On my screen I have 2 containers - left for 3 fragments in view pager, right for single fragment. From this on the right I increment some temp variable and through inteface I pass this variable to fragments. I switch fragments in view pager and everything seems to act all right. But, there are two problems.
First is that when I start my app and try to actualize temp variable in third fragment in view pager there is NPE. And of course it should be, because at this point third fragment is not initialized (view pager only initialize actual fragment and the ones on his sides, to be able to slide between fragments). How can I initialize third fragment at the begining? I thought I can store data temporarily in second fragment and when second is initialized I can pass the data to third, but it seems not good solution.
Second question is when I initialize all fragments by sliding on it and I come back to first fragment view of third is gone (but it's initialized). When I actualize temp variable and slide to third fragment I can see this variable but after +- one second. Can someone explain me why? Without this knowledge I can't solve this problem :/
Here you have some code of mine:
public class ThirdFragment extends Fragment {
View thisView;
TextView tempTextView;
String iterator;
public AchievFragment() {
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
iterator = "Start";
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
thisView = inflater.inflate(R.layout.fragment_third, container, false);
tempTextView= (TextView) thisView.findViewById(R.id.tempTextView);
tempTextView.setText(iterator);
return thisView;
}
public void getVariable(String text) {
iterator = text;
tempTextView.setText(iterator);
}
So it's third fragment class. At the beginning I initialize iterator (it's this temp variable) as a global variable to avoid npe after initializing fragments. And in onCreateView i set the view of TextView to value of this variable. Should work fine, but this +-1 sec offset makes me sad.
I think this sample of code should be enough, the rest is standard I suppose, but if anyone will be really interested I'll past the rest.
I really hope you will understand what I just wrote.
Here is the main (hosting) activity code:
public class MainActivity extends AppCompatActivity implements OnFragmentInteractionListener {
ViewPager mViewPager;
FragmentPageAdapter ft;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mViewPager = (ViewPager) findViewById(R.id.pager_container);
ft = new FragmentPageAdapter(getSupportFragmentManager());
mViewPager.setAdapter(ft);
FragmentManager fm = getFragmentManager();
FragmentTransaction ft = fm.beginTransaction();
RightFragment gameFragment = new RightFragment();
ft.replace(R.id.rightFragment_container, rightFragment,"RightFragment");
ft.commit();
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
return super.onOptionsItemSelected(item);
}
#Override
public void OnUpdateFirst(String text) {
FirstFragment firstFragment = (FirstFragment) ft.instantiateItem(mViewPager,0);
firstFragment.getVariable(text);
}
#Override
public void OnUpdateSecond(String text) {
SecondFragment secondFragment = (SecondFragment) ft.instantiateItem(mViewPager,1);
secondFragment.getVariable(text);
}
#Override
public void OnUpdateThird(String text) {
ThirdFragment thirdFragment = (ThirdFragment) ft.instantiateItem(mViewPager,2);
thirdFragment.getVariable(text);
}
}
Fragment Page Adapter code:
public class FragmentPageAdapter extends FragmentPagerAdapter {
public FragmentPageAdapter(FragmentManager fm) {
super(fm);
}
#Override
public Fragment getItem(int arg0) {
switch (arg0)
{
case 0:
return new FirstFragment();
case 1:
return new SecondFragment();
case 2:
return new ThirdFragment();
default:
break;
}
return null;
}
#Override
public int getCount() {
return 3;
}
Expection when I try to actualize variable on third fragment before I initialize it (in example right after I start app)
06-14 16:47:25.621 27246-27246/com.package.app E/AndroidRuntime﹕ FATAL EXCEPTION: main
java.lang.NullPointerException
at com.package.app.ThirdFragment.getVariable(ThirdFragment.java:37)
at com.package.app.MainActivity.OnUpdateThird(MainActivity.java:59)
at com.package.app.RightFragment$3.onClick(RightFragment.java:57)
at android.view.View.performClick(View.java:4101)
at android.view.View$PerformClick.run(View.java:17082)
at android.os.Handler.handleCallback(Handler.java:615)
at android.os.Handler.dispatchMessage(Handler.java:92)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:4940)
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:798)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:565)
at dalvik.system.NativeStart.main(Native Method)
As to your first question you can call setOffscreenPageLimit(2) method on your ViewPager right after initializing it. By default it is set to 1 that means that adapter creates one page which is on the screen right now and one that is next.
Related
I'm pretty new to Android.
This is my scenario: I have a simple app with 3 tabs. In each tab i want to use one or more fragments. This is the situation:
Tab 1:
Fragment A
Tab 2:
Fragment B
Fragment C
Fragment D
Tab 3:
Fragment E
Fragment F
In "Tab 1" I have no issue. All works pretty good. Issues arise when I need to move in "Tab 2" and "Tab 3".
In Tab 2 I have to propagate some parameters from "Fragment B" to "Fragment C" and from "Fragment C" to "Fragment D".
Then it can happen that when user clicks on some button in "Fragment D" I have to pass to "Tab 3" and I have to propagate some parameters from "Fragment D" to "Fragment E".
In my main Activity for Tab handling I'm using these components:
android.support.design.widget.TabLayout
android.support.v4.view.ViewPager
android.support.v4.app.FragmentStatePagerAdapter (I created a custom
class)
android.support.design.widget.TabLayout.OnTabSelectedListener (I created a custom class)
My very simple FragmentStatePagerAdapter extension is:
public class MyOwnPageAdapter extends FragmentStatePagerAdapter {
private int numeroTab;
public MyOwnPageAdapter(FragmentManager fm, int numeroTab) {
super(fm);
this.numeroTab = numeroTab;
}
#Override
public Fragment getItem(int position) {
switch (position){
case 0:
return new FragmentA() ;
case 1:
return new FragmentB() ;
case 2:
return new FragmentC() ;
default:
return null;
}
}
#Override
public int getCount() {
return numeroTab;
}
}
My very simple TabLayout.OnTabSelectedListener extension is:
public class TabSelectedListener implements TabLayout.OnTabSelectedListener {
private ViewPager viewPager;
public TabSelectedListener(ViewPager viewPager){
this.viewPager = viewPager;
}
#Override
public void onTabSelected(TabLayout.Tab tab) {
viewPager.setCurrentItem(tab.getPosition());
}
#Override
public void onTabUnselected(TabLayout.Tab tab) {
}
#Override
public void onTabReselected(TabLayout.Tab tab) {
}
}
I'm able in switching fragments inside tabs that is in Tab 2 i can switch from Fragment B to Fragment C and so on. I'm having issues in passing parameters between fragments and above all from Fragment D in Tab 2 to Fragment E in Tab 3
In my Fragments implementation byt using the android.support.v4.app.FragmentManager I can add and remove views (e.g. fragments) by doing something like this:
mFragmentManager.beginTransaction().add(rootView.getId(),mListaEdificiFragment, "BUILDS").addToBackStack(null).commit();
The problem is the param propagation that since the FragmentStatePagerAdapter seems to cache views it happens that the fragment constructor is called but the onCreate and onCreateView are no more called so I can't handle the propagated parameters.
Is there any solution to this? Or am I simply wrong in my navigation pattern? I would like to avoid to collapse Fragment B,Fragment C and Fragment D in one "big view" where to hide some section (the same for Fragment E e Fragment F)
Any suggestion is more then welcome
Angelo
One simple solution to transfer a variable value from one fragment to another is shared preferences (can also be used to transfer values from one activity to another too). Shared preference will save data against variables that will persist across all the activities and fragments in an android app.
Now in your case, lets assume you want to transfer a value name = angelo from your fragment A to fragment B. In your fragment A, write this code:
Button updateName = findViewById(R.id.btnupdateTeamName);
updateTeamName .setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
SharedPreferences.Editor editor = sharedpreferences.edit();
editor.putString("name", "angelo");
editor.commit();
}
});
When executed, the above code will update a value name with angelo in shared preferences. This will be available throughout your app.
For more info about shared preference, check out this official document.
I write my Fragment like this for passing data to it.
public class MyFragment extends Fragment {
private static String ARG_PARAM1 = "data";
private String data;
public MyFragment() {
// Required empty public constructor
}
public static MyFragment newInstance(String data) {
MyFragment fragment = new MyFragment();
Bundle args = new Bundle();
args.putString(ARG_PARAM1, data);
fragment.setArguments(args);
return fragment;
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (getArguments() != null) {
data = getArguments().getString(ARG_PARAM1);
}
}
}
Now data can be passed to the Fragment by calling MyFragment.newInstance("Hello"). I hope this helps.
I have faced a similar issue in my project.
In my case, I have viewpager and each tab has multiple fragment.
So one of the simple solutions is to use LiveData and ViewModel.
In your Tab2:
Fragment B
Fragment C
Fragment D
TabTwoViewModel (with live data)
In mutable Live data observer this live data to Fragment B, C, and D.
When you update live data object, Live data notify automatically all fragment.
Finally I got a solution.
Since the main problem is the fragments communication, I followed the official documentation
Let's suppose I have Fragment A with list of articles and Fragment B where to see the selected article detail, in my Fragment A i wrote:
public class FragmentA extends Fragment {
private OnArticleSelectionListener mCallback;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (getArguments() != null) {
}
}
#Override
public void onStart() {
super.onStart();
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.activityedifici, container, false);
return rootView;
}
public interface OnArticleSelectionListener {
void onArticleSelection(String articleId);
}
#Override
public void onDetach() {
super.onDetach();
mCallback = null;
}
public void setOnArticleSelectionListener(OnArticleSelectionListener mCallback) {
this.mCallback = mCallback;
}
}
As you can see I declared the following interface
public interface OnArticleSelectionListener {
void onArticleSelection(String articleId);
}
This is the article selection listener.
In my Main Activity I wrote the following:
public class MainActivity implements FragmentA.OnArticleSelectionListener{
//All my own stuffs
#Override
public void onAttachFragment(Fragment fragment) {
if (fragment instanceof FragmentA){
FragmentA ef = (FragmentA)fragment;
ef.setOnArticleSelectionListener(this);
}
}
#Override
public void onArticleSelection(String articleId) {
if( getSupportFragmentManager().findFragmentByTag(TAG_ARTICLE_DETAIL) != null ){
//FragmentB is the article detail and it has already been created and cached
FragmentB dcf = (FragmentB)getSupportFragmentManager().findFragmentByTag(TAG_ARTICLE_DETAIL);
dcf.updateArticleDetail( articleId );
}else{
//FragmentB is the article detail and it has never been created I create and replace the container with this new fragment
FragmentB dcf = new FragmentB();
//Parameter propagation
Bundle args = new Bundle();
args.putString(FragmentB.ARG_ARTICLE_ID, articleId);
dcf.setArguments(args);
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
transaction.replace(R.id.container_articles, dcf, TAG_ARTICLE_DETAIL);
transaction.addToBackStack(null);
transaction.commit();
}
}
}
In this way I'm able in intercepting events in FragmentA and propagate them to the FragmentB; when I need to open a Tab all remains the same and finally (after transaction.commit() or the dcf.updateArticleDetail( articleId )) I do the following tabLayout.getTabAt(2).select(); and the third tab (tab index starts from 0) is open and the Detail is showed.
I hope this can be useful
Angelo
Im having an issue that only appears after several hours of inactivity, I researched it ive tried various ways of fixing it to no avail. The issue is after my app has been dormant for several hours the references for my fragments are null, however; they still exist in the frag manager. I use the references to pull the tag, or id by findfragmentby...() so I can call specific methods within them for updating themselves and what not. The fragments are dynamic and have a UI. I have several activities and a service that are called on by the main activity. I can close the app and resume, call activities, pull info from the service, close, use the back button, all without an issue. To give you an idea of how the app is structured...
public class appClass extends Application {
public Fragment fragmentA;
public Fragment fragmentB;
public Fragment fragmentC;
#Override
public void onCreate() {
super.onCreate();
new fragmentTemplate();
fragemntA = fragmentTemplate.newInstance(getDbName(), usefuldata, "A List");
new fragmentTemplate();
fragemntB = fragmentTemplate.newInstance(getDbName(), usefuldata, "B list");
new fragmentTemplate();
fragemntC = fragmentTemplate.newInstance(getDbName(), usefuldata, "C list");
}
}
Moving on to activity where fragments are used in a viewager...
public class mainActivity extends AppCompatActivity implements ...listeners{
appClass myAppClass;
FragmentManager FragMgr;
ViewPager viewPager;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
myAppClass = (appClass) getApplication();
setTheme(myAppClass.getAppTheme());
setContentView(R.layout.activity_my_layout);
//toolbar actionbar stuff
FragMgr = getSupportFragmentManager();
viewPager = (ViewPager) findViewById(R.id.viewpager);
viewPager.setAdapter(new ViewPagerAdapter(FragMgr));
//tab setup
}
//inner class pager adapter is here
}
This is my pager adapter
class ViewPagerAdapter extends FragmentPagerAdapter implements ViewPager.OnPageChangeListener{
Fragment fragment;
public ViewPagerAdapter(FragmentManager fm) {
super(fm);
}
#Override
public Fragment getItem(int position) {
switch (position) {
case 0:
if (myAppClass.fragmentA != null) {
fragment = myAppClass.fragemntA ;
}
break;
case 1:
if (myAppClass.fragmentB != null) {
fragment = myAppClass.fragmentB ;
}
break;
case 2:
if (myAppClass.fragmentC != null) {
fragment = myAppClass.fragmentC ;
}
break;
}
return fragment;
}
#Override
public int getCount() {
return 3;
}
}
I have a FAB and its listener looks like this
#Override
public void onClick(View v) {
Fraggment fragment;
int i = viewPager.getCurrentItem();
if (v.getId() == floatingActionButton.getId()) {
switch (i) {
case 0:
fragment= (Fragment) FragMgr.findFragmentByTag(myAppClass.fragmentA.getTag());
fragment.addItem(fragment.getSomeString());
break;
case 1:
fragment= (Fragment) FragMgr.findFragmentByTag(myAppClass.fragmentB.getTag());
fragment.addItem(fragment.getSomeString());
break;
case 2:
fragment= (Fragment) FragMgr.findFragmentByTag(myAppClass.fragmentC.getTag());
fragment.addItem(fragment.getSomeString());
break;
}
}
}
code for a fragment
public class fragmentTemplate extends Fragment implements RecyclerAdapter.aListener {
private appClass myAppclassReference;
private RecyclerView recyclerView;
private View view;
private FragmentTitle;
public static fragmentTemplate newInstance(String a, String b, String c) {
Bundle args = new Bundle();
args.putString(KEY_A, a);
args.putString(KEY_B, b);
args.putString(KEY_C, c);
fragmentTemplate fragment = new fragmentTemplate();
fragment.setArguments(args);
return fragment;
}
public String getFragmentTitle() {
return fragmentTitle;
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, final Bundle savedInstanceState) {
view = inflater.inflate(R.layout.list, container, false);
myAppclassReference= ((appClass) getActivity().getApplication());
recyclerView = (RecyclerView) view.findViewById(R.id.listView);
//get list is a local function that loads a list from a db source
RecyclerAdapter recycler = new RecyclerAdapter(getActivity(), getList());
recycler.setListener(this);
recyclerView.setAdapter(recycler);
recyclerView.setLayoutManager(newLearLayoutManager(getActivity()));
recyclerView.addOnItemTouchListener(new RecyclerTouchListener(getActivity(), recyclerView, new ClickListener() {}};
return view;
}
}
When things go wonky the app does not crash right away, the tabs still scroll, the viewpager still scrolls, but it is empty, its not until I hit the FAB do I get a nullpointerexception, trying to invoke a method on a nullpointer reference within the onClick Listener does it actually crash.
This is happening because you are messing up with the way that the Android Framework handles Fragments for you. When the ViewPagerAdapter gets Fragments from you in getItem(int), it's using the FragmentManager that you gave it to attach the Fragments. Once the Activity is killed because of low memory, the FragmentManager will automatically create new instances of your Fragments. At this point there are two copies of the fragments, the ones the FragmentManager created and the ones you recreated in your appClass.
You should never keep references to your Fragments. The FragmentManager is free to destroy them and create new ones. If you need to communicate between the Activity and the Fragments in the ViewPager, you can either make the Fragment ask its Activity for commands, use an Event Bus, or explore the sketchy solutions here.
This is the situation. I have an activity with 5 tabs (5 fragments). One of the fragments uses a RecyclerView to show a list of posts (like a forum). When users tap on an item menu, I need to implement the possibility of send a new post and update the list. I have no problems sending the new post to my DB and managing the response, but I don’t know how to, from the activity, tell the fragment to tell de adapter to update the list. I hope I’m explaining myself (English is not my first language).
This is my code so far.
The activity:
public class UsuarioActivity extends AppCompatActivity {
public ViewPager mPager;
public SlidingTabLayout mTabs;
...
protected void onCreate (Bundle savedInstanceState) {
mPager = (ViewPager) findViewById(R.id.pagerUsuario);
mTabs = (SlidingTabLayout) findViewById(R.id.tabsUsuario);
...
mPager.setAdapter(new MyPagerAdapter(getSupportFragmentManager()));
mTabs.setCustomTabView(R.layout.custom_tab_view, R.id.tabText);
mTabs.setDistributeEvenly(true);
mTabs.setBackgroundColor(getResources().getColor(R.color.white));
mTabs.setViewPager(mPager);
}
class MyPagerAdapter extends FragmentStatePagerAdapter {
FragmentManager fragmentManager;
public MyPagerAdapter (FragmentManager fm) {
super(fm);
fragmentManager = fm;
}
#Override
public Fragment getItem (int position) {
Fragment fragment = null;
switch (position) {
case TAB_INFO:
fragment = FragmentUserInfo.getInstance(usuario);
break;
case TAB_COM:
fragment = FragmentUserComment.getInstance(usuario);
break;
case TAB_SEG:
fragment = FragmentUserSeg.getInstance(usuario);
break;
case TAB_IM:
fragment = FragmentUserImages.getInstance(usuario);
break;
case TAB_FILES:
fragment = FragmentUserFiles.getInstance(usuario);
break;
}
return fragment;
}
#Override
public CharSequence getPageTitle (int position) { ... }
#Override
public int getCount () { return TAB_COUNT; }
}
}
The fragment:
...
import android.support.v4.app.Fragment;
...
public class FragmentUserComment extends Fragment {
private RecyclerView recyclerView;
private RVIndexCommetAdapter indexCommetAdapter;
private static final String KEY_USUARIO = "KEY_USUARIO";
public static FragmentUserComment getInstance (Usuario usuario) {
FragmentUserComment fragmentUserComment = new FragmentUserComment();
Bundle args = new Bundle();
args.putLong(KEY_USUARIO, idusuario);
fragmentUserComment.setArguments(args);
return fragmentUserComment;
}
#Override
public View onCreateView (LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setHasOptionsMenu(true);
usuario = getArguments().getLong(KEY_USUARIO);
View layout = inflater.inflate(R.layout.fragment_user_comment, container, false);
recyclerView = (RecyclerView) layout.findViewById(R.id.recViewUsuariosComment);
recyclerView.setLayoutManager(new LinearLayoutManager(getContext()));
indexCommetAdapter = new RVIndexCommetAdapter(getContext());
indexCommetAdapter.setListaComentarios(usuario.list);
recyclerView.setAdapter(indexCommetAdapter);
}
I think it’s not necessary to copy here the adapter class since my main problem is how to send the new post data from the activity to the fragment.
PS: In case anyone suggests this to me, I know I could send the new post to my DB and managing the response directly in the fragment, not in the activity. In fact, that was my first try, but onOptionsItemSelected doesn’t catch the event of tapping the item menu and I lost enough time trying to solve it (reading lots of questions here included), so I tried this new approach.
Thanks in advance.
To refresh the list from Activity you should make your Adapter static and call from your Activity notifyDataSetChanged(), it probably look like this
FragmentUserComment.mAdapter.notifyDataSetChanged();
To send data from Activity to Fragment you could make class with static variables and write them datas in your Activity and read them in Fragment. It's rather not the most professional method, but it works and it's very easy to implement.
create the method in the FragmentUserComment,look like this:
public void updateList(datas){
mAdapter.setdatas(datas);
mAdapter.notifyDataSetChanged();
}
you can call updateList() in activity when you refresh the list
((FragmentUserComment)fragment).updateList(datas);
I have two fragments SearchFragment and CreateFragment in a view pager inside a activity called TicketManagementActivity. Now when the user presses the search button in SearchFragment, I want SearchFragment to be replaced with SearchResultFragment. I should then be able to swipe between SeachResultFragment and CreateFragment in the ViewPager. Also when I press back from SearchResultFragment I should go back to SearchFragment.
Right now, when I press the button I get a blank screen instead of the layout of SearchResultFragment. When I press back I get to SearchFragment but now I have to click the button twice for the blank screen to come. Now after the blank screen comes after the double click, whenever I swipe to CreateFragment tab I get a blank screen instead of CreateFragment layout.
I looked at quite a number of questions on SO but none of them seem to be working for me. Most useful seems to be the first two answers in this question, but the first answer doesn't handle the back press, nor am I able to implement it. The second answer seems very implementable but I get errors which I have mentioned below.
My main TicketManagemementActivity:
public class TicketManagementActivity extends FragmentActivity implements
ActionBar.TabListener {
ViewPager viewPager;
TabsPagerAdapter adapter;
ActionBar actionBar;
String[] tabs={"Search", "Create"};
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_ticket_management);
viewPager=(ViewPager)findViewById(R.id.pager);
actionBar=getActionBar();
adapter=new TabsPagerAdapter(getSupportFragmentManager());
viewPager.setAdapter(adapter);
actionBar.setHomeButtonEnabled(false);
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
for(String tab_name : tabs){
actionBar.addTab(actionBar.newTab().setText(tab_name).setTabListener(this));
}
viewPager.setOnPageChangeListener(new ViewPager.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) {
}
});
}
//removed methods for menu creation and filling and placeholder fragment for brevity on SO
#Override
public void onTabSelected(Tab tab, FragmentTransaction ft) {
viewPager.setCurrentItem(tab.getPosition());
}
#Override
public void onTabUnselected(Tab tab, FragmentTransaction ft) {
}
#Override
public void onTabReselected(Tab tab, FragmentTransaction ft) {
}
}
My activity_ticket_management.xml which is layout set in onCreate of ticket management activity, just contains the viewpager
<android.support.v4.view.ViewPager xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/pager"
android:layout_width="match_parent"
android:layout_height="match_parent">
</android.support.v4.view.ViewPager>
My TabsPagerAdapter class extending FragmentPagerAdapter:
public class TabsPagerAdapter extends FragmentPagerAdapter {
public TabsPagerAdapter(android.support.v4.app.FragmentManager fm) {
super(fm);
}
#Override
public Fragment getItem(int index) {
switch (index) {
case 0:
// Top Rated fragment activity
return new SearchFragment();
case 1:
// Games fragment activity
return new CreateFragment();
}
return null;
}
#Override
public int getCount() {
// get item count - equal to number of tabs
return 2;
}
}
Relevant part of my SearchFragment:
public class SearchFragment extends Fragment implements View.OnClickListener {
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_search, container, false);
.
.//some widget initializations
.
return rootView;
}
#Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.ticket_search_btn: searchSigmaTickets();
break;
}
}
public void searchSigmaTickets(){
.
.
.
.//some operations
.
new SearchAsyncTask().execute();
}
}
private class SearchAsyncTask extends AsyncTask<Void, Void, Void>{
protected Void doInBackground(Void... params){
.
.//some more operation
.
}
protected void onPostExecute(Void param){
Fragment newFragment = new SearchResultFragment();
//Here I use getFragmentManager and not getChildFragmentManager
FragmentTransaction transaction = getFragmentManager().beginTransaction();
//HERE I try to replace the fragment. I'm not sure what id to pass, I pass the id of the main veiwpager in ticketmanagement activity
transaction.replace(R.id.pager, newFragment);
transaction.addToBackStack(null);
transaction.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_OPEN);
transaction.commit();
}
}
}
If I use getChildFragmentManager instead of getFragmentManager as mentioned in the second answer I get
06-25 06:55:32.045: E/AndroidRuntime(2797): java.lang.IllegalArgumentException: No view found for id 0x7f06003c (com.amberroad.sigmaticket:id/pager) for fragment SearchResultFragment{b2fed358 #0 id=0x7f06003c}
Sorry for the lengthy question, how should I solve this?
Kartik, get ready for a lengthy answer to your lenghty question. Replacing fragments in a viewpager is quite involved but is very possible and can look super slick. First, you need to let the viewpager itself handle the removing and adding of the fragments. What is happening is when you replace the fragment inside of SearchFragment, your viewpager retains its fragment views. So you end up with a blank page because the SearchFragment gets removed when you try to replace it.
The solution is to create a listener inside of your viewpager that will handle changes made outside of it so first add this code to the bottom of your adapter.
public interface nextFragmentListener {
public void fragment0Changed(String newFragmentIdentification);
}
Then you need to create a private class in your viewpager that becomes a listener for when you want to change your fragment. For example you could add something like this. Notice that it implements the interface that was just created. So whenever you call this method, it will run the code inside of the class below.
private final class fragmentChangeListener implements nextFragmentListener {
#Override
public void fragment0Changed(String fragment) {
//I will explain the purpose of fragment0 in a moment
fragment0 = fragment;
manager.beginTransaction().remove(fragAt0).commit();
switch (fragment){
case "searchFragment":
fragAt0 = SearchFragment.newInstance(listener);
break;
case "searchResultFragment":
fragAt0 = Fragment_Table.newInstance(listener);
break;
}
notifyDataSetChanged();
}
There are two main things to point out here: 1)fragAt0 is a "flexible" fragment. It can take on whatever fragment type you give it. This allows it to become your best friend in changing the fragment at position 0 to the fragment you desire. 2) Notice the listeners that are placed in the 'newInstance(listener)constructor. These are how you will callfragment0Changed(String newFragmentIdentification)`. The following code shows how you create the listener inside of your fragment.
static nextFragmentListener listenerSearch;
public static Fragment_Journals newInstance(nextFragmentListener listener){
listenerSearch = listener;
return new Fragment_Journals();
}
You could then call the change inside of your onPostExecute
private class SearchAsyncTask extends AsyncTask<Void, Void, Void>{
protected Void doInBackground(Void... params){
.
.//some more operation
.
}
protected void onPostExecute(Void param){
listenerSearch.fragment0Changed("searchResultFragment");
}
}
This would trigger the code inside of your viewpager to switch your fragment at position zero fragAt0 to become a new searchResultFragment. There are two more small pieces you would need to add to the viewpager before it became functional.
One would be in the getItem override method of the viewpager.
#Override
public Fragment getItem(int index) {
switch (index) {
case 0:
//this is where it will "remember" which fragment you have just selected. the key is to set a static String fragment at the top of your page that will hold the position that you had just selected.
if(fragAt0 == null){
switch(fragment0){
case "searchFragment":
fragAt0 = FragmentSearch.newInstance(listener);
break;
case "searchResultsFragment":
fragAt0 = FragmentSearchResults.newInstance(listener);
break;
}
}
return fragAt0;
case 1:
// Games fragment activity
return new CreateFragment();
}
Now without this final piece you would still get a blank page. Kind of lame, but it is an essential part of the viewPager. You must override the getItemPosition method of the viewpager. Ordinarily this method will return POSITION_UNCHANGED which tells the viewpager to keep everything the same and so getItem will never get called to place the new fragment on the page. Here's an example of something you could do
public int getItemPosition(Object object)
{
//object is the current fragment displayed at position 0.
if(object instanceof SearchFragment && fragAt0 instanceof SearchResultFragment){
return POSITION_NONE;
//this condition is for when you press back
}else if{(object instanceof SearchResultFragment && fragAt0 instanceof SearchFragment){
return POSITION_NONE;
}
return POSITION_UNCHANGED
}
Like I said, the code gets very involved, but you basically have to create a custom adapter for your situation. The things I mentioned will make it possible to change the fragment. It will likely take a long time to soak everything in so I would be patient, but it will all make sense. It is totally worth taking the time because it can make a really slick looking application.
Here's the nugget for handling the back button. You put this inside your MainActivity
public void onBackPressed() {
if(mViewPager.getCurrentItem() == 0) {
if(pagerAdapter.getItem(0) instanceof FragmentSearchResults){
((FragmentSearchResults) pagerAdapter.getItem(0)).backPressed();
}else if (pagerAdapter.getItem(0) instanceof FragmentSearch) {
finish();
}
}
}
You will need to create a method called backPressed() inside of FragmentSearchResults that calls fragment0changed. This in tandem with the code I showed before will handle pressing the back button. Good luck with your code to change the viewpager. It takes a lot of work, and as far as I have found, there aren't any quick adaptations. Like I said, you are basically creating a custom viewpager adapter, and letting it handle all of the necessary changes using listeners
Here is the code all together for the TabsPagerAdapter.
public class TabsPagerAdapter extends FragmentPagerAdapter{
Fragment fragAt0;
fragmentChangeListener listener = new fragmentChangeListener();
FragmentManager manager;
static String fragment0 = "SearchFragment";
//when you declare the viewpager in your adapter, pass it the fragment manager.
public viewPager(FragmentManager fm) {
super(fm);
manager = fm;
}
private final class fragmentChangeListener implements nextFragmentListener {
#Override
public void fragment0Changed(String fragment) {
//I will explain the purpose of fragment0 in a moment
fragment0 = fragment;
manager.beginTransaction().remove(fragAt0).commit();
switch (fragment){
case "searchFragment":
fragAt0 = SearchFragment.newInstance(listener);
break;
case "searchResultFragment":
fragAt0 = Fragment_Table.newInstance(listener);
break;
}
notifyDataSetChanged();
}
}
#Override
public Fragment getItem(int index) {
switch (index) {
case 0:
//this is where it will "remember" which fragment you have just selected. the key is to set a static String fragment at the top of your page that will hold the position that you had just selected.
if(fragAt0 == null){
switch(fragment0){
case "searchFragment":
fragAt0 = FragmentSearch.newInstance(listener);
break;
case "searchResultsFragment":
fragAt0 = FragmentSearchResults.newInstance(listener);
break;
}
}
return fragAt0;
case 1:
// Games fragment activity
return new CreateFragment();
}
#Override
public int getCount() {
// Show 3 total pages.
return 3;
}
#Override
public CharSequence getPageTitle(int position) {
Locale l = Locale.getDefault();
String[] tab = {"Journals", "Charts", "Website"};
switch (position) {
case 0:
return tab[0].toUpperCase(l);
case 1:
return tab[1].toUpperCase(l);
case 2:
return tab[2].toUpperCase(l);
}
return null;
}
public int getItemPosition(Object object)
{
//object is the current fragment displayed at position 0.
if(object instanceof SearchFragment && fragAt0 instanceof SearchResultFragment){
return POSITION_NONE;
//this condition is for when you press back
}else if{(object instanceof SearchResultFragment && fragAt0 instanceof SearchFragment){
return POSITION_NONE;
}
return POSITION_UNCHANGED
}
public interface nextFragmentListener {
public void fragment0Changed(String fragment);
}
I have a ViewPager which contains 3 fragments which is working fine. I start an activity from my any of my fragments inside the viewpager and the activity is displayed. After that when i press the back button, my application crashes with the following excepion:
FATAL EXCEPTION: main
java.lang.RuntimeException: Unable to resume activity {AppName.Activities/AppName.Activities.ViewPagerActivity}: java.lang.IndexOutOfBoundsException: Invalid index 2, size is 0
at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2120)
at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:2135)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:957)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:123)
at android.app.ActivityThread.main(ActivityThread.java:3683)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:507)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.IndexOutOfBoundsException: Invalid index 2, size is 0
at java.util.ArrayList.throwIndexOutOfBoundsException(ArrayList.java:257)
at java.util.ArrayList.set(ArrayList.java:484)
at android.support.v4.app.FragmentStatePagerAdapter.destroyItem(FragmentStatePagerAdapter.java:97)
at android.support.v4.view.ViewPager.populate(ViewPager.java:415)
at android.support.v4.view.ViewPager.setCurrentItemInternal(ViewPager.java:271)
at android.support.v4.view.ViewPager.setCurrentItem(ViewPager.java:244)
at AppName.Activities.ViewPagerActivity.setUpView(ViewPagerActivity.java:36)
at AppName.Activities.ViewPagerActivity.onStart(ViewPagerActivity.java:28)
at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1129)
at android.app.Activity.performStart(Activity.java:3791)
at android.app.Activity.performRestart(Activity.java:3821)
at android.app.Activity.performResume(Activity.java:3826)
at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2110)
The following is my code for ViewPagerActivity that extends FragmentActivity::
public class ViewPagerActivity extends FragmentActivity
{
private ViewPager mViewPager;
private ViewPagerAdapter adapter;
boolean flag = false;
#Override
protected void onCreate(Bundle arg0)
{
super.onCreate(arg0);
setContentView(R.layout.view_pager);
}
#Override
protected void onStart()
{
super.onStart();
setUpView();
}
private void setUpView()
{
mViewPager = (ViewPager) findViewById(R.id.viewPager);
adapter = new ViewPagerAdapter(getApplicationContext(),getSupportFragmentManager());
mViewPager.setAdapter(adapter);
mViewPager.setCurrentItem(0);
}
#Override
public boolean onCreateOptionsMenu(Menu menu)
{
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.menu, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item)
{
switch (item.getItemId())
{
case R.id.settings:
startActivity(new Intent(this, AppSettingsActivity.class));
return true;
case R.id.addSituationMenu:
Intent i = new Intent(this, MainLayout.class);
i.putExtra("parentActivity", "SplashScreenLayout");
startActivity(i);
return true;
case R.id.historyActivity:
startActivity(new Intent(this, HistoryActivity.class));
return true;
case R.id.chartActivity:
startActivity(new Intent(this, ViewPagerActivity.class));
return true;
default:
return super.onOptionsItemSelected(item);
}
}
}
The line mViewPager.setCurrentItem(0); causes the crash.
This is the ViewPagerAdapter code:
public class ViewPagerAdapter extends FragmentStatePagerAdapter
{
private final Context context;
ArrayList<ArrayList<Object>> data;
int totalMoodEntries = 0;
static Fragment f = null;
public ViewPagerAdapter(Context mcontext, FragmentManager fm)
{
super(fm);
context = mcontext;
}
#Override
public Fragment getItem(int position)
{
switch (position)
{
case 0:
{
f = new ChartFragment(context, totalMoodEntries, data);
break;
}
case 1:
{
f = new ViewRecordsFragment(context, data);
break;
}
case 2:
{
f = new LearnMoreFragment(context);
break;
}
}
return f;
}
#Override
public int getCount()
{
return 3;
}
}
Can you try by moving following line in the onCreate() method:
mViewPager = (ViewPager) findViewById(R.id.viewPager);
adapter = new ViewPagerAdapter(getApplicationContext(),getSupportFragmentManager());
mViewPager.setAdapter(adapter);
The application is crashing because when you call the setCurrentItem(0) method of the ViewPager it tries to destroy the non-visible fragments to release memory. But at that point of the activity lifecycle, they aren't still there (hence the Invalid index 2, size is 0).
The number of fragments that it will keep alive is specified through the method setOffscreenPageLimit(), 1 by default, which means that at most 3 fragments will be retained in memory (the one it´s being shown, the previous one and the next one).
The process of creation and destruction of fragments is managed automatically by the ViewPager, and you should let it do its stuff. Besides, you are using a FragmentStatePagerAdapter, which already saves the states of the different fragments when they are destroyed, but it also makes it a little bit more complex passing information between fragments, because they don´t necessarily exist.
If you really need to programatically set the first fragment as the visible fragment, simply try calling the setCurrentItem() in onResume() instead of onStart(), and see if the fragments are already there.
The problem is that you are setting current item 0, after creating a new ViewPageAdapter and setting it to the ViewPager. Your fragments are still not created so it return a out of bounds exception.
Put a log on the getItem method, and a log before setCurrentItem, and check that your getItem is not called before the setCurrent (Your getItem is creating the fragments).
I'm not sure, but in my opinion it's not necesary to force a setCurrentItem, and the another thing is that you are creating a new fragment in each getItem call. Save them on a collection to avoid memory leaks
In my case the problem was a bit different I think. I had the same type of exception thrown by the instantiateItem() method of my PagerAdapter whenever I replaced the current Fragment I was in and then pressed the Back button to go back to the original one with the ViewPager. The exact line throwing the exception was:
((ViewPager) viewPagerContainer).addView(page, position);
in:
private class SmartViewPagerAdapter extends PagerAdapter {
// [...]
#Override
public int getCount() {
return ABOUT_VIEW_PAGER_IMAGES.length;
}
#Override
public boolean isViewFromObject(View arg0, Object arg1) {
return arg0 == (View) arg1;
}
#Override
public Object instantiateItem(ViewGroup viewPagerContainer, int position) {
Drawable pageImage = getResources().getDrawable(ABOUT_VIEW_PAGER_IMAGES[position]);
Drawable pageTitle = getResources().getDrawable(ABOUT_VIEW_PAGER_TITLES[position]);
String pageDescription = getString(ABOUT_VIEW_PAGER_DESCRIPTIONS[position]);
SmartViewPagerPage page =
new SmartViewPagerPage(getActivity(), pageImage, pageTitle, pageDescription);
((ViewPager) viewPagerContainer).addView(page, position);
return page;
}
}
As it turned out, when you add a View to your ViewPager, you should not use the int argument of the instantiateItem() method but just use 0. Thus, the line should look like this:
((ViewPager) viewPagerContainer).addView(page, 0);
I hope this helps someone :)