Develop Reference

Updating listview fragment on viewpager tab changes

I have a ViewPager using a FragmentPagerAdapter for displaying three tabs, each represented by its ow fragment. One of these fragments contains a list, that should be updated on switching / swiping to that tab. But I don't find any way to make it happen. I tried using the onResume method, but the fragments seem not to be paused and resumed on tab change. I also tried using ViewPager.OnPageChangeListener in my MainActivity:
#Override
public void onPageSelected(int position)
{
FragmentRefreshInterface currentFragment = (FragmentRefreshInterface) mSectionsPagerAdapter.getItem(position);
currentFragment.onRefreshed();
}
And in the fragment I use the following:
#Override
public void onRefreshed()
{
List<Record> records = mRecordingService.getRecords();
mRecordAdapter.clear();
mRecordAdapter.add(record);
}
But using this code I can't access my RecordingService class that is used to provide the database functions (because mRecordingService seems to be null). I initialize it in the fragment like this:
#Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
mRecordingService = new RecordingService(getContext());
}

Using the onPageChangeListener is the correct way to do it. I believe the reason why your code is not working, is because you are calling getItem on your pager adapter: getItem() actually returns a new instance of the fragment. In order to get the current instance, you use instantiateItem() (which returns a reference to the fragment actually being used).
Change your code to look something like this:
#Override
public void onPageSelected(int position)
{
FragmentRefreshInterface currentFragment = (FragmentRefreshInterface) mSectionsPagerAdapter.instantiateItem(viewPager,position);
currentFragment.onRefreshed();
}
And it should work.

I suggest that the code you have in onRefreshed() go in onResume() instead. Fragment doesn't have an onRefreshed() method. You must be implementing another interface that declares this method.
Since you are storing data in a database, you should be use a CursorAdapter or subclass such as SimpleCursorAdapter. If you do this correctly, the ListView will automatically update when you add a record to the database. Then the service can add records without needing to access the service from the fragment.

In your MainActivity:
private FirstFragment firstFragment;
private WantedFragment wantedFragment;
private ThirdFragment thirdfragment;
In getItem
switch(postition){
//return first, wanted, third fragments depending on position
}
onPageSelected:
if(position == 1) // position of the wanted fragment
wantedfragment.onRefreshed()

How to restore state of android fragment where recyclerView has selected item

I have created a fragment where i used recyclerview and recyler items can be select/unselect . But problem is that when i move to other fragment and back to the same fragment then selected data lost .
How can i get the fragment as like previous condition where selected items will be at selected condition .

Try to use SaveInstanceState lets check one sample below
public class MainFragment extends Fragment {
// These variable are destroyed along with Activity
private int someVarA;
private String someVarB;
...
#Override
public void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
outState.putInt("someVarA", someVarA);
outState.putString("someVarB", someVarB);
}
#Override
public void onActivityCreated(#Nullable Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
someVarA = savedInstanceState.getInt("someVarA");
someVarB = savedInstanceState.getString("someVarB");
}
}
There is no onRestoreInstanceState method inside Fragment.
For Fragment, there is some special case that is different from Activity and I think that you need to know about it. Once Fragment is returned from backstack, its View would be destroyed and recreated.

Passing ListView to another Listview

I have listview in one fragment that displays item from a sqlite database. When I click on one item it opens a menu to allow to open, add to another listview or delete. I want to be able to add it to another listview in another fragment on press. I tried adding it to another listview using bundles but I had no luck. I have a plan of creating another database table to store the added data and display it in a new listview. Would this work? or do any of you guys have another suggestion?

You can send data from one fragment to another. The best way to do this is by going through the parent activity. Something like this:
public class MyActivity extends FragmentActivity implements MyFragmentListener {
MyFragment1 frag1;
MyFragment2 frag2;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(0);
FragmentManager fm = getSupportFragmentManager();
frag1 = (MyFragment1) fm.findFragmentByTag("frag1");
frag1.setListener(this);
frag2 = (MyFragment2) fm.findFragmentByTag("frag2");
}
// Call this function from frag1 when you want to send the data to frag2
public void addToFrag2(ListItem item) {
frag2.addToList(item);
}
}
// Define whatever methods the fragments want to use to pass data back and forth
public interface MyFragmentListener {
void addToFrag2(ListItem item);
}

Cannot refresh/update listview in a fragment from another fragment in ViewPager

I am having a hard time figuring out the next thing.
What I have: I have a viewpager and several pages in it. In this question only two of them is important, lets call them Fragment1 and Fragment2 and they are next to each other. Fragment1 contains a listview which is filled with data from the internet (external database). Fragment2 contains a simple button.
My goal: If I click on the button in Fragment2, I add a new item to the external database. I would like to update/refresh the listview in the Fragment1 with this new item.
The notifyDataChanged() doesnt work in my case, however so far I was convinced that it reinstantiates every pages.. I am going to introduce my problem the clearest way I can, so lets see the code I have, this is my ViewPager adapter:
class MyPagerAdapter extends FragmentStatePagerAdapter {
public List<String> fragmentsA;
public MyPagerAdapter(FragmentManager fm) {
super(fm);
fragmentsA = fragments;
}
#Override
public Fragment getItem(int position) {
return Fragment.instantiate(context, fragmentsA.get(position));
}
#Override
public CharSequence getPageTitle(int position) {
return mEntries.get(position % CONTENT.length).toUpperCase();
}
#Override
public int getCount() {
return mEntries.size();
}
#Override
public int getItemPosition(Object object) {
return POSITION_NONE;
}
}
Fragment1 onCreateView() (shortly):
public View onCreateView(LayoutInflater inflater, final ViewGroup container,
Bundle savedInstanceState) {
getData();
View view = inflater.inflate(R.layout.latestapps_tab, container, false);
lw = (ListView) view.findViewById(R.id.lw);
context = getActivity().getApplicationContext();
act = this.getActivity();
m_adapter = new ItemAdapter();
lw.setAdapter(m_adapter);
return view;
}
I create the ViewPager and the adapter, I set the adapter for the ViewPager afterwards I fill the my viewpager with my fragments in my Main class. After this I am goint to have a fully functional ViewPager with 2 fragments.
pager = (ViewPager)findViewById( R.id.viewpager );
adapter = new MyPagerAdapter(getSupportFragmentManager());
indicator = (TabPageIndicator)findViewById( R.id.indicator );
pager.setAdapter( adapter );
indicator.setViewPager( pager );
pager.setCurrentItem(INITIAL_PAGE);
pager.setOffscreenPageLimit(3);
//adding fragments to the pager
fragments.add( Fragment1.class.getName());
fragments.add( Fragment2.class.getName());
In the Fragment1 I have a listview with some textviews in every list item. The loading works perfectly: I create the ArrayLists and I fill thoes lists with data from the external database. After loading is done, I fill the listviews with these tons of data.
In Fragment 2 I click on the button and I would like that listview to be updated so a new row should be created in the listview with some data from the external database. (of course writing into the database works)
My guess, that I might not refresh the ArrayLists or I dont reinstantiate the Fragment1, so the getDataFromSQL() method never turns only if I exit and launch the application again or I swipe so much in the ViewPager that the Fragment1 gets detached. So I cannot update or refresh the Fragment1. Could someone help in this questionL?
EDIT
I managed to make it happen with delivering a message to the fragment2 to update itself. But I am not sure if it is a good solution and there is not a better way, i.e. just refreshing somehow the whole fragment.
SOLUTION
Okay I think it must have been my laziness but I solved it now. For everyone who still wants to refresh a fragment from another one or just make conection between fragments, I tell you the appropriate approach:
You have to implement your own listener which helps you communicate between the fragments through the holder activity. This can be found here: http://developer.android.com/training/basics/fragments/communicating.html . Very simple and useful.
You have to retrieve the fragment, which is again simple: Retrieve a Fragment from a ViewPager These Q offers several acceptable way, I used the SpareArray solution.
Thank you for the help anyway!

you need be able to get your fragments from your activity, to do that you need to get the fragment from your adapter, you will need to add a couple methods to your page adapter
public Fragment getFragment(ViewPager container, int position, FragmentManager fm) {
String name = makeFragmentName(container.getId(), position);
return fm.findFragmentByTag(name);
}
private String makeFragmentName(int viewId, int index) {
return "android:switcher:" + viewId + ":" + index;
}
then from your activity make the following method
public Fragment getFragmentbyPosition(int position) {
return adapter.getFragment(pager, position, getSupportFragmentManager());
}
now on fragment2 call the following:
Fragment1 fragment1 = (Fragment1) ((MyActivity)getActivity()).getFragmentbyPosition(0);
now you will be able to call public methods on fragment1 from fragment 2, so just use that in your onClick and tell fragment1 to update it's listview.
now the reason makeFragmentName works is that is how the FragmentPagerAdapter creates the tag for the fragments it makes.

How to create a Fragment loading information from SQLDatabase?

I am creating an activity that implements a fragment list and a regular fragment showing details of the list. i am having a VERY hard time trying to take the android developer tutorial on fragment cursor and use it.
I am trying to load the title's from my SQLdatabse into the fragment list. And when the item is clicked show details for it. I know i will just store the id of the item in a extra and pick it out in the details fragment to get the information.
Im just kind of confused on the whole ListFragment class.
Here is my source code where im at so far...
public class Main extends Activity {
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
FragmentManager fm = new getFragmentManager();
if(fm.findFragmentById(android.R.id.content)== null){
CursorLoaderListFragment list = new CursorLoaderListFragment();
fm.beginTransaction().add(android.R.id.content, list).commit();
}
}
public static class CursorLoaderListFragment extends ListFragment{
SimpleCursorAdapter mAdapter;
String mCurFilter;
#Override
public void onActivityCreated(Bundle savedInstanceState){
super.onActivityCreated(savedInstanceState);
setEmptyText("No Task");
setHasOptionsMenu(true);
}
}
}
If someone has a better way than what im doing PLEASE let me know and provide an example.
Thanks!