We Keep Coding

Fragment Crashing when receiving data from an Activity

Good day all,
I have an issue where my activity is making a network call and when the network call is completed, it makes some changes in the activity using the data from the JSON object received from the call, it then passes the object down to the fragments in the same activity. These fragments are in a TabLayout.
I had this same issue which I asked here at this SO Question That sorted it out but I seem to be having the same issue, even after it worked for a little bit after not changing anything significant. I was just adding more fields I wanted to change?
The issue I have is that if I put a System.out.println() it prints out the correct data. The minute I want to set say a TextView with the data I receive in the Fragment the app Crashes with Nullpointer. When I debug it with the Debug in Android studio, the TextView I'm setting is always null for some reason.
Activity Code that does the initial Network call:
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_listings);
ButterKnife.bind(this);
setSupportActionBar(toolbar);
handleIntent(getIntent());
}
private void handleIntent(Intent aIntent) {
if (aIntent != null) {
String tradeType = aIntent.getStringExtra("itemType");
String tradeId = aIntent.getStringExtra("itemId");
presenter = new ItemPresenterImpl(this, ItemBuyNowActivity.this);
presenter.doListingServiceCall(tradeId); // <------- This is the where I send the Trade Id so I can do the network call.
} else {
System.out.println("Intent is null in " + ItemBuyNowActivity.class.getSimpleName());
}
}
Interface between Activity and Presenter:
public interface ItemPresenter {
void doListingServiceCall(String itemId); //<------- Comes to this Interface
void doToolbarBackgroundImageCall(TradeItem aTradeItem);
}
Class the implements the Presenter:
#Override
public void doListingServiceCall(String aItemId) { // <------- This is where the network call starts
String homeURL = BobeApplication.getInstance().getWsURL() + mContext.getString(R.string.ws_url_item) + aItemId;
BobeJSONRequest jsObjRequest = new BobeJSONRequest(Request.Method.GET, homeURL, null, this, this);
VolleySingleton.getInstance().addToRequestQueue(jsObjRequest, "ListingRequest");
}
#Override
public void doToolbarBackgroundImageCall(TradeItem aTradeItem) {
ImageRequest request = new ImageRequest(aTradeItem.getItem().getImageUrl(),
new Response.Listener<Bitmap>() {
#Override
public void onResponse(Bitmap bitmap) {
Drawable drawable = new BitmapDrawable(mContext.getResources(), bitmap);
mItemView.loadBackgroundImage(drawable);
}
}, 0, 0, null,
new Response.ErrorListener() {
public void onErrorResponse(VolleyError error) {
mItemView.displayErrorMessage(VolleyErrorHelper.getErrorType(error, mContext) + " occurred downloading background image");
}
});
VolleySingleton.getInstance().addToRequestQueue(request, "ListItemToolbarBackgroundImageRequest");
}
#Override
public void onResponse(Object response) {
Gson gson = new Gson();
TradeItem tradeItem = gson.fromJson(response.toString(), TradeItem.class);
mItemView.populateListViews(tradeItem); // <------- This is the where I send the Object so the views in the activity can be manipulated
doToolbarBackgroundImageCall(tradeItem);
}
Method in the Activity that handles
#Override
public void populateListViews(TradeItem aTradeItem) {
mOverviewPresenter = new OverviewPresenterImpl(new OverviewListItemFragment(), aTradeItem);
OverviewListItemFragment.setData(aTradeItem); //<------- This is the where I send the Object to the fragment so i can manipulate the views in the fragment
}
class TabAdapter extends FragmentPagerAdapter {
public TabAdapter(FragmentManager fm) {
super(fm);
}
#Override
public Fragment getItem(int position) {
Fragment fragment = null;
if (position == 0) {
fragment = new OverviewListItemFragment();
}
if (position == 1) {
fragment = new DescriptionListItemFragment();
}
if (position == 2) {
fragment = new ShippingListItemFragment();
}
if (position == 3) {
fragment = new PaymentListItemFragment();
}
return fragment;
}
#Override
public int getCount() {
return 4;
}
#Override
public CharSequence getPageTitle(int position) {
if (position == 0) {
return "Overview";
}
if (position == 1) {
return "Description";
}
if (position == 2) {
return "Shipping";
}
if (position == 3) {
return "Payment";
}
return null;
}
}
The Fragment that receives the data:
public class OverviewListItemFragment extends Fragment implements OverviewView {
private static TextView mOverViewHeading;
public OverviewListItemFragment() {
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
#Nullable
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.overview_list_item_fragment, container, false);
mOverViewHeading = (TextView) view.findViewById(R.id.frag_overview_heading_textview);
return view;
}
#Override
public void populateOverviewViews(final TradeItem aTradeItem) {
System.out.println("Overview Trade Object title is:" + aTradeItem.getItem().getTradeTitle()); // <------- This is print statement works 100% but when I try setting mOverViewHeading to the text in aTradeItem.getItem().getTradeTitle() I get a Null pointer Exception.
}
public static void setData(TradeItem aTradeItem) {
System.out.println("Overview Trade Object title is:" + aTradeItem.getItem().getTradeTitle()); // <------- This is print statement works 100% but when I try setting mOverViewHeading to the text in aTradeItem.getItem().getTradeTitle() I get a Null pointer Exception.
mOverViewHeading.setText(aTradeItem.getItem().getTradeTitle());// <------- This is where it crashes and mOverViewHeading is still null at this point.
}
}
EDIT: Sorry I forgot the LogCat:
02-05 17:08:21.554 30512-30512/com.example.app E/AndroidRuntime: FATAL EXCEPTION: main
java.lang.NullPointerException
at com.example.app.ui.fragments.OverviewListItemFragment.setData(OverviewListItemFragment.java:46)
at com.example.app.ui.activities.ItemBuyNowActivity.populateListViews(ItemBuyNowActivity.java:95)
at com.example.app.listing.ItemPresenterImpl.onResponse(ItemPresenterImpl.java:62)
at com.android.volley.toolbox.JsonRequest.deliverResponse(JsonRequest.java:65)
at com.android.volley.ExecutorDelivery$ResponseDeliveryRunnable.run(ExecutorDelivery.java:99)
at android.os.Handler.handleCallback(Handler.java:725)
at android.os.Handler.dispatchMessage(Handler.java:92)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:5041)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
at dalvik.system.NativeStart.main(Native Method)
My thinking is that the view I'm trying to set isn't "Active" (if thats the right word) at the time it receives the data, because when I run the debugger with a break point at the method that receives the data in the Fragment, the mOverViewHeading TextView id is null, even though I have the findViewById in the onCreate, also tried placing it in the onCreateView() but both times failed. I also tried placing the findViewById in the same method that gets called when the response is successful but before I try setting the setText() on the TextView.
Thank you

OverviewListItemFragment I assume this is not your added fragment instance, but the class.
I suggest the following changes: remove static from setData and your TextView, leave it, if you really know how it works. I don't think it is necessary or recommendable.
private OverviewListItemFragment mFrag; //declare globally
mFrag = new OverviewListItemFragment();
//if you do not want to add it now, ignore the following line
getSupportFragmentManager().beginTransaction().add(R.id.yourContainer, mFrag, "mFrag").commit();
now call mFrag.setData everytime you want to set your data. Check if your mFrag is null, then reinitialize, and maybe re-add, or whatever you want to do.
Edit: Now that I know that you use a ViewPager, I suggest the following:
Do the above. I don't think it is recommendable to have static methods in this Context. You get an error because you are trying to reach a TextView in your Fragment. This was initialized in a ViewPager/PagerAdapter, and the PagerAdapter holds the reference to the used instance of your fragment.
You can access your used fragment through
Fragment mFragment = pagerAdapter.getFragment(0); //frag at position 0
with some casting, you will be able to find your (now NOT static) method:
((OverviewListItemFragment)pagerAdapter.getFragment(0)).setData(YOUR_DATA);
Please add some try/catch. check if your fragment is null, because it is possible that your fragment is recycled in the FragmentPagerAdapter, because it reached the offset. Another way to achieve this, would be to store your required data, and update it everytime your fragment gets visible as described here.
Edit 2: Obviously, You'll need some changed in your Adapter:
I would recommend creating an array containing your fragment in the constructor:
//global in your adapter:
private Fragment[] fragments;
public CustomPagerAdapter(FragmentManager fm) {
super(fm);
fragments = new GameFragment[4];
fragments[0] = new MyFragment();
fragments[1] = new SecondFragment();
....
}
public Fragment getItem(int position) {
return fragments[position];
}
public Fragment getFragment(int position) {
return fragments[position];
}

Attempt to invoke virtual method 'android.view.View android.view.View.findViewById(int)' on a null object reference

I've been looking for a similar problem to mine in order to find a solution, but I seriously couldn't find anything like that.
I was trying to download from parse an array of posts with an asynctask class, and after it gets the posts, it suppose to set the posts array in my page, and perform the setAdapter function in order to set my new posts array.
the problem is, after I've initialized listView and listAdapter in my home fragment,and then I perform the postArray taking from parse function, after it finishes taking the posts array from parse, it cannot update listAdapter because it says the listAdapter and my listView "haven't initialized yet", even though they have.
p.s.
sorry for not posting my code in a convenient way, I don't tend to post my code problems that often.
here's my code:
my home fragment:
public class HomeFragment extends Fragment {
View root;
ArrayList<PostClass> postsArrayList = new ArrayList<>();
static boolean isPostsArrayUpdated = false;
ListAdapter listAdapter;
PullToRefreshListView listView;
public void updatePostsArrayList(ArrayList<PostClass> postsArrayList){
if(!isPostsArrayUpdated){
// First time updating posts array list
listAdapter = new ListAdapter(getActivity(), root);
listView = (PullToRefreshListView) root.findViewById(R.id.list_container);
this.postsArrayList = postsArrayList;
listView.setAdapter(listAdapter);
isPostsArrayUpdated = true;
root.findViewById(R.id.homeFragmentLoadingPanel).setVisibility(View.GONE);
}else{
// Have updated posts before
this.postsArrayList = postsArrayList;
listAdapter.notifyDataSetChanged();
}
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
root = inflater.inflate(R.layout.fragment_home, container, false);
listView = (PullToRefreshListView) root.findViewById(R.id.list_container);
listAdapter = new ListAdapter(getActivity(), root);
Home_Model.getInstance().setPostsArrayList();
return root;
}
public class ListAdapter extends BaseAdapter implements View.OnClickListener{//....}
my home model:
public class Home_Model {
Home_Model(){}
static final Home_Model instance = new Home_Model();
public static Home_Model getInstance() {
return instance;
}
public void setPostsArrayList(){
new setHomePostsArray().execute();
}
public class setHomePostsArray extends AsyncTask<Void, ArrayList<PostClass>, Void>{
ArrayList<String> followersList;
ArrayList<PostClass> postsArrayList;
#Override
protected Void doInBackground(Void... params) {
// Getting posts from parse
String userName = Parse_model.getInstance().getUserClass().get_userName();
followersList = Parse_model.getInstance().getFollowersByUserNameToString(userName);
followersList.add(userName);
postsArrayList = Parse_model.getInstance().getAllUsersPostsByFollowings(followersList);
for (PostClass currPost : postsArrayList) {
for (PostClass currLocalDBPost : LocalDBPostsArray) {
if (currPost.getObjectID().equals(currLocalDBPost.getObjectID())) {
currPost.set_postPicture(currLocalDBPost.get_postPicture());
}
}
}
//Updating home page
onProgressUpdate(postsArrayList);
// Updating local data base in new posts
//checking in local DB if there are any new posts from parse and update them
for (PostClass currPost : postsArrayList) {
boolean isPostExists = false;
for (PostClass currLocalPost : LocalDBPostsArray) {
if (currPost.getObjectID().equals(currLocalPost.getObjectID())) {
isPostExists = true;
}
}
if (!isPostExists) {
ModelSql.getInstance().addPost(currPost);
Log.e("post not exist", "adding local DB");
}
}
//updating followers list in local DB
Parse_model.getInstance().getUserClass().setFollowersArray(followersList);
ModelSql.getInstance().updateFollowersArray(currUser);
return null;
}
#Override
protected void onProgressUpdate(ArrayList<PostClass>... values) {
//pass the updated postsArrayList to home fragment
if(setPostsInHomePageDelegate!= null){
setPostsInHomePageDelegate.setPosts(values[0]);
}
}
}
public interface SetPostsInHomePage {
public void setPosts(ArrayList<PostClass> postsArrayList);
}
SetPostsInHomePage setPostsInHomePageDelegate;
public void setSetPostsInHomePageDelegate(SetPostsInHomePage setPostsInHomePageDelegate) {
this.setPostsInHomePageDelegate = setPostsInHomePageDelegate;
}
main activity:
public class MainActivity extends Activity {
static HomeFragment homeFragment = new HomeFragment();
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// the home fragment has already been opened during the app opening
//...
setPostsImHomePage();
}
//...
public void setPostsImHomePage(){
Home_Model.getInstance().setSetPostsInHomePageDelegate(new Home_Model.SetPostsInHomePage() {
#Override
public void setPosts(ArrayList<PostClass> postsArrayList) {
homeFragment.updatePostsArrayList(postsArrayList);
}
});
}
}

Try to move your method setPostsImHomePage(...) from MainActivity to HomeFragmentand call it in OnCreateView before return root;.

Try initializing homeFragment in onCreate before your method call. It's also helpful to know which line(s) are giving you errors.

Obviously your fragment has no View when the result arrives.
You should properly add the fragment to the Activity using the FragmentManager, then in the Fragment's onActivityCreated() callback (which is called by the system after the Fragment has its view properly set), start your AsyncTask.

Where is my static context?

I'm brand new to android programming and I'm trying to use a gridviewpager with fragments. My code is:
public class Main extends Activity {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.grid);
final Resources res = getResources();
GridViewPager pager = (GridViewPager) findViewById(R.id.gridpager);
pager.setOnApplyWindowInsetsListener(new OnApplyWindowInsetsListener() {
#Override
public WindowInsets onApplyWindowInsets(View v, WindowInsets insets) {
// Adjust page margins:
// A little extra horizontal spacing between pages looks a bit
// less crowded on a round display.
final boolean round = insets.isRound();
int rowMargin = res.getDimensionPixelOffset(R.dimen.page_row_margin);
int colMargin = res.getDimensionPixelOffset(round ?
R.dimen.page_column_margin_round : R.dimen.page_column_margin);
pager.setPageMargins(rowMargin, colMargin);
// GridViewPager relies on insets to properly handle
// layout for round displays. They must be explicitly
// applied since this listener has taken them over.
pager.onApplyWindowInsets(insets);
return insets;
}
});
// MyPagerAdapter adapter=new MyPagerAdapter();
pager.setAdapter(new MyPagerAdapter(Activity.getFragmentManager()));
}
public class MyPagerAdapter extends FragmentPagerAdapter {
public MyPagerAdapter(FragmentManager fm) {
super(fm);
}
#Override
public Fragment getItem(int pos) {
switch(pos) {
case 0: return FirstFragment.newInstance("FirstFragment, Instance 1");
case 1: return SecondFragment.newInstance("SecondFragment, Instance 1");
case 2: return SecondFragment.newInstance("SecondFragment, Instance 2");
default: return SecondFragment.newInstance("SecondFragment, Default");
}
}
#Override
public int getCount() {
return 3;
}
}
}
I've collapsed some to be concise. The error is in this line:
pager.setAdapter(new MyPagerAdapter(Activity.getFragmentManager()));
This returns the error:
Non-static method 'getFragmentManager()' cannot be referenced from a static context
But I don't know what is static in my code. I've tried assigning everything I can think of to variables but still can't get this. Thanks for your help.

Activity is the name of a class. By stating Activity.getFragmentManager(), you are attempting to call a method on the class itself rather than a specific instance of the class.
In your case, you don't need the Activity. section at all - just call getFragmentManager() itself:
pager.setAdapter(new MyPagerAdapter(getFragmentManager()));

Android: Passing Objects Between Fragments

Before i start, i have look through question such as:
Passing data between fragments: screen overlap
How to pass values between Fragments
as well as Android docs:
http://developer.android.com/training/basics/fragments/communicating.html
as well as this article:
http://manishkpr.webheavens.com/android-passing-data-between-fragments/
Though all the cases mentioned above similar to what i have, it is not entirely identical. I followed a good tutorial here (Some portion of my code is based on this article):
http://www.androidhive.info/2013/10/android-tab-layout-with-swipeable-views-1/
I have the following files:
RegisterActivity.java
NonSwipeableViewPager.java
ScreenSliderAdapter.java
RegisterOneFragment.java
RegisterTwoFragment.java
And the following layouts:
activity_register.xml
fragment_register_one.xml
fragment_register_two.xml
What i am trying to achieve is passing an Serializable object from RegisterFragmentOne to RegisterFragmentTwo.
So far this is what i have done (some codes are omitted):
RegisterActivity.java
public class RegisterActivity extends FragmentActivity
implements RegisterOneFragment.OnEmailRegisteredListener{
public static NonSwipeableViewPager viewPager;
private ScreenSliderAdapter mAdapter;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_register);
// Initilization
mAdapter = new ScreenSliderAdapter(getSupportFragmentManager());
viewPager = (NonSwipeableViewPager) findViewById(R.id.pager);
viewPager.setAdapter(mAdapter);
}
public void onEmailRegistered(int position, Registration regData){
Bundle args = new Bundle();
args.putSerializable("regData", regData);
viewPager.setCurrentItem(position, true);
}
}
ScreenSliderAdapter.java
public class ScreenSliderAdapter extends FragmentPagerAdapter{
public ScreenSliderAdapter(FragmentManager fm) {
super(fm);
}
#Override
public Fragment getItem(int index) {
switch (index) {
case 0:
return new RegisterOneFragment();
case 1:
return new RegisterTwoFragment();
case 2:
return new RegisterThreeFragment();
}
return null;
}
#Override
public int getCount() {
return 3;
}
}
NonSwipeableViewPager.java (extending ViewPager class, and overrides the following)
#Override
public boolean onInterceptTouchEvent(MotionEvent arg0) {
// Never allow swiping to switch between pages
return false;
}
#Override
public boolean onTouchEvent(MotionEvent event) {
// Never allow swiping to switch between pages
return false;
}
RegisterOneFragment.java
public class RegisterOneFragment extends Fragment {
OnEmailRegisteredListener mCallBack;
public interface OnEmailRegisteredListener {
/** Called by RegisterOneFragment when an email is registered */
public void onEmailRegistered(int position, Registration regData);
}
public void onAttach(Activity activity){
super.onAttach(activity);
// This makes sure that the container activity has implemented
// the callback interface. If not, it throws an exception.
try {
mCallBack = (OnEmailRegisteredListener) activity;
} catch (ClassCastException e) {
throw new ClassCastException(activity.toString()
+ " must implement OnEmailRegisteredListener");
}
}
... And some to execute some HTTP request via separate thread...
}
What i am trying to accomplish is that when ever a user pressed a button on RegisterOneFragment, a data will be sent to a server (and returns some validation over JSON). If the returned data is valid, the the application should go to the next fragment which is RegistrationTwoFragment.
I am having some confusion as how to pass objects between fragments, since my Fragments is created using an Adapter. And that Adapter is then attached to my Activity.
Can anyone help me with this? Thx
Edit 1:
I tried to make a shortcut (unfortunately does not work) like so:
In RegisterActivity i created:
public Registration regData;
and in RegisterOneFragment:
/* PLACED ON POST EXECUTE */
((RegisterActivity)getActivity()).regData = regData;
Finally called it in RegisterTwoFragment
Registration regData;
regData = ((RegisterActivity) getActivity()).regData;
It throws a nullPointerExceptions
Edit 2
Just to be clear, RegisterActivty contains multiple fragments. And the only way user can navigate between fragment is by clicking a button. The Activity has no Tab bar.

It's easy to share objects via implementing Serializable to your custom Object. I wrote a tutorial about this here.
From Fragment One:
android.support.v4.app.FragmentTransaction ft =
getActivity().getSupportFragmentManager().beginTransaction();
ft.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_OPEN);
OfficeCategoryFragment frag = new OfficeCategoryFragment();
Bundle bundles = new Bundle();
Division aDivision = divisionList.get(position);
// ensure your object has not null
if (aDivision != null) {
bundles.putSerializable("aDivision", aDivision);
Log.e("aDivision", "is valid");
} else {
Log.e("aDivision", "is null");
}
frag.setArguments(bundles);
ft.replace(android.R.id.content, frag);
ft.addToBackStack(null);
ft.commit();
In Fragment two:
Bundle bundle = getArguments();
Division division= (Division) bundle.getSerializable("aDivision");
Log.e("division TEST", "" + division.getName());

I would normally have setters or methods similar to this in the containing activity.
So if I understand correctly, you want the user to access RegistrationOneFragment, then when completed, use this data, validate it, and if valid, pass it along to RegistrationTwoFragment and move the user to this Fragment.
Could you simply call validateJson(regData) in your onEmailRegistered method to handle the validation in your activity, if it succeeds, commit a transaction to RegistrationTwoFragment.
Then all you need are getters and setters in your activity or Fragment to say getRegistrationOneData() in the activity or setData(Registration args) in the fragment as your examples show above.
I don't know of any way to pass the args directly into the Fragment.

I found a solution to my question, which i am sure not the correct way to do that...
So in RegisterActivity.java i add + modified the following lines (thx to #sturrockad):
public Registration getRegistrationData(){
return this.regData;
}
public void onEmailRegistered(int position, Registration regData){
this.regData = regData;
viewPager.setCurrentItem(position, true);
}
Then in RegisterTwoFragments.java (or in the Fragment to which i want to receive the Object):
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_register_two, container, false);
regData = ((RegisterActivity) getActivity()).getRegistrationData();
...

I used to set object with Pacelable or Serializable to transfer, but whenever I add other variables to object(model), I have to register it all. It's so inconvenient.
It's super easy to transfer object between activities or fragments.
Android DataCache
put your data object to KimchiDataCache instance in your activity or fragment.
User userItem = new User(1, "KimKevin"); // Sample Model
KimchiDataCache.getInstance().put(userItem);
// add your activity or fragment
Get your data object in your activity of fragment that you added.
public class MainFragment extends Fragment{
private User userItem;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
userItem = KimchiDataCache.getInstance().get(User.class);
}

Updating Fragments - FrameStatePagerAdapter and HTTP Calls

I have been searching for an answer to my problem, but I seem to get none, despite of how many tutorials I followed, how many questions I've gone through and how many things I've tried to do what I want. Basically, I stumbled upon some good tips, and still couldn't manage to do what wanted.
THE PROBLEM
I am creating an Android Application that will use Fragments (alongside with tabs). In these fragments, I have crucial information relating the application, such as text boxes, and buttons. However, I want to do something really simple, which is updating one of my fragments as I come back to it (imagine I swipe back to a fragment, and I update it with the relevant information). Where is the information stored? On a node.js server, to which I call every time I want information. So for that, I created the following structure.
THE STRUCTURE
First of all, I started off creating my Activity.
public class CentralActivity extends FragmentActivity {
CentralPagerAdapter mCentralActivity;
ViewPager mViewPager;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_central);
tabHandler();
}
public void tabHandler() {
mCentralActivity = new CentralPagerAdapter(getSupportFragmentManager());
mViewPager = (ViewPager) findViewById(R.id.CentralPager);
mViewPager.setAdapter(mCentralActivity);
mViewPager.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
#Override
public void onPageSelected(int position) {
getActionBar().setSelectedNavigationItem(position);
}
});
//Action Bar Stuff
}
}
With this said, I need my CentralPagerAdapter, which I created as follows.
public class CentralPagerAdapter extends FragmentStatePagerAdapter {
private int nSwipes = 3;
public CentralPagerAdapter(FragmentManager fm) {
super(fm);
}
#Override
public Fragment getItem(int i) {
Fragment fragment = new CentralFragment();
Bundle args = new Bundle();
args.putInt(CentralFragment.ARG_OBJECT, i + 1);
fragment.setArguments(args);
return fragment;
}
#Override
public int getCount() {
return nSwipes;
}
}
And now, my fragment, which is only a class that contains all of my views, and options and so on.
public class CentralFragment extends Fragment {
public static final String ARG_OBJECT = "object";
private View rootView;
private RESTFunction currentFunction;
//Has the info I want
private ArrayList<Integer> tickets = new ArrayList<Integer>();
#SuppressLint("HandlerLeak")
private Handler threadConnectionHandler = new Handler() {
#Override
public void handleMessage(Message msg) {
switch (currentFunction) {
case GET_CLIENT_TICKETS:
handleGetTickets(msg);
break;
case BUY_CLIENT_TICKETS:
break;
default:
break;
}
}
};
#Override
public View onCreateView(final LayoutInflater inflater, final ViewGroup container,
Bundle savedInstanceState) {
final Bundle args = getArguments();
handleFragments(inflater, container);
getTicketInfo(null);
return rootView;
}
private void handleFragments(LayoutInflater inflater, ViewGroup container) {
Bundle args = getArguments();
if (args.getInt(ARG_OBJECT) == 1) {
rootView = inflater.inflate(R.layout.fragment_show_tickets,
container, false);
showTicketsHandler();
} else if (args.getInt(ARG_OBJECT) == 2) {
rootView = inflater.inflate(R.layout.fragment_buy_tickets,
container, false);
buyTicketsHandler();
} else {
rootView = inflater.inflate(R.layout.fragment_history_tickets,
container, false);
}
}
public void showTicketsHandler() {
//Get stuff from the tickets array that the REST call will handle
//And set them to boxes or radio buttons
}
public void buyTicketsHandler() {
//Get stuff from the tickets array that the REST call will handle
//And set them to boxes or radio buttons
//As well as button click listeners
}
public void getTicketInfo(ProgressDialog progDialog) {
//Connect to the thread to get the information
//In this case, I have no parameters
ConnectionThread dataThread = new ConnectionThread("myLink", Method.GET, null, threadConnectionHandler, progDialog);
dataThread.start();
}
//Get stuff from the resulting JSON and store it in the tickets ArrayList
private void handleGetTickets(Message msg) {
JSONObject ticketListing = (JSONObject) msg.obj;
try {
tickets.add(ticketListing.getInt("t1"));
tickets.add(ticketListing.getInt("t2"));
tickets.add(ticketListing.getInt("t3"));
} catch (JSONException e) {
e.printStackTrace();
}
}
}
And then, I have my thread..
public class ConnectionThread extends Thread {
private ConnectionRunnable runConnection;
private Handler mHandler;
private ProgressDialog progDialog;
public ConnectionThread(String link, Method method, ArrayList<NameValuePair> payload, Handler handler, ProgressDialog progDialog) {
runConnection = new ConnectionRunnable(link, method.toString(), payload);
mHandler = handler;
this.progDialog = progDialog;
}
#Override
public void run() {
runConnection.run();
threadMsg();
if(progDialog != null)
progDialog.dismiss();
}
public JSONObject getJSON() {
return runConnection.getResultObject();
}
private void threadMsg() {
Message msgObj = mHandler.obtainMessage();
msgObj.obj = getJSON();
mHandler.sendMessage(msgObj);
}
}
And ConnectionRunnable is where I run my HttpURLConnection.
SO WHAT DO I NEED?
Basically, what I'm trying to do, is to get the ticket information from the ConnectionThread BEFORE I load all my view and update them. Plus, I want to be able to swipe back and forth, and update my information on the array as I swipe through the screens (if I go to the second screen, the tickets will update, and if I come back to the first, they will re-update). So basically, call the ConnectionThread everytime I swipe around. If that is possible that, is.
WHAT HAVE I TRIED?
I've tried several things already, and all of them didn't actually help..
The usage of ProgressDialogs to stop the UI Thread on the onCreateView method of the fragment (no use, because it returns the rootView before it handles everything);
Making the UI Thread sleep for 1 second (I don't know why, it blocks all of them);
Overriding the instantiateMethod() of the Adapter, although I think I didn't do it correctly;
Overriding the saveState() of the Adapter, in order to prevent its saved states, and to then get new ticket information;
Giving the fragments tags to update their rootViews on the Adapter, but to no avail;
Getting the information in the activity, and everytime I make a purchase (second fragment), restart the whole activity to get the tickets, which I believe is a really, really bad solution.
I've read several articles, and I still couldn't find my answers.. It's really frustrating. Because it's something so simple, however, the fact that I have to run the HTTP calls on a different thread delays the whole UI updating process.
I've also read the AsyncTask's method. However, I feel like both Threads and AsyncTasks end up in the same.
WHAT TO DO NOW?
Well, that's what I was hoping to find. Because it ends up being annoying as it is.
POSSIBLE REASONS
Is it because I'm separating all classes into spread files, therefore making my work difficult?
Thank you for your time, guys, hope we can find a solution or something.
THE EDIT
So basically, after 4 hours of reading documents and tutorials, I figured that what I needed was setOffscreenPageLimit(int). However, it can't be set to 0, so I will have to do with a setOnPageChangeListener. Now, to figure how to refresh the fragment, and I'll be as good as new.
Alright, it works perfectly! Basically, I did this:
mViewPager.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
#Override
public void onPageSelected(int position) {
((CentralFragment)((CentralPagerAdapter) mViewPager.getAdapter()).instantiateItem(mViewPager, position)).refresh();
getActionBar().setSelectedNavigationItem(position);
}
});
Where my .refresh is:
public void refresh() {
Bundle args = getArguments();
if (args.getInt(ARG_OBJECT) == 0) {
getTicketInfo(0);
} else if (args.getInt(ARG_OBJECT) == 1) {
getTicketInfo(1);
buyTicketsHandler();
} else {
//To Handle Later
}
}
It's as simple as refreshing the page before you go to it. Why didn't I remember this before..? So, here's the reference for those who ever need this!