gallery_thumb));
return v;
}
}
A function that creates a new instance of the fragment, replacing whatever current fragment instance is being shown and pushing that change on to the back stack could be written as:
void addFragmentToStack() {
mStackLevel++;
// Instantiate a new fragment.
Fragment newFragment = CountingFragment.newInstance(mStackLevel);
// Add the fragment to the activity, pushing this transaction
// on to the back stack.
FragmentTransaction ft = getFragmentManager().beginTransaction();
ft.replace(R.id.simple_fragment, newFragment);
ft.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_OPEN);
ft.addToBackStack(null);
ft.commit();
}
After each call to this function, a new entry is on the stack, and pressing back will pop it to return the user to whatever previous state the activity UI was in.
Source: https://developer.android.com/reference/android/app/Fragment.html
You need to get the same instance of FragOne from the viewpager.
First, you can only access the FragOne instance after the ViewPager is setup.
Then, try this:
fo = adapter.getItem(0)
Note:
Since you already have fragments, it would be better to let the fragment itself handle the UI-related actions (such as setting the textview) rather than from the Activity.
I keep having an issue with my android app where it is crashing with the following error when swiping between tabs:
09-16 16:19:27.142 4750-4750/com.khackett.runmate E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.khackett.runmate, PID: 4750
java.lang.IllegalStateException: Content view not yet created
at android.support.v4.app.ListFragment.ensureList(ListFragment.java:328)
at android.support.v4.app.ListFragment.getListView(ListFragment.java:222)
at com.khackett.runmate.ui.MyRunsFragment$1.done(MyRunsFragment.java:167)
at com.khackett.runmate.ui.MyRunsFragment$1.done(MyRunsFragment.java:135)
at com.parse.ParseTaskUtils$2$1.run(ParseTaskUtils.java:115)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5254)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
This is the MyRunsFragment:
public class MyRunsFragment extends ListFragment {
protected SwipeRefreshLayout mSwipeRefreshLayout;
// member variable to store the list of routes the user has accepted
protected List<ParseObject> mAcceptedRoutes;
private int MY_STATUS_CODE = 1111;
// Default constructor for MyRunsFragment
public MyRunsFragment() {
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_my_runs, container, false);
// Set SwipeRefreshLayout component
mSwipeRefreshLayout = (SwipeRefreshLayout) rootView.findViewById(R.id.swipeRefreshLayout);
// Set the onRefreshListener
mSwipeRefreshLayout.setOnRefreshListener(mOnRefreshListener);
mSwipeRefreshLayout.setColorSchemeResources(
R.color.swipeRefresh1,
R.color.swipeRefresh2,
R.color.swipeRefresh3,
R.color.swipeRefresh4);
return rootView;
}
#Override
public void onViewCreated(View view, Bundle savedInstanceState) {
// Retrieve the accepted routes from the Parse backend
retrieveAcceptedRoutes();
}
#Override
public void onResume() {
super.onResume();
}
#Override
public void onListItemClick(ListView l, View v, int position, long id) {
super.onListItemClick(l, v, position, id);
// create the message object which is set to the message at the current position
ParseObject route = mAcceptedRoutes.get(position);
// String messageType = message.getString(ParseConstants.KEY_FILE_TYPE);
JSONArray parseList = route.getJSONArray(ParseConstants.KEY_LATLNG_POINTS);
JSONArray parseListBounds = route.getJSONArray(ParseConstants.KEY_LATLNG_BOUNDARY_POINTS);
String objectId = route.getObjectId();
String routeName = route.getString(ParseConstants.KEY_ROUTE_NAME);
// JSONArray ids = route.getJSONArray(ParseConstants.KEY_RECIPIENT_IDS);
// Start a map activity to display the route
Intent intent = new Intent(getActivity(), MapsActivityTrackRun.class);
intent.putExtra("parseLatLngList", parseList.toString());
intent.putExtra("parseLatLngBoundsList", parseListBounds.toString());
intent.putExtra("myRunsObjectId", objectId);
intent.putExtra("myRunsRouteName", routeName);
// Start the MapsActivityDisplayRoute activity
startActivityForResult(intent, MY_STATUS_CODE);
}
#Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
}
private void retrieveAcceptedRoutes() {
// query the routes class/table in parse
// get messages where the logged in user ID is in the list of the recipient ID's (we only want to retrieve the messages sent to us)
// querying the message class is similar to how we have been querying users
ParseQuery<ParseObject> queryRoute = new ParseQuery<ParseObject>(ParseConstants.CLASS_ROUTES);
// use the 'where' clause to search through the messages to find where our user ID is one of the recipients
queryRoute.whereEqualTo(ParseConstants.KEY_ACCEPTED_RECIPIENT_IDS, ParseUser.getCurrentUser().getObjectId());
// order results so that most recent message are at the top of the inbox
queryRoute.addDescendingOrder(ParseConstants.KEY_CREATED_AT);
// query is ready - run it
queryRoute.findInBackground(new FindCallback<ParseObject>() {
// When the retrieval is done from the Parse query, the done() callback method is called
#Override
public void done(List<ParseObject> routes, ParseException e) {
// dismiss the progress indicator here
// getActivity().setProgressBarIndeterminateVisibility(false);
// End refreshing once routes are retrieved
// done() is called from onResume() and the OnRefreshListener
// Need to check that its called from the the OnRefreshListener before ending it
if (mSwipeRefreshLayout.isRefreshing()) {
mSwipeRefreshLayout.setRefreshing(false);
}
// the list being returned is a list of routes
if (e == null) {
// successful - routes found. They are stored as a list in messages
mAcceptedRoutes = routes;
// adapt this data for the list view, showing the senders name
// create an array of strings to store the usernames and set the size equal to that of the list returned
String[] usernames = new String[mAcceptedRoutes.size()];
// enhanced for loop to go through the list of users and create an array of usernames
int i = 0;
for (ParseObject message : mAcceptedRoutes) {
// get the specific key
usernames[i] = message.getString(ParseConstants.KEY_SENDER_NAME);
i++;
}
// Create the adapter once and update its state on each refresh
if (getListView().getAdapter() == null) {
// the above adapter code is now replaced with the following line
RouteMessageAdapter adapter = new RouteMessageAdapter(getListView().getContext(), mAcceptedRoutes);
// Force a refresh of the list once data has changed
adapter.notifyDataSetChanged();
// need to call setListAdapter for this activity. This method is specifically from the ListActivity class
setListAdapter(adapter);
} else {
// refill the adapter
// cast it to RouteMessageAdapter
((RouteMessageAdapter) getListView().getAdapter()).refill(mAcceptedRoutes);
}
}
}
});
}
protected SwipeRefreshLayout.OnRefreshListener mOnRefreshListener = new SwipeRefreshLayout.OnRefreshListener() {
#Override
public void onRefresh() {
// When list is swiped down to refresh, retrieve the users runs from the Parse backend
retrieveAcceptedRoutes();
}
};
}
And the fragment_my_runs layout file:
<RelativeLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity$PlaceholderFragment">
<android.support.v4.widget.SwipeRefreshLayout
android:id="#+id/swipeRefreshLayout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_alignParentStart="true"
android:layout_alignParentTop="true">
<ListView
android:id="#android:id/list"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_alignParentStart="true"
android:layout_alignParentTop="true"
android:clipToPadding="false"
android:paddingBottom="#dimen/inbox_vertical_margin"/>
</android.support.v4.widget.SwipeRefreshLayout>
<TextView
android:id="#android:id/empty"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="#string/empty_inbox_label"
android:textSize="#dimen/default_text_size"/>
</RelativeLayout>
The TabFragmentContainer
public class TabFragmentContainer extends Fragment {
// Create the FragmentPagerAdapter that will provide and manage tabs for each section.
public static MyFragmentPagerAdapter myFragmentPagerAdapter;
public static TabLayout tabLayout;
// The ViewPager is a layout widget in which each child view is a separate tab in the layout.
// It will host the section contents.
public static ViewPager viewPager;
#Nullable
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
// Inflate tab_layout_fragment_container view and setup views for the TabLayout and ViewPager items.
View view = inflater.inflate(R.layout.tab_layout_fragment_container, null);
tabLayout = (TabLayout) view.findViewById(R.id.tabs);
// Set up the ViewPager with the sections adapter.
viewPager = (ViewPager) view.findViewById(R.id.viewpager);
// Instantiate the adapter that will return a fragment for each of the three sections of the main activity
myFragmentPagerAdapter = new MyFragmentPagerAdapter(getActivity(), getChildFragmentManager());
// Set up the adapter for the ViewPager
viewPager.setAdapter(myFragmentPagerAdapter);
// Runnable() method required to implement setupWithViewPager() method
tabLayout.post(new Runnable() {
#Override
public void run() {
tabLayout.setupWithViewPager(viewPager);
viewPager.setCurrentItem(1, false);
// tabLayout.getTabAt(1).select();
}
});
// Return the created View
return view;
}
}
The FragmentPagerAdapter:
public class MyFragmentPagerAdapter extends FragmentPagerAdapter {
// The context to be passed in when the adapter is created.
private Context mContext;
// The number of tabs in the layout.
public static int numberOfTabs = 3;
/**
* Default constructor that accepts a FragmentManager parameter to add or remove fragments.
*
* #param context the context from the activity using the adapter.
* #param fragmentManager the FragmentManager for managing Fragments inside of the TabFragmentContainer.
*/
public MyFragmentPagerAdapter(Context context, FragmentManager fragmentManager) {
super(fragmentManager);
mContext = context;
}
/**
* Method to return the relevant fragment for the selected tab.
*/
#Override
public Fragment getItem(int position) {
switch (position) {
case 0:
return new MyRunsFragment();
case 1:
return new InboxRouteFragment();
case 2:
return new FriendsFragment();
}
return null;
}
/**
* Method that gets the number of tabs in the layout.
*
* #return the number of tabs in the layout.
*/
#Override
public int getCount() {
return numberOfTabs;
}
/**
* Method that returns the title of each tab in the layout.
*/
#Override
public CharSequence getPageTitle(int position) {
Locale locale = Locale.getDefault();
switch (position) {
case 0:
return mContext.getString(R.string.title_section1).toUpperCase(locale);
case 1:
return mContext.getString(R.string.title_section2).toUpperCase(locale);
case 2:
return mContext.getString(R.string.title_section3).toUpperCase(locale);
}
return null;
}
}
The tab_layout_fragment_container file that contains the ViewPager widget:
<?xml version="1.0" encoding="utf-8"?>
<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="wrap_content"
android:orientation="vertical">
<android.support.design.widget.TabLayout
android:id="#+id/tabs"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="#color/ColorPrimaryPurple"
app:tabGravity="fill"
app:tabIndicatorColor="#color/ColorPrimaryPurple"
app:tabMode="fixed"
app:tabSelectedTextColor="#color/textColorPrimary"
app:tabTextColor="#color/pressedPurpleButton">
</android.support.design.widget.TabLayout>
<android.support.v4.view.ViewPager
android:id="#+id/viewpager"
android:layout_width="match_parent"
android:layout_height="match_parent">
</android.support.v4.view.ViewPager>
</LinearLayout>
The onCreate() method in my MainActivity:
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Initialise the DrawerLayout and NavigationView views.
mDrawerLayout = (DrawerLayout) findViewById(R.id.drawerLayout);
mNavigationView = (NavigationView) findViewById(R.id.navigationDrawerMenu);
// Inflate the first fragment to be displayed when logged into the app.
mFragmentManager = getSupportFragmentManager();
mFragmentTransaction = mFragmentManager.beginTransaction();
mFragmentTransaction.replace(R.id.containerView, new TabFragmentContainer()).commit();
// Setup click events on the NavigationView items.
// When an item is selected, replace the tab fragment container with the requested fragment.
mNavigationView.setNavigationItemSelectedListener(new NavigationView.OnNavigationItemSelectedListener() {
#Override
public boolean onNavigationItemSelected(MenuItem menuItem) {
mDrawerLayout.closeDrawers();
if (menuItem.getItemId() == R.id.navItemHome) {
FragmentTransaction tabFragmentContainer = mFragmentManager.beginTransaction();
tabFragmentContainer.replace(R.id.containerView, new TabFragmentContainer()).commit();
}
if (menuItem.getItemId() == R.id.navItemRunHistory) {
FragmentTransaction runHistoryFragment = mFragmentManager.beginTransaction();
runHistoryFragment.replace(R.id.containerView, new RunHistoryFragment()).commit();
}
if (menuItem.getItemId() == R.id.navItemSettings) {
FragmentTransaction settingsFragment = mFragmentManager.beginTransaction();
settingsFragment.replace(R.id.containerView, new SettingsFragment()).commit();
}
if (menuItem.getItemId() == R.id.navItemHelp) {
FragmentTransaction instructionsFragment = mFragmentManager.beginTransaction();
instructionsFragment.replace(R.id.containerView, new InstructionsFragment()).commit();
}
if (menuItem.getItemId() == R.id.navItemMyProfile) {
FragmentTransaction myProfileFragment = mFragmentManager.beginTransaction();
myProfileFragment.replace(R.id.containerView, new MyProfileFragment()).commit();
}
if (menuItem.getItemId() == R.id.navItemLogOut) {
// User has selected log out option. Log user out and return to login screen.
ParseUser.logOut();
navigateToLogin();
}
return false;
}
});
// Set up the Toolbar.
setupToolbar();
}
I have followed other answers here and added the getListView() functionality to the onViewCreated() method but the problem still persists... Can anyone point out where I might be going wrong?
Based on these facts:
The exception is thrown because there is no root view yet when done() calls getListView().
done() is called when the query made by retrieveAcceptedRoutes() gets a response.
retrieveAcceptedRoutes is called in multiple places, including the OnRefreshListener mOnRefreshListener, which is registered as the refresh listener in onCreateView() before there is a root view (that is, before onCreateView() returns).
...it is possible for getListView() to be called before there is a root view.
Try moving these 3 statements from onCreateView() to onViewCreated(), so that way the refresh listener can only be called when there is a root view.
// Set SwipeRefreshLayout component
mSwipeRefreshLayout = (SwipeRefreshLayout) rootView.findViewById(R.id.swipeRefreshLayout);
// Set the onRefreshListener
mSwipeRefreshLayout.setOnRefreshListener(mOnRefreshListener);
mSwipeRefreshLayout.setColorSchemeResources(
R.color.swipeRefresh1,
R.color.swipeRefresh2,
R.color.swipeRefresh3,
R.color.swipeRefresh4);
onViewCreated is called immediately after onCreateView, but the super.onViewCreated call is missing, perhaps this is root cause of your issue.
#Override
public void onViewCreated(View view, Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState); // add this line back in
// Retrieve the accepted routes from the Parse backend
retrieveAcceptedRoutes();
}
I read your question again then I guess that:
Your ListFragment is destroyed while your background task keeps running. So when it's done, your callback would like to update the ListView which is no longer alive.
Actually, viewPager.setOffscreenPageLimit(3); may do the trick, but it's not a good practice. It forces your ViewPager to create and store more Fragments in memory which is not necessary. You can solve this without doing so.
What you should do: one of the following two practice should be fine, or both:
Destroy your task in your onPause or whatever lifecycle method, before your onDestroyView.
Exclude the code where you update your ListView inside your done() method. Make it a local method where you will check your ListView carefully, and there, you should ask your update process to run on UI thread to avoid any threading problem. Make sure to check if your getView() is not null (but not your getListView(), since it throws Exception if getView() returns null).
I recommend you to use both of them to make sure: your view is still useable and you don't waste your resource when running task in invisible fragment. Don't forget that by default, once your fragment is invisible, it is considered to be destroyed (not always, for example ViewPager keep reference of 2 fragments, but keep in mind that case).
remove all these imports:
import com.yourName.runmate.R;
Then resync your gradle and rebuild your project.
Also see here:
"cannot resolve symbol R" in Android Studio
edit
Your first obvious mistake in your Main is
mFragmentManager = getSupportFragmentManager();
should be:
mFragmentManager = getFragmentManager();
or change your Main activity to:
MainActivity extends FragmentActivity to make use of the support fragment manager.
You have a lot of unnecessary code in your question, majority of comments can be removed and imports for the purpose of this question.
What I have come up with is there is no activity, being used. The ListFragment needs to be attached to an Activity or you are trying to call that activity view before it is created.
java.lang.IllegalStateException: Content view not yet created
at android.support.v4.app.ListFragment.ensureList(ListFragment.java:328)
at android.support.v4.app.ListFragment.getListView(ListFragment.java:222)
If you are using Main, then you are not pulling them together well, from what I can see.
Firstly:
Take everything out of your onCreate and onCreateView (for all fragments) except the view inflater.
Place all the extra code into either onViewCreated or onActivityCreated. That way no methods can be called on a null view, as these are called after it is created.
Secondly, you need to sort out your activities and with what you're exactly trying to achieve.
You want a page viewer and a fragmentlist. The pageviewer needs to be associated with an activity, or activity fragment, not a fragment. Otherwise there is no view to attach the pageviewer pages to.
Use a FragmentActivity not a Fragment. To be the activity you run your ListFragment from.
public class TabFragmentContainer extends FragmentActivity {
MyPageAdapter pageAdapter;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.tab_layout_fragment_container); // change to view layout.
// Instantiate the adapter that will return a fragment for each of the three sections of the main activity
myFragmentPagerAdapter = new MyFragmentPagerAdapter(getFragmentManager(), getFragments());
tabLayout = (TabLayout) view.findViewById(R.id.tabs);
// Set up the ViewPager with the sections adapter.
viewPager = (ViewPager) view.findViewById(R.id.viewpager);
// Set up the adapter for the ViewPager
viewPager.setAdapter(myFragmentPagerAdapter);
}
}
I would suggest putting this into your ListFragment, to ensure your activity is created. You will need to move most of your code from your onCreate methods and put them in onViewCreated or onActivityCreated
#Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
ArrayAdapter adapter = ArrayAdapter.createFromResource(getActivity(), R.layout.my_listview)layout, android.R.layout.simple_list_item_1);
setListAdapter(adapter);
getListView().setOnItemClickListener(this);
}
This code is just a guide, you'll need to tweak it.
Let me know if this helps.
These Q&As are excellent.
Content view not yet created
android Illegal state exception content view not yet create?
Fragment same principles applies to viewpager fragments ViewPager
Try to declare:
viewPager = (ViewPager) view.findViewById(R.id.viewpager);
viewPager.setAdapter(myFragmentPagerAdapter);
myFragmentPagerAdapter = new MyFragmentPagerAdapter(getActivity(), getChildFragmentManager());
before:
tabLayout = (TabLayout) view.findViewById(R.id.tabs);
tabLayout.post(new Runnable() {
#Override
public void run() {
tabLayout.setupWithViewPager(viewPager);
viewPager.setCurrentItem(1, false);
// tabLayout.getTabAt(1).select();
}
});
// Return the created View
return view;
I have a main activity that extents ActionBarActivity and implements ActionBar.TabListener
public class MainActivity extends ActionBarActivity implements ActionBar.TabListener {
SectionsPagerAdapter mSectionsPagerAdapter;
ViewPager mViewPager;
View mView;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Set up the action bar.
final ActionBar actionBar = getSupportActionBar();
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
// 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.pager);
mViewPager.setAdapter(mSectionsPagerAdapter);
// When swiping between different sections, select the corresponding
// tab. We can also use ActionBar.Tab#select() to do this if we have
// a reference to the Tab.
mViewPager.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
#Override
public void onPageSelected(int position) {
actionBar.setSelectedNavigationItem(position);
}
});
// For each of the sections in the app, add a tab to the action bar.
for (int i = 0; i < mSectionsPagerAdapter.getCount(); i++) {
// Create a tab with text corresponding to the page title defined by
// the adapter. Also specify this Activity object, which implements
// the TabListener interface, as the callback (listener) for when
// this tab is selected.
actionBar.addTab(
actionBar.newTab()
.setText(mSectionsPagerAdapter.getPageTitle(i))
.setTabListener(this));
}
}
}
When a button is clicked on one of the fragments controlled by MainActivity, I have to create an intent and start another activity:
public void goToHighScore(View view) {
Intent intent = new Intent(this, DisplayScoreActivity.class);
//TextView nView = (TextView) mViewPager.getChildAt(2).findViewById(R.id.label);
TextView nView = (TextView) findViewById(R.id.label);
String highScore = nView.getText().toString();
intent.putExtra(HIGH_SCORE, highScore);
startActivity(intent);
}
However the "highScore" value is always the one equal to the fragment proceeding it?
All answers are appreciated. Thank you for bearing with me.
-Paul T.
You can get the current fragment by:
Fragment currentFragment = mSectionsPagerAdapter.getItem(mViewPager.getCurrentItem());
Update your fragment to get the score:
Class CustomFragment extends Fragment{
private TextView nView;
public void onViewCreated(View view, Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
nView = view.findViewById(R.id.label);
}
public String getScore(){
return nView.getText().toString();
}
}
And function will look like:
public void goToHighScore(View view) {
Intent intent = new Intent(this, DisplayScoreActivity.class);
Fragment currentFragment = mSectionsPagerAdapter.getItem(mViewPager.getCurrentItem());
String highScore = currentFragment.getScore();
intent.putExtra(HIGH_SCORE, highScore);
startActivity(intent);
}
However, I will suggest you to handle the onClick event in your fragment to provide better encapsulation. Update your fragment as follows:
Class CustomFragment extends Fragment{
private TextView nView;
public void onViewCreated(View view, Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
nView = view.findViewById(R.id.label);
Button button = (Button)findViewByid(R.id.button)
button.setOnClickListener(new View.OnClickListener(){
public void onClick(View v){
String highScore = nView.getText().toString()
intent.putExtra(HIGH_SCORE, highScore);
startActivity(intent);
}
});
}
}
By doing this your Fragment can be attached to different activity without functionality broke down.