Develop Reference

Textview not updating on first Tab unless scrolled to 3rd Tab

I have a tablayout (with 3 tabs) with viewpager and fragments.
I m trying to send the parsed Json data from MainActivity( When searchview data submitted ) to show in the textview of tabs fragments
See this Image link
The data is succesfully parsing but textview with data(in first tab) is not showing unless scrolled to 3rd tab
//Passing data from MainActivity
public String getMyData() {
return meaning;
}
//Setting value to textview from Fragment
#Override
public View onCreateView(#NonNull LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View v=inflater.inflate(R.layout.fragment_meaning, container, false);
MainActivity mainActivity= (MainActivity) getActivity();
assert mainActivity != null;
String data= mainActivity.getMyData();
TextView textView=v.findViewById(R.id.textVIew);
textView.setText(data);
return v;
}
Want to able to show data changes instantly as it is parsed, instead of scrolling to 3rd tab to see changes

Here are some steps that might help you.
On the ViewPager adaptor you have created, make the fragment objects. like below
FragmentOne fragOne; // this should be global
On the viewPager adaptor, do some thing like this,
fragOne = new FragmentOne() // whatever your implementation is.
Then after fetching the data from the server,
if ( fragOne != null ) {
fragOne.setValueOnView( " your data to be passed" );
}
and on the FragmentOne, create a function called setValueOnView
void setValueOnView(String yourString) {
v.findViewById(R.id.textVIew).setText(yourString);
}
And one more thing, while initializing the fragment onCreateView, create an object of View
View v; // global variable
#Override
public View onCreateView(#NonNull LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
v=inflater.inflate(R.layout.fragment_meaning, container, false);
Use this approach for other fragments as well

Inside getItem() method in ViewPager class use Fragment constructors with String parameter
#Override
public Fragment getItem(int position) {
switch (position) {
case 0:
FragmentOne tab1 = new FragmentOne("string parameter");
return tab1;
case 1:
FragmentTwo tab2 = new FragmentTwo("string parameter");
return tab2;
case 2:
FragmentThree tab3 = new FragmentThree("string parameter");
return tab3;
default:
return null;
}
}
Inside your Fragment:
public FragmentOne(String stringParameter) {
yourLocalVariable = stringParameter; // yourLocalVariable is declared inside Fragment class;
//now you can setText() for your TextView inside onViewCreated()
}
Of course you pass your String from MainActivity to ViewPager like you did earlier.

Use Observer
public class FragmentObserver extends Observable {
#Override
public void notifyObservers() {
setChanged(); // Set the changed flag to true, otherwise observers won't be notified.
super.notifyObservers();
}
}
Activity:
public class MyActivity extends Activity {
private MyAdapter mPagerAdapter;
#Override
public void onCreate(Bundle savedInstanceState) {
setContentView(R.layout.my_activity);
ViewPager pager = (ViewPager) findViewById(R.id.pager);
mPagerAdapter = new MyAdapter();
pager.setAdapter(mPagerAdapter);
}
private void updateFragments() {
mPagerAdapter.updateFragments();
}
}
Viewpager adapter
public class MyAdapter extends FragmentPagerAdapter {
private Observable mObservers = new FragmentObserver();
public MyAdapter(FragmentManager fm) {
super(fm);
}
#Override
public Fragment getItem(int position) {
mObservers.deleteObservers(); // Clear existing observers.
Fragment fragment = new MyFragment();
if(fragment instanceof Observer)
mObservers.addObserver((Observer) fragment);
return fragment;
}
public void updateFragments() {
mObservers.notifyObservers();
}
}
Your Fragment
public class MyFragment extends Fragment implements Observer {
/* Fragment related stuff... */
#Override
public void update(Observable observable, Object data) {
View root = getView();
// Update your views here.
}
}
You will get data to update method even your fragment already loaded

Android: Fragments inside the ViewPager not showing

I have a Fragment. This fragment contains a view pager where the view page has multiple fragments. I can scroll the pages but seeing nothing even though getItem did call when scroll and initialised the fragment.
I have changed the code with support.v4.app.Fragment and support.v4.app.FragmentManager and change the main activity to FragmentActivity. In addition, I use getChildFragmentManager to the adapter but still can't showing anything.
I also change the line below to return true always but it can show the first fragment. Subsequent fragment aren't showing and behave badly when start paging it.
#Override
public boolean isViewFromObject(View view, Object object) {
return true;
}
Below is the code I implement the ViewPager.
public class AppsPagerAdapter extends FragmentPagerAdapter {
private int appsSize;
private int appsPerPage = 12;
private Activity activity;
public AppsPagerAdapter (Activity activity1, FragmentManager manager, int size)
{
super(manager);
appsSize = size;
activity = activity1;
}
#Override
public int getCount() {
int offset = appsSize % appsPerPage;
int pageExtra = (offset > 0)? 1: 0;
return appsSize / appsPerPage + pageExtra;
}
#Override
public boolean isViewFromObject(View view, Object object) {
return view == object;
}
public Fragment getItem(int position) {
Bundle bundle = new Bundle();
bundle.putInt (AppPageFragment.PAGE_NUMBER_PARAMS, position);
return Fragment.instantiate(activity, AppPageFragment.class.getName(), bundle);
}
}
Outer Fragment:
#Override
public View onCreateView (LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
{
View view = inflater.inflate (R.layout.fragment_all_app, container, false);
ViewPager appsPager = (ViewPager) view.findViewById(R.id.grid_allapps);
//adapter = new AppsPagerAdapter(((AppCompatActivity)getActivity()).getSupportFragmentManager(), GlobalData.getInstance().getApps().getAll().size());
adapter = new AppsPagerAdapter(getActivity(), getChildFragmentManager(), GlobalData.getInstance().getApps().getAll().size());
appsPager.setAdapter(adapter);
appsPager.addOnPageChangeListener(pageChangeListener);
return view;

ViewPager creates duplicate views

This is the PagingAdapter I am using:
public class PagingAdapter extends FragmentStatePagerAdapter {
Context context;
public PagingAdapter(FragmentManager fm, Context con) {
super(fm);
context = con;
}
#Override
public Fragment getItem(int index) {
try {
switch (index) {
case 0:
return Fragment.instantiate(context, ActivityFragment.class.getName());
case 1:
return Fragment.instantiate(context, GroupFragment.class.getName());
case 2:
return Fragment.instantiate(context, MessageFragment.class.getName());
case 3:
return Fragment.instantiate(context, NotificationFragment.class.getName());
}
return null;
}
catch (Exception ex)
{
ex.printStackTrace();
return null;
}
}
#Override
public int getCount() {
// get item count - equal to number of tabs
return 4;
}
}
This creates same view for first two tabs. I want separate content for all tabs.
I am placing WebView in all 4 tabs.
In Activity, I am doing this :
mViewPager.setOffscreenPageLimit(3);

Use SparseArray<Fragment> in your adapter, and in your getItem use new instantiate your fragments like
return new ActivityFragment();
If you want to add bundle info than first create your fragment than add bundle in your
fragment.setArgument(bundle);
And use these line in your deateyItem before calling super
if(0<=sparseArray.indexOfKey(position))
sparseArray.remove(position);

First of all your method instantiate is returning a Fragment right?
Does it add the param implicitly in that method using setArguements if not you may want to change to it. On the other hand FragmentManager will call default constructor of each fragment when needed. So you have to keep them (do not overload constructor) and in destroyItem try removing the fragment for real.
#Override
public void destroyItem(ViewGroup container, int position, Object object) {
getFragmentManager().beginTransaction().remove((Fragment)(object)).commit();
}

What do you mean by separate view? are you sure that you are not inflating the wrong layout in.
GroupClassFragment.java class
Do check int the method.
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View myCorrectView = inflater.inflate(R.layout.my_correct_view,container,false);
return myCorrectView;
}

Is it possible to access the current Fragment being viewed by a ViewPager?

I have an app with a ViewPager and three Fragments. I'm trying to figure out how to get the current Fragment being viewed so I can get at its arguments.
I have an OnPageChangeListener grabbing the current page index, but
ViewPager.getChildAt(int position);
returns a View. What's the relationship between this View and the current Fragment?

I finally found an answer that worked for me. Basically, you can access the fragment for a viewPager page by using the tag "android:switcher:"+R.id.viewpager+":0".

I've solved this problem the other way round.
Instead of searching for the fragment from the activity, I'm registering the Fragment during it's onAttach() method at it's owner activity and de-registering it in the onStop() method.
Basic Idea:
Fragment:
#Override
public void onAttach(Activity activity) {
super.onAttach(activity);
try{
mActivity = (IMyActivity)activity;
}catch(ClassCastException e){
throw new ClassCastException(activity.toString() +" must be a IMyActivity");
}
mActivity.addFragment(this);
}
#Override
public void onStop() {
mActivity.removeFragment(this);
super.onStop();
}
IMyActivity:
public interface IFriendActivity {
public void addFragment(Fragment f);
public void removeFragment(Fragment f);
}
MyActivity:
public class MyActivity implements IMyActivity{
[...]
#Override
public void addFragment(Fragment f) {
mFragments.add(f);
}
#Override
public void removeFragment(Fragment f) {
mFragments.remove(f);
}
}

Edit - Don't do this. If you're tempted to, read the comments for why it's a bad idea.
On the odd-chance you're still trying to solve this problem:
Extend FragmentPagerAdapter. In the constructor, build the Fragments you need and store them in a List (array/ArrayList) of Fragments.
private final int numItems = 3;
Fragment[] frags;
public SwipeAdapter (FragmentManager fm) {
super(fm);
//Instantiate the Fragments
frags = new Fragment[numItems];
Bundle args = new Bundle();
args.putString("arg1", "foo");
frags[0] = new MyFragment();
frags[1] = new YourFragment();
frags[2] = new OurFragment();
frags[2].setArguments(args);
}
Then for getItem(int position), you can do something like
public Fragment getItem(int position) {
return frags[position];
}
I'm not sure if this is the generally accepted way of doing it but it worked for me.
Edit
This is really not a good way to go. If you plan on handling orientation changes or your app going into the background, then this will probably break your code. Please read the comments below this answer for more info. Rather use #James 's answer

Yes, it's possible if you are using FragmentStatePagerAdapter.
ViewPager vp;
//...
YourFragment fragment = (YourFragment) adapter.instantiateItem(vp, vp.getCurrentItem());

PLEASE DON'T USE THIS
Make your adapter extend the following FragmentStatePagerWithCurrentAdapter class and instead of implementing getItem implement the same code into getItemAtIndex
Set the ViewPager OnPageChangeListener, to the instance of the adapter.
When you need to access the current Fragment you just call adapter.getCurrentItem().
package your.package;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentStatePagerAdapter;
import android.support.v4.view.ViewPager.OnPageChangeListener;
import android.util.SparseArray;
import android.view.ViewGroup;
public abstract class FragmentStatePagerWithCurrentAdapter
extends FragmentStatePagerAdapter
implements OnPageChangeListener {
int currentPage = 0;
private SparseArray<Fragment> mPageReferenceMap = new SparseArray<Fragment>();
public FragmentStatePagerWithCurrentAdapter(FragmentManager fm) {
super(fm);
}
#Override
public final Fragment getItem(int index) {
Fragment myFragment = getItemAtIndex(index);
mPageReferenceMap.put(index, myFragment);
return myFragment;
}
public abstract Fragment getItemAtIndex(int index);
#Override
public void destroyItem(ViewGroup container, int position, Object object) {
super.destroyItem(container, position, object);
mPageReferenceMap.remove(Integer.valueOf(position));
}
public Fragment getCurrentItem() {
return mPageReferenceMap.get(currentPage);
}
#Override
public void onPageScrollStateChanged(int arg0) {
}
#Override
public void onPageScrolled(int arg0, float arg1, int arg2) {
}
#Override
public void onPageSelected(int newPageIndex) {
currentPage = newPageIndex;
}
}
I used as reference the following blog post: http://tamsler.blogspot.com/2011/11/android-viewpager-and-fragments-part-ii.html

It's been explained here : http://developer.android.com/guide/topics/fundamentals/fragments.html
In OnCreateView you must return a view to draw a UI for your fragment, I think that's the relationship.
Also this question might be similar: Get focused View from ViewPager

You can do so:
- On the class extent of a view pager adapter (such as PagerAdapter , FragmentStatePagerAdapter...) override method instantiateItem :
#Override
public Object instantiateItem(ViewGroup container, int position) {
final Fragment frag = (Fragment) super.instantiateItem(container, position);
if(frag instanceof ListNoteOfTypeFragment){
final ListNoteOfTypeFragment listNoteOfTypeFragment = (ListNoteOfTypeFragment) frag;
//do whatever you want with your fragment here
listNoteOfTypeFragment.setNoteChangeListener(mListener);
}
return frag;
}

Definitive answer that works seamlessly (but small hack):
somewhere in page fragment's layout:
<FrameLayout android:layout_width="0dp" android:layout_height="0dp" android:visibility="gone" android:id="#+id/fragment_reference">
<View android:layout_width="0dp" android:layout_height="0dp" android:visibility="gone"/>
</FrameLayout>
in fragment's onCreateView():
...
View root = inflater.inflate(R.layout.fragment_page, container, false);
ViewGroup ref = (ViewGroup)root.findViewById(R.id.fragment_reference);
ref.setTag(this);
ref.getChildAt(0).setTag("fragment:" + pageIndex);
return root;
and method to return Fragment from ViewPager, if exists:
public Fragment getFragment(int pageIndex) {
View w = mViewPager.findViewWithTag("fragment:" + pageIndex);
if (w == null) return null;
View r = (View) w.getParent();
return (Fragment) r.getTag();
}

Jorge Garcia's FragmentStatePagerWithCurrentAdapter is a very good solution but it needs a minor improvement. In case the activity gets destroyed and re-created in response to a configuration change or something like that the getItem will not be called for the fragments that were saved and retrieved by the fragment manager. So I override getItem normally in my subclass and I put the following in the FragmentStatePagerWithCurrentAdapter
#Override
public Object instantiateItem(ViewGroup container, int position) {
Object item = super.instantiateItem(container, position);
if ( item instanceof Fragment ) {
pageReferenceMap.put(position, (Fragment)item);
}
return item;
}
The instantiateItem is called every time the fragment in that position is accessed.

Or just save all Fragments in a map:
public class MyFragment extends Fragment implements OnPageChangeListener {
private ViewPager viewPager;
private FragmentStatePagerAdapter viewAdapter;
private View rootView;
private Map<Integer, Fragment> fragments = new HashMap<Integer, Fragment>();
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
rootView = inflater.inflate(R.layout.introdution, container, false);
viewPager = (ViewPager) rootView.findViewById(R.id.pager);
viewAdapter = new ViewAdapter(getFragmentManager());
viewPager.setAdapter(viewAdapter);
viewPager.addOnPageChangeListener(this);
return rootView;
}
private class ViewAdapter extends FragmentStatePagerAdapter {
public ViewAdapter(FragmentManager fragmentManager) {
super(fragmentManager);
}
#Override
public Fragment getItem(int position) {
Fragment result = null;
switch (position) {
case 0: result = Fragment1.newInstance(); break;
case 1: result = Fragment2.newInstance(); break;
}
if (result != null)
fragments.put(position, result);
return result;
}
#Override
public int getCount() {
return 2;
}
}
#Override
public void onPageScrollStateChanged(int arg0) {
}
#Override
public void onPageScrolled(int arg0, float arg1, int arg2) {
}
#Override
public void onPageSelected(int position) {
Fragment currentFragment = fragments.get(position);
}
}

I think there is the better way by using this
Log.i(TAG, "getCurrentItem " + mViewPager.getCurrentItem());
Can get the current display fragment page.

Saving Fragment state in ViewPager

I tried out the sample code from the API and it didn't really work so I implemented my own:
FragmentPagerSupport
public class FragmentPagerSupport extends FragmentActivity {
static final int NUM_ITEMS = 10;
MyAdapter mAdapter;
ViewPager mPager;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
mAdapter = new MyAdapter(getSupportFragmentManager());
Log.i("Pager", "mAdapter = " + mAdapter.toString());
mPager = (ViewPager)findViewById(R.id.pager);
if (mPager == null)
Log.i("Pager", "mPager = null");
else
Log.i("Pager", "mPager = " + mPager.toString());
Log.i("Pager", "Setting Pager Adapter");
mPager.setAdapter(mAdapter);
}
public static class MyAdapter extends FragmentPagerAdapter {
public MyAdapter(FragmentManager fm) {
super(fm);
Log.i("Pager", "MyAdapter constructor");
}
#Override
public int getCount() {
Log.i("Pager", "MyAdapter.getCount()");
return NUM_ITEMS;
}
#Override
public Fragment getItem(int position) {
Log.i("Pager", "MyAdapter.getItem()");
return TestFragment.newInstance(position);
}
}
public static class TestFragment extends Fragment {
public static TestFragment newInstance(int position) {
Log.i("Pager", "TestFragment.newInstance()");
TestFragment fragment = new TestFragment();
Bundle args = new Bundle();
args.putInt("position", position);
fragment.setArguments(args);
return fragment;
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// TODO Auto-generated method stub
Log.i("Pager", "TestFragment.onCreateView()");
LinearLayout layout = (LinearLayout)inflater.inflate(R.layout.fragment_item, null);
int position = getArguments().getInt("position");
TextView tv = (TextView)layout.findViewById(R.id.text);
tv.setText("Fragment # " + position);
tv.setTextColor(Color.WHITE);
tv.setTextSize(30);
return layout;
}
}
}
main.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
>
<android.support.v4.view.ViewPager
android:id="#+id/pager"
android:layout_width="match_parent"
android:layout_height="match_parent"
/>
</LinearLayout>
fragment_item.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
>
<TextView
android:id="#+id/text"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:gravity="center"
android:text="#string/hello"
/>
</LinearLayout>
My question is, instead of creating a new Fragment instance each time the user swipes left and right, how do I save a fragment's state (to some data structure) and then restore it?
The API demo doesn't seem to have any state information saving code at all.

Use ViewPager.setOffscreenPageLimit() in FragmentActivity
ViewPager pager = (ViewPager) findViewById(R.id.viewPager);
pager.setOffscreenPageLimit(2);
See more at How do I tell my custom FragmentPagerAdapter to stop destroying my fragments?

just override this method in FragmentpagerAdapter
#Override
public void destroyItem(ViewGroup container, int position, Object object) {
// TODO Auto-generated method stub
super.destroyItem(ViewGroup container, int position, Object object);
}
remove super.destroyItem(ViewGroup container, int position, Object object);
from your code

Update:
In the getItem of MyAdapter you return a new instance of your Fragment. Android will not call getItem on every swipe. It will only call getItem to get a new instance, but will reuse the existing instances as long as they are availible.
About the state part of the Demo. I can't help you. I think the normal techniques for restoring state in Fragements/Activities apply here, so nothing special when loading it in a ViewPager (but I might be wrong).

If you override
public void destroyItem(View container, int position, Object object)
without calling super, the fragment will not be destroyed and will be reused.

The adapter should be extended from FragmentStatePagerAdapter instead of FragmentPageAdapter and the adapter will keep reference from position to fragment item. On the activity or fragment parent, set listener OnPageChangeListener for PageIndicator to detect the position of fragment item has been activated and update related data's state.
About the data state of fragment item, I think should save/restore state from Activity or Fragement parent.
The adapter can add some code as following:
public static class MyAdapter extends FragmentStatePagerAdapter {
private SparseArray<TestFragment> mPageReferenceMap
= new SparseArray<TestFragment>();
...
#Override
public Object instantiateItem(ViewGroup viewGroup, int position) {
Object obj = super.instantiateItem(viewGroup, position);
//Add the reference when fragment has been create or restore
if (obj instanceof TestFragment) {
TestFragment f= (TestFragment)obj;
mPageReferenceMap.put(position, f);
}
return obj;
}
#Override
public void destroyItem(ViewGroup container, int position, Object object) {
//Remove the reference when destroy it
mPageReferenceMap.remove(position);
super.destroyItem(container, position, object);
}
public TestFragment getFragment(int key) {
return mPageReferenceMap.get(key);
}
...
}
Hope this help.

I tripped on some similar ground...
I wanted to keep my fragments saved within my adapter to avoid useless reloading since I only had 5 fragments in the FragmentPagerAdapter.
I basically had to create an array and override the getItem(position) method:
private StoryListFragment[] fragmentsArray
= new StoryListFragment[getCount()];
public SectionsAdapter(FragmentManager fm) {
super(fm);
}
#Override
public Fragment getItem(int position) {
if(fragmentsArray[position]!=null)
return fragmentsArray[position];
StoryListFragment storyListFragment = null;
switch(position){
case(0):
storyListFragment = StoryListFragment.newInstance(StoriesBank.NEWS);
break;
case(1):
storyListFragment = StoryListFragment.newInstance(StoriesBank.FEATURES);
break;
case(2):
storyListFragment= StoryListFragment.newInstance(StoriesBank.ARTS);
break;
}
fragmentsArray[position] = storyListFragment;
return storyListFragment;
}
#Override
public Object instantiateItem(ViewGroup container, int position) {
StoryListFragment fragment = (StoryListFragment) super.instantiateItem(container, position);
fragmentsArray[position] = fragment;
return fragment;
}