New to Android, I got a simple application with spinners and associated ArrayAdapters working: when things get selected, I seem to be able and trigger some calculations. I am then saving the current selected item.
At some point, I retrieve the saved value, and want to position the spinner at that value: basically setPosition() the spinner to that object.
I have found lots of tutorials with the same format I have: use the getPosition() on the ArrayAdapter, and pass in the object you are looking for... Trouble is, it keeps returning -1 (not found).
Debugging, I have verified that the object I pass is not null, and so is the ArrayAdapter, and also the ArrayAdapter getCount returns me the items it should have (so it's not empty).
I'm at loss. Appreciate any... pointers? :-)
/* ArrayAdapter class looks like this*/
public class MyAdapter extends ArrayAdapter<MyClass> {
// Constructor
MyAdapter(#NonNull Context context, int resource, #NonNull List<MyClass> objects) {
super(context, resource, objects);
}
}
/* Fragment looks like this*/
final MyAdapter mAdapter = new MyAdapter(
requireActivity(),
android.R.layout.simple_spinner_item,
objects);
Spinner mySpinner = fragment_view.findViewById(R.id.my_spinner);
mySpinner.setAdapter(mAdapter);
// assume I have one "object" of MyClass,
// and want to search for it in "MyAdapter"
int spinnerPosition = mAdapter.getPosition(objectToBeFound); // returns -1
mySpinner.setSelection(spinnerPosition);
Adapter internally works with List
public int getPosition(#Nullable T item) {
return mObjects.indexOf(item);
}
so getPosition internally depends upon List#indexOf(T) and which relies on equals method
(o==null ? get(i)==null : o.equals(get(i)))
so you are getting -1 because you haven't implemented equals and hashcode method properly in MyClass so implement both methods and you will be able to get the precise index.
Referene:
Use Auto Generate
difference between equals() and hashCode()
I have a SortedList being displayed in a RecyclerView by my RecyclerView.Adapter.
I use 2 custom Comparator instances from withing the SortedListAdapterCallback.compare() method to either sort A-Z or Z-A.
static class A2Z implements Comparator<Item> {
#Override
public int compare(Item t0, Item t1) {
return t0.mText.compareTo(t1.mText);
}
}
static class Z2A extends A2Z {
#Override
public int compare(Item t0, Item t1) {
return -1 * super.compare(t0, t1);
}
}
Item simply contains a single String mText;
I use my comparators in the SortedListAdapterCallback.compare() method:
private Comparator<Item> a2z = new A2Z();
private Comparator<Item> z2a = new Z2A();
private Comparator<Item> comparator = z2a;
#Override
public int compare(Item t0, Item t1) {
return comparator.compare(t0, t1);
}
I change the comparators on a button press. The list on screen does not update.
After logging values in the various methods, I can tell that the list itself is not updating. Notifying the adapter of changes simply redraws the old list, without resorting it.
So how do I force the underlying SortedList to resort all the items?
Perhaps it is best to just create a new Adapter each time, as in this question:
RecyclerView change data set
SortedList does not have functionality to resort itself - each instance only has a single sort order.
Went with creating a new adapter for each resort, as per Yigit's answer to the above referenced question:
If you have stable ids in your adapter, you can get pretty good
results (animations) if you create a new array containing the filtered
items and call
recyclerView.swapAdapter(newAdapter, false);
Using swapAdapter hints RecyclerView that it can re-use view holders.
(vs in setAdapter, it has to recycle all views and re-create because
it does not know that the new adapter has the same ViewHolder set with
the old adapter).
Use a switch statement inside the compare method with a local control flag (an enum is a good idea).
After changing the switch flag, call sortedList.replaceAll.
#Override
public int compare(PmpRole pmpRoleA, PmpRole pmpRoleB) {
switch (mSorter){
case IDX:
return pmpRoleA.getIdx().compareTo(pmpRoleB.getIdx());
case TITLE:
return pmpRoleA.getTitleIdx().compareTo(pmpRoleB.getTitleIdx());
case ID_IDX:
return pmpRoleA.getIdIdx().compareTo(pmpRoleB.getIdIdx());
}
return -1;
}
public void setSorter(Sorter sorter){
mSorter = sorter;
mPmpRoleSortedList.replaceAll(mPmpRoles);
}
Maintains animation functionality etc.
I am following a great coding example over here: This SO question. It is regarding implementing a SectionIndexer interface to an array adapter.
However, how would you do the same thing if your ArrayAdapter is passing an ArrayList< MyObject > not an ArrayList< String >?
For example, this is where my code is different then his code. He has:
class AlphabeticalAdapter extends ArrayAdapter<String> implements SectionIndexer {
private HashMap<String, Integer> alphaIndexer;
private String[] sections;
public AlphabeticalAdapter(Context c, int resource, List<String> data) {
alphaIndexer = new HashMap<String, Integer>();
for (int i = 0; i < data.size(); i++) {
String s = data.get(i).substring(0, 1).toUpperCase();
alphaIndexer.put(s, i);
}
// other stuff
}
I am having problems adapting that for loop to my situation. I can't measure the size like he does. Where he has the above, my adapter begins with.
public class CustomAdapter extends ArrayAdapter<Items> implements
SectionIndexer {
public ItemAdapter(Context context, Items[] objects) {
Where he is passing one ArrayList, I have to pass in three, but to make that happen, had to wrap in a custom object class. One of the ArrayLists that I want to sort is one of three fields in the class called "name". It is a string obviously.
I want to scroll through that alphabetically with SectionIndex based on that name field. How do I change the example code from the other question to work in this scenario?
Where he has "data.size()", I need something like "name.size()" - I think?
Where he is passing one ArrayList, I have to pass in three, but to
make that happen, had to wrap in a custom object class. One of the
ArrayLists that I want to sort is one of three fields in the class
called "name".
You don't have three ArrayLists, you have an ArrayList of custom objects that were built from three ArrayLists(so the size is the size of the List that you pass to the adapter). From this point of view the only change in your code is to use the name from that custom object Items to build the sections:
for (int i = 0; i < data.size(); i++) {
String s = data.get(i).name.substring(0, 1).toUpperCase();
if (!alphaIndexer.containsKey(s)) {
alphaIndexer.put(s, i);
}
}
// ...
There aren't other changes. Also you may need to sort the List of Items that you pass to the adapter using:
Collections.sort(mData);
where your Items class must implement the Comparable<Items> interface:
class Items implements Comparable<Items> {
String name;
// ... rest of the code
#Override
public int compareTo(Items another) {
// I assume that you want to sort the data after the name field of the Items class
return name.compareToIgnoreCase(another.name);
}
}
I've seen quite a few examples of how to add alphabetical section headers to list views online. Example:
I implemented the functionality from
this website
. However, I have a list of approximately 8000 items. When trying to load this page it takes about 8 seconds which is obviously way too slow. With just a normal AlphabetIndexer it takes about 1.5 seconds (still slow, but much better).
Does anyone have any ideas on how to speed this up? If not, are there any other examples that are quicker than this?
Thanks!
What exactly do you mean by trying to load the page? How long does it take if you just load the items and don't do any indexing? 8000 items is not that many to iterate over. It could however be a lot of items to load from disk, or the internet. You might want to consider showing a loading screen and reading in the data for your rows in the background.
The code you showed looks particularly complicated for what you're trying to do. Below is a solution I've used. You can google for SectionIndexer. In my code itemManager is basically just an abstraction on a list, placeholders are null values, everything else is the data structure containing the information for the rows. Some code is omitted:
//based on http://twistbyte.com/tutorial/android-listview-with-fast-scroll-and-section-index
private class ContactListAdapter extends BaseAdapter implements SectionIndexer {
final HashMap<String, Integer> alphaIndexer = new HashMap<String, Integer>();
final HashMap<Integer, String> positionIndexer = new HashMap<Integer, String>();
String[] sections;
public ContactListAdapter() {
setupHeaders();
}
public void setupHeaders(){
itemManager.clearPlaceholders();
for (int i = 0; i < itemManager.size(); i++) {
String name = itemManager.get(i).displayName();
String firstLetter = name.substring(0, 1);
if (!alphaIndexer.containsKey(firstLetter)) {
itemManager.putPlaceholder(i);
alphaIndexer.put(firstLetter, i);
positionIndexer.put(i, firstLetter);
++i;
}
}
final Set<String> sectionLetters = alphaIndexer.keySet();
final ArrayList<String> sectionList = new ArrayList<String>(sectionLetters);
Collections.sort(sectionList);
sections = new String[sectionList.size()];
sectionList.toArray(sections);
}
#Override
public int getItemViewType(int position) {
return itemManager.isPlaceholder(position) ? ViewType.HEADER.ordinal() : ViewType.CONTACT.ordinal();
}
#Override
public int getViewTypeCount() {
return ViewType.values().length;
}
#Override
public int getPositionForSection(int section) {
return alphaIndexer.get(sections[section]);
}
#Override
public int getSectionForPosition(int position) {
return 1;
}
#Override
public Object[] getSections() {
return sections;
}
ListView adapters have a class you can override called getViewType(int position) and getViewTypeCount().
Those you would override to allow Android to know how many different type of views your adapter uses.
In your case override getViewTypeCount() to return 2 since you will have two types of views. One your standard and second your header view.
Than you will need to know at what position you will have your header views shown. Once you do you can easily return your views on the getView(...) function.
How to refresh an Android ListView after adding/deleting dynamic data?
Call notifyDataSetChanged() on your Adapter object once you've modified the data in that adapter.
Some additional specifics on how/when to call notifyDataSetChanged() can be viewed in this Google I/O video.
Also you can use this:
myListView.invalidateViews();
Please ignore all the invalidate(), invalidateViews(), requestLayout(), ... answers to this question.
The right thing to do (and luckily also marked as right answer) is to call notifyDataSetChanged() on your Adapter.
Troubleshooting
If calling notifyDataSetChanged() doesn't work all the layout methods won't help either. Believe me the ListView was properly updated. If you fail to find the difference you need to check where the data in your adapter comes from.
If this is just a collection you're keeping in memory check that you actually deleted from or added the item(s) to the collection before calling the notifyDataSetChanged().
If you're working with a database or service backend you'll have to call the method to retrieve the information again (or manipulate the in memory data) before calling the notifyDataSetChanged().
The thing is this notifyDataSetChanged only works if the dataset has changed. So that is the place to look if you don't find changes coming through. Debug if needed.
ArrayAdapter vs BaseAdapter
I did find that working with an adapter that lets you manage the collection, like a BaseAdapter works better. Some adapters like the ArrayAdapter already manage their own collection making it harder to get to the proper collection for updates. It's really just an needless extra layer of difficulty in most cases.
UI Thread
It is true that this has to be called from the UI thread. Other answers have examples on how to achieve this. However this is only required if you're working on this information from outside the UI thread. That is from a service or a non UI thread. In simple cases you'll be updating your data from a button click or another activity/fragment. So still within the UI thread. No need to always pop that runOnUiTrhead in.
Quick Example Project
Can be found at https://github.com/hanscappelle/so-2250770.git. Just clone and open the project in Android Studio (gradle). This project has a MainAcitivity building a ListView with all random data. This list can be refreshed using the action menu.
The adapter implementation I created for this example ModelObject exposes the data collection
public class MyListAdapter extends BaseAdapter {
/**
* this is our own collection of data, can be anything we
* want it to be as long as we get the abstract methods
* implemented using this data and work on this data
* (see getter) you should be fine
*/
private List<ModelObject> mData;
/**
* our ctor for this adapter, we'll accept all the things
* we need here
*
* #param mData
*/
public MyListAdapter(final Context context, final List<ModelObject> mData) {
this.mData = mData;
this.mContext = context;
}
public List<ModelObject> getData() {
return mData;
}
// implement all abstract methods here
}
Code from the MainActivity
public class MainActivity extends Activity {
private MyListAdapter mAdapter;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ListView list = (ListView) findViewById(R.id.list);
// create some dummy data here
List<ModelObject> objects = getRandomData();
// and put it into an adapter for the list
mAdapter = new MyListAdapter(this, objects);
list.setAdapter(mAdapter);
// mAdapter is available in the helper methods below and the
// data will be updated based on action menu interactions
// you could also keep the reference to the android ListView
// object instead and use the {#link ListView#getAdapter()}
// method instead. However you would have to cast that adapter
// to your own instance every time
}
/**
* helper to show what happens when all data is new
*/
private void reloadAllData(){
// get new modified random data
List<ModelObject> objects = getRandomData();
// update data in our adapter
mAdapter.getData().clear();
mAdapter.getData().addAll(objects);
// fire the event
mAdapter.notifyDataSetChanged();
}
/**
* helper to show how only changing properties of data
* elements also works
*/
private void scrambleChecked(){
Random random = new Random();
// update data in our adapter, iterate all objects and
// resetting the checked option
for( ModelObject mo : mAdapter.getData()) {
mo.setChecked(random.nextBoolean());
}
// fire the event
mAdapter.notifyDataSetChanged();
}
}
More Information
Another nice post about the power of listViews is found here: http://www.vogella.com/articles/AndroidListView/article.html
Call runnable whenever you want:
runOnUiThread(run);
OnCreate(), you set your runnable thread:
run = new Runnable() {
public void run() {
//reload content
arraylist.clear();
arraylist.addAll(db.readAll());
adapter.notifyDataSetChanged();
listview.invalidateViews();
listview.refreshDrawableState();
}
};
i got some problems with dynamic refresh of my listview.
Call notifyDataSetChanged() on your Adapter.
Some additional specifics on how/when to call notifyDataSetChanged() can be viewed in this Google I/O video.
notifyDataSetChanged() did not work properly in my case[ I called the notifyDataSetChanged from another class]. Just in the case i edited the ListView in the running Activity (Thread). That video thanks to Christopher gave the final hint.
In my second class i used
Runnable run = new Runnable(){
public void run(){
contactsActivity.update();
}
};
contactsActivity.runOnUiThread(run);
to acces the update() from my Activity. This update includes
myAdapter.notifyDataSetChanged();
to tell the Adapter to refresh the view.
Worked fine as far as I can say.
If you are using SimpleCursorAdapter try calling requery() on the Cursor object.
if you are not still satisfied with ListView Refreshment, you can look at this snippet,this is for loading the listView from DB, Actually what you have to do is simply reload the ListView,after you perform any CRUD Operation
Its not a best way to code, but it will refresh the ListView as you wish..
It works for Me....if u find better solution,please Share...
.......
......
do your CRUD Operations..
......
.....
DBAdapter.open();
DBAdapter.insert_into_SingleList();
// Bring that DB_results and add it to list as its contents....
ls2.setAdapter(new ArrayAdapter(DynTABSample.this,
android.R.layout.simple_list_item_1, DBAdapter.DB_ListView));
DBAdapter.close();
The solutions proposed by people in this post works or not mainly depending on the Android version of your device. For Example to use the AddAll method you have to put android:minSdkVersion="10" in your android device.
To solve this questions for all devices I have created my on own method in my adapter and use inside the add and remove method inherits from ArrayAdapter that update you data without problems.
My Code: Using my own data class RaceResult, you use your own data model.
ResultGpRowAdapter.java
public class ResultGpRowAdapter extends ArrayAdapter<RaceResult> {
Context context;
int resource;
List<RaceResult> data=null;
public ResultGpRowAdapter(Context context, int resource, List<RaceResult> objects) {
super(context, resource, objects);
this.context = context;
this.resource = resource;
this.data = objects;
}
#Override
public View getView(int position, View convertView, ViewGroup parent) {
........
}
//my own method to populate data
public void myAddAll(List<RaceResult> items) {
for (RaceResult item:items){
super.add(item);
}
}
ResultsGp.java
public class ResultsGp extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
...........
...........
ListView list = (ListView)findViewById(R.id.resultsGpList);
ResultGpRowAdapter adapter = new ResultGpRowAdapter(this, R.layout.activity_result_gp_row, new ArrayList<RaceResult>()); //Empty data
list.setAdapter(adapter);
....
....
....
//LOAD a ArrayList<RaceResult> with data
ArrayList<RaceResult> data = new ArrayList<RaceResult>();
data.add(new RaceResult(....));
data.add(new RaceResult(....));
.......
adapter.myAddAll(data); //Your list will be udpdated!!!
For me after changing information in sql database nothing could refresh list view( to be specific expandable list view) so if notifyDataSetChanged() doesn't help, you can try to clear your list first and add it again after that call notifyDataSetChanged(). For example
private List<List<SomeNewArray>> arrayList;
List<SomeNewArray> array1= getArrayList(...);
List<SomeNewArray> array2= getArrayList(...);
arrayList.clear();
arrayList.add(array1);
arrayList.add(array2);
notifyDataSetChanged();
Hope it makes sense for you.
If you want to maintain your scroll position when you refresh, and you can do this:
if (mEventListView.getAdapter() == null) {
EventLogAdapter eventLogAdapter = new EventLogAdapter(mContext, events);
mEventListView.setAdapter(eventLogAdapter);
} else {
((EventLogAdapter)mEventListView.getAdapter()).refill(events);
}
public void refill(List<EventLog> events) {
mEvents.clear();
mEvents.addAll(events);
notifyDataSetChanged();
}
For the detail information, please see Android ListView: Maintain your scroll position when you refresh.
Just use myArrayList.remove(position); inside a listener:
myListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
#Override public void onItemClick(AdapterView<?> parent, android.view.View view, int position, long id) {
myArrayList.remove(position);
myArrayAdapter.notifyDataSetChanged();
}
});
You need to use a single object of that list whoose data you are inflating on ListView. If reference is change then notifyDataSetChanged() does't work .Whenever You are deleting elements from list view also delete them from the list you are using whether it is a ArrayList<> or Something else then Call
notifyDataSetChanged() on object of Your adapter class.
So here see how i managed it in my adapter see below
public class CountryCodeListAdapter extends BaseAdapter implements OnItemClickListener{
private Context context;
private ArrayList<CountryDataObject> dObj;
private ViewHolder holder;
private Typeface itemFont;
private int selectedPosition=-1;
private ArrayList<CountryDataObject> completeList;
public CountryCodeListAdapter(Context context, ArrayList<CountryDataObject> dObj) {
this.context = context;
this.dObj=dObj;
completeList=new ArrayList<CountryDataObject>();
completeList.addAll(dObj);
itemFont=Typeface.createFromAsset(context.getAssets(), "CaviarDreams.ttf");
}
#Override
public int getCount() {
return dObj.size();
}
#Override
public Object getItem(int position) {
return dObj.get(position);
}
#Override
public long getItemId(int position) {
return position;
}
#Override
public View getView(int position, View view, ViewGroup parent) {
if(view==null){
holder = new ViewHolder();
LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
view = inflater.inflate(R.layout.states_inflator_layout, null);
holder.textView = ((TextView)view.findViewById(R.id.stateNameInflator));
holder.checkImg=(ImageView)view.findViewById(R.id.checkBoxState);
view.setTag(holder);
}else{
holder = (ViewHolder) view.getTag();
}
holder.textView.setText(dObj.get(position).getCountryName());
holder.textView.setTypeface(itemFont);
if(position==selectedPosition)
{
holder.checkImg.setImageResource(R.drawable.check);
}
else
{
holder.checkImg.setImageResource(R.drawable.uncheck);
}
return view;
}
private class ViewHolder{
private TextView textView;
private ImageView checkImg;
}
public void getFilter(String name) {
dObj.clear();
if(!name.equals("")){
for (CountryDataObject item : completeList) {
if(item.getCountryName().toLowerCase().startsWith(name.toLowerCase(),0)){
dObj.add(item);
}
}
}
else {
dObj.addAll(completeList);
}
selectedPosition=-1;
notifyDataSetChanged();
notifyDataSetInvalidated();
}
#Override
public void onItemClick(AdapterView<?> parent, View view, int position,
long id) {
Registration reg=(Registration)context;
selectedPosition=position;
reg.setSelectedCountryCode("+"+dObj.get(position).getCountryCode());
notifyDataSetChanged();
}
}
Consider you have passed a list to your adapter.
Use:
list.getAdapter().notifyDataSetChanged()
to update your list.
After deleting data from list view, you have to call refreshDrawableState().
Here is the example:
final DatabaseHelper db = new DatabaseHelper (ActivityName.this);
db.open();
db.deleteContact(arg3);
mListView.refreshDrawableState();
db.close();
and deleteContact method in DatabaseHelper class will be somewhat looks like
public boolean deleteContact(long rowId) {
return db.delete(TABLE_NAME, BaseColumns._ID + "=" + rowId, null) > 0;
}
I was not able to get notifyDataSetChanged() to work on updating my SimpleAdapter, so instead I tried first removing all views that were attached to the parent layout using removeAllViews(), then adding the ListView, and that worked, allowing me to update the UI:
LinearLayout results = (LinearLayout)findViewById(R.id.results);
ListView lv = new ListView(this);
ArrayList<HashMap<String,String>> list = new ArrayList<HashMap<String,String>>();
SimpleAdapter adapter = new SimpleAdapter( this, list, R.layout.directory_row,
new String[] { "name", "dept" }, new int[] { R.id.name, R.id.dept } );
for (...) {
HashMap<String, String> map = new HashMap<String, String>();
map.put("name", name);
map.put("dept", dept);
list.add(map);
}
lv.setAdapter(adapter);
results.removeAllViews();
results.addView(lv);
while using SimpleCursorAdapter can call changeCursor(newCursor) on the adapter.
I was the same when, in a fragment, I wanted to populate a ListView (in a single TextView) with the mac address of BLE devices scanned over some time.
What I did was this:
public class Fragment01 extends android.support.v4.app.Fragment implements ...
{
private ListView listView;
private ArrayAdapter<String> arrayAdapter_string;
...
#Override
public void onActivityCreated(Bundle savedInstanceState)
{
...
this.listView= (ListView) super.getActivity().findViewById(R.id.fragment01_listView);
...
this.arrayAdapter_string= new ArrayAdapter<String>(super.getActivity(), R.layout.dispositivo_ble_item, R.id.fragment01_item_textView_titulo);
this.listView.setAdapter(this.arrayAdapter_string);
}
#Override
public void onLeScan(BluetoothDevice device, int rssi, byte[] scanRecord)
{
...
super.getActivity().runOnUiThread(new RefreshListView(device));
}
private class RefreshListView implements Runnable
{
private BluetoothDevice bluetoothDevice;
public RefreshListView(BluetoothDevice bluetoothDevice)
{
this.bluetoothDevice= bluetoothDevice;
}
#Override
public void run()
{
Fragment01.this.arrayAdapter_string.add(new String(bluetoothDevice.toString()));
Fragment01.this.arrayAdapter_string.notifyDataSetChanged();
}
}
Then the ListView began to dynamically populate with the mac address of the devices found.
I think it depends on what you mean by refresh. Do you mean that the GUI display should be refreshed, or do you mean that the child views should be refreshed such that you can programatically call getChildAt(int) and get the view corresponding to what is in the Adapter.
If you want the GUI display refreshed, then call notifyDataSetChanged() on the adapter. The GUI will be refreshed when next redrawn.
If you want to be able to call getChildAt(int) and get a view that reflects what is what is in the adapter, then call to layoutChildren(). This will cause the child view to be reconstructed from the adapter data.
I had an ArrayList which I wanted to display in a listview. ArrayList contained elements from mysql.
I overrided onRefresh method and in that method I used tablelayout.removeAllViews(); and then repeated the process for getting data again from the database.
But before that make sure to clear your ArrayList or whatever data structre or else new data will get appended to the old one..
If you want to update the UI listview from a service, then make the adapter static in your Main activity and do this:
#Override
public void onDestroy() {
if (MainActivity.isInFront == true) {
if (MainActivity.adapter != null) {
MainActivity.adapter.notifyDataSetChanged();
}
MainActivity.listView.setAdapter(MainActivity.adapter);
}
}
If you are going by android guide lines and you are using the ContentProviders to get data from Database and you are displaying it in the ListView using the CursorLoader and CursorAdapters ,then you all changes to the related data will automatically be reflected in the ListView.
Your getContext().getContentResolver().notifyChange(uri, null); on the cursor in the ContentProvider will be enough to reflect the changes .No need for the extra work around.
But when you are not using these all then you need to tell the adapter when the dataset is changing. Also you need to re-populate / reload your dataset (say list) and then you need to call notifyDataSetChanged() on the adapter.
notifyDataSetChanged()wont work if there is no the changes in the datset.
Here is the comment above the method in docs-
/**
* Notifies the attached observers that the underlying data has been changed
* and any View reflecting the data set should refresh itself.
*/
I was only able to get notifyDataSetChanged only by getting new adapter data, then resetting the adapter for the list view, then making the call like so:
expandableAdapter = baseFragmentParent.setupEXLVAdapter();
baseFragmentParent.setAdapter(expandableAdapter);
expandableAdapter.notifyDataSetChanged();
on other option is onWindowFocusChanged method, but sure its sensitive and needs some extra coding for whom is interested
override fun onWindowFocusChanged(hasFocus: Boolean) {
super.onWindowFocusChanged(hasFocus)
// some controls needed
programList = usersDBHelper.readProgram(model.title!!)
notesAdapter = DailyAdapter(this, programList)
notesAdapter.notifyDataSetChanged()
listview_act_daily.adapter = notesAdapter
}
If I talked about my scenario here, non of above answers will not worked because I had activity that show list of db values along with a delete button and when a delete button is pressed, I wanted to delete that item from the list.
The cool thing was, I did not used recycler view but a simple list view and that list view initialized in the adapter class. So, calling the notifyDataSetChanged() will not do anything inside the adapter class and even in the activity class where adapter object is initialized because delete method was in the adapter class.
So, the solution was to remove the object from the adapter in the adapter class getView method(to only delete that specific object but if you want to delete all, call clear()).
To you to get some idea, what was my code look like,
public class WordAdapter extends ArrayAdapter<Word> {
Context context;
public WordAdapter(Activity context, ArrayList<Word> words) {}
//.......
#NonNull
#Override
public View getView(final int position, View convertView, ViewGroup group) {
//.......
ImageButton deleteBt = listItemView.findViewById(R.id.word_delete_bt);
deleteBt.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
if (vocabDb.deleteWord(currentWord.id)) {
//.....
} else{
//.....
}
remove(getItem(position)); // <---- here is the trick ---<
//clear() // if you want to clear everything
}
});
//....
Note: here remove() and getItem() methods are inherit from the Adapter class.
remove() - to remove the specific item that is clicked
getItem(position) - is to get the item(here, thats my Word object
that I have added to the list) from the clicked position.
This is how I set the adapter to the listview in the activity class,
ArrayList<Word> wordList = new ArrayList();
WordAdapter adapter = new WordAdapter(this, wordList);
ListView list_view = (ListView) findViewById(R.id.activity_view_words);
list_view.setAdapter(adapter);
After adding/deleting dynamic data in your "dataArray" do:
if you use an ArrayAdapter
adapter.notifyDataSetChanged();
if you use a customAdapter that extends ArrayAdapter
adapter.clear();
adapter.addAll(dataArray);
adapter.notifyDataSetChanged();
if you use a customAdapter that extends BaseAdapter
adapter.clear();
adapter.getData().addAll(dataArray);
adapter.getData().notifyDataSetChanged();
The easiest is to just make a new Adaper and drop the old one:
myListView.setAdapter(new MyListAdapter(...));