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Unable to design viewpager in the layout with dynamic data

I'm new in android and want an app with viewpager. I am unable to design the viewpager in the layout. The layout fetch the data dynamatically. I want to create a matreial UI viewpager which swipes the page left or right like a paper.I have made a view which shows the data but is unable to swipe like a viewpager left or right...
The code is as below:
public class DetailNewsActivity extends AppCompatActivity {
private PullToZoomScrollViewEx scrollView;
private ArrayList<NewsItemModel> newsArr;
private TextView tvNewsTitle;
private TextView tvNewsPublishDate;
private TextView tvNewsFull;
private int newsPosition = 0;
private ImageView ivYoutubeEnable;
private SharedPreferences sharedPref;
int textSize = 16;
boolean isHighQuality = false;
private Typeface typeface;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_detail_news);
init();
AdView mAdView = (AdView) findViewById(R.id.adView);
AdRequest adRequest = new AdRequest.Builder()
.addTestDevice("5745FD6726ACCBEE8324DB158D021FA5")
.build();
mAdView.loadAd(adRequest);
}
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.activity_detail_news, container, false);
return view;
}
private void init() {
typeface = Typeface.createFromAsset(getAssets(), "AnmolUni.ttf");
// newsArr = (ArrayList<NewsItemModel>) getIntent().getSerializableExtra("newsArray");
newsArr = AppController.getAppController().getMainNewsArr();
AppController.getAppController().setMainNewsArr(null);
newsPosition = getIntent().getIntExtra("newsPosition", 0);
findViewById(R.id.iv_back).setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
finish();
}
});
findViewById(R.id.iv_share).setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
generateBranchURL(newsPosition);
}
});
sharedPref = getSharedPreferences(Constants.SHARED_PREF_NAME, Context.MODE_PRIVATE);
textSize = sharedPref.getInt("text_size", 16);
isHighQuality = sharedPref.getBoolean("isHighQuality",false);
loadViewForCode();
scrollView = (PullToZoomScrollViewEx) findViewById(R.id.scroll_view);
setNewsFromArray(newsPosition);
// ((ImageView) scrollView.getZoomView().findViewById(R.id.iv_zoom)).setImageResource(android.R.drawable.arrow_down_float);
(scrollView.getZoomView().findViewById(R.id.iv_zoom)).setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
Intent intent = new Intent(DetailNewsActivity.this, ImageVideoActivity.class);
intent.putExtra("viewType", "image");
if(isHighQuality)
intent.putExtra("imageArr", newsArr.get(newsPosition).getImage());
else
intent.putExtra("imageArr", newsArr.get(newsPosition).getMedium());
startActivity(intent);
}
});
DisplayMetrics localDisplayMetrics = new DisplayMetrics();
getWindowManager().getDefaultDisplay().getMetrics(localDisplayMetrics);
int mScreenHeight = localDisplayMetrics.heightPixels;
int mScreenWidth = localDisplayMetrics.widthPixels;
LinearLayout.LayoutParams localObject = new LinearLayout.LayoutParams(mScreenWidth, (int) (9.0F * (mScreenWidth / 16.0F)));
scrollView.setHeaderLayoutParams(localObject);
scrollView.setParallax(true);
// scrollView.getPullRootView().findViewById(R.id.container_layout).setOnTouchListener(new OnSwipeTouchListener(DetailNewsActivity.this) {
scrollView.getPullRootView().setOnTouchListener(new OnSwipeTouchListener(DetailNewsActivity.this) {
#Override
public void onSwipeLeft() {
if (newsPosition < newsArr.size() - 1) {
newsPosition++;
setNewsFromArray(newsPosition);
} else {
CommonUtils.showToast(DetailNewsActivity.this, "No more news");
}
}
#Override
public void onSwipeRight() {
if (newsPosition > 0) {
newsPosition--;
setNewsFromArray(newsPosition);
} else {
CommonUtils.showToast(DetailNewsActivity.this, "This is the first news");
}
}
});
scrollView.setOnPullZoomListener(new PullToZoomBase.OnPullZoomListener() {
#Override
public void onPullZooming(int newScrollValue) {
Log.d("MainActivity", "onPullZooming: " + newScrollValue);
// Intent intent = new Intent(DetailNewsActivity.this, ImageVideoActivity.class);
// intent.putExtra("viewType", "image");
// intent.putExtra("imageArr", newsArr.get(newsPosition).getImage());
// startActivity(intent);
}
#Override
public void onPullZoomEnd() {
}
});
}
void setNewsFromArray(int position) {
if (position >= newsArr.size()) {
finish();
return;
}
if (!newsArr.get(position).getMedium().get(0).isEmpty()) {
if(isHighQuality)
Picasso.with(DetailNewsActivity.this).load(newsArr.get(position).getImage().get(0)).placeholder(R.drawable.logo).error(R.drawable.logo).
into((ImageView) scrollView.getZoomView().findViewById(R.id.iv_zoom));
else
Picasso.with(DetailNewsActivity.this).load(newsArr.get(position).getMedium().get(0)).placeholder(R.drawable.logo).error(R.drawable.logo).
into((ImageView) scrollView.getZoomView().findViewById(R.id.iv_zoom));
} else {
((ImageView) scrollView.getZoomView().findViewById(R.id.iv_zoom)).setImageResource(R.drawable.logo);
}
tvNewsTitle.setText(newsArr.get(position).getTitle());
tvNewsPublishDate.setText(newsArr.get(position).getPublish_dt());
//String style = "<html><body style='text-align:justify'>";
//Log.i("RAJEEV",style + newsArr.get(position).getFullnews());
tvNewsFull.setText(Html.fromHtml( newsArr.get(position).getFullnews()));
if (newsArr.get(position).getYoutube_video().isEmpty()) {
ivYoutubeEnable.setVisibility(View.GONE);
} else {
ivYoutubeEnable.setVisibility(View.VISIBLE);
}
ivYoutubeEnable.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Intent intent = new Intent(DetailNewsActivity.this, ImageVideoActivity.class);
intent.putExtra("viewType", "youtube");
intent.putExtra("youtube_code", newsArr.get(newsPosition).getYoutube_video());
startActivity(intent);
}
});
}
private void loadViewForCode() {
PullToZoomScrollViewEx scrollView = (PullToZoomScrollViewEx) findViewById(R.id.scroll_view);
View headView = LayoutInflater.from(this).inflate(R.layout.ptz_head_view, null, false);
View zoomView = LayoutInflater.from(this).inflate(R.layout.ptz_zoom_view, null, false);
View contentView = LayoutInflater.from(this).inflate(R.layout.ptz_content_view, null, false);
scrollView.setHeaderView(headView);
scrollView.setZoomView(zoomView);
scrollView.setScrollContentView(contentView);
tvNewsTitle = (TextView) scrollView.getPullRootView().findViewById(R.id.tv_news_title);
tvNewsPublishDate = (TextView) scrollView.getPullRootView().findViewById(R.id.tv_news_publish_date);
tvNewsFull = (TextView) scrollView.getPullRootView().findViewById(R.id.tv_news_full);
tvNewsFull.setTextSize(textSize);
if (!AppController.isPunjabiSupported()) {
tvNewsTitle.setTypeface(typeface);
tvNewsFull.setTypeface(typeface);
}
ivYoutubeEnable = (ImageView) scrollView.getHeaderView().findViewById(R.id.iv_youtube_header);
}
void generateBranchURL(final int newsPosition) {
// String imageUrl = "";
// if (newsArr.get(newsPosition).getMedium().size() <= 1)
// imageUrl = newsArr.get(newsPosition).getMedium().get(0);
BranchUniversalObject branchUniversalObject = new BranchUniversalObject()
.setCanonicalIdentifier("NewsDetails")
///.setCanonicalUrl("https://branch.io/deepviews")
//.setTitle("" + newsArr.get(newsPosition).getTitle())
//.setContentDescription("" + newsArr.get(newsPosition).getIntro())
//.setContentImageUrl("" + imageUrl)
// You use this to specify whether this content can be discovered publicly - default is public
.setContentIndexingMode(BranchUniversalObject.CONTENT_INDEX_MODE.PUBLIC);
// Here is where you can add custom keys/values to the deep link data
//.addContentMetadata("property1", "blue")
//.addContentMetadata("property2", "red");
LinkProperties linkProperties = new LinkProperties()
.addControlParameter("$desktop_url", "http://www.newsnumber.com/news/share/" + newsArr.get(newsPosition).getFn_id())
.addControlParameter("$ios_url", "itms-apps://itunes.apple.com/us/app/newsnumber/id1022442357?mt=8")
.addControlParameter("NewsId", "" + newsArr.get(newsPosition).getFn_id())
.addControlParameter("CatId", "" + newsArr.get(newsPosition).getCat_id())
.addControlParameter("$og_title", newsArr.get(newsPosition).getTitle())
.addControlParameter("$og_description", newsArr.get(newsPosition).getIntro())
.addControlParameter("$og_image_url", newsArr.get(newsPosition).getImage().get(0))
.addControlParameter("$twitter_title", newsArr.get(newsPosition).getTitle())
.addControlParameter("$twitter_description", newsArr.get(newsPosition).getIntro())
.addControlParameter("$twitter_image_url", newsArr.get(newsPosition).getImage().get(0))
;
branchUniversalObject.generateShortUrl(this, linkProperties, new Branch.BranchLinkCreateListener() {
#Override
public void onLinkCreate(String url, BranchError error) {
if (error == null) {
Log.i("MyApp", "got my Branch link to share: " + url);
Intent sharingIntent = new Intent(Intent.ACTION_SEND);
sharingIntent.setType("text/plain");
sharingIntent.putExtra(Intent.EXTRA_SUBJECT, "News Number\n");
sharingIntent.putExtra(Intent.EXTRA_TEXT, url);
startActivity(Intent.createChooser(sharingIntent, "Share via"));
}
}
});
}
}
can anyone help??
thanks in advance.

It seems like you might be trying to make a new Activity for each "page" of a ViewPager. The Android support library already has their own ViewPager that uses fragments.
You basically need three things to use a ViewPager:
The ViewPager itself
An adapter for the ViewPager
The fragment that will be used in the ViewPager (esentially the "template" that will be used for each "page" in the ViewPager)
First, we'll create the fragment. This is just a simple example that uses only one TextView, but it will work for any amount of views and data. You'll notice that static method "newInstance()" that creates and returns an instance of this fragment. Google recommends using this method to instantiate new Fragments for a ViewPager as it makes passing data to the fragment much easier. All fragments have a "setArguments()" method that lets you pass in a Bundle when you instantiate it with whatever data you want. The method "getArguments()" can be used to access that bundle and get the values out of it in onCreate() or onCreateView(). This is how you pass in an object or objects to bind its data to the views. In this example, were just passing in a String and setting that String to a TextView. You'll see how it's used when we create the adapter for the ViewPager.
//You should be using android.support.v4.app.Fragment here
public class ExampleFragment extends Fragment {
private static final String DAY_NAME_KEY = "day_name";
private TextView dayName;
#Nullable
#Override
public View onCreateView(LayoutInflater inflater,
#Nullable ViewGroup container, #Nullable Bundle savedInstanceState) {
View fragmentView = inflater.inflate(R.layout.fragment_example, container, false);
dayName = (TextView) fragmentView.findViewById(R.id.day_name);
return fragmentView;
}
#Override
public void onActivityCreated(#Nullable Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
//Set the name of the day to the dayName TextView
String day = getArguments().getString(DAY_NAME_KEY);
dayName.setText(day);
}
public static ExampleFragment newInstance(String day) {
Bundle bundle = new Bundle();
bundle.putString(DAY_NAME_KEY, day);
ExampleFragment fragment = new ExampleFragment();
fragment.setArguments(bundle);
return fragment;
}
}
Now, we need to make an adapter that will create the views when the ViewPager is swiped. You need to extend either FragmentPagerAdapter or FragmentStatePagerAdapter. FragmentPagerAdapter is used for a small number of static fragments and it will use more memory. So you only want to use this if you have 4 or 5 pages and aren't adding any more dynamically.
For your case, it sounds like you want to swipe through a variable number of pages that are dynamically added, so you want to use FragmentStatePagerAdapter. It's optimized for memory efficiency and it will handle the saving and restoring of the fragments' state for you.
The adapter is simple.
First, you need to make your constructor match the super class's constructor. What that means is that your constructor must have a FragmentManager parameter. All you do with that is pass it to the super class. (You'll see below.)
Secondly, you have to implement just 2 methods from the FragmentStatePagerAdapter class:
public Fragment getItem(int position)
and
public int getCount()
getItem will be automatically called by the ViewPager when it is swiped. You just have to tell it what type of fragment to return. We'll be using the newInstance() method from the ExampleFragment class here.
getCount is the number of views that your ViewPager will be using. For example, I will have an ArrayList that will contain 7 strings (one for each day of the week). I want each one of those strings to be displayed on a different page of my ViewPager. So I'm just going to return the size of the ArrayList for this method.
Here's the class:
public class ViewPagerAdapter extends FragmentStatePagerAdapter {
//A reference to the array of data that will be used to populate
//each fragment. In this case it's an array of Strings, but it
//could be any type of object. The Strings within this array are what
//we'll be passing to the newInstance() method of each fragment.
private ArrayList<String> days;
//Constructor must take a FragmentManager to match the superclass.
public ViewPagerAdapter(FragmentManager fm, ArrayList<String> days) {
//All you have to do with the fragment manager is pass it to super
super(fm);
//The array will be passed in when we create the Adapter in our Activity
this.days = days;
}
#Override
public Fragment getItem(int position) {
/*
Automatically called when another page is needed.
The adapter will keep track of the position of the current page
so the first time this is called, it will be 0, then when a
swipe occurs, it will be one. If it is swiped backward, it will go back to 0.
So when the position is 0, a new Fragment will be created and the
String at days.get(0) ("Monday") will be passed to it.
*/
return ExampleFragment.newInstance(days.get(position));
}
#Override
public int getCount() {
return days.size();
}
}
Now we just have to set the adapter for the ViewPager in our Activity and it will automatically handle swipes for us.
public class MainActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ArrayList<String> daysOfWeek = new ArrayList<>();
daysOfWeek.add("Monday");
daysOfWeek.add("Tuesday");
daysOfWeek.add("Wednesday");
daysOfWeek.add("Thursday");
daysOfWeek.add("Friday");
daysOfWeek.add("Saturday");
daysOfWeek.add("Sunday");
ViewPager pager = findViewById(R.id.view_pager);
//Pass the activity's fragmentmanager by calling getSupportFragmentManager().
ViewPagerAdapter adapter = new ViewPagerAdapter(getSupportFragmentManager(), daysOfWeek);
pager.setAdapter(adapter);
}
}
This is what we get (I've added some padding and color to make it clear):
As for changing the way the pages "turn" (for example, like a newspaper), you need to look into PageTransformer

ViewPager/RecyclerView initialization best practices

I am developing an android weather application that includes a Tablelayout with 3 pages. The adapter is a FragmentStatePagerAdaptater and in each of them is a Fragment that contains a RecyclerView.
The application receives and processes the weather datas in an asynctask and then updates the ViewPager with the received datas.
My question is to know that it is the best practice when initializing the ViewPager, ie, I initialize the ViewPager in my MainActivity OnCreate() with empty datas in Fragment because I do not yet have the weather datas at this moment.
Once the data received I notify the ViewPager that the datas has changed and then in the FragmentStatePagerAdapter in getItemPosition() method I perform the update of the RecyclerView of the fragments. The RecyclerView are updated with a method equivalent of a contrustor that pass the new datas in the RecyclerViewAdaptater and a notifyDataSetChanged() to notify that the data has changed.
But maybe a best practice would be to wait for receiving the weather datas and then initialize the Viewpager adapter with the datas.
After if the user requests a data updates only notify the ViewPager that the data has changed as is already the case in my application.
This is the code of my approach :
MainActivity OnCreate() :
viewPager = (ViewPager)findViewById(R.id.viewpager);
viewPager.setOffscreenPageLimit(2);
SampleFragmentPagerAdapter adapter = new SampleFragmentPagerAdapter(getSupportFragmentManager());
adapter.addFrag(PageFragment.newInstance(0), "today");
adapter.addFrag(PageFragment.newInstance(1), "tomorrow");
adapter.addFrag(PageFragment.newInstance(2), "7 days");
viewPager.setAdapter(adapter);
Asynctask onPostExecute(Climat climat)
mSwipeRefreshLayout.setRefreshing(false);
if (climat != null) {
MainActivity.climat = climat;
viewPager.getAdapter().notifyDataSetChanged();
// Set page 1
viewPager.setCurrentItem(0);
}
FragmentStatePagerAdaptater :
class SampleFragmentPagerAdapter extends FragmentStatePagerAdapter {
private final List<Fragment> mFragmentList = new ArrayList<>(3);
private final List<String> mFragmentTitleList = new ArrayList<>(3);
SampleFragmentPagerAdapter(FragmentManager fragmentManager) {
super(fragmentManager);
}
// Returns total number of pages
#Override
public int getCount() {
return mFragmentList.size();
}
// Returns the fragment to display for that page
#Override
public Fragment getItem(int position) {
Log.i(TAG, "Fragment getItem position " + position);
return mFragmentList.get(position);
}
void addFrag(Fragment fragment, String title) {
mFragmentList.add(fragment);
mFragmentTitleList.add(title);
}
// Refresh fragment
#Override
public int getItemPosition(Object object) {
PageFragment f = (PageFragment ) object;
if (f != null) {
f.update();
}
return super.getItemPosition(object);
}
// Returns the page title for the top indicator
#Override
public CharSequence getPageTitle(int position) {
// Generate title based on item position
return mFragmentTitleList.get(position);
}
}
PageFragment :
public class PageFragment extends Fragment implements Updateable {
private static final String ARG_PAGE = "ARG_PAGE";
private int mPage;
private Climat climat = null;
private RecyclerView rv1;
private RecyclerView rv2;
private RecyclerView rv3;
private ClimatAdaptateurToday climatAdaptateurTodayRv1;
private ClimatAdaptateurToday climatAdaptateurTodayRv2;
private ClimatAdaptateur climatAdaptateur;
// newInstance constructor for creating fragment with arguments
public static PageFragment newInstance(int page) {
PageFragment fragment = new PageFragment();
// Supply num input as an argument.
Bundle args = new Bundle();
args.putInt(ARG_PAGE, page);
fragment.setArguments(args);
return fragment;
}
/**
* When creating, retrieve this instance's number from its arguments.
*/
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mPage = getArguments() != null ? getArguments().getInt(ARG_PAGE) : 0;
}
#Override
public void onViewCreated(View view, Bundle savedInstanceState) {
switch (mPage) {
case 0:
rv1 = (RecyclerView) view.findViewById(R.id.recyclerView);
// use this setting to improve performance if you know that changes
// in content do not change the layout size of the RecyclerView
rv1.setHasFixedSize(true);
// use a linear layout manager
RecyclerView.LayoutManager layoutRv1 = new LinearLayoutManager(getActivity());
rv1.setLayoutManager(layoutRv1);
rv1.setItemAnimator(new DefaultItemAnimator());
climatAdaptateurTodayRv1 = new ClimatAdaptateurToday(climat, mPage);
climatAdaptateurTodayRv1.setHasStableIds(true);
rv1.setAdapter(climatAdaptateurTodayRv1);
break;
case 1:
rv2 = (RecyclerView) view.findViewById(R.id.recyclerView);
// use this setting to improve performance if you know that changes
// in content do not change the layout size of the RecyclerView
rv2.setHasFixedSize(true);
// use a linear layout manager
RecyclerView.LayoutManager layoutRv2 = new LinearLayoutManager(getActivity());
rv2.setLayoutManager(layoutRv2);
rv2.setItemAnimator(new DefaultItemAnimator());
climatAdaptateurTodayRv2 = new ClimatAdaptateurToday(climat, mPage);
climatAdaptateurTodayRv2.setHasStableIds(true);
rv2.setAdapter(climatAdaptateurTodayRv2);
break;
case 2:
rv3 = (RecyclerView) view.findViewById(R.id.recyclerView);
// use this setting to improve performance if you know that changes
// in content do not change the layout size of the RecyclerView
rv3.setHasFixedSize(true);
// use a linear layout manager
RecyclerView.LayoutManager layoutRv3 = new LinearLayoutManager(getActivity());
rv3.setLayoutManager(layoutRv3);
rv3.setItemAnimator(new DefaultItemAnimator());
climatAdaptateur = new ClimatAdaptateur(null,
null, null);
climatAdaptateur.setHasStableIds(true);
rv3.setAdapter(climatAdaptateur);
break;
}
}
// Inflate the view for the fragment based on layout XML
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
return inflater.inflate(R.layout.content_main, container, false);
}
// To update fragment in ViewPager, we should implement a public method for the fragment,
// and do updating stuff in this method.
#Override
public void update() {
this.climat = MainActivity.climat;
if (climat != null) {
switch (mPage) {
case 0:
climatAdaptateurTodayRv1.updateData(climat, mPage);
climatAdaptateurTodayRv1.notifyDataSetChanged();
rv1.smoothScrollToPosition(0);
break;
case 1:
climatAdaptateurTodayRv2.updateData(climat, mPage);
climatAdaptateurTodayRv2.notifyDataSetChanged();
rv2.smoothScrollToPosition(0);
break;
case 2:
climatAdaptateur.updateData(climat.getClimatInfoDailyArray(),
climat.getTempsArray(), climat.getLieux());
climatAdaptateur.notifyDataSetChanged();
rv3.smoothScrollToPosition(0);
break;
}
}
}
}
interface Updateable {
void update();
}
Thanks for your help !!

How to properly use ViewPager in android

I want to make a quiz application. So far I have 3 activities - home, quiz, score. Since the quiz activity contains multiple equivalent views ( image header, question and 4 answer buttons ), I did some reading and decided that
ViewPager with FragmentStatePagerAdapter show do the trick. So I made an xml template and inflated couple of test views and it was all looking good, until I started handling the user interaction.
I want to simulate a toggle button and there is only one correct answer to each question, so selecting one button should deselect the previous one ( if any ). When the button is pressed I change my Question model, then I find all 4 buttons with findViewById and reset their color filter. Then I set that filter back on my selected button. To determine which question model to update I use the current fragment position, which I have set ( using setTag, in fragment's onCreate ) in my template root view.
This is how I call my fragmets:
public Fragment getItem(int position) {
Question question = Repository.findById(position);
int correctAnswerBtnId;
switch (question.getCorrectAnswerIndex()) {
case 0: correctAnswerBtnId = R.id.quiz_answer_0_btn; break;
case 1: correctAnswerBtnId = R.id.quiz_answer_1_btn; break;
case 2: correctAnswerBtnId = R.id.quiz_answer_2_btn; break;
case 3: correctAnswerBtnId = R.id.quiz_answer_3_btn; break;
this.ACTIVITY_ROOT.setTag(question.getID());
Fragment fragment = new QuestionFragment();
Bundle args = new Bundle();
args.putSerializable(QuestionFragment.QUESTION, question);
fragment.setArguments(args);
return fragment;
}
My QuestionFragment onCreateView is as per documentation:
public View onCreateView(
LayoutInflater inflater,
ViewGroup container,
Bundle questionData) {
this.rootView = inflater.inflate(
R.layout.layout_question_template,
container,
false);
Bundle args = getArguments();
this.question = (Question) args.getSerializable(QuestionFragment.QUESTION);
populateInflatable();
rootView.findViewById(R.id.layout_question_template_root).setTag(this.question.getID());
return rootView;
}
In populateInflatable I use this.rootView to fintViewById and populate it with my question data. Then I change the color of a button, if there is selected one from the Question.
On button click I call selectAnserButton :
public void selectAnswerButton(View selectedButton) {
int questionId =
(int) this.activityRoot.findViewById(
R.id.layout_question_template_root).getTag(); //??
unSelectAllButtons();
changeColor(selectedButton);
Repository.findById(questionId).selectAnswer(selectedButton.getId());
}
Where unSelectAllButtons represents buttonToUnSelect.getBackground().clearColorFilter(); on the four buttons. and Repository is just a static class with example question data.
It all goes terribly wrong, when I have more then one view. On each fragment I inflate the same xml with same View IDs, as I have defined them. And as I now understand calling findViewById retrieves not one, but all views with that Id from my current, but also from my previous and next fragment as well. So every time I want to select my current fragment's view, I also modify the same view in the previous and next fragments as well. You can imagine how this is problematic. This makes me feel I have a fundamental mistake, because I don't think there is supposed to be more then one View with same ID.
I really don't understand how I should do this using ViewPager. At this point it feels like I'm trying to make a wood carving, but instead I am hacking the framework to pieces. There must be a better way to do this with ViewPager.
RESOLVED: Thanks to Soo Chun Jung for pointing me to the answer. In short what got it working for me was:
Passing my Question model id to each fragment with Bundle.
Storing each fragment in inside an ArrayMap with fragment position as key and fragment as value.
Getting each individual fragment from my selectAnswer function is now easy: first get the current fragment's position with myViewPager.getCurrentItem, then calling getter function which returns a fragment on the current position.
Now that I have the fragment I can easily change its button's because they are kept as private fields, assigned in the 'onCreateView` method.

Hope it's helpful~
adapter
class CustomAdapter extends FragmentPagerAdapter {
private final String[] TITLES = {"A", "B"};
private final String TAG = CustomAdapter.class.getSimpleName();
private final ArrayList<Fragment> mFragments;
private final FragmentManager fm;
public CustomAdapter(FragmentManager fm) {
super(fm);
mFragments = new ArrayList<>(getCount());
this.fm = fm;
}
#Override
public CharSequence getPageTitle(int position) {
return TITLES[position];
}
#Override
public int getCount() {
return TITLES.length;
}
#Override
public void destroyItem(ViewGroup container, int position, Object object) {
Log.d(TAG, "destroyItem position = " + position);
mFragments.remove(object);
super.destroyItem(container, position, object);
}
#Override
public Object instantiateItem(ViewGroup container, int position) {
Object object = super.instantiateItem(container, position);
mFragments.add((Fragment) object);
return object;
}
#Override
public Fragment getItem(int position) {
Log.d(TAG, "getItem position = " + position);
if (position == 0) {
return MyFragmentA.newInstance();
} else if (position == 1) {
return MyFragmentB.newInstance();
}
return null;
}
public MyFragmentA getMyFragmentA() {
synchronized (mFragments) {
for (Fragment f : mFragments) {
if (f instanceof MyFragmentA) {
return (MyFragmentA) f;
}
}
}
return null;
}
public MyFragmentB getMyFragmentB() {
synchronized (mFragments) {
for (Fragment f : mFragments) {
if (f instanceof MyFragmentB) {
return (MyFragmentB) f;
}
}
}
return null;
}
}
Fragment class
public class MyFragmentB extends Fragment {
...
public updateYourUI(){
//update something
}
}
Usage
mPager = (CustomViewPager) findViewById(R.id.pager);
mAdapter = new CustomAdapter(getChildFragmentManager());
mPager.setAdapter(mAdapter);
mAdapter.getMyFragmentB().updateYourUI();
for your comment below If you only have one kind Fragment. You can modify some function like this.
public static MyFragmentB newInstance(int ID) {
MyFragmentB fragment = new MyFragmentB();
Bundle bundle = new Bundle();
bundle.putInt("ID", ID);
fragment.setArguments(bundle);
return fragment;
}
#Override
public void onViewCreated(View view, #Nullable Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
myID = getArguments().getInt("ID");
....
}
public int getMyID() {
return myID;
}
public MyFragmentB getMyFragmentByID(String id) {
synchronized (mFragments) {
for (Fragment f : mFragments) {
if (f instanceof MyFragmentB) {
MyFragmentB temp = (MyFragmentB)f;
if(temp.getID.equals(id){
return (MyFragmentB) f;
}
}
}
}
return null;
}

Fragment State Pager Adapter Showing Wrong Fragment

I have a FragmentStatePagerAdapter which shows the details of current Fragment in the next Fragment. Here is the Page Adapter
public class CustomerPagerAdapter extends FragmentStatePagerAdapter
{
public SectionsPagerAdapter(FragmentManager fm)
{
super(fm);
}
#Override
public Fragment getItem(int position) {
Gson gson = new Gson();
Customer selectedCustomer = mCustomers.get(position);
String serializedCustomer = gson.toJson(selectedCustomer);
return CustomerDetailsFragment.newInstance(serializedCustomer);
}
#Override
public int getCount()
{
return mCustomers.size();
}
#Override
public CharSequence getPageTitle(int position)
{
Customer selectedCustomer = mCustomers.get(position);
String CustomerTitle = selectedCustomer.getFirstName() + " " + selectedCustomer.getLastName();
return CustomerTitle;
}
}
And here is the Fragment where the detail are displayed
public static class CustomerDetailsFragment extends Fragment {
private Customer passedInCustomer;
public CustomerDetailsFragment() {
// Required empty public constructor
}
public static CustomerDetailsFragment newInstance(String serializedCustomer){
CustomerDetailsFragment fragment = new CustomerDetailsFragment();
if (serializedCustomer != null && !serializedCustomer.isEmpty()){
Bundle args = new Bundle();
args.putString("customerInfo", serializedCustomer);
fragment.setArguments(args);
}
return fragment;
}
private void getPosition(){
Bundle args = getArguments();
if (args != null && args.containsKey("customerInfo")){
String serializedCustomer = (getArguments().getString("customerInfo"));
Gson gson = new Gson();
passedInCustomer = gson.fromJson(serializedCustomer, Customer.class);
}
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
mRootView = inflater.inflate(R.layout.fragment_Customer_details, container, false);
if (passedInCustomer != null) {
showCustomerInfo();
}
return mRootView;
}
}
The problem stems from the fact that getItem is called twice for each swipe and the information that need to be displayed are contained in an List so when getItem is called twice the second object in the list is fetched and displayed in the screen where the first object was supposed to be displayed.
Has anyone dealt with displaying an nth number of items in a scrollable ViewPager where you have to create the Fragments on demand. If yes, can you give me suggestions how to deal with this.
Thanks

I notice that this problem is showing only when I have same fragments with diferent values ( what is probably in the most case ). So after long searching for right answer, i decided to in getItem() method every odd time return one fragment and every even time return another fragment ( These fragment are completely same, except their names:
#Override
public Fragment getItem(int position) {
if(position % 2 == 0){
return FragmentGalleryImage.newInstance(images.get(position), activity);
}else{
return FragmentGalleryImage2.newInstance(images.get(position), activity);
}
}
And i solved problem nice and smooth.

I solved the problem by calling on pager.getCurrentItem() to get the position of the currently displayed item.

Fragment in ViewPager not restored after popBackStack

Problem
A Fragment is not reattached to its hosting ViewPager after returning from another fragment.
Situation
One Activity hosting a Fragment whose layout holds a ViewPager (PageListFragment in the example below). The ViewPager is populated by a FragmentStateViewPagerAdapter. The single Fragments hosted inside the pager (PageFragment in the example below) can open sub page lists, containing a new set of pages.
Behaviour
All works fine as long as the back button is not pressed. As soon as the user closes one of the sub PageLists the previous List is recreated, but without the Page that was displayed previously. Swiping through the other pages on the parent PageList still works.
Code
A sample application can be found on github:
Activity
public class MainActivity extends FragmentActivity {
private static final String CURRENT_FRAGMENT = MainActivity.class.getCanonicalName() + ".CURRENT_FRAGMENT";
public static final String ARG_PARENTS = "Parents";
public void goInto(String mHostingLevel, String mPosition) {
Fragment hostingFragment = newHostingFragment(mHostingLevel, mPosition);
addFragment(hostingFragment);
}
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
addBaseFragment();
}
private void addBaseFragment() {
Fragment hostingFragment = newHostingFragment("", "");
addFragment(hostingFragment);
}
private Fragment newHostingFragment(String mHostingLevel, String oldPosition) {
Fragment hostingFragment = new PageListFragment();
Bundle args = new Bundle();
args.putString(ARG_PARENTS, mHostingLevel + oldPosition +" > ");
hostingFragment.setArguments(args);
return hostingFragment;
}
private void addFragment(Fragment hostingFragment) {
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
transaction.replace(R.id.fragmentSpace, hostingFragment, CURRENT_FRAGMENT);
transaction.addToBackStack(null);
transaction.commit();
}
}
PageListFragment
public class PageListFragment extends Fragment {
private String mParentString;
public PageListFragment() {
// Required empty public constructor
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
// Inflate the layout for this fragment
return inflater.inflate(R.layout.fragment_hosting, container, false);
}
#Override
public void onResume() {
mParentString = getArguments().getString(MainActivity.ARG_PARENTS);
ViewPager viewPager = (ViewPager) getView().findViewById(R.id.viewPager);
viewPager.setAdapter(new SimpleFragmentStatePagerAdapter(getFragmentManager(),mParentString));
super.onResume();
}
private static class SimpleFragmentStatePagerAdapter extends FragmentStatePagerAdapter {
private String mHostingLevel;
public SimpleFragmentStatePagerAdapter(FragmentManager fm, String hostingLevel) {
super(fm);
this.mHostingLevel = hostingLevel;
}
#Override
public android.support.v4.app.Fragment getItem(int position) {
PageFragment pageFragment = new PageFragment();
Bundle args = new Bundle();
args.putString(MainActivity.ARG_PARENTS, mHostingLevel);
args.putInt(PageFragment.ARG_POSITION, position);
pageFragment.setArguments(args);
return pageFragment;
}
#Override
public int getCount() {
return 5;
}
}
}
PageFragment
public class PageFragment extends Fragment {
public static final String ARG_POSITION = "Position";
private String mHostingLevel;
private int mPosition;
public PageFragment() {
// Required empty public constructor
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View contentView = inflater.inflate(R.layout.fragment_page, container, false);
setupTextView(contentView);
setupButton(contentView);
return contentView;
}
private void setupTextView(View contentView) {
mPosition = getArguments().getInt(ARG_POSITION);
mHostingLevel = getArguments().getString(MainActivity.ARG_PARENTS);
TextView text = (TextView) contentView.findViewById(R.id.textView);
text.setText("Parent Fragments " + mHostingLevel + " \n\nCurrent Fragment "+ mPosition);
}
private void setupButton(View contentView) {
Button button = (Button) contentView.findViewById(R.id.button);
button.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
openNewLevel();
}
});
}
protected void openNewLevel() {
MainActivity activity = (MainActivity) getActivity();
activity.goInto(mHostingLevel, Integer.toString(mPosition));
}
}

After a lengthy investigation it turns out to be a problem with the fragment manager.
When using a construct like the one above the fragment transaction to reattach the fragment to the page list is silently discarded. It is basically the same problem that causes a
java.lang.IllegalStateException: Recursive entry to executePendingTransactions
when trying to alter the fragments inside the FragmentPager.
The same solution, as for problems with this error, is also applicable here. When constructing the FragmentStatePagerAdapter supply the correct child fragment manager.
Instead of
viewPager.setAdapter(new SimpleFragmentStatePagerAdapter(getFragmentManager(),mParentString));
do
viewPager.setAdapter(new SimpleFragmentStatePagerAdapter(getChildFragmentManager(),mParentString));
See also: github

What Paul has failed to mention is, if you use getChildFragmentManager, then you will suffer the "blank screen on back pressed" issue.

The hierarchy in my case was:
MainActivity->MainFragment->TabLayout+ViewPager->AccountsFragment+SavingsFragment+InvestmentsFragment etc.
The problem I had was that I couldn't use childFragmentManagerfor the reason that a click on the item Account view (who resides inside one of the Fragments of the ViewPager) needed to replace MainFragment i.e. the entire screen.
Using MainFragments host Fragment i.e. passing getFragmentManager() enabled the replacing, BUT when popping the back-stack, I ended up with this screen:
This was apparent also by looking at the layout inspector where the ViewPager is empty.
Apparently looking at the restored Fragments you would notice that their View is restored but will not match the hierarchy of the popped state. In order to make the minimum impact and not force a re-creation of the Fragments I re-wrote FragmentStatePagerAdapter with the following changes:
I copied the entire code of FragmentStatePagerAdapter and changed
#NonNull
#Override
public Object instantiateItem(#NonNull ViewGroup container, int position) {
// If we already have this item instantiated, there is nothing
// to do. This can happen when we are restoring the entire pager
// from its saved state, where the fragment manager has already
// taken care of restoring the fragments we previously had instantiated.
if (mFragments.size() > position) {
Fragment f = mFragments.get(position);
if (f != null) {
return f;
}
}
...
}
with
#NonNull
#Override
public Object instantiateItem(#NonNull ViewGroup container, int position) {
// If we already have this item instantiated, there is nothing
// to do. This can happen when we are restoring the entire pager
// from its saved state, where the fragment manager has already
// taken care of restoring the fragments we previously had instantiated.
if (mFragments.size() > position) {
Fragment f = mFragments.get(position);
if (f != null) {
if (mCurTransaction == null) {
mCurTransaction = mFragmentManager.beginTransaction();
}
mCurTransaction.detach(f);
mCurTransaction.attach(f);
return f;
}
}
...
}
This way I am effectively making sure that that the restored Fragments are re-attached to the ViewPager.

Delete all page fragments, enabling them to be re-added later
The page fragments are not attached when you return to the viewpager screen as the FragmentStatePagerAdapter is not re-connecting them. As a work-around, delete all the fragments in the viewpager after popbackstack() is called, which will allow them to be re-added by your initial code.
[This example is written in Kotlin]
//Clear all fragments from the adapter before they are re-added.
for (i: Int in 0 until adapter.count) {
val item = childFragmentManager.findFragmentByTag("f$i")
if (item != null) {
adapter.destroyItem(container!!, i, item)
}
}