Develop Reference

Communicate between Adapter, fragments and Sqlite Data base to refresh Fragments

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the method Notifies the attached observers that the underlying data is no longer valid or available. Once invoked this adapter is no longer valid and should not report further data set changes.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

Restore Android GridView after screen orientation change (without reloading it)

I'm new to Android (this is my first application) and I made a GridView in an Activity which I'd like it to be responsive according to screen position (portrait / landscape). Of course I made some custom layout values of GridView rows width for portrait as well as for landscape, and it works perfectly.
Except that, on every screen orientation change, the GridView is reloading again. And that's not good for user experience. I only like the GridView (and definitely its rows) to adjust to new screen width without doing all the onCreate() instructions (retrieving GridView's data from internet, assigning retrieved data in a HashMap object, setting the GridView's Adapter, then display the GridView's rows).
I went through many forum threads and some Google documentation that talk about restoring simple values, but never found an answer for restoring a GridView without having it to reload again.
I read about onSaveInstanceState() and onRestoreInstanceState(), but I didn't know how to use them in my case (GridView case).
Could any one provide a simple code sample for this? Or at least some headlines to follow?
Here's some of what I tried in my code, in the Activity class :
private Parcelable mListInstanceState;
private Parcelable mAdapterInstanceState;
private GridView gridView = null;
private MyAdapter myAdapter = null;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
gridView = (GridView) findViewById(R.id.gridview);
// Check whether we're recreating a previously destroyed instance
if(savedInstanceState != null) {
// Restore value of members from saved state
mListInstanceState = savedInstanceState.getParcelable("gridview");
mAdapterInstanceState = savedInstanceState.getParcelable("adapter");
}
else {
// Retrieve data from internet, fill HashMap object,
// set Adapter and display GridView only for the first time the activity is created
attemptToDisplayGirdViewItems();
}
}
#Override
protected void onSaveInstanceState(Bundle state) {
// Save activity state
super.onSaveInstanceState(state);
state.putParcelable("gridview", gridView.onSaveInstanceState());
// state.putParcelable("adapter", myAdapter);
}
#Override
protected void onRestoreInstanceState(Bundle savedInstanceState) {
// Retrieve and restore activity state
// Restore state members from saved instance
mListInstanceState = savedInstanceState.getParcelable("gridview");
mAdapterInstanceState = savedInstanceState.getParcelable("adapter");
super.onRestoreInstanceState(savedInstanceState);
}

You don't need to save the views. If they have ID, they'll be saved automatically (such as scroll position of a GridView). What you need to save is the adapter's data set.
Your adapter presumably holds a list of items. Unless these items are primitives or String or implement Serializable, they need to implement Parcelable for this to work.
See here how to do that: How can I make my custom objects Parcelable?
Your adapter needs a getItems method which returns the data set - an ArrayList of your parcelable items. It also needs to have a setItems(...) method or a constructor taking a list of items as parameter.
Then your activity will look like this:
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
gridView = (GridView) findViewById(R.id.gridview);
myAdapter = new MyAdapter(); // Create empty adapter.
if(savedInstanceState != null) {
ArrayList<MyItem> items = savedInstanceState.getParcelableArrayList("myAdapter");
myAdapter.setItems(items); // Load saved data if any.
}
gridView.setAdapter(myAdapter);
}
#Override
protected void onSaveInstanceState(Bundle state) {
super.onSaveInstanceState(state);
state.putParcelableArrayList("myAdapter", myAdapter.getItems());
}

How to reload listview on a activity?

I have 2 activity.
In activity 1, i have a listview show data from database and button Insert
Activity 2 use to add something to database.
When I click button ADD in activity 2, i call method finish() and return to activity 1.
So, somebody can show me how to reload listview in activity 1 please?

Recreating the adapter should help, because you need to get a new dataset as Kaaaarll said.
So for example you have something like this in your code:
MyData data = database.getData();
MyAdapter adapter = new MyAdapter(data);
ListView list = new ListView();
list.setAdapter(adapter);
and in the next run, in the onResume(), get fresh data and reapply the adapter:
MyData data = database.getData();
MyAdapter adapter = new MyAdapter(data);
list.setAdapter(adapter);

You can re-query the database to get the latest data and then repopulate your listview's adapter.

Notify the dataset in the onResume() method activity 1. It should be something like listViewAdapter.notifyDataSetChanged();. Don't forget to check whether they are null or not.
Let me know if it worked.
EDIT:
Something like this should do the work (in activity 1):
#Override
protected void onResume() {
super.onResume();
if (listViewAdapter != null) {
listViewAdapter.notifyDataSetChanged();
}
}

How do I update ListView in another Fragment?

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.

ViewPager updates listView in fragment B from a fragment A

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