Develop Reference

notifyDataSetChanged Method Takes Away Smooth Scrolling From Tabs

I am currently using Material Design in an Android app that I am making. In this app, I am using the Material Design tab layout to display some information that I am receiving. However when I tap the tabs, the animation is not smooth, and it is very abrupt. Sliding to go to the other tab, however is very smooth.
mTabLayout = (TabLayout) findViewById(R.id.chem_tab_layout);
mGenericAdapter = new GenericPagerAdapter(getSupportFragmentManager());
mPager = (ViewPager) findViewById(R.id.view_pager);
mPager.setAdapter(mGenericAdapter);
//Notice how the Tab Layout links with the Pager Adapter
mTabLayout.setTabsFromPagerAdapter(mGenericAdapter);
//Notice how The Tab Layout and View Pager object are linked
mTabLayout.setupWithViewPager(mPager);
mPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(mTabLayout){
#Override
public void onPageSelected(int position) {
mGenericAdapter.notifyDataSetChanged();
}
});
That is my code for setting the adapter, etc.
This is my custom adapter code for the tabs:
class GenericPagerAdapter extends FragmentStatePagerAdapter {
public GenericPagerAdapter(FragmentManager fm) {
super(fm);
}
#Override
public Fragment getItem(int position) {
ChemGridActivity.MyFragment myFragment = new ChemGridActivity.MyFragment();
return myFragment;
}
#Override
public int getCount() {
return 3; //returns number of tabs that need to be created
}
#Override
public CharSequence getPageTitle(int position) {
if (position == 0) return "Chemistry";
if (position == 1) return "Mathematics";
if (position == 2) return "Physics";
else return null;
}
#Override
public int getItemPosition(Object object) {
return POSITION_NONE;
}
I feel that the choppy transition between tabs is caused by the overriden method onPageSelected method when I add onPageChangeListener. What do I add to this method to make tapping on tabs a smoother animation?

Without knowing much about the internals of your classes, I imagine the problem is not that you have a listener, but what you are doing inside that listener.
In the case of most adapters notifyDataSetChanged() will cause it to re-render the entire view again (including all pages).
Seeing as you haven't specified what the intent here with the notification is, it's hard to tell you how you can do this in an alternative way, but you do need to do something less intensive if you want the animation to remain smooth.
I suspect you just want to change which fragment is shown, in which case just use the FragmentManager where necessary, remembering to reuse fragments which have already been seen once.
EDIT Based on additional info in comments
#Override
public Fragment getItem(int position) {
//POSITION_SOMETHINHG would be one of a set of constants to indicate hwa to display
return ChemGridActivity.MyFragment.newInstance(ChemGridActivity.MyFragment.POSITION_SOMETHINHG);
}
public class ChemGridActivity.MyFragment ... {
private static final String KEY_DISPLAY_TYPE = "KEY_DISPLAY_TYPE";
public static final int POSITION_SOMETHINHG = 11111;
public static MyFragment newInstance(int display) {
MyFragment f = new MyFragment();
Bundle bund = new Bundle();
bund.putInt(KEY_DISPLAY_TYPE, display);
f.setArguments(bund);
return f;
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Bundle args = getArguments();
if (args != null) {
mDisplay = args.getInt(KEY_DISPLAY_TYPE, 0);
}
}
#Override
public View onCreateView(final LayoutInflater inflater, final ViewGroup container, final Bundle savedInstanceState) {
final View view = inflater.inflate(R.layout.my_layout, container, false);
//TODO: change something based on mDisplay
return view;
}

Viewpager gets the wrong page

I have looked in several topics like this but didn't see how to fix my problem
I have a resturant for say.. with dynamic number of categories.. I put all the categories in a list.. and create fragments by from those categories
so I cant just
case 0 : fragment0
case 1 :frament 1
because I dont know how much categories I have untill runtime
class MyPageAdapter extends FragmentStatePagerAdapter {
private List<MyFragment> fragments = new ArrayList<>();
private List<menuCat> Categories = new ArrayList<>();
public MyPageAdapter(FragmentManager fm, List<menuCat> Categories) {
super(fm);
this.Categories = Categories;
for (int i = 0; i<Categories.size();i++)
{
fragments.add(MyFragment.newInstance(Categories.get(i)));
}
}
#Override
public String getPageTitle(int position)
{
return Categories.get(position).catName();
}
#Override
public MyFragment getItem(int position) {
return this.fragments.get(position);
}
#Override
public int getCount() {
return this.fragments.size();
}
MyFragment.class
public class MyFragment extends Fragment {
public static final MyFragment newInstance(menuCat category)
{
Bundle bun = new Bundle();
bun.putString("category", category.toJson());
MyFragment f = new MyFragment();
f.setArguments(bun);
return f;
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.fragment_my, container, false);
String json = getArguments().getString("category");
menuCat category = menuCat.fromJson(json);
System.out.println(category.catName());
ArrayList<Card> cards = new ArrayList<Card>();
for(menuItem item : category.getItems())
{
Card card = new Card(getActivity());
// Create a CardHeader
CardHeader header = new CardHeader(getActivity());
// Add Header to card
header.setTitle(item.getName());
card.setTitle(item.getPrice());
card.addCardHeader(header);
CardThumbnail thumb = new CardThumbnail(getActivity());
//thumb.setDrawableResource(listImages[i]);
//card.addCardThumbnail(thumb);
cards.add(card);
}
CardArrayAdapter mCardArrayAdapter = new CardArrayAdapter(getActivity(), cards);
CardListView listView = (CardListView) getActivity().findViewById(R.id.myList);
if (listView != null) {
listView.setAdapter(mCardArrayAdapter);
}
return v;
}
}
this is my adapter, my problem is for example
if I am in page 1 and I need page 3 data.. if I will go to page 2.. it will display data of page 3 OR if I go to page 5 then go backward.. to 4 it will also show data of page 3.. I mean it gets me like the data of the next page instead of current one.

Creating all of your fragments in the constructor is very poor design, as you're creating references to these objects which will later be attached to an Activity, but when they are detached, you continue to hold the reference. In the end, this is going to cause you a lot of frustration with memory leaks.
Is it not possible to simply remove fragments and change your methods to the following:
#Override
public MyFragment getItem(int position) {
return MyFragment.newInstance(Categories.get(position));
}
#Override
public int getCount() {
return Categories.size();
}
I'm not certain this will solve all of your problems, but it is a start.

Random Out Of Bounds after removing item from static list used by multiple fragments

I have a fragment with a viewpager with adapter extending FragmentStatePagerAdapter with three slidable fragments inside. the main fragment has a static list of data, and three sub-fragments references and show the same list (don't ask why). The list item can be removed by a button inside the row layout or by clicking clear-all button after the list in each of those three fragments.
My problem is that after removing one or all the items with the buttons, sometimes i get an instant index out of bounds exception (no application code in stack trace, to find where the exception is coming from) or randomly sometimes removal work, but fragments nearby display old data with the extra item, and clicking to remove it ofcourse throws out of bounds exception, because after some debugging I can see that size of list passed to adapter to recreate the nearby fragment is lower by one (removal is successful) so I believe the list is not notified/invalidated correctly. Any help, since stacktrace can't help?
Btw I'm using FragmentStatePagerAdapter.POSITION_NONE to recreate the fragments with new data on each swipe, notifyDataSetChanged to notify the adapter of changed data, and invalidate() the listview in onViewCreated(), but they don't help.
relevant code:
Main Fragment
public class MainFragment extends BaseFragment<CategoryTreeItem> {
public static List<Map.Entry<EventTreeItem, String>> betList = new ArrayList<>();
...
#Override
public void onViewCreated(View view, Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
ViewPager mViewPager = (ViewPager) view.findViewById(R.id.viewpager);
mViewPager.setAdapter(new MyPagerAdapter(getChildFragmentManager()));
SlidingTabLayout mSlidingTabLayout = (SlidingTabLayout) view.findViewById(R.id.sliding_tabs);
mSlidingTabLayout.setViewPager(mViewPager);
}
}
class MyPagerAdapter extends FragmentStatePagerAdapter {
private List<String> items;
public MyPagerAdapter(FragmentManager fm) {
super(fm);
items = getResources().getStringArray(R.array.three_categories);
}
#Override
public Fragment getItem(int i) {
Fragment fragment;
switch (i) {
case 0:
fragment = new FirstFragment();
return fragment;
case 1:
fragment = new SecondFragment();
return fragment;
case 2:
fragment = new ThirdFragment();
return fragment;
default:
return null;
}
}
...
#Override
public int getItemPosition(Object object) {
return FragmentStatePagerAdapter.POSITION_NONE;
}
}
Three fragments (they are needed since the layout and functionality is a bit different)
public class First/Second/ThirdFragment extends BaseListFragment<ArrayList<EventTreeItem>> {
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
return inflater.inflate(R.layout.fragment_main, container, false);
}
#Override
public void onViewCreated(View view, Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
MyListAdapter adapter = new MyListdapter(getActivity(), R.layout.item_first/second/thirdfragment, MainFragment.betList);
getListView().setItemsCanFocus(true);
View footerView = getLayoutInflater(savedInstanceState).inflate(R.layout.include_first/second/third_footer, getListView(), false);
getListView().addFooterView(footerView);
adapter.notifyDataSetChanged();
setListAdapter(adapter);
getListView().invalidate();
//handles REMOVE ALL button for all fragments footer button
Helper.setUpClearOption(footerView, adapter);
}
}
MyListAdapter
#CompileStatic
public class MyListAdapter extends ArrayAdapter<Map.Entry<EventTreeItem,String>> {
private int mResourceId;
private List<Map.Entry<EventTreeItem,String>> mObjects;
public MyListAdapter(Context context, int resource, List<Map.Entry<EventTreeItem,String>> objects) {
super(context, resource, objects);
mResourceId = resource;
mObjects = objects;
}
#Override
public View getView(final int position, View convertView, ViewGroup parent) {
View view = convertView;
if (view == null) {
view = LayoutInflater.from(getContext()).inflate(mResourceId, parent, false);
}
//------setting a lot of text for textViews
// .....
//------
ImageView ivRemove = (ImageView) view.findViewById(R.id.ivRemove);
ivRemove.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
//Tried removing directly from adapter, not helping
// MyListAdapter.this.remove(mObjects.get(position));
MainFragment.betList.remove(position);
MyListAdapter.this.notifyDataSetChanged();
}
});
return view;
}
}
Remove All helper method (also returning instant OOB or not notifying neighbor fragments)
public static void setUpClearOption(View view, final ArrayAdapter adapter) {
ImageView ivRemoveAll = (ImageView) view.findViewById(R.id.ivRemoveAll);
ivRemoveAll.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
adapter.clear();
adapter.notifyDataSetChanged();
}
});
}
So any help is much appreciated!

I managed to fix My problem by creating three listadapters for each of my fragments (static adapters instantiaiting with null value ) and in onClick I check each of those three adapters if they are not null (since adapters are null until after onViewCreated, and it is called only when the current fragment is a neighbor). All three adapters use the same data.

ListFragments Wrong Data Weird Pager

I hope someone can assist please. I have a Fragment hosting multiple list fragments using support library. The list fragments are supposed to display data that i retrieve form an async task in the parent fragment. I have been trying to figure out exactly how the data is being loaded because it is not loading correctly.
Each time the list display fragment is launched it preforms an async task to get and parse Json into an ArrayList <ArrayList <HashMap <String, String> > >
Each List fragment queries the parent fragment for data at its position in the ArrayList.
eg. For the 3rd page in it should retrieve arrList[2] which contains an `ArrayList <HashMap <String, String> > to display as a list.
The pager is acting weird. Maybe i am not understanding the lifecycle of the fragments or how the pager uses them. I have 7 Fragments. If i start on frag3 the pager will show fragment 3 with no data on it. It also loads fragment 2 and 4 with no data. If i go left to frag 1 it will display fragment 1 correctly and load fragment 0. I can properly switch to frag 0 but if i switch to frag 2 it loads data from frag 0 and loads frag 0's data into all of the rest of the views. If i go back and forth enough it will replace all data in every fragment with data from frag 0. I believe that it does not load data immediately because it does not have the data when the viewpager launches. I have not made it wait for the async task yet.
I thought that each fragment gets its view redrawn each time it is taken far enough from view. So i put Update in the onCreateView() of the fragment. I feel like this is a small thing that i have just misplaced or i am overlooking it. I tried to implement FragmentStatePagerAdapter but i do not think that i did it right.
Any Help is much Appreciated And i am very open to discussion if i am just doing things horribly wrong. I usually do. It never fails. Create something to find out i need to rewrite everything.
public class ListFragmentDisplay extends SherlockFragment {
public static final String TAG = "listFragmentDisplay";
Calendar calendar = Calendar.getInstance();
private int dayOfWeek = calendar.get(Calendar.DAY_OF_WEEK);
// listbyday is a list of hash maps each list of hash maps represents a day
// of the week with items for that Object
private ArrayList<ArrayList<HashMap<String, String>>> listByDay = null;
private String objectName = null;
private ViewPager pager;
private FragAdapter adapter;
public ArrayList<HashMap<String, String>> getList(int day) {
return listByDay.get(day);
}
private void getObjectName() {
barName = ((MainFragActivity) getActivity()).getobjectSelected();
}
public static ListFragmentDisplay newInstance() {
return new ListFragmentDisplay();
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the ListView layout file.
initArrList();
getObjectName();
fillList();
return inflater.inflate(R.layout.list_view, container, false);
}
#Override
public void onViewCreated(View view, Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
pager = (ViewPager) view.findViewById(R.id.viewPager);
adapter =new FragAdapter(getChildFragmentManager());
if (pager.getAdapter() == null)
pager.setAdapter(adapter);
reload();
pager.setOnPageChangeListener(new OnPageChangeListener() {
#Override
public void onPageScrollStateChanged(int arg0) {}
#Override
public void onPageScrolled(int arg0, float arg1, int arg2) {reload();}
#Override
public void onPageSelected(int arg0) {
}
});
pager.setCurrentItem(dayOfWeek-1);
}
private void initArrList() {
if (listByDay == null) {
listByDay = new ArrayList<ArrayList<HashMap<String, String>>>();
} else {
listByDay.clear();
}
for (int i = 0; i < 7; i++) {
ArrayList<HashMap<String, String>> hm = new ArrayList<HashMap<String, String>>();
listByDay.add(hm);
}
}
synchronized private void fillList() {
LoadWebTask lWT = new LoadWebTask();
executeAsyncTask(lWT, getSherlockActivity().getApplicationContext());
}
FragmentPager
public class FragAdapter extends FragmentPagerAdapter {
private static final String[] CONTENT = new String[] { "frag0", "frag1",
"frag2", "frag3", "frag4", "frag5", "frag6" };
public FragAdapter(FragmentManager fm) {
super(fm);
}
#Override
public Fragment getItem(int arg0) {
return MyListFragment.newInstance(arg0);
}
#Override
public int getCount() {
return CONTENT.length;
}
#Override
public CharSequence getPageTitle(int position) {
return CONTENT[position % CONTENT.length];
}
}
ListFragment
public class MyListFragment extends SherlockListFragment {
public static final String NAME_TAG = "name";
public static final String DESCRIPTION_TAG = "description";
private static int dow;
public static final String TAG = "listFragment";
// Keys used in Hashmap that will be mapped to the rows
String[] dFrom = { NAME_TAG, DESCRIPTION_TAG };
private ArrayList<HashMap<String, String>> list;
int[] dTo = { R.id.name, R.id.description };
public void upDateList() {
//**************************Not really sure if this is how things are supposed
//** to be done. For my small data- set i feel like it will work but i would
//** be interested in knowing how else this might be done.
ListFragmentDisplay lFD = (ListFragmentDisplay) this
.getParentFragment();
dList = lFD.getList(dow);
}
public static MyListFragment newInstance(int pos) {
MyListFragment frag = new MyListFragment();
dow = pos;
return (frag);
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
upDateList();
View results = inflater.inflate(R.layout.list_fragment, container,
false);
SimpleAdapter adapter = new SimpleAdapter(getParentFragment()
.getActivity(), list, R.layout.listrow, dFrom, dTo);
setListAdapter(adapter);
return results;
}
}
Edit. Solved Code: In List Fragment
The Initial Question has been solved. I am only in the process of implementing the onPostExecute callback to the ListFragmentDisplay. Much Thanks to Luksprog for solving my very noobish mistake. I made dow static without knowing its affect. I think it was actually something that Eclipse offered to solve a conflict. I should have read it closer.
public class MyListFragment extends SherlockListFragment {
public static final String NAME_TAG = "name";
public static final String DESCRIPTION_TAG = "description";
public static final String TAG = "listFragment";
// Keys used in Hashmap that will be mapped to the rows
String[] dFrom = { NAME_TAG, DESCRIPTION_TAG };
private ArrayList<HashMap<String, String>> list;
int[] dTo = { R.id.name, R.id.description };
SimpleAdapter adapter = null; **NEW**
public void upDateList() {
ListFragmentDisplay lFD = (ListFragmentDisplay) this
.getParentFragment();
dList = lFD.getList(getArguments().getInt(TAG)); **NEW**
if(adapter != null) **NEW**
adapter.notifyDataSetChanged(); **NEW**
}
public static MyListFragment newInstance(int pos) {
MyListFragment frag = new MyListFragment();
Bundle args = new Bundle(); **NEW**
args.putInt(TAG, pos); **NEW**
frag.setArguments(args); **NEW**
return (frag);
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
upDateList();
View results = inflater.inflate(R.layout.list_fragment, container,
false);
adapter = new SimpleAdapter(getParentFragment()
.getActivity(), list, R.layout.listrow, dFrom, dTo);
setListAdapter(adapter);
return results;
}
}

Is there any reason why you made the dow variable from MyListFragment as static? With the static keyword your fragments from the ViewPager will share their position so you'll call the lFD.getList(dow); method with the wrong position most of the cases. Make dow a private instance field: private int dow;
About the rest of the code, it looks ok, see if the change above solves the problem. To update your data in the inner fragments you could follow this scenario:
start with an empty list of data in ListFragmentDisplay and start the task
initially, your inner ListFragmnents will see that the data list is empty so you'll initialize them with an empty list(the getList(int day) method should just return an empty list if there is no data in the listByDay field)
your task now finishes. Suppose you have a callback from the onPostExecute method of the AsyncTask. In that callback which the ListFragmentDisplay will implement you'll update every Fragment from the ViewPager which is either currently visible to the user or it's in the FragmentPagerAdapter alive(so each Fragment which is not null and its getView() method doesn't return null from the ViewPager will be updated). The other Fragments will self update because the onCreateView method will need to be called for them and you have the updateList call in there.
For the point above keep in mind that calling the updateList method will not update a visible Fragment because in that method you just update the list of the Fragment you don't call notifyDataSetChanged on the adapter to let it know that the data has changed.

How to display different text on each page in ViewPager, instantiateItem() confusion

In the CustomPagerAdapter of the ViewPager, in instantiateItem() method I'm trying to create an TextView and then for each page set a different text depending on certain condition. Text is read from a pages Cursor. Here is a code:
#Override
public Object instantiateItem(ViewGroup collection, int position) {
sc = new ScrollView(context);
sc.setLayoutParams(new LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT));
sc.setFillViewport(true);
tv = new TextView(context);
if(position < count) {
tv.setText(pages.getString(1));
pages.moveToPosition(position);
}else {
tv.setText("LOCKED");
}
tv.setTag(TAG_PAGE + position);
tv.setGravity(Gravity.CENTER);
tv.setTextColor(Color.BLACK);
tv.setTextSize(30);
sc.addView(tv);
((ViewPager) collection).addView(sc);
return sc;
}
However ViewPager behaves not as expected. The first and the second page have the same text, rest of the pages has a sign "LOCKED" as expected. When I swipe into the 4th page and come back to the first page then the first page consists of the text that suppose to be in the second page. I also tried to use myViewPager.setOffscreenPageLimit(numberOfPages) however it doesn't help.
I found this answer:
"Inside of instantiateItem, the position parameter is the position that is in need of rendering. It is NOT the position of the currently focused item that the user would see. The pages to the left and right of the currently displayed view need to be pre rendered in memory so that the animations to those screens will be smooth. "
It make sense to me but how then can I correctly display the pages content and then update it if desired? Please advise if there is different way to do it with skipping instantiateItem() method that introduce the mess and confusion into the problem. Thank you.

I have solved this problem by using a different implementation:
// Adapter class
private static class MyFragmentPagerAdapter extends FragmentPagerAdapter {
public MyFragmentPagerAdapter(FragmentManager fm) {
super(fm);
}
#Override
public Fragment getItem(int index) {
return PageFragment.newInstance(pages[index]); // Pages is an array of Strings
}
#Override
public int getCount() {
return numberOfPages;
}
}
// PageFragment class
public class PageFragment extends Fragment {
TextView tv;
public static PageFragment newInstance(String page) {
PageFragment pageFragment = new PageFragment();
Bundle bundle = new Bundle();
bundle.putString("pageContent", page);
pageFragment.setArguments(bundle);
return pageFragment;
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment, container, false);
tv = (TextView) view.findViewById(R.id.text_view);
tv.setText(getArguments().getString("pageContent"));
return view;
}
}

You can Create ViewPager Object and then set Listener onthis object.
ViewPager myPager = (ViewPager) findViewById(R.id.yourPagerid);
myPager.setAdapter(adapter);
myPager.setCurrentItem(0);
myPager.setOnPageChangeListener(new OnPageChangeListener() {
#Override
public void onPageSelected(int position) {
//You can change textview word according to current page
switch (position) {
case 0:
break;
case 1:
break;
case 2:
break;
}
}
#Override
public void onPageScrolled(int arg0, float arg1, int arg2) {
// Log.d("check","onPageScrolled");
}
#Override
public void onPageScrollStateChanged(int arg0) {
// Log.d("check","onPageScrollStateChanged");
}
});