Im trying to implement switching of fragments inside first tab of view pager.I tried with approach found here link which uses root fragment in first tab and then switches child fragments. But when in second child fragment screen rotation occurs app switches back to first child fragment and besides that it seems like a hack.
I tried searching for other approaches but found dozens of answers that all seems messy.
Explanation from here seems right but i dont fully understand it.Here is the explanation and code from that link:
This approach is to switch the fragment that displays inside the FragmentPagerAdapter by overriding the getItem(...) method as well as getItemPosition(Object object) which is invoked every time you call viewPager.getAdapter().notifyDataSetChanged(). For example:
public static class MyPagerAdapter extends FragmentStatePagerAdapter {
// Return a different fragment for position based on additional state tracked in a member variable
#Override
public Fragment getItem(int position) {
// For a given position, return two different potential fragments based on a condition
}
// Force a refresh of the page when a different fragment is displayed
#Override
public int getItemPosition(Object object) {
// this method will be called for every fragment in the ViewPager
if (object instanceof SomePermanantCachedFragment) {
return POSITION_UNCHANGED; // don't force a reload
} else {
// POSITION_NONE means something like: this fragment is no longer valid
// triggering the ViewPager to re-build the instance of this fragment.
return POSITION_NONE;
}
}
}
Lets say i have ListFragment and DetailFragment that should switch in first tab.
Where will i call viewPager.getAdapter().notifyDataSetChanged() ?
(...based on additional state tracked in a member variable) how do i implement this?
SomePermanantCachedFragment refers to ListFragment in my case?
I also tried searching github for example but with no success...
If your fragments in a PagerAdapter are dynamic, then you should use a Dynamic FragmentPagerAdapter.
public class DynamicFragmentPagerAdapter extends PagerAdapter {
private static final String TAG = "DynamicFragmentPagerAdapter";
private final FragmentManager fragmentManager;
public static abstract class FragmentIdentifier implements Parcelable {
private final String fragmentTag;
private final Bundle args;
public FragmentIdentifier(#NonNull String fragmentTag, #Nullable Bundle args) {
this.fragmentTag = fragmentTag;
this.args = args;
}
protected FragmentIdentifier(Parcel in) {
fragmentTag = in.readString();
args = in.readBundle(getClass().getClassLoader());
}
#Override
public void writeToParcel(Parcel dest, int flags) {
dest.writeString(fragmentTag);
dest.writeBundle(args);
}
protected final Fragment newFragment() {
Fragment fragment = createFragment();
Bundle oldArgs = fragment.getArguments();
Bundle newArgs = new Bundle();
if(oldArgs != null) {
newArgs.putAll(oldArgs);
}
if(args != null) {
newArgs.putAll(args);
}
fragment.setArguments(newArgs);
return fragment;
}
protected abstract Fragment createFragment();
}
private ArrayList<FragmentIdentifier> fragmentIdentifiers = new ArrayList<>();
private FragmentTransaction currentTransaction = null;
private Fragment currentPrimaryItem = null;
public DynamicFragmentPagerAdapter(FragmentManager fragmentManager) {
this.fragmentManager = fragmentManager;
}
private int findIndexIfAdded(FragmentIdentifier fragmentIdentifier) {
for (int i = 0, size = fragmentIdentifiers.size(); i < size; i++) {
FragmentIdentifier identifier = fragmentIdentifiers.get(i);
if (identifier.fragmentTag.equals(fragmentIdentifier.fragmentTag)) {
return i;
}
}
return -1;
}
public void addFragment(FragmentIdentifier fragmentIdentifier) {
if (findIndexIfAdded(fragmentIdentifier) < 0) {
fragmentIdentifiers.add(fragmentIdentifier);
notifyDataSetChanged();
}
}
public void removeFragment(FragmentIdentifier fragmentIdentifier) {
int index = findIndexIfAdded(fragmentIdentifier);
if (index >= 0) {
fragmentIdentifiers.remove(index);
notifyDataSetChanged();
}
}
#Override
public int getCount() {
return fragmentIdentifiers.size();
}
#Override
public void startUpdate(#NonNull ViewGroup container) {
if (container.getId() == View.NO_ID) {
throw new IllegalStateException("ViewPager with adapter " + this
+ " requires a view id");
}
}
#SuppressWarnings("ReferenceEquality")
#NonNull
#Override
public Object instantiateItem(#NonNull ViewGroup container, int position) {
if (currentTransaction == null) {
currentTransaction = fragmentManager.beginTransaction();
}
final FragmentIdentifier fragmentIdentifier = fragmentIdentifiers.get(position);
// Do we already have this fragment?
final String name = fragmentIdentifier.fragmentTag;
Fragment fragment = fragmentManager.findFragmentByTag(name);
if (fragment != null) {
currentTransaction.attach(fragment);
} else {
fragment = fragmentIdentifier.newFragment();
currentTransaction.add(container.getId(), fragment, fragmentIdentifier.fragmentTag);
}
if (fragment != currentPrimaryItem) {
fragment.setMenuVisibility(false);
fragment.setUserVisibleHint(false);
}
return fragment;
}
#Override
public void destroyItem(#NonNull ViewGroup container, int position, #NonNull Object object) {
if (currentTransaction == null) {
currentTransaction = fragmentManager.beginTransaction();
}
currentTransaction.detach((Fragment) object);
}
#SuppressWarnings("ReferenceEquality")
#Override
public void setPrimaryItem(#NonNull ViewGroup container, int position, #NonNull Object object) {
Fragment fragment = (Fragment) object;
if (fragment != currentPrimaryItem) {
if (currentPrimaryItem != null) {
currentPrimaryItem.setMenuVisibility(false);
currentPrimaryItem.setUserVisibleHint(false);
}
fragment.setMenuVisibility(true);
fragment.setUserVisibleHint(true);
currentPrimaryItem = fragment;
}
}
#Override
public void finishUpdate(#NonNull ViewGroup container) {
if (currentTransaction != null) {
currentTransaction.commitNowAllowingStateLoss();
currentTransaction = null;
}
}
#Override
public boolean isViewFromObject(#NonNull View view, #NonNull Object object) {
return ((Fragment) object).getView() == view;
}
#Override
public Parcelable saveState() {
Bundle bundle = new Bundle();
bundle.putParcelableArrayList("fragmentIdentifiers", fragmentIdentifiers);
return bundle;
}
#Override
public void restoreState(Parcelable state, ClassLoader loader) {
Bundle bundle = ((Bundle)state);
bundle.setClassLoader(loader);
fragmentIdentifiers = bundle.getParcelableArrayList("fragmentIdentifiers");
}
}
Once you have that, you can use removeFragment and addFragment to change the fragments inside your ViewPager.
You could technically add a setFragment(int index) method to replace it at index 0 specifically.
If the fragments don't seem to update, the trick to refreshing a ViewPager is always setAdapter(null); setAdapter(adapter);.
I am setting up the fragment A,B thru FragmentStatePagerAdapter and having activity with FragmentActivity inside
Acitivity#onCreate
journeyDetailInfos = Manager.INSTANCE.getSeatOffline();
binding = DataBindingUtil.setContentView(this, R.layout.layout);
viewModel = ViewModelProviders.of(this).get(XYZModelView.class);
binding.pager.setAdapter(new SeatJourneyAdapter(this, getSupportFragmentManager(), journeyDetailInfos));
binding.pager.setOffscreenPageLimit(10);
binding.pager.addOnPageChangeListener(this);
binding.tablayout.setupWithViewPager(binding.pager);
binding.tablayout.setOnClickListener(view -> onTabChange());
lastSelectedPage = binding.tablayout.getSelectedTabPosition();
int length = binding.tablayout.getTabCount();
for (int i = 0; i < length; i++) {
binding.tablayout.getTabAt(i).setCustomView(getTabView(i));
}
SeatJourneyAdapter.java Adpater has following code
HashMap<Integer,XYZFragment> fragments;
ArrayList<JourneyDetailsInfo> journeyDetailInfos;
Context context;
private int container_id;
HashMap mFragmentTags ;
SeatJourneyAdapter(Context context, FragmentManager fragmentManager, ArrayList<JourneyDetailsInfo> journeyDetailInfos)
{
super(fragmentManager);
frgaments = new HashMap<Integer,XYZFragment>();
this.journeyDetailInfos = journeyDetailInfos;
mFragmentTags = new HashMap<Integer, String>();
}
#Override
public Fragment getItem(int position) {
XYZFragement fragment = null;
fragment = new XYZFragement();
fragment.setPosition(position);
fragment.setSeatDetails(journeyDetailInfos.get(position).getPaxDetailsInfos());
fragment.setCountJourney(journeyDetailInfos.size());
frgaments.put(position,fragment);
return fragment;
}
#Override
public int getCount() {
return journeyDetailInfos.size();
}
And onCreateView of Fragment is
binding = DataBindingUtil.inflate(inflater, R.layout.layout_name, container, false);
binding.paxWithSeatList.setLayoutManager(new LinearLayoutManager(this.getContext()));
binding.setSeatPax(viewModel);
viewModel.setPassengers(seatDetails);
return binding.getRoot();
Problem is when the data list "journeyDetailInfos" has count of 2 the Fragment shows a data of second item of data list "journeyDetailInfos". It works smooth if the count is more than 2 While I tried with all possible solution discussed in issue nothing worked for me.
Try FragmentPagerAdapter instead of FragmentStatePagerAdapter and Override getItemId to update pager smoothly.
SeatJourneyAdapter.java
private class SeatJourneyAdapter extends FragmentPagerAdapter {
final SparseArray<Fragment> registeredFragments = new SparseArray<Fragment>();
public SeatJourneyAdapter() {
super(getChildFragmentManager());
}
#Override
public Fragment getItem(final int pos) {
XYZFragement fragment = null;
fragment = new XYZFragement();
fragment.setPosition(position);
fragment.setSeatDetails(journeyDetailInfos.get(position).getPaxDetailsInfos());
fragment.setCountJourney(journeyDetailInfos.size());
frgaments.put(position,fragment);
return fragment;
}
/**
* Implementing this method is IMPORTANT for detorying the fragment.
* Use unique id for each item on pagerData.
*/
#Override
public long getItemId(int position) {
return journeyDetailInfos.get(position).getId(); // Unique id by position and pager data.
}
#NonNull
#Override
public Object instantiateItem(ViewGroup container, int position) {
Fragment fragment = (Fragment) super.instantiateItem(container, position);
registeredFragments.put(position, fragment);
return fragment;
}
#Override
public void destroyItem(ViewGroup container, int position, Object object) {
registeredFragments.remove(position);
super.destroyItem(container, position, object);
}
public Fragment getRegisteredFragment(int position) {
return registeredFragments.get(position);
}
#Override
public int getCount() {
return journeyDetailInfos.size();
}
}
Here's the inner class that contains fragments and changes fragment views on swipe. This class is defined in an Activity.
private class ViewPagerAdapter extends FragmentPagerAdapter {
private int count;
ViewPagerAdapter(FragmentManager fm, int count) {
super(fm);
this.count = count;
}
#Override
public Fragment getItem(int position) {
switch(position) {
case 0:
return new FriendsListFragment();
case 1:
Bundle bundle = new Bundle();
bundle.putString(Keys.TAG, ChatListFragment.class.getSimpleName());
ChatListFragment chatListFragment = new ChatListFragment();
chatListFragment.setArguments(bundle);
return chatListFragment;
case 2:
return new MoreFragment();
default:
return null;
}
}
#Override
public int getCount() {
return count;
}
}
Here I would like to add a code that sets tags to each fragment, so that I can recognize which fragment I'm at.
I searched quite much, and I haven't found a proper answer for this question, so please help.
You can override the setPrimaryItem method of your FragmentPagerAdapter.
private class ViewPagerAdapter extends FragmentPagerAdapter {
protected int currentPosition = -1;
protected Fragment currentFragment;
public ViewPagerAdapter(FragmentManager fm) {
super(fm);
}
#Override
public Fragment getItem(int position) {
// ....
}
#Override
public void setPrimaryItem(ViewGroup container, int position, Object object) {
super.setPrimaryItem(container, position, object);
this.currentPosition = position;
if (object instanceof Fragment) {
this.currentFragment = (Fragment) object;
}
}
public int getCurrentPosition() {
return currentPosition;
}
public Fragment getCurrentFragment() {
return currentFragment;
}
}
Just use getCurrentPosition or getCurrentFragment methods to get information about current Fragment.
From my FragmentActivity, i want to update my ListView of a Fragment(created by code) at onRestart of the FragmentActivity. There is no fragment and tag in XML file. Here is my FragmentActivity.
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
viewPager = (ViewPager) findViewById(R.id.pager);
mAdapter = new ProfilePagerAdapter(getSupportFragmentManager(),
myFriendsList, notifiedFriendsList);
viewPager.setAdapter(mAdapter);
..........
my FragmentPagerAdapter is
public class ProfilePagerAdapter extends FragmentPagerAdapter {
private ArrayList<Friend> myFriends;
private ArrayList<ExpandableChild> notifiedFriendsList;
private SparseArray<Fragment> registeredFragments = new SparseArray<Fragment>();
public ProfilePagerAdapter(FragmentManager fm, ArrayList<Friend> myFriends, ArrayList<ExpandableChild> notifiedFriendsList) {
super(fm);
// TODO Auto-generated constructor stub
this.myFriends = myFriends;
this.notifiedFriendsList = notifiedFriendsList;
}
#Override
public Fragment getItem(int index) {
switch (index) {
case 0:
return new FriendsFragment(myFriends);
case 1:
return new MyProfileFragment(notifiedFriendsList);
}
return null;
}
#Override
public int getCount() {
return 2;
}
#Override
public Object instantiateItem(ViewGroup container, int position) {
Fragment fragment = (Fragment) super.instantiateItem(container, position);
registeredFragments.put(position, fragment);
return fragment;
}
#Override
public void destroyItem(ViewGroup container, int position, Object object) {
registeredFragments.remove(position);
super.destroyItem(container, position, object);
}
public Fragment getRegisteredFragment(int position) {
return registeredFragments.get(position);
}
In my FriendsFragment class, i have a ListView. I used following two methods to update the ListView from my FragmentActivity in the class.
public void setNewFriendList(ArrayList<Friend> myFriends){
this.friendsList = myFriends;
}
public void updateList(){
adapter.notifyDataSetChanged();
}
Now i want to update the ListView of FriendsFragment at onRestart() of FragmentActivity in following way.
#Override
protected void onRestart() {
// TODO Auto-generated method stub
super.onRestart();
android.support.v4.app.Fragment frag = mAdapter
.getRegisteredFragment(0);
if (frag != null) {
((FriendsFragment) frag).setNewFriendList(myFriendsList);
((FriendsFragment) frag).updateList();
Toast.makeText(UserProfileTab.this, "Updated",Toast.LENGTH_LONG).show();
} else {
Toast.makeText(UserProfileTab.this, "Not Updated:",Toast.LENGTH_LONG).show();
}
}
But in Toast shows Not Updated as frag returns null. I followed link1 and link1. Thanks in advance.
I'm using the v4 compatibility ViewPager in Android. My FragmentActivity has a bunch of data which is to be displayed in different ways on different pages in my ViewPager. So far I just have 3 instances of the same ListFragment, but in the future I will have 3 instances of different ListFragments. The ViewPager is on a vertical phone screen, the lists are not side-by-side.
Now a button on the ListFragment starts an separate full-page activity (via the FragmentActivity), which returns and FragmentActivity modifies the data, saves it, then attempts to update all views in its ViewPager. It is here, where I am stuck.
public class ProgressMainActivity extends FragmentActivity
{
MyAdapter mAdapter;
ViewPager mPager;
#Override
public void onCreate(Bundle savedInstanceState)
{
...
mAdapter = new MyAdapter(getSupportFragmentManager());
mPager = (ViewPager) findViewById(R.id.viewpager);
mPager.setAdapter(mAdapter);
}
#Override
protected void onActivityResult(int requestCode, int resultCode, Intent data)
{
...
updateFragments();
...
}
public void updateFragments()
{
//Attempt 1:
//mAdapter.notifyDataSetChanged();
//mPager.setAdapter(mAdapter);
//Attempt 2:
//HomeListFragment fragment = (HomeListFragment) getSupportFragmentManager().findFragmentById(mAdapter.fragId[0]);
//fragment.updateDisplay();
}
public static class MyAdapter extends FragmentPagerAdapter implements
TitleProvider
{
int[] fragId = {0,0,0,0,0};
public MyAdapter(FragmentManager fm)
{
super(fm);
}
#Override
public String getTitle(int position){
return titles[position];
}
#Override
public int getCount(){
return titles.length;
}
#Override
public Fragment getItem(int position)
{
Fragment frag = HomeListFragment.newInstance(position);
//Attempt 2:
//fragId[position] = frag.getId();
return frag;
}
#Override
public int getItemPosition(Object object) {
return POSITION_NONE; //To make notifyDataSetChanged() do something
}
}
public class HomeListFragment extends ListFragment
{
...
public static HomeListFragment newInstance(int num)
{
HomeListFragment f = new HomeListFragment();
...
return f;
}
...
Now as you can see, my first attempt was to notifyDataSetChanged on the entire FragmentPagerAdapter, and this showed to update the data sometimes, but others I got an IllegalStateException: Can not perform this action after onSaveInstanceState.
My second attempt involed trying to call an update function in my ListFragment, but getId in getItem returned 0. As per the docs I tried by
acquiring a reference to the Fragment from FragmentManager, using
findFragmentById() or findFragmentByTag()
but I don't know the tag or id of my Fragments! I have an android:id="#+id/viewpager" for ViewPager, and a android:id="#android:id/list" for my ListView in the ListFragment layout, but I don't think these are useful.
So, how can I either:
a) update the entire ViewPager safely in one go (ideally returning the user to the page he was on before) - it is ok that the user see the view change.
Or preferably,
b) call a function in each affected ListFragment to update the ListView manually.
Any help would be gratefully accepted!
Barkside's answer works with FragmentPagerAdapter but doesn't work with FragmentStatePagerAdapter, because it doesn't set tags on fragments it passes to FragmentManager.
With FragmentStatePagerAdapter it seems we can get by, using its instantiateItem(ViewGroup container, int position) call. It returns reference to fragment at position position. If FragmentStatePagerAdapter already holds reference to fragment in question, instantiateItem just returns reference to that fragment, and doesn't call getItem() to instantiate it again.
So, suppose, I'm currently looking at fragment #50, and want to access fragment #49. Since they are close, there's a good chance the #49 will be already instantiated. So,
ViewPager pager = findViewById(R.id.viewpager);
FragmentStatePagerAdapter a = (FragmentStatePagerAdapter) pager.getAdapter();
MyFragment f49 = (MyFragment) a.instantiateItem(pager, 49)
OK, I think I've found a way to perform request b) in my own question so I'll share for others' benefit. The tag of fragments inside a ViewPager is in the form "android:switcher:VIEWPAGER_ID:INDEX", where VIEWPAGER_ID is the R.id.viewpager in XML layout, and INDEX is the position in the viewpager. So if the position is known (eg 0), I can perform in updateFragments():
HomeListFragment fragment =
(HomeListFragment) getSupportFragmentManager().findFragmentByTag(
"android:switcher:"+R.id.viewpager+":0");
if(fragment != null) // could be null if not instantiated yet
{
if(fragment.getView() != null)
{
// no need to call if fragment's onDestroyView()
//has since been called.
fragment.updateDisplay(); // do what updates are required
}
}
I've no idea if this is a valid way of doing it, but it'll do until something better is suggested.
Try to record the tag each time a Fragement is instantiated.
public class MPagerAdapter extends FragmentPagerAdapter {
private Map<Integer, String> mFragmentTags;
private FragmentManager mFragmentManager;
public MPagerAdapter(FragmentManager fm) {
super(fm);
mFragmentManager = fm;
mFragmentTags = new HashMap<Integer, String>();
}
#Override
public int getCount() {
return 10;
}
#Override
public Fragment getItem(int position) {
return Fragment.instantiate(mContext, AFragment.class.getName(), null);
}
#Override
public Object instantiateItem(ViewGroup container, int position) {
Object obj = super.instantiateItem(container, position);
if (obj instanceof Fragment) {
// record the fragment tag here.
Fragment f = (Fragment) obj;
String tag = f.getTag();
mFragmentTags.put(position, tag);
}
return obj;
}
public Fragment getFragment(int position) {
String tag = mFragmentTags.get(position);
if (tag == null)
return null;
return mFragmentManager.findFragmentByTag(tag);
}
}
If you ask me, the second solution on the below page, keeping track of all the "active" fragment pages, is better: http://tamsler.blogspot.nl/2011/11/android-viewpager-and-fragments-part-ii.html
The answer from barkside is too hacky for me.
you keep track of all the "active" fragment pages. In this case, you keep track of the fragment pages in the FragmentStatePagerAdapter, which is used by the ViewPager.
private final SparseArray<Fragment> mPageReferences = new SparseArray<Fragment>();
public Fragment getItem(int index) {
Fragment myFragment = MyFragment.newInstance();
mPageReferences.put(index, myFragment);
return myFragment;
}
To avoid keeping a reference to "inactive" fragment pages, we need to implement the FragmentStatePagerAdapter's destroyItem(...) method:
public void destroyItem(View container, int position, Object object) {
super.destroyItem(container, position, object);
mPageReferences.remove(position);
}
... and when you need to access the currently visible page, you then call:
int index = mViewPager.getCurrentItem();
MyAdapter adapter = ((MyAdapter)mViewPager.getAdapter());
MyFragment fragment = adapter.getFragment(index);
... where the MyAdapter's getFragment(int) method looks like this:
public MyFragment getFragment(int key) {
return mPageReferences.get(key);
}
"
Okay, after testing the method by #barkside above, I could not get it to work with my application. Then I remembered that the IOSched2012 app uses a viewpager as well, and that is where I found my solution. It does not use any fragment ID's or Tags as these are not stored by viewpager in an easily accessible way.
Here's the important parts from the IOSched apps HomeActivity. Pay particular attention to the comment, as therein lies the key.:
#Override
protected void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
// Since the pager fragments don't have known tags or IDs, the only way to persist the
// reference is to use putFragment/getFragment. Remember, we're not persisting the exact
// Fragment instance. This mechanism simply gives us a way to persist access to the
// 'current' fragment instance for the given fragment (which changes across orientation
// changes).
//
// The outcome of all this is that the "Refresh" menu button refreshes the stream across
// orientation changes.
if (mSocialStreamFragment != null) {
getSupportFragmentManager().putFragment(outState, "stream_fragment",
mSocialStreamFragment);
}
}
#Override
protected void onRestoreInstanceState(Bundle savedInstanceState) {
super.onRestoreInstanceState(savedInstanceState);
if (mSocialStreamFragment == null) {
mSocialStreamFragment = (SocialStreamFragment) getSupportFragmentManager()
.getFragment(savedInstanceState, "stream_fragment");
}
}
And store instances of you Fragments in the FragmentPagerAdapter like so:
private class HomePagerAdapter extends FragmentPagerAdapter {
public HomePagerAdapter(FragmentManager fm) {
super(fm);
}
#Override
public Fragment getItem(int position) {
switch (position) {
case 0:
return (mMyScheduleFragment = new MyScheduleFragment());
case 1:
return (mExploreFragment = new ExploreFragment());
case 2:
return (mSocialStreamFragment = new SocialStreamFragment());
}
return null;
}
Also, remember to guard your Fragment calls like so:
if (mSocialStreamFragment != null) {
mSocialStreamFragment.refresh();
}
You can copy FragmentPagerAdapter and modify some source code, add getTag() method
for example
public abstract class AppFragmentPagerAdapter extends PagerAdapter {
private static final String TAG = "FragmentPagerAdapter";
private static final boolean DEBUG = false;
private final FragmentManager mFragmentManager;
private FragmentTransaction mCurTransaction = null;
private Fragment mCurrentPrimaryItem = null;
public AppFragmentPagerAdapter(FragmentManager fm) {
mFragmentManager = fm;
}
public abstract Fragment getItem(int position);
#Override
public void startUpdate(ViewGroup container) {
}
#Override
public Object instantiateItem(ViewGroup container, int position) {
if (mCurTransaction == null) {
mCurTransaction = mFragmentManager.beginTransaction();
}
final long itemId = getItemId(position);
String name = getTag(position);
Fragment fragment = mFragmentManager.findFragmentByTag(name);
if (fragment != null) {
if (DEBUG) Log.v(TAG, "Attaching item #" + itemId + ": f=" + fragment);
mCurTransaction.attach(fragment);
} else {
fragment = getItem(position);
if (DEBUG) Log.v(TAG, "Adding item #" + itemId + ": f=" + fragment);
mCurTransaction.add(container.getId(), fragment,
getTag(position));
}
if (fragment != mCurrentPrimaryItem) {
fragment.setMenuVisibility(false);
fragment.setUserVisibleHint(false);
}
return fragment;
}
#Override
public void destroyItem(ViewGroup container, int position, Object object) {
if (mCurTransaction == null) {
mCurTransaction = mFragmentManager.beginTransaction();
}
if (DEBUG) Log.v(TAG, "Detaching item #" + getItemId(position) + ": f=" + object
+ " v=" + ((Fragment) object).getView());
mCurTransaction.detach((Fragment) object);
}
#Override
public void setPrimaryItem(ViewGroup container, int position, Object object) {
Fragment fragment = (Fragment) object;
if (fragment != mCurrentPrimaryItem) {
if (mCurrentPrimaryItem != null) {
mCurrentPrimaryItem.setMenuVisibility(false);
mCurrentPrimaryItem.setUserVisibleHint(false);
}
if (fragment != null) {
fragment.setMenuVisibility(true);
fragment.setUserVisibleHint(true);
}
mCurrentPrimaryItem = fragment;
}
}
#Override
public void finishUpdate(ViewGroup container) {
if (mCurTransaction != null) {
mCurTransaction.commitAllowingStateLoss();
mCurTransaction = null;
mFragmentManager.executePendingTransactions();
}
}
#Override
public boolean isViewFromObject(View view, Object object) {
return ((Fragment) object).getView() == view;
}
#Override
public Parcelable saveState() {
return null;
}
#Override
public void restoreState(Parcelable state, ClassLoader loader) {
}
public long getItemId(int position) {
return position;
}
private static String makeFragmentName(int viewId, long id) {
return "android:switcher:" + viewId + ":" + id;
}
protected abstract String getTag(int position);
}
then extend it, override these abstract method,don't need to be afraid of Android Group change
FragmentPageAdapter source code in the future
class TimeLinePagerAdapter extends AppFragmentPagerAdapter {
List<Fragment> list = new ArrayList<Fragment>();
public TimeLinePagerAdapter(FragmentManager fm) {
super(fm);
list.add(new FriendsTimeLineFragment());
list.add(new MentionsTimeLineFragment());
list.add(new CommentsTimeLineFragment());
}
public Fragment getItem(int position) {
return list.get(position);
}
#Override
protected String getTag(int position) {
List<String> tagList = new ArrayList<String>();
tagList.add(FriendsTimeLineFragment.class.getName());
tagList.add(MentionsTimeLineFragment.class.getName());
tagList.add(CommentsTimeLineFragment.class.getName());
return tagList.get(position);
}
#Override
public int getCount() {
return list.size();
}
}
Also works without problems:
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();
}
Alternatively you can override setPrimaryItem method from FragmentPagerAdapter like so:
public void setPrimaryItem(ViewGroup container, int position, Object object) {
if (mCurrentFragment != object) {
mCurrentFragment = (Fragment) object; //Keep reference to object
((MyInterface)mCurrentFragment).viewDidAppear();//Or call a method on the fragment
}
super.setPrimaryItem(container, position, object);
}
public Fragment getCurrentFragment(){
return mCurrentFragment;
}
I want to give my approach in case it can help anyone else:
This is my pager adapter:
public class CustomPagerAdapter extends FragmentStatePagerAdapter{
private Fragment[] fragments;
public CustomPagerAdapter(FragmentManager fm) {
super(fm);
fragments = new Fragment[]{
new FragmentA(),
new FragmentB()
};
}
#Override
public Fragment getItem(int arg0) {
return fragments[arg0];
}
#Override
public int getCount() {
return fragments.length;
}
}
In my activity I have:
public class MainActivity {
private ViewPager view_pager;
private CustomPagerAdapter adapter;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
adapter = new CustomPagerAdapter(getSupportFragmentManager());
view_pager = (ViewPager) findViewById(R.id.pager);
view_pager.setAdapter(adapter);
view_pager.setOnPageChangeListener(this);
...
}
}
Then to get the current fragment what I do is:
int index = view_pager.getCurrentItem();
Fragment currentFragment = adapter.getItem(index);
This is my solution since I don't need to keep track of my tabs and need to refresh them all anyway.
Bundle b = new Bundle();
b.putInt(Constants.SharedPreferenceKeys.NUM_QUERY_DAYS,numQueryDays);
for(android.support.v4.app.Fragment f:getSupportFragmentManager().getFragments()){
if(f instanceof HomeTermFragment){
((HomeTermFragment) f).restartLoader(b);
}
}