Hi friends i have a listview and the contents are fetched from a webservice call. In that webservice call, there are fields like
"OGType": "ORG" and "OGType": "GROUP"
If click a button, the listview must shows the item having "OGType": "ORG", and hide the item having "OGType": "GROUP". Hope you understand what i meant. Please anyone help me for that. Thanks in Advance.
Try to set new data (only with ORG) to adapter and then call
adapter.notifyDataSetChanged();
You can do it in your getView Method in your Adapter Class. That's the header
public View getView(int pos, View convertView, ViewGroup, parent)
There you can properly hide the element(s) you want, you know, using the method setVisibility()
For more help you can take a look here
You can create a custom adapter and pass data to it in the form of Array or ArrayList (ArrayList is better when dealing with Custom Adapters). Whenever you need to add or remove the data from ListView, just add or remove the item to or from you ArrayList and call notifyDataSetChanged() on your custom adapter and it will update the ListView automatically.
In your case, whenever you click a button, edit you ArrayList and call your custom adapter's method called notifyDataSetChanged() and that's it. You'll see every time you call this method ListView will refresh itself if you have made any changes to the data. Hope it helps.
NOTE - CUSTOM ADAPTER IS NOT COMPULSORY. ANY ADAPTER CAN BE USED e.g SimpleAdapter, ArrayAdapter etc.
You can use a visible list and filters lists. You should use "visible" for complete the BaseAdpter as always, then, you can change the pointer of visible to other list (all, filter...)
Don't worry by the memory, are pointers, you only have each element only once.
public class MyAdapter extends BaseAdapter {
private ArrayList<MyItem> visible;
private ArrayList<MyItem> all;
private ArrayList<MyItem> filter;
public MyAdapter(ArrayList<MyItem> items) {
all = items;
visible = all; //Set all as visible
filter = new ArrayList<Item>();
for (Item i : items)
if (i.getType().equals("ORG"))
filter.add(i);
}
//Complete adapter using "visible"
public void showOnlyOrg() {
visible = filter;
notifydatasetchanged();
}
}
The non hackish way will be to remove the items from your Collection which you use to generate the listview and then call notifyDataSetChanged();
I'm developing a Androidapplication using ListView.
ListView have a one file in each and every ListItem. Here, I have set onItemClickin ListView. So, that if user clicks the ListItememail application gets open and attach the particular file in email. Its for the single File, this gets implemented and working fine.
Now I want attach the multiple file in email. i.e. the implementing the CheckBoxin each ListItemand checked items have to attached into the Mail.
I know its possible because its very similar to the file manager application that checking the multiple file and deleting the all file by clicking the single Button. But don't know how to do.
In you ListAdapter create a SparseBooleanArray
private SparseBooleanArray checkStatus;
This SparseBooleanArray stores the checked items. Now in getView do the following
#Override
public View getView(int position, View view, ViewGroup parent) {
ViewCache viewCache;
if (view == null){
viewCache = new ViewCache();
view = layoutInflater.inflate(R.layout.list_box, null, false);
viewCache.checkBox = view.findViewById(R.id.check_box);
viewCache.checkBox.setOnCheckedChangeListener(onCheckedChangeListener);
//other views in the list box
...........
}
vewCache = (ViewCache)view.getTag();
viewCache.checkBox.setTag(position);
viewCache.checkBox.setChecked(isChecked(position));
//set other views
........
}
This is the class ViewCache
private static class ViewCache{
CheckBox checkBox;
//other views in the list box
.......
}
This method checks whether the position is checked
private boolean isChecked(int position){
return checkStatus.get(position, false);
}
This is the onCheckChangeListener
CompoundButton.OnCheckedChangeListener onCheckedChangeListener = new CompoundButton.OnCheckedChangeListener() {
#Override
public void onCheckedChanged(CompoundButton compoundButton, boolean b) {
checkStatus.put(((Integer)compoundButton.getTag()), b);
}
};
Finally you can get the checked items from the SparseBooleanArray checkStatus. Think it will help you.
You can try implementing your own ArrayAdapter. Initialize it with an array of your file objects and use it in the list view.
Next make a list of indexes that is visible by the adapter and can be manipulated from the outside. In your onItemClick method you have the position of the clicked item. If it's in that list remove it, otherwise - insert it. Let's call that list selection.
Next in your adapter's getView method construct a view with a checkbox inside. Again you have the current position, because it's passed as an argument. Set the checkbox state depending on the presence of the position in selection.
Finally implement your button's onClick so that it does whatever you do with your file objects only for those objects of your file_array whose positions are in your selection.
Hope that helps
In the above answers Sreejith has given a good explanation of how to store the states of the checked items in the list view using a SparseBooleanArray. This solves the first part of your problem.
The second part regarding the passing of the states of these items to the other activities can be achieved using the Application class.
Application class:
Base class for those who need to maintain global application state. Sometimes you want to store data, like global variables which need to be accessed from multiple Activities - sometimes everywhere within the application. In this case, the Application object will help you.
Here is a sample code for this:
public class TopClass extends Application {
private static TopClass topClass;
public TopClass getInstance()
{
return topClass;
}
#Override
public void onCreate ( )
{
super.onCreate();
topClass = this;
}
public ArrayList<String> arrList = new ArrayList<String>();
}
You need to set tag android:name="TopClass" in the application manifest file under the application tag. Something like this:
<application
android:icon="#drawable/ic_launcher"
android:label="#string/app_name"
android:name="TopClass" >
....
....
Here is how you can access it from the activity:
TopClass top = (TopClass)getApplicationContext();
top.arrList.add("StackOverflow");
Now you can access the same variable from other activities similarly.
can you help me, if there is any way, how to call method startActivityForResult(..) from class extends ArrayAdapter?
Thanks.
EDIT: ADDED CODE OF ARRAYADAPTER:
There is code of MyAdapter class:
public class MyAdapter extends ArrayAdapter {
public static final String bundle_text = "some_text";
public MyAdapter(Context context, int textViewResourceId, List<MyAdapterItem> data) {
super(context, textViewResourceId, data);
}
#Override
public View getView(int position, View convertView, ViewGroup parent) {
View row = convertView;
// ...
row.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
Intent intent = new Intent(getContext(), MyNewActivity.class);
intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
int id = 1;
Bundle bundle = new Bundle();
bundle.putLong(MyAdapter.bundle_text, id);
intent.putExtras(bundle);
getContext().startActivity(intent);
}
});
return super.getView(position, convertView, parent);
}
}
All works, but from ArrayAdapter class is not possible to call startActivityForResult, I can call only startActivty.
But after MyNewActivity is finished, I would like to refresh listview, but I do not know how, when I cannot call startActivityForResult.
This a common misconception (as is old thread, I will just give an outline)
Adapter is only for data to list view - it does return a view as in your getView for a row, but doesn't really handle any GUI events - those are done in activity. In fact, if adapter is loading a lot of rows from internet or database it should be done outside the UI thread.
ACTIVITY IS FOR EVENTS. You attach a click listener to a listview within your activity. Then there is no problem calling e.g. a detail edit activity - it is all on UI thread. So no problem starting an activity from UI thread.
PROBLEM OF UPDATING ADAPTER! If you back return from detail activity you will find the list is NOT updated as adapter was NOT updated. To do this, start detail Activity for RESULT. Don't clutter up the detail "form" with any adapter stuff. In fact, you may choose to return the POJO that was created or edited in detail record, and not bother with the database at all.
Now in your activity you listen for onActivityResult() and do the insert into the adapter (and database backend if you have e.g. SQLite in app), then notify Data changed for list view. It will update the list view automatically.
PERFORMANCE can be an issue if listview is reloaded. In most cases you can get away by adding to adapter and simply notify the list view data is changed. Since data display is "incremental" you may have edited row 3 of rows 1 - 5 shown. Then list view will only refresh those 1-5 rows display positions. But if you reload say 500 rows when only 1 is changed you could get performance issues :)
I'm working on refreshing a list in Android but can't seem to get it right.
I've used notifyDataSetChanged(); at every point that I thought applicable (currently using dialogs for input), but it doesn't work, and I've got to the point of plastering it around all over the place and it still won't refresh.
Am I right in saying this should refresh the list while your looking at it, or it will rebuild the list and you still have to refresh the view?
If anyone has got any suggestions for the positioning of it in relation to constructing a list I'd be glad to hear.
Is this a ListActivity? I have a ListActivity in my project at the moment and I have my own adapter class within it that extends ArrayAdapter.
My experience is that calling notifyDataSetChanged() on my extended list adapter class instance does immediately cause a refresh of the list View being displayed. So, as soon as I call .notifyDataSetChanged() on my adapter instance, the list View is regenerated which therefore causes my adapter's implementation of getView() to be called to generate each individual row view again. So, the user selects a context menu item which triggers some change to the data and then a call to .notifyDataSetChanged(), and the screen instantly refreshes with the new data.
So to add some code snippets to be clear:
I have a ListActivity
public class VarListActivity extends ListActivity {
Within it, I extend ArrayAdapter
class VarAdapter extends ArrayAdapter{
...
#Override
public View getView(int position, View convertView, ViewGroup parent){
// Creates the views based upon myData
...
#Override
public int getCount(){
...
And I create an instance of that array adapter
la = new VarAdapter(this, R.layout.row0);
And when a context menu item is selected
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case R.id.a_context_menu_option:
// Does a call to perform modifications to myData
la.notifyDataSetChanged();
return true;
I'm just chucking this all down just in case it's of any similarity to your situation, but really we need to know a bit more about your code.
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(...));