I am trying to use FragmentStatePagerAdapter with ViewPager to achieve a sequential slide scroll view (similar to most pdf readers). However, while running the code, the following is happening:
When the activity becomes visible, the first page is instantiated with a different (2nd) page's value. However, when scrolled to some other page and then back to page 1, the page displays default text from layout file.
Only 2nd and 2nd to last pages instantiate with the passed value (that too with values from other pages, not their own). Rest of the pages display default text from layout file.
On debugging, I noticed that the index/currentItemNumber changes when ViewPager.populate() calls ViewPager.addNewItem(). Ever more strange is the fact that setText() is called on the TextView (part of fragment layout), but text does not change from the default text.
Am I missing something?
Here is the code below:
MainActivity.java
public class MainActivity extends ActionBarActivity implements View.OnClickListener {
private ViewPager mPager;
private Button mButtonFirst;
private Button mButtonPrev;
private Button mButtonGoTo;
private Button mButtonNext;
private Button mButtonLast;
private TextView mPageCount;
private EditText mPageNumber;
private TextView mError;
private int mNumScreens;
private int mCurrScreen;
private MyPagerAdapter mMyPagerAdapter;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
setUpViews();
setUpListeners();
setUpPager();
}
private void setUpViews() {
mPager = (ViewPager) findViewById(R.id.my_pager);
// Get other view handles...
mError = (TextView) findViewById(R.id.error_details);
}
private void setUpListeners() {
// Set this class as click handler for all buttons
}
private void setUpPager() {
String[] strings = new String[] {
"1",
"2",
"3",
"4",
"5",
"6"
};
// Success!
// Set adapter and update views
mMyPagerAdapter = new MyPagerAdapter(getSupportFragmentManager(), strings);
mPager.setAdapter(mMyPagerAdapter);
mNumScreens = strings.length;
mPageCount.setText("/" + Integer.toString(mNumScreens));
mCurrScreen = -1;
GoToScreen(1);
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
int id = item.getItemId();
// Handle options
return super.onOptionsItemSelected(item);
}
#Override
public void onClick(View v) {
switch(v.getId()) {
case R.id.button_first:
GoToScreen(1);
break;
case R.id.button_prev:
GoToScreen(mCurrScreen - 1);
break;
case R.id.button_goto:
{
int screen;
boolean reset = false;
try {
screen = Integer.parseInt(mPageNumber.getText().toString());
reset = !SetToScreen(screen);
} catch (NumberFormatException e) {
e.printStackTrace();
reset = true;
}
if(reset) {
mPageNumber.setText(Integer.toString(mCurrScreen));
}
}
break;
case R.id.button_next:
GoToScreen(mCurrScreen + 1);
break;
case R.id.button_last:
GoToScreen(mNumScreens);
break;
}
}
private void GoToScreen(int screen) {
if(SetToScreen(screen)) {
mPageNumber.setText(Integer.toString(mCurrScreen));
}
}
private boolean SetToScreen(int screen) {
// Switch to a valid screen
if(screen >= 1 && screen <= mNumScreens && mCurrScreen != screen) {
mPager.setCurrentItem(screen - 1, false);
// Handle button visibility
// Update current screen
mCurrScreen = screen;
return true;
}
return false;
}
MyPagerAdapter.java
public class MyPagerAdapter extends FragmentStatePagerAdapter {
private final String[] mStrings;
public MyPagerAdapter(FragmentManager fm, String[] strings) {
super(fm);
mStrings = strings;
}
#Override
public int getCount() {
return mStrings.length;
}
#Override
public Fragment getItem(int position) {
return ScreenFragment.newInstance(mStrings[position]);
}
}
ScreenFragment.java
public class ScreenFragment extends Fragment {
private static final String ARG_SCREEN_STRING= "screen_string";
private String mScreenInfo;
private TextView mStatementLabel;
public static ScreenFragment newInstance(String screenString) {
ScreenFragment fragment = new ScreenFragment();
Bundle args = new Bundle();
args.putString(ARG_SCREEN_STRING, screenString);
fragment.setArguments(args);
return fragment;
}
public ScreenFragment() {
// Required empty public constructor
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (getArguments() != null) {
mScreenInfo = getArguments().getString(ARG_SCREEN_STRING);
}
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
return inflater.inflate(R.layout.fragment_screen, container, false);
}
#Override
public void onActivityCreated(#Nullable Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
setUpViews();
setUpFields();
}
private void setUpFields() {
mStatementLabel.setText(mScreenInfo);
}
private void setUpViews() {
mStatementLabel = (TextView) getActivity().findViewById(R.id.qnr_screen_statement);
}
}
The problem was solved when I moved calls to setUpViews() and setUpFields() to onCreateView() from onActivityCreated(), with little modifications. This is how the new onCreateView() looks like (I moved the content of the above mentioned functions here)
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View v = inflater.inflate(R.layout.fragment_screen, container, false);
mStatementLabel = (TextView) v.findViewById(R.id.qnr_screen_statement);
mStatementLabel.setText(mScreenInfo);
return v;
}
I am yet to figure out why that was causing the problem. Will update if I find anything.
Related
My app has a tablayout with a view pager. Each page has a fragment. There are 4 different fragments, three of them are basically the same for now (I'm in the development phase right now). One of them has a RecyclerView with a basic list.
I am implementing the Two-pane template in the fragment with the RecyclerView.
Everything seems to be works]ing well. While I move across the tabs the fragments are loaded fine.
But, when I rotate the device and tap on the first tab, and then go back to the one with the recyclerview, I can see the previous intance below. See attached images.
I decided to use static final instances of the fragments in the page adapter and in the recyclerview fragment.
How can I get rid of this problem?
Thanks in advance stackers!
public class MainActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
TabLayout tabLayout = findViewById(R.id.tab_layout);
tabLayout.addTab(tabLayout.newTab().setIcon(R.drawable.icon1).setText(R.string.dashboard));
tabLayout.addTab(tabLayout.newTab().setIcon(R.drawable.icon2).setText(R.string.fragment2));
tabLayout.addTab(tabLayout.newTab().setIcon(R.drawable.icon3).setText(R.string.fragmentDualPane));
tabLayout.addTab(tabLayout.newTab().setIcon(R.drawable.icon4).setText(R.string.frag4));
final ViewPager viewPager = findViewById(R.id.pager);
final PagerAdapter pageAdapter = new TabPagerAdapter(getSupportFragmentManager());
viewPager.setAdapter(pageAdapter);
tabLayout.setupWithViewPager(viewPager);
} // protected void onCreate
} // public class MainActivity
TabPagerAdapter has static final intances of the fragments
public class TabPagerAdapter extends FragmentPagerAdapter {
static final Fragment tabs[] = {new DashboardFragment(),
new Fragment2(),
new ExpensesFragment(),
new Fragment4()
};
public TabPagerAdapter(#NonNull FragmentManager fm) {
super(fm, FragmentPagerAdapter.BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT);
} // public TabPagerAdapter
#NonNull
#Override
public Fragment getItem(int position) {
if (position<tabs.length)
return tabs[position];
else
return null;
} // public Fragment getItem
#Override
public int getCount() {
return this.tabs.length;
} // public int getCount
} // class TabPagerAdapter
General fragment template for dashboard, fragment2, and fragment4
public class DashboardFragment extends Fragment {
public DashboardFragment() {
// Required empty public constructor
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
} // onCreate
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
return inflater.inflate(R.layout.fragment_dashboard, container, false);
}
}
This is the code for the fragment with the dual pane. Look that it uses the OnItemSelected implementation of fragments communications.
This fragment loads another fragment with the recyclerview.
public class ExpensesFragment extends Fragment
implements IOnItemSelected {
#Override
public void onAccountSelected(Account item) {
System.out.println("Clicking on " + item.getTitle() + ", and isTwoPane=" + isTwoPane);
} // public void onAccountSelected
public static final String TAG="Expenses Fragment";
private boolean isTwoPane = false; // Let's assume we're on a phone
private FragmentManager fragmentManager;
private View fragmentView = null;
public ExpensesFragment() {
// Required empty public constructor
} // ExpensesFragment()
public static final ExpensesListFragment lListFragment = new ExpensesListFragment();
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
} // onCreate
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
fragmentView = inflater.inflate(R.layout.fragment_expenses, container, false);
isTwoPane = fragmentView.findViewById(R.id.expensesDetailContainer) != null;
fragmentManager = getChildFragmentManager();
if (savedInstanceState==null) {
if ( !lListFragment.isAdded() ) {
fragmentManager.
beginTransaction().
add(R.id.expensesListContainer,lListFragment).
commit();
} // if ( !lListFragment.isAdded() )
} // if (savedInstanceState==null)
if ( isTwoPane ) {
fragmentManager.
beginTransaction().
replace(R.id.expensesDetailContainer,new EmptyFragment()).
commit();
} // if ( isTwoPane )
return fragmentView;
} // onCreateView
} // ExpensesFragment
And this is the fragment with the recyclerview:
public class ExpensesListFragment extends Fragment {
private IOnItemSelected mCallback;
private RecyclerView rv;
private RecyclerView.LayoutManager rvlm;
private RecyclerAdapterAccounts rva;
public ExpensesListFragment() {
// Required empty public constructor
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mCallback = (IOnItemSelected)getParentFragment();
} // onCreate
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View fragmentView = inflater.inflate(R.layout.fragment_expenses_list, container, false);
if ( isVisible() ) return fragmentView;
FragmentManager fragmentManager = getChildFragmentManager();
// Setting the recyclerview environment
rv = fragmentView.findViewById(R.id.expensesRV); // recycler view
rvlm = new LinearLayoutManager(getActivity());
rv.setLayoutManager(rvlm);
rva = new RecyclerAdapterAccounts();
rva.setCallBackFunction(mCallback);
rv.setAdapter(rva);
// Setting the floating action button and snackbar
FloatingActionButton fab = fragmentView.findViewById(R.id.fabAdd);
fab.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
Snackbar.make(view, "Load a Create Item frag", Snackbar.LENGTH_LONG)
.setAction("Action", null).show();
}
});
return fragmentView;
} // onCreateView
} // public class ExpensesListFragment
The RecyclerAdapterAccounts creates a generic set of data:
public class RecyclerAdapterAccounts extends
RecyclerView.Adapter<RecyclerAdapterAccounts.ViewHolderAccounts> {
private IOnItemSelected callBackFunction;
public IOnItemSelected getCallBackFunction() {return callBackFunction;}
public void setCallBackFunction(IOnItemSelected callBackFunction) {this.callBackFunction = callBackFunction;}
class ViewHolderAccounts extends RecyclerView.ViewHolder {
ImageView icon, isRepeating, isAlert;
TextView title, total;
public Account getAccount() {return account;}
public void setAccount(Account account) {this.account = account;}
Account account;
public ViewHolderAccounts(View itemView) {
super(itemView);
icon = itemView.findViewById(R.id.list_item_ico_account);
isRepeating = itemView.findViewById(R.id.list_item_isrepeating);
isAlert = itemView.findViewById(R.id.list_item_isalert);
title = itemView.findViewById(R.id.list_item_title_account);
total = itemView.findViewById(R.id.list_item_desc_account);
account = null; // The account needs to be set using the setter/getter method
} // ViewHolderAccounts
} // class ViewHolderAccounts
List<Account> accts = new ArrayList<Account>();
ViewGroup parent;
#NonNull
#Override
public ViewHolderAccounts onCreateViewHolder(#NonNull ViewGroup parent, int viewType) {
View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.list_item_account,parent,false);
this.parent = parent;
ViewHolderAccounts vh = new ViewHolderAccounts(v);
return vh;
} // onCreateViewHolder
#Override
public void onBindViewHolder(#NonNull ViewHolderAccounts holder, int position) {
// Look into the list the item with id=position
Optional<Account> la = accts.stream()
.filter(ac->ac.getId()==(long)position)
.findFirst();
if ( la.isPresent() ) {
int res = parent.getResources().getIdentifier(la.get().getIcon(), "drawable", "com.almonisolutions.elgddt");
holder.icon.setImageResource(res);
holder.isRepeating.setImageResource(R.drawable.automatic);
holder.isAlert.setImageResource(R.drawable.notifications);
holder.title.setText(la.get().getTitle());
holder.total.setText(la.get().getDescription());
holder.setAccount(la.get());
holder.itemView.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
if (holder.getAccount() != null) {
callBackFunction.onAccountSelected(holder.getAccount());
} // if (account != null)
} // public void onClick
});
} // if
} // onBindViewHolder
#Override
public int getItemCount() {
return accts.size();
} // getItemCount
RecyclerAdapterAccounts() {
super();
for(int i=0;i<16;i++) {
Account la = new Account();
la.setId((long) i);
la.setTitle("The item number " + i);
la.setDescription("$" + (1000*i));
switch(i%3) {
case 0: la.setIcon("imaged"); break;
case 1: la.setIcon("person_old"); break;
case 2: la.setIcon("pet"); break;
default: la.setIcon("add");
} // switch
accts.add(la);
} // for
} // RecyclerAdapterAccounts
} // class RecyclerAdapterAccounts
At first, In the ExpensesFragment I was getting an Exception that throw the message "Fragment already added". When I changed the ExpensesListFragment to static final, that error was gone.
Again, to recreate the error, you need to run in portrait mode, move through the tabs. Finish on anyone but the first one. Them rotate the device. Tap on the first tab. Then tap on the 3rd one, the one with the recyclerview. Swipe through the list and you will see it is double.
Any help will be appreciated.
Thanks in advance!!!
So I found the answer. ADM (see comment above) sent me to a previous article where part of the solution was to extend ViewPager and override instantiateItem. But I did not want to extend ViewPager.
However, in the same article was another link to this other article where there was the following explanation:
Blockquote By default, [FragmentPagerAdapter] will only preload one Fragment in front and behind the current position (although it does not destroy them unless you are using FragmentStatePagerAdapter).
So, I made TabPagerAdapter extend FragmentStatePagerAdapter instead of FragmentPageAdapter... and that was it!!
Thanks ADM for pointing to the right series of articles.
I have 4 Fragments in a ViewPager that is integrated with a TabLayout. Each of those Fragments holds a RecyclerView because I'm displaying an unknown amount of list items. The items are loaded by date, so I have two buttons that let you change days, and then the appropriate data in the list items is loaded based on the date that is set. The buttons are part of the outer activity.
Everything so far works perfectly BUT once I rotate the device the fragments don't load anything. Nothing is displayed inside the Fragments. The views in the outer activity are displayed fine though. The weird thing is that if I touch one of the buttons that changes the date, the Fragments are loaded and the data is displayed correctly. But I need everything to be displayed immediately after rotation not just when I click one of those buttons. Here is my code:
public class MainActivity extends AppCompatActivity implements DatePickerFragment.DateDialogInterface
{
private final static String COLOR_CONTROL_CHOSEN = "color_control_chosen";
private static final String DIALOG_DATE = "dialog_date";
private static final String TAG = "MainActivity";
private static final String SET_LOCATION = "set_location";
public static final String LEAGUE_POSITION = "league_position";
private Toolbar mToolbar;
private ViewPager mViewPager;
private TabLayout mTabLayout;
private ImageButton mPrevDateButton, mNextDateButton;
private TextView mDateTextView, mLeagueTextView;
private String mTodaysDate;
private Date mLastSelectedDate, mTodaysDateObj;
private ProgressBar mProgressBar;
private FragmentPagerAdapter mAdapterViewPager;
#Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mToolbar = (Toolbar) findViewById(R.id.outnix_toolbar);
mViewPager = (ViewPager) findViewById(R.id.main_activity_view_pager);
mTabLayout = (TabLayout) findViewById(R.id.main_activity_tab_layout);
mDateTextView = (TextView) findViewById(R.id.display_date_text_view);
mLeagueTextView = (TextView) findViewById(R.id.league_title_header);
mPrevDateButton = (ImageButton) findViewById(R.id.previous_date_button);
mNextDateButton = (ImageButton) findViewById(R.id.next_date_button);
mProgressBar = (ProgressBar) findViewById(R.id.loading_circle);
mProgressBar.setVisibility(View.GONE);
setTodaysDate();
mDateTextView.setText("Today");
setSupportActionBar(mToolbar);
assert getSupportActionBar() != null;
getSupportActionBar().setDisplayShowTitleEnabled(false);
NavDrawerFragment navDrawerFrag = (NavDrawerFragment) getSupportFragmentManager().findFragmentById(R.id.fragment_nav_drawer);
navDrawerFrag.setUp((DrawerLayout) findViewById(R.id.nav_drawer), mToolbar);
setUpViewPagerAdapterOnCreate();
mTabLayout.setupWithViewPager(mViewPager);
mDateTextView.setOnClickListener(new View.OnClickListener()
{
#Override
public void onClick(View v)
{
FragmentManager fm = getSupportFragmentManager();
DatePickerFragment dialog = new DatePickerFragment();
Bundle args = new Bundle();
args.putSerializable("ARG_DATE", mLastSelectedDate);
dialog.setArguments(args);
dialog.show(fm, DIALOG_DATE);
}
});
THESE TWO LISTENERS ARE WHAT DISPLAY THE DATA AFTER A ROTATION CHANGE
//////////////////////////////////////////////////////////////////
mPrevDateButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v)
{
mProgressBar.setVisibility(View.VISIBLE);
updateDate(-1);
setupViewPagerAdapter(getViewPagerPos());
}
});
mNextDateButton.setOnClickListener(new View.OnClickListener()
{
#Override
public void onClick(View v)
{
mProgressBar.setVisibility(View.VISIBLE);
updateDate(1);
setupViewPagerAdapter(getViewPagerPos());
}
});
}
////////////////////////////////////////////////////////////////////
/* #Override
protected void onResume()
{
super.onResume();
setupViewPagerAdapter(getViewPagerPos());
}*/
private void setUpViewPagerAdapterOnCreate() //only called when opened from LauncherActivity
{
setupViewPagerAdapter(0);
int touchColorPixel = getIntent().getIntExtra(COLOR_CONTROL_CHOSEN, ContextCompat.getColor(this, R.color.blue));
if(touchColorPixel == ContextCompat.getColor(this, R.color.orange))
mViewPager.setCurrentItem(0);
else if(touchColorPixel == ContextCompat.getColor(this, R.color.blue))
mViewPager.setCurrentItem(1);
else
mViewPager.setCurrentItem(3);
}
private void setupViewPagerAdapter(int currentPos)
{
mAdapterViewPager = new MainPagerAdapter(getSupportFragmentManager());
mViewPager.setAdapter(mAdapterViewPager);
mViewPager.setOffscreenPageLimit(4);
mViewPager.setCurrentItem(currentPos);
}
#Override
protected void onSaveInstanceState(Bundle outState)
{
super.onSaveInstanceState(outState);
outState.putSerializable(DIALOG_DATE, mLastSelectedDate); //save the last date selected (or last date displayed) on rotation change.
}
#Override
protected void onRestoreInstanceState(Bundle savedInstanceState)
{
super.onRestoreInstanceState(savedInstanceState);
setDateFromDialog((Date) savedInstanceState.getSerializable(DIALOG_DATE)); //restore the last date selected to the new rotation change
}
public ProgressBar getProgressBar()
{
return mProgressBar;
}
#Override
public void setDateFromDialog(Date date)
{
String newDate = getFormattedDate(date);
updateTodaysDate();
mLastSelectedDate = date;
setupViewPagerAdapter(getViewPagerPos());
if(newDate.equals(mTodaysDate))
mDateTextView.setText("Today");
else
mDateTextView.setText(newDate);
}
private int getViewPagerPos()
{
return mViewPager.getCurrentItem();
}
}
The 2 buttons mPrevDateButton and mNextDateButtonare the buttons that when clicked "fix" the problem. Inside their click listeners, the updateDate() method is only doing stuff related to a TextView object and is why I didn't include the definitions (I'm trying to keep the post as short as possible). So I know for sure it has something to do with my setupViewPagerAdapter() method. I've tried adding this method in onCreate() and onResume() but the Fragments still stay blank.
Here is my ViewPager adapter code:
public class MainPagerAdapter extends FragmentPagerAdapter
{
private final String[] mFragmentTitleList = {"My Games", "All Games", "All Places", "My Places"}; //tab title names
private final static int NUM_FRAGMENTS = 4;
public MainPagerAdapter(FragmentManager fm)
{
super(fm);
}
#Override
public Fragment getItem(int position)
{
switch(position)
{
case 0:
return MyGamesFragment.newInstance();
case 1:
return AllGamesFragment.newInstance();
case 2:
return AllPlacesFragment.newInstance();
case 3:
return MyPlacesFragment.newInstance();
default:
return null;
}
}
#Override
public int getCount()
{
return NUM_FRAGMENTS;
}
#Override
public CharSequence getPageTitle(int position)
{
return mFragmentTitleList[position];
}
}
Here is one of the 4 fragments. They pretty much all have similar design.
public class AllGamesFragment extends Fragment
{
private SwipeRefreshLayout mSwipeRefreshLayout;
private RecyclerView mAllGamesRecyclerView;
private GameAdapter mGameAdapter;
private List<Game> mGameList = new ArrayList<>();
private MainActivity mMainActivity; //keeps a reference to MainActivity to access public methods
public static AllGamesFragment newInstance()
{
return new AllGamesFragment();
}
#Override
public void onAttach(Context context)
{
super.onAttach(context);
mMainActivity = (MainActivity) context;
}
#Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setRetainInstance(true);
mMainActivity.getProgressBar().setVisibility(View.VISIBLE);
}
#Nullable
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
{
View view = inflater.inflate(R.layout.recycler_view_all_games, container, false);
mAllGamesRecyclerView = (RecyclerView) view.findViewById(R.id.all_games_recycler_view);
mAllGamesRecyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));
mSwipeRefreshLayout = (SwipeRefreshLayout) view.findViewById(R.id.swipe_refresh);
mSwipeRefreshLayout.setOnRefreshListener(new SwipeRefreshLayout.OnRefreshListener()
{
#Override
public void onRefresh()
{
getGamesData();
mSwipeRefreshLayout.setRefreshing(false);
}
});
return view;
}
#Override
public void onResume()
{
super.onResume();
getGamesData();
}
private void setupAdapter()
{
if(isAdded())
{
mGameAdapter = new GameAdapter(mGameList);
mAllGamesRecyclerView.setAdapter(mGameAdapter);
}
}
private void getGamesData()
{
new GetDataTask(mMainActivity.getLastSelectedDate()).execute();
}
private class GetDataTask extends Scraper.GameDataTask
{
GetDataTask(Date date)
{
super(date, getActivity());
}
#Override
protected void onPostExecute(List<Game> games)
{
mGameList = games;
setupAdapter();
mMainActivity.getProgressBar().setVisibility(View.GONE);
}
}
private class GameAdapter extends RecyclerView.Adapter<GameHolder>
{
private List<Game> mGames;
public GameAdapter(List<Game> games)
{
mGames = games;
}
#Override
public GameHolder onCreateViewHolder(ViewGroup parent, int viewType)
{
LayoutInflater inflater = LayoutInflater.from(getActivity());
View view = inflater.inflate(R.layout.list_game_item, parent, false);
return new GameHolder(view, getActivity());
}
#Override
public void onBindViewHolder(GameHolder holder, int position)
{
holder.bindGameData(mGames.get(position));
}
#Override
public int getItemCount()
{
return mGames.size();
}
}
I've looked at so many posts on here, changed my code many times and I still can't get it to work. I'm just baffled that it "fixes" when I click one of the date buttons. If you would like me to post more code of something let me know. Sorry for the long post but I feel the context is needed. I really appreciate any help!
I figured it out! I had to switch to a FragmentStatePagerAdapter rather than use a FragmentPagerAdapter. I believe it has something to do with the Fragments being destroyed and recreated again.
I also read that another way would be to wrap the ViewPager in a Fragment and when you create its adapter you use getChildFragmentManager() rather than getSupportFragmentManager() like this:
mAdapterViewPager = new MyPagerAdapter(getChildFragmentManager());
I didn't want to have to add an entire Fragment around my ViewPager just to fix this issue so I switched to using FragmentStatePagerAdapter and it worked! Hope this helps someone else out there.
Making viewPager adapter extends FragmentStatePagerAdapter and not FragmentPagerAdapter should solve the problem.
I have 3 fragments in a ViewPager Activity. All 3 fragments have input fields. Here I am trying to pass first two fragments data to third fragment. I read few posts here and most of them suggested to use interfaces(i.e. to pass data through parent activity)
I have also gone through this link
http://developer.android.com/training/basics/fragments/communicating.html
Interface: using interfaces is good approach when we are sending data through some user event. Here I am trying to send data without any user event. Hence I thought of onPause() since onPause() is always called. But ViewPager functions differently. When a fragment is loaded,the adjacent fragments are also loaded. I would be successful to pass data between 1st fragment to 3rd fragment. But 2nd fragment's onPause() wont be called unless I am navigating to some fragment that is not adjacent to it(which in my case is not there)
Setter/Getters:I have read in few posts people saying not to use setter/getters(I still havent understood the reason yet) Are getters and setters poor design? Contradictory advice seen
Bundle: I havent considered this yet. Since I am again confused here how would I pass data using bundle.(inside which method should I send data? and how?)
Sorry if my question sounds dumb.I am trying to understand fragments and i would like to know best way to pass data between fragments in viewpager.
Thank You in advance.
TabPAgerAdapter -- >
package com.jbandroid.model;
import com.jbandroid.fragment.LocationInfoFragment;
import com.jbandroid.fragment.PersonalInfoFragment;
import com.jbandroid.fragment.PostInfoFragment;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
public class TabsPagerAdapter extends FragmentPagerAdapter {
public TabsPagerAdapter(FragmentManager fm){
super(fm);
}
#Override
public Fragment getItem(int index) {
switch(index) {
case 0 : //PostInfoFragment
return new PostInfoFragment();
case 1 : //LocationInfoFragment
return new LocationInfoFragment();
case 2 : //PersonalInfoFragment
return new PersonalInfoFragment();
}
return null;
}
#Override
public int getCount() {
// get item count - equal to number of tabs
return 3;
}
}
ViewPagerActivity -- >
package com.jbandroid;
public class SubmitPostActivity extends FragmentActivity implements ActionBar.TabListener,PostInfoFragment.setPostInfo,LocationInfoFragment.setLocationInfo{
private ViewPager viewpager;
private ActionBar actionBar;
private TabsPagerAdapter mAdapter;
FragmentManager manager;
PersonalInfoFragment frag;
List<String> location;
/*private MenuItem myActionMenuItem;
private Button myActionButton;*/
//Tab titles
private String[] tabs = {"Post Info" , "Location Info" , "Personal Info" };
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.action_submit_post);
viewpager = (ViewPager) findViewById(R.id.pager);
actionBar = getActionBar();
manager = getSupportFragmentManager();
mAdapter = new TabsPagerAdapter(getSupportFragmentManager());
//viewpager.setOffscreenPageLimit(2);
viewpager.setAdapter(mAdapter);
//actionBar.setHomeButtonEnabled(false);
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
for (String tab : tabs){
actionBar.addTab(actionBar.newTab().setText(tab).setTabListener(this));
}
if(savedInstanceState != null){
actionBar.setSelectedNavigationItem( savedInstanceState.getInt("tab",0));
}
/**
* on swiping the viewpager make respective tab selected
* */
viewpager.setOnPageChangeListener(new OnPageChangeListener() {
#Override
public void onPageSelected(int position) {
// on changing the page
// make respected tab selected
actionBar.setSelectedNavigationItem(position);
}
#Override
public void onPageScrolled(int arg0, float arg1, int arg2) {
}
#Override
public void onPageScrollStateChanged(int arg0) {
}
});
}
#Override
protected void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
outState.putInt("tab", getActionBar().getSelectedNavigationIndex());
}
#Override
public void onTabReselected(Tab tab, FragmentTransaction ft) {
}
#Override
public void onTabSelected(Tab tab, FragmentTransaction ft) {
// on tab selected
// show respected fragment view
viewpager.setCurrentItem(tab.getPosition());
}
#Override
public void onTabUnselected(Tab tab, FragmentTransaction ft) {
}
#Override
public void pass_location_details(List<String> location) {
frag = (PersonalInfoFragment) manager.findFragmentByTag("android:switcher:" + viewpager.getId() + ":" + 2);
frag.get_post_location_details(location);
Log.d("submitarea", location.get(0));
}
#Override
public void pass_post_details(List<String> post_details,ArrayList<CustomGallery> selected) {
frag = (PersonalInfoFragment) manager.findFragmentByTag("android:switcher:" + viewpager.getId() + ":" + 2);
frag.get_post_details(post_details,selected);
Log.d("submitpostinfo","hello"+ post_details.get(5));
}
}
1st Fragment(Here I am trying to pass data using interface in onPause()-->
package com.jbandroid.fragment;
public class PostInfoFragment extends Fragment {
private MenuItem myActionMenuItem;
private Button myActionButton;
private ActionBar actionBar;
private String post_title, post_desc,post_status;
private EditText submit_post_title, submit_post_desc;
private Resources res;
setPostInfo info;
List<String> post_details;
//RelativeLayout rel_submit_post_start_date,rel_submit_post_end_date;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_post_info,
container, false);
/*if(!imageLoader.isInited()){*/
initImageLoader();
/*}*/
//handler = new Handler();
submit_post_title = (EditText) rootView
.findViewById(R.id.submit_post_title);
submit_post_desc = (EditText) rootView
.findViewById(R.id.submit_post_description);
actionBar = getActivity().getActionBar();
setHasOptionsMenu(true);
post_details = new ArrayList<String>();
res = getResources();
setListeners();
Log.d("postinfo_oncreate view", "postinfo_oncreate view");
return rootView;
}
//interface to pass data to activity and then to PersonalInfoFragment
public interface setPostInfo {
//public void pass_post_details(List<String> post_details);
public void pass_post_details(List<String> post_details,ArrayList<CustomGallery> selected);
}
//making sure if the parent activity has implemented interface
#Override
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 {
info = (setPostInfo) activity;
} catch (ClassCastException e) {
throw new ClassCastException(activity.toString()
+ "must implemet setPostInfo");
}
Log.d("postinfo_onattach", "postinfo_onattach");
}
//passing form inputs to personalinfofragments
#Override
public void onPause() {
super.onPause();
// setFormInputs();
passFormInputs(); ---> passing in onPause() This executes successfully
Log.d("postinfo_onPAuse", "postinfo_onPause");
}
//method to pass data to personalinfofragment
private void passFormInputs() {
try {
post_title = submit_post_title.getText().toString();
post_desc = submit_post_desc.getText().toString();
post_status = "1";
if(post_title != null && post_title.length() > 0
&& post_desc != null && post_desc.length() > 0
&& post_status != null && post_status.length() > 0
){
post_details.add(post_title);
post_details.add(post_desc);
post_details.add(post_status);
info.pass_post_details(post_details,dataT); -->here I am passing values via
}else{ activity to 3rd fragment
Log.d("post_info", "values are null");
}
} catch (Exception e) {
e.printStackTrace();
}
}
//setting next button on actionbar
public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
super.onCreateOptionsMenu(menu, inflater);
// Inflate the menu items for use in the action bar
inflater.inflate(R.menu.mymenu, menu);
// Here we get the action view we defined
myActionMenuItem = menu.findItem(R.id.my_action);
View actionView = myActionMenuItem.getActionView();
// We then get the button view that is part of the action view
if (actionView != null) {
myActionButton = (Button) actionView.findViewById(R.id.action_btn);
myActionButton.setText(R.string.txt_next);
if (myActionButton != null) {
// We set a listener that will be called when the return/enter
// key is pressed
myActionButton.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
actionBar.setSelectedNavigationItem(1);
}
});
}
}
}
}
2nd Fragment-->
package com.jbandroid.fragment;
public class LocationInfoFragment extends Fragment implements OnClickListener {
private MenuItem myActionMenuItem;
private Button myActionButton;
private ActionBar actionBar;
Dialog dialog;
private EditText submit_post_exact_location;
private TextView selected_country, selected_city,
submit_post_exact_time;
String country, city, exact_location, exact_time;
setLocationInfo info;
List<String> location;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_location_info,
container, false);
actionBar = getActivity().getActionBar();
setHasOptionsMenu(true);
submit_post_exact_location = (EditText) rootView
.findViewById(R.id.submit_post_exact_location);
submit_post_exact_time = (TextView) rootView
.findViewById(R.id.submit_post_exact_time);
selected_country = (TextView) rootView
.findViewById(R.id.selected_country);
selected_city = (TextView) rootView.findViewById(R.id.selected_city);
location = new ArrayList<String>();
setListeners();
return rootView;
}
public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
super.onCreateOptionsMenu(menu, inflater);
// Inflate the menu items for use in the action bar
inflater.inflate(R.menu.mymenu, menu);
// Here we get the action view we defined
myActionMenuItem = menu.findItem(R.id.my_action);
View actionView = myActionMenuItem.getActionView();
// We then get the button view that is part of the action view
if (actionView != null) {
myActionButton = (Button) actionView.findViewById(R.id.action_btn);
myActionButton.setText(R.string.txt_next);
if (myActionButton != null) {
// We set a listener that will be called when the return/enter
// key is pressed
myActionButton.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
actionBar.setSelectedNavigationItem(2);
}
});
}
}
}
public interface setLocationInfo {
public void pass_location_details(List<String> location);
}
#Override
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 {
info = (setLocationInfo) activity;
} catch (ClassCastException e) {
throw new ClassCastException(activity.toString()
+ "must implement setLocationInfo");
}
}
#Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
//setLocationDetails();
}
#Override
public void onPause() {
super.onPause();
setLocationDetails(); ----> doesnt executes since onPause isnt called when I navigate to 3rd fragment as it is an adjacent fragment of this fragment
// Log.d("location : onPause", area);
}
private void setLocationDetails() {
try {
exact_location = submit_post_exact_location.getText().toString();
exact_time = submit_post_exact_time.getText().toString();
country = selected_country.getText().toString();
city = selected_city.getText().toString();
if (country != null && country.length() > 0
&& !country.equalsIgnoreCase("select") && city != null
&& city.length() > 0 && !city.equalsIgnoreCase("select")
&& exact_location != null && exact_location.length() > 0
&& exact_time != null && exact_time.length() > 0) {
location.add(country);
location.add(city);
location.add(exact_location);
location.add(exact_time);
info.pass_location_details(location);
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
In my 3rd Fragment I am trying to get this values
public class PersonalInfoFragment extends Fragment {
List<String> post_details;
List<String> location;
Button submit;
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_personal_info,
container, false);
submit = (Button)rootView.findViewById(R.id.submitBtn);
submit.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
//performing operations with the values obtained
setPostItems();
insertintodb();
}
});
return rootView;
}
public void get_post_details(List<String> post_details,
ArrayList<CustomGallery> selected) { -->receiving values from
this.post_details = post_details; 1st fragment
this.selected = selected;
Log.d("personalfrag(postinfo)", "hello" + post_details.get(5));
}
//receiving values from 2nd fragment
public void get_post_location_details(List<String> location) {
this.location = location;
Log.d("personalfrag(locationinfo)", "hello" + location.get(0));
}
}
Okay, I Had same issue to pass data(not just string) between two tabs in a ViewPager. So here is what i did.
I Use interfaces to communicate between the different components.
The data passes this way:
Tab 1 -> Activity -> VewPageAdapter -> Tab 2
In Tab 1
create an interface.
OnCartsDataListener mOncarOnCartsDataListener;
public interface OnCartsDataListener {
public void onCartsDataReceived(ArrayList<CartsViewModel> cartsViewModels);
}
#Override
public void onAttach(Activity activity) {
super.onAttach(activity);
try {
mOncarOnCartsDataListener = (OnCartsDataListener)activity;
}catch (ClassCastException e){
}
}
// now call mOncarOnCartsDataListener.onCartsDataReceived(data) when you have the data
In Activity
Implement the interface and override the method
ViewPagerAdapter adapter;
adapter = new ViewPagerAdapter(getSupportFragmentManager(), Titles, Numboftabs);
#Override
public void onCartsDataReceived(ArrayList<CartsViewModel> cartsViewModels) {
Log.d(TAG, "data received to Activity... send to view pager");
adapter.onCartsDataReceived(cartsViewModels);
}
3.IN ViewPagerAdapter
Also implements the interface and override the method
#Override
public void onCartsDataReceived(ArrayList<CartsViewModel> cartsViewModels) {
Log.d(TAG, "data received to view pager... sending to tab 2");
if(tab2!=null){
tab2.onCartsDataReceived(cartsViewModels);
}else{
Log.d(TAG, "tab2 is null");
}
}
Finally tab 2
Also implements the interface and override the method
#Override
public void onCartsDataReceived(ArrayList<CartsViewModel> cartsViewModels) {
Log.d(TAG, "Finally ! received data to tab 2");
if(cartsViewModels!=null){
for(CartsViewModel cart : cartsViewModels){
Log.d(TAG,"got it :"+cart.getCartName());
}
}
}
Since AndroidX, you can create a ViewModel and share data between Activity and all fragments within ViewPager
Read here how to
Can you do something like this? First create any data structure like Arraylist in your main activity. Then send a reference of that data model to your fragments. Now update that data when, on change your text fields. By doing this all the fragment can see updated values. So fragments can update this data itself and we don't need to send that data since it is already shared. I'll explain this using your example. Try to improve this. You can maintain fragment specific data model then each fragment can access data with the knowledge of that data owner.
TabsPagerAdapter.java
public class TabsPagerAdapter extends FragmentPagerAdapter {
public TabsPagerAdapter(FragmentManager fm,SubmitPostActivity activity){
super(fm);
}
#Override
public Fragment getItem(int index) {
switch(index) {
case 0 : //PostInfoFragment
return new PostInfoFragment(0,activity);
case 1 : //LocationInfoFragment
return new LocationInfoFragment(1,activity);
case 2 : //PersonalInfoFragment
return new PersonalInfoFragment(2,activity);
}
return null;
}
#Override
public int getCount() {
return 3;
}
}
ViewPagerActivity -- >
package com.jbandroid;
public class SubmitPostActivity extends FragmentActivity implements ActionBar.TabListener,LocationInfoFragment.setLocationInfo{
private ViewPager viewpager;
private ActionBar actionBar;
private TabsPagerAdapter mAdapter;
FragmentManager manager;
PersonalInfoFragment frag;
List<String> location;
/*private MenuItem myActionMenuItem;
private Button myActionButton;*/
//Tab titles
private String[] tabs = {"Post Info" , "Location Info" , "Personal Info" };
public List<String> dataModel = new ArrayList<String>();
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.action_submit_post);
viewpager = (ViewPager) findViewById(R.id.pager);
actionBar = getActionBar();
manager = getSupportFragmentManager();
mAdapter = new TabsPagerAdapter(getSupportFragmentManager(),this);
//viewpager.setOffscreenPageLimit(2);
viewpager.setAdapter(mAdapter);
//actionBar.setHomeButtonEnabled(false);
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
for (String tab : tabs){
actionBar.addTab(actionBar.newTab().setText(tab).setTabListener(this));
}
if(savedInstanceState != null){
actionBar.setSelectedNavigationItem( savedInstanceState.getInt("tab",0));
}
}
}
1st Fragment =>
public class PostInfoFragment extends Fragment {
private MenuItem myActionMenuItem;
private Button myActionButton;
private ActionBar actionBar;
private String post_title, post_desc,post_status;
private EditText submit_post_title, submit_post_desc;
private int position;
private Resources res;
SubmitPostActivity callingActivity;
List<String> post_details;
public PostInfoFragment(int position,SubmitPostActivity callingActivity )
{
this.callingActivity = callingActivity;
this.position = position;
}
//RelativeLayout rel_submit_post_start_date,rel_submit_post_end_date;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_post_info,
container, false);
/*if(!imageLoader.isInited()){*/
initImageLoader();
/*}*/
//handler = new Handler();
submit_post_title = (EditText) rootView
.findViewById(R.id.submit_post_title);
submit_post_desc = (EditText) rootView
.findViewById(R.id.submit_post_description);
actionBar = getActivity().getActionBar();
setHasOptionsMenu(true);
post_details = new ArrayList<String>();
res = getResources();
setListeners();
Log.d("postinfo_oncreate view", "postinfo_oncreate view");
//this is editText onchange listner do the same for submit_post_desc as well
submit_post_title.addTextChangedListener( new TextWatcher()
{
#Override
public void onTextChanged( CharSequence s, int start, int before, int count )
{
}
#Override
public void beforeTextChanged( CharSequence s, int start, int count, int after )
{
}
#Override
public void afterTextChanged( Editable s )
{
if( callingActivity != null )
{
//use this.position in order to update relevant data
List<String> post_details = callingActivity.dataModel;
if( post_details == null )
{
post_details = new ArrayList<String>();
}
post_details.add(s.toString());
}
}
} );
return rootView;
}
//making sure if the parent activity has implemented interface
#Override
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 {
callingActivity = (SubmitPostActivity) activity;
} catch (ClassCastException e) {
throw new ClassCastException(activity.toString()
+ "must implemet setPostInfo");
}
Log.d("postinfo_onattach", "postinfo_onattach");
}
}
Please not that this may not compile as it is. Try to get the concept.
My app uses a ViewPager in portrait mode and a dual-fragment layout in landscape.
I am trying to kick off an AsyncTask, that is in the Fragment, from Activity. The AsyncTask is normally started from a menu item in the Actionbar, but I have a need to start it programatically from the Activity.
The menu item is an ImageView and I'm animating it while the AsyncTask is running. The code I have works fine in the dual-fragment landscape view, but I'm getting a NullPointerException on the menu item when in portrait mode.
Activity
public class Main extends SherlockFragmentActivity
{
private static List<Integer> mIds;
private static SparseArray<Fragment> mPageReferenceMap = new SparseArray<Fragment>();
#Override
public void onCreate(final Bundle icicle)
{
super.onCreate(icicle);
setContentView(R.layout.main);
mViewPager = (ViewPager)findViewById(R.id.viewpager); //view pager exists, so we are using the portait layout
if (mViewPager != null)
{
mIds = new ArrayList<Integer>();
mIds.add(0);
mIds.add(1);
mIds.add(2);
}
else //in landscape
{
ListFragment lf = (ListFragment)getSupportFragmentManager().findFragmentById(R.id.fragmentList);
if (lf == null)
lf = new ListFragment();
DetailFragment df = (DetailFragment)getSupportFragmentManager().findFragmentById(R.id.fragmentDetail);
if (df == null)
{
df = new DetailFragment();
df.setArguments(getIntent().getExtras());
}
getSupportFragmentManager().beginTransaction().add(R.id.fragmentList, lf).commit();
getSupportFragmentManager().beginTransaction().add(R.id.fragmentDetail, df).commit();
}
final MyFragmentPagerAdapter fpa = (MyFragmentPagerAdapter)mViewPager.getAdapter();
ListFragment lf2 = (ListFragment)fpa.getFragment(0);
//this works if I use:
//(ListFragment)getSupportFragmentManager().findFragmentById(R.id.fragmentList);
lf2.RunTask();
}
private static class MyFragmentPagerAdapter extends FragmentStatePagerAdapter {
public MyFragmentPagerAdapter(FragmentManager fm) {
super(fm);
}
#Override
public Fragment getItem(int index) {
if (index == 0)
{
ListFragment lf = ListFragment.newInstance();
mPageReferenceMap.put(index, lf);
return lf;
}
else
{
DetailFragment df = DetailFragment.newInstance(mIds.get(index-1));
mPageReferenceMap.put(index, df);
return df;
}
public Fragment getFragment(int key) {
return mPageReferenceMap.get(key);
}
public void destroyItem(View container, int position, Object object) {
super.destroyItem(container, position, object);
mPageReferenceMap.remove(position);
}
#Override
public int getCount() {
return 4;
}
}
}
Fragment
public class ListingFragment extends SherlockListFragment
{
private MenuItem refreshItem;
public static ListingFragment newInstance() {
ListingFragment lf = new ListingFragment();
return lf;
}
#Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setHasOptionsMenu(true);
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
return inflater.inflate(R.layout.listing_layout, container, false);
}
private void StartAnimation() {
final LayoutInflater inflater = (LayoutInflater)getActivity().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
final ImageView ivRefresh = (ImageView)inflater.inflate(R.layout.refresh_view, null);
final Animation rotation = AnimationUtils.loadAnimation(getActivity(), R.anim.refresh);
ivRefresh.startAnimation(rotation);
//this is null
refreshItem.setActionView(ivRefresh);
}
public void StopAnimation()
{
if (refreshItem != null && refreshItem.getActionView() != null)
{
refreshItem.getActionView().clearAnimation();
refreshItem.setActionView(null);
}
}
public void RunTask()
{
new GetItems().execute();
}
private class GetItems extends AsyncTask<Void, Void, Void>
{
#Override
protected void onPreExecute()
{
StartAnimation();
}
#Override
protected Void doInBackground(Void... unused)
{
...
}
protected void onPostExecute(final Void unused)
{
StopAnimation();
}
}
#Override
public void onCreateOptionsMenu(final Menu menu, final MenuInflater inflater) {
inflater.inflate(R.menu.keyword_menu, menu);
refreshItem = menu.findItem(R.id.get);
super.onCreateOptionsMenu(menu, inflater);
}
#Override
public boolean onOptionsItemSelected(final MenuItem item)
{
if (item.getItemId() == R.id.get) {
gi = new GetItems(getActivity(), null);
gi.execute();
return true;
} else {
return super.onOptionsItemSelected(item);
}
}
}
I think following link provide you with your answer on how to avoid the nullpointer exception.
Fragment's instances may be recreated by the system at any time, that's why it's not easy to "hold a reference to them". You have to use the fragmentmanager.
adapter instance gone in fragment with listview
In order to focus on the problem I ended with the following test app which contains one activity and two fragments which are connected to FragmentStatePagerAdapter / ViewPager. I also have Runnable and Handler printing getView() every second (in production version it is used to show time in fragment's TextView).
When I start app, getView() shows maybe few nulls (I suppose due to fragment life cycle) and then I get some non nulls which is ok...
But if I suspend and wake up my device LogCat shows nulls all the time.
public class MainActivity extends SherlockFragmentActivity {
private SectionsPagerAdapter sectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());
private Fragment myFragment1 = new MyFragment1();
private Fragment myFragment2 = new MyFragment2();
private Handler handler = new Handler();
private Runnable timer;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ViewPager viewPager = (ViewPager) findViewById(R.id.pager);
viewPager.setAdapter(sectionsPagerAdapter);
}
#Override
protected void onResume() {
super.onResume();
timer = new Runnable() {
public void run() {
System.out.println(myFragment1.getView()); // HERE getView gives null
handler.postDelayed(this, 1000); // refreshing every 1 sec
}
};
handler.removeCallbacks(timer);
handler.postDelayed(timer, 0);
}
#Override
protected void onPause() {
super.onPause();
handler.removeCallbacks(timer);
}
public class SectionsPagerAdapter extends FragmentStatePagerAdapter {
public SectionsPagerAdapter(FragmentManager fm) {
super(fm);
}
#Override
public Fragment getItem(int position) {
Fragment fragment;
if (position == 0) {
fragment = myFragment1;
} else {
fragment = myFragment2;
}
return fragment;
}
#Override
public int getCount() {
return 2;
}
#Override
public CharSequence getPageTitle(int position) {
switch (position) {
case 0:
return "Fragment 1";
case 1:
return "Fragment 2";
}
return null;
}
}
}
My fragment
public class MyFragment1 extends SherlockFragment {
private TextView textView2;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
return inflater.inflate(R.layout.fragment_layout, container, false);
}
#Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
((TextView) getView().findViewById(R.id.textView1)).setText("Fragment 1");
textView2 = (TextView) this.getView().findViewById(R.id.textView2);
}
public void updateTextView2(String text) {
textView2.setText(text);
}
Ok I solved my problem simply by adding:
if (myFragment1.getView() == null) {
viewPager.setAdapter(sectionsPagerAdapter);
}
I'm not happy about this solution but it works...