I have an Activity which holds a ViewPager with 2 Fragments. One fragment is for adding items to ListView and another fragment is holding the ListView.
I've been trying for almost 3 days now without any positive results. How do I update the other fragment's ListView from the first fragment?
I'm trying to call the method that updates ListView from the Activity that holds ViewPager but it doesn't work.
Calling the method from ViewPager activity :
#Override
public void onPageSelected(int position) {
library.populateListView(getApplicationContext());
aBar.setSelectedNavigationItem(position);
}
This is the populateListView method:
public void populateListView(Context context){
CustomListViewAdapter customAdapter = new CustomListViewAdapter(getDatabaseArrayList(context), getActivity());
if (lView != null)
{
lView.setAdapter(customAdapter);
}
customAdapter.notifyDataSetChanged();
}
However this doesn't work because the lView variable (ListView) is null because the fragment isn't shown at the moment when this is being called.
I am assuming that function populateListView() is a function of the Fragment containing the ListView. You are calling populateListView() on every call to onPageSelected. Should you not check what is the position that is being selected. Anyway the populateListView() method should be a public method of the Fragment containing ListView. And You Can Instantiate The Fragment from the Viewpager adapter in the Activity and than call this method. In That way the listView should not be null.
#Override
public void onPageSelected(int position) {
ListViewFragment frag=(ListViewFragment)adapter.instantiateItem(viewPager, 1);
//here adapter is the ViewPager Adapter and you must supply the viewpager that contains
//the fragments and also the position of the fragment to instantiate.
//For example 0 or 1 etc.
frag.populateListView(getApplicationContext());
aBar.setSelectedNavigationItem(position);
}
Understand Fragments
Please see this link. I have gone in great detail explaining the concept of fragments.
Pay particular attention to the definition of rootview:
public void onActivityCreared(Bundle savedInstanceState){
super.onActivityCreated(savedInstanceState);
// Do stuff on creation. This is usually where you add the bulk of your code. Like clickListners
// You can define this object as any element in any of your xml's
View rootview = inflater.inflate(R.layout.xml_the_fragment_uses container,false);
rootview.findViewById(R.id.your_id).setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
//Do something
}
});
}
In the above case I defined a button for an on click listener, but you can just as easily define a ListView along with its appropriate methods.
Alternate Solution
A second method could be using getView or getActivity (check the communicating with activity section).
For example:
ListView listView = (ListView) getView().findViewById(R.id.your_listView_id);
OR (more likely solution for your problem)
View listView = getActivity().findViewById(R.id.list);
Please read this post for additional information.
Good Luck.
To do this safely, you have to keep your listview data in a higher level Parent-Activity not the fragments. Make your MainActivityclass singleton class by making the constructor private and create a getInstance method that return the only initialized instance of your `MainActivity.
This will allow you to keep your data instance safe from being re-initialized or lost. Then, in onResume of your fragment re-set the data (get it from the MainActivity) to your listview adapter and call notifyDataSetChanged() method from the adapter instance.
This will do the trick.
Related
I'm making an activity with a listView fragment in it. I am having a button click on the MainActivity load items for an rss feed that populate the listview fragment.
My question is, how should I go about setting it up? I already have the code for it.
My plan now is to have the button click on MainActivity point to my method in my RSSFragment which extends ListFragment. I'm confused about some things like which activity to pass here:
#Override
protected void onPostExecute(Exception s) {
super.onPostExecute(s);
ArrayAdapter<String> adapter = new ArrayAdapter<String>(getActivity(), android.R.layout.simple_list_item_1, titles);
lvRss.setAdapter(adapter);
progressDialog.dismiss();
}
}
Should I use getActivity()? or Pass MainActivity or RSSFragment.this?
Also, how do I set list adapter to a listview fragment? Imagine lvRss isn't there.
I know it's a long question.
Thanks.
Should I use getActivity()? or Pass MainActivity or RSSFragment.this?
If you are in Activity the use this or Activity.this . IF you are in Fragment the use getActivity().
Also, how do I set list adapter to a listview fragment? Imagine lvRss isn't there.
Use setListAdapter method setting Adapter to ListFragment
I have three fragments that contains three ListView created using a BaseAdapter. Like the image below:
Anyway my listView is fetching data from an SqliteDatabase. What I need to know is: when I delete an item from my ListView My(Favorite,Rejected) Fragments ListViews are not notified and are not refreshing.
What I have tried so far is :
Call listView.invalidateViews() after notifyDataSetChanged() in the onResume() Method of my fragments .
I tried these solution two Android ListView not refreshing after notifyDataSetChanged
My code is :
In My BaseAdapter I'am using these method to refresh my adapter :
public void UpdateView(List<Voiture> items)
{
this.voitureList = items;
notifyDataSetChanged();
}
In My fragments I'am using these method to notify the adapter :
#Override
public void onResume() {
super.onResume();
adapterLogin.UpdateView(databaseHelper.getAllVoiture(username,currentLength));
listView.setAdapter(new AdapterLogin(getActivity(),voitureList,username,currentLength,1));
}
In the OncreateView() Method I'am using :
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
inflate = inflater ;
x = inflater.inflate(R.layout.fragemnt_favoris,null);
empty = (TextView) x.findViewById(R.id.texteempty);
listView = (ListView) x.findViewById(R.id.list);
activity = (Main2Activity) getActivity() ;
username = activity.getUsername();
databaseHelper = new DatabaseHelper(getActivity());
databaseHelper.InsertActivity(2,username);
voitureList = databaseHelper.getAllVoitureFavourite(1,username);
adapterLogin = new AdapterLogin(getActivity(),voitureList,username,currentLength,2);
if (voitureList.size()>0)
{
listView.setAdapter(adapterLogin);
((BaseAdapter)listView.getAdapter()).notifyDataSetChanged();
}
else
{
empty.setVisibility(View.VISIBLE);
}
// Inflate the layout for this fragment
return x;
}
Any help would be greatly appreciated.
Thanks to Paul answer the idea was to add the notifyDataSetInvalidated in my UpdateView() Method in my adapter and it works just fine and my fragments are refreshing correctly now :
void notifyDataSetInvalidated ()
the method Notifies the attached observers that the underlying data is no longer valid or available. Once invoked this adapter is no longer valid and should not report further data set changes.
refer link :
notifyDataSetInvalidated
I have this code, which gets data from various EditTexts and adds this info into a ListView_item in fragment 1. This ListView_item is supposed to be populated in the ListView in fragment 2. I was thinking this might be possible with the help of the EventBus library but I have not quite yet gotten my head around how.
Here is my populate list method
public void populateList() {
ArrayAdapter<Appointment> adapter = new AppointmentListAdapter();
(The listview in fragment 2).setAdapter(adapter);
}
You have two ways to do this :
1) Using Interface: You will find lots of links for how to use interface for data passing.
2) Pass adapter through the activity :
step 1 : In your Fragment1 Make getParent() method :
private MyActivity getParent() {
return ((MyActivity) getActivity());
}
step 2 : In MyActivity Make populateList() method :
public void populateList(ArrayAdapter<Appointment> adapter){
SecondFragment mSecondFragment = (SecondFragment) getFragmentManager().findFragmentByTag(SecondFragment.TAG);
mSecondFragment.setAdapter(adapter);
}
step 3 : In your Fragment1 populateList method look like below :
public void populateList() {
ArrayAdapter<Appointment> adapter = new AppointmentListAdapter();
getParent().populateList(adapter);
}
I have a ViewPager with two Fragments. On the first one, there are buttons (it is a menu) and they represent different categories. On the second one, it is a listView which display data.
I am looking for a way to change the data to display on the listView when the user click on one of the menu items.
For example : the user click on the menu item 1 (fragment 1), the listView on the fragment 2 have to be updated with the corresponding data.
I read the documentations from Google Android developer about fragments but I couldn't work it out, I didn't find a solution to my problem.
Maybe I'm missing something ?
EDIT : I tried to clear my ListView by clearing the list of data (ArrayList> listItems) with listItems.clear(). I didn't find how to do adapter.clear(), it seems that this method doesn't exist in the class Adapter.
So to summarize : I created an update method in my fragment which contains the ListView (Fragment2). I called it through a callback method in the main activity, that part seems to work (I checked it with debug mode).
In the update method of my Fragment 2, I clear data with listItems.clear() and then the OnActivityCreated() of the fragment is executed. In it, there is the call of my thread which download data and then it create the ListView in OnPostExecute.
Here is a sample of my code (fragment2) :
// After data are ready
lvListe = (ListView) getView().findViewById(R.id.lvListe);
lvListe.setSelected(true);
lvListe.setScrollingCacheEnabled(false);
adapter = new LazyAdapter(getActivity(),
getActivity().getBaseContext(), listItems,
R.layout.affichageitem, new String[] { "image", "title",
"subtitle" }, new int[] { R.id.img_title,
R.id.titre_main, R.id.soustitre_main });
lvListe.setAdapter(adapter);
lvListe.setClickable(true);
lvListe.setOnItemClickListener(onItemClickListener);
// Update method :
public void update(String requete, String type)
{
this.type = type;
this.requete = requete;
listItems.clear();
}
The way that I would probably do it is to create a callback method in the Activity hosting the ViewPager and also a method in the second Fragment to update the data.
Then you would call it like:
class Fragment1...
{
...
callBackUpdate(data);
}
class Activity...
{
...
public void callBackUpdate(String data)
{
Fragment2.update(data);
}
}
class Fragment2...
{
...
public void update(String data)
{
//do whatever
}
}
The developers page shows how to create a callback method to the Activity.
edit: Actually that's how the Developer's page says to do it. They create the interface OnArticleSelectedListener for the callback.
edit: I'm assuming you are using this library for the LazyLoader: https://github.com/thest1/LazyList
If so, then you can just add the method to clear the data yourself. To do so, add a method like this in ListAdapter:
public void clear()
{
data = new String[](); //depends on what data is, if it's a List then just call data.clear() for example
imageLoader=new ImageLoader(activity.getApplicationContext()); //clear the images
notifyDataSetChanged(); //notify the adapter that the data has changed
}
This might not exactly fit how you currently have it, but you should get the idea.
Try using something known as a FragmentTransaction manager at http://developer.android.com/reference/android/app/FragmentTransaction.html
and also the FragmentManager http://developer.android.com/reference/android/app/FragmentManager.html
Check out some of the questions on stackoverflow related to FragmentManager and FragmentTransaction to figure this out. All you need to do is replace the fragment with a new one which is inflated by a particular xml
I have an app using fragments, all of which are contained in a single activity. The activity starts with a fragment containing a menu of buttons, all of which cause various listfragments to replace the original button/menu fragment.
My problem is that upon an orientation change, if the activity is displaying one of the listviews, it goes away and the button menu returns. I understand why this is happening... the activity is destroyed and re-created, but not how to work around it and maintain the list view/current fragment through the orientation change.
I've found setRetainInstance and the example of use here, but I can't figure out how to apply it to my situation with the button menu or the possibility that the fragment I want to retain could be one of several different ones.
Below is code simplified to show the main activity and one of the listfragments.
Any pointers in what to add where to make it so that the list fragment will be retained would be greatly appreciated.
Activity
public class Main extends FragmentActivity {
private MainMenuFragment menu;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
menu = new MainMenuFragment();
getSupportFragmentManager().beginTransaction().replace(R.id.pane, menu).commit();
}
}
ListFragment
public class ItemListFragment extends ListFragment {
private TextView header;
private TextView empty;
private Button add;
public static Cursor itemCursor;
private GroceryDB mDbHelper;
public static long mRowId;
public static CheckCursorAdapter lists;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.common_list, container, false);
header = (TextView) v.findViewById(R.id.header);
empty = (TextView) v.findViewById(android.R.id.empty);
header.setText(R.string.header_item);
empty.setText(R.string.empty_items);
return v;
}
#Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
mRowId=0;
mDbHelper = new GroceryDB(getActivity());
mDbHelper.open();
itemCursor = mDbHelper.fetchAllItems();
getActivity().startManagingCursor(itemCursor);
String[] from = new String[] { GroceryDB.ITEM_NAME };
int[] to = new int[] { R.id.ListItem };
lists = new CheckCursorAdapter(getActivity(),
R.layout.listlayout_itemlist, itemCursor, from, to);
setListAdapter(lists);
}
}
how to work around it and maintain the list view/current fragment through the orientation change
You are blindly replacing the fragment every time onCreate() is called. Instead, only add/replace the fragment if savedInstanceState() is null. If it is not null, you are coming back from a configuration change, and your existing fragments will be recreated (or, if they were retained, they are already there).
setRetainInstance(true) means that the fragment itself will be retained across configuration changes, instead of being destroyed/recreated like the activity is. However, it will still be called with onCreateView(). In your code, that means that your data members of ItemListFragment would stick around, but you would still need to call setListAdapter() even if you do not requery the database.
I know that this has been resolved a long time ago, but for the sake of people searching for a solution who have as much issues as I've (repeatedly) had with retaining lists during an orientation change I would like to add that you could also use a custom class which holds the list of data for your listadapter.
This way it keeps the data when recreating the activity (and listfragment) and you can just test to see if it has any data in your oncreate. If the list == null or the list.size < 0 you proceed as usual and get the data whatever way you normally get it. Otherwise you just set your listadapter with the data it already has.
To me this is a lot easier, and seeing as Eclipse automatically creates a similar DummyContent class for your data when creating an android master/detail flow project it basically only requires a change of the oncreate of your listfragment.