In my Fragment, I have 2 views. A Textview and a RecyclerView. The Textview essentially displays the current size of the RecyclerView. So, when a row is removed in the adapter class, I need to update the TextView's value accordingly.
The row is removed successfully when removeBtn is clicked, but I need to update the TextView in the Fragment accordingly.
FRAGMENT
titleText.text = "SIZE (" + arrayStringList().size.toString() + ")"
//...
//...
//Set RecyclerView Adapter
mRecyclerView.layoutManager = androidx.recyclerview.widget.LinearLayoutManager(context)
val adapter = MRecyclerView(context!!, arrayStringList)
mRecyclerView.adapter = adapter
RECYCLERVIEW
holder.removeBtn{
mData.removeAt(position)
notifyItemRemoved(position)
}
Is there some sort of listener that I can put in my fragment to detect when the data changes? Or is there a way to send data from the recyclerview back to the fragment when removeBtn is clicked?
Create a interface in recyclerView class , and implement that interface in fragment . Once you click the remove button , call this interface . In Fragment class , update the text view with adapter.getItemCount.
In Adapter
interface ItemCallback{
void updateTextView();
}
This interface will be implemented in fragment class ,where you can update your textView with itemCount .
public class Fragment implements Adapter.ItemCallback{
#Override
public void updateTextView() {
tvTextView.setText(adapter.getItemCount()); // This will return the current item count of adapter
}
}
You can do this via call back. Make an interface and implement that on Fragment. And pass the reference of the interface to the adapter. When you trigger the event to delete item from recycler view call the interface method (That you implemented on Activity). And in that call back method, you need to set the value to your text view. To set value on TextView, you can call size() method and set the value whatever is returned from it. For example the List you are passing to the adapter is mData. When you get call back the call size method on the reference and set the value as mentioned below code.
titleText.setText(String.valueOf(mData.size())).
Hope this will help you.
NOTE: You need to call String.valueOf method because size method returns integer value so it needs to be cast.
"Or is there a way to send data from the recyclerview back to the fragment when removeBtn is clicked?" the answer is yes
One approach is to pass your adapter your own click listener (an interface), this way you can control the click from the fragment something like this,
A1) create an interface
public interface ItemTouchListener {
void onCardClick(View view, int position);
boolean onCardLongClick(View view, int position);
}
A2) implement this interface in your fragment
public class YourFragment extends Fragment implements ItemTouchListener
A3) implement the methods you created in your fragment
#Override
public void onCardClick(View view, int position) {
if (view.getId() == R.id.removeBtn){
//update your text
}else{
//other buttons
}
}
#Override
public boolean onCardLongClick(View view, int position) {
if (view.getId() == R.id.removeBtn){
//update your text
} else {
//other buttons
}
return true;
}
A4) create this interface in your adapter and set it to your button
private ItemTouchListener onItemTouchListener;
public YourAdapter(List<Object> list, ItemTouchListener onItemTouchListener) {
this.onItemTouchListener = onItemTouchListener;
this.list = list;
}
removeBtn = view.findViewById(R.id.removeBtn);
removeBtn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
onItemTouchListener.onCardClick(v, getAdapterPosition());
}
});
removeBtn.setOnLongClickListener(new View.OnLongClickListener() {
#Override
public boolean onLongClick(View view) {
onItemTouchListener.onCardLongClick(view, getAdapterPosition());
return true;
}
});
A5) and now when you create your adapter it will ask for the ItemTouchListener which you can give it by just passing 'this'
YourAdapter adapter = new YourAdapter(this);
A6) you may also want to give your adapter a method something like getCount which return the list size
public int getCount(){
list.size();
}
and then you can call this like myAdapter.getCount
Generally
I want to control the ViewHolder inflated Views of my RecyclerView from outside of the ViewHolder and the RecyclerView classes. In other words, I want to have control of these views from other methods/classes.
My case (en example)
In my specific case, I made a photo gallery activity which allows the user to perform selection and deselection of each inflated view, notifying which items are selected by highlighting them.
For now, the user is able to do that by clicking each generated object / View; then, actions on specific child of RecyclerView / adapter are possible thanks to "setOnClickListener" and "setOnLongClickListener" methods, which perform the corresponding actions in methods inside the ViewHolder class.
But when activity is restarted (i.e. for device rotation) the selection goes lost and the user should perform the selection again (i.e. for deleting photos).
Assuming that positions of the selected photos are kept (for example via bundle, or via an array) is possible to restore selection (i.e. highlighting the corresponding item / views) on the adapter views after that the activity is re-started? If yes, how?
Some code
The code below contains the Recyclerview class and the AdapterView class, which both are child of an activity Class.
private class ImageGalleryAdapter extends RecyclerView.Adapter<ImageGalleryAdapter.MyViewHolder> {
private ArrayList<PhotoObject.PhotoElement> photoAL;
private Context mContext;
public ImageGalleryAdapter(Context context, ArrayList<PhotoObject.PhotoElement> photosToPreviewInGallery) {
mContext = context;
photoAL = photosToPreviewInGallery;
}
#Override
public ImageGalleryAdapter.MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
Context context = parent.getContext();
LayoutInflater inflater = LayoutInflater.from(context);
// Inflate the layout
View itemView = inflater.inflate(R.layout.item_photo, parent, false);
ImageGalleryAdapter.MyViewHolder viewHolder = new ImageGalleryAdapter.MyViewHolder(itemView);
// Retrieving the itemView
return viewHolder;
}
#Override
public void onBindViewHolder(ImageGalleryAdapter.MyViewHolder holder, int position) {
PhotoObject.PhotoElement previewPhotoInGallery = photoAL.get(position);
ImageView imageView = holder.mPhotoImageView;
GlideApp.with(mContext)
.load(previewPhotoInGallery.getUrl())
.placeholder(R.drawable.ic_cloud_off_red)
.into(imageView);
}
//The method which gives back the number of items to load as photo.
#Override
public int getItemCount() {
return (photoAL.size());
}
// The class that assigns a view holder for each Image and checkbox in the RecyclerView.
public class MyViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener, View.OnLongClickListener {
public ImageView mPhotoImageView;
public CheckBox mPhotoCheckBox;
public MyViewHolder(View item_view) {
super(item_view);
mPhotoImageView = (ImageView) item_view.findViewById(R.id.item_photo_iv);
mPhotoCheckBox = (CheckBox) item_view.findViewById(R.id.item_photo_checkbox);
item_view.setOnClickListener(this);
item_view.setOnLongClickListener(this);
// Retrieving the item_view
}
// The method for managing the click on an image.
#Override
public void onClick(View view) {
itemSelection(view);
}
// Manages the selection of the items.
private void itemSelection(View item) {
// Retrieving the item
int position = getAdapterPosition();
if (position != RecyclerView.NO_POSITION) {
if (!item.isSelected()) {
// Add clicked item to the selected ones
MultiPhotoShootingActivity.manageSelection(true, position);
// Visually highlighting the ImageView
item.setSelected(true);
mPhotoCheckBox.setChecked(true);
mPhotoCheckBox.setVisibility(View.VISIBLE);
} else {
// Remove clicked item from the selected ones
MultiPhotoShootingActivity.manageSelection(false, position);
// Removing the visual highlights on the ImageView
item.setSelected(false);
mPhotoCheckBox.setChecked(false);
mPhotoCheckBox.setVisibility(View.INVISIBLE);
}
}
}
// The method for managing the long click on an image.
#Override
public boolean onLongClick(View view) {
int position = getAdapterPosition();
if(position != RecyclerView.NO_POSITION) {
Intent intent = new Intent(mContext, PhotoDetail.class);
intent.putExtra("KEY4URL", activityPhotoObject.getPath(position));
startActivity(intent);
}
// return true to indicate that the click was handled (if you return false onClick will be triggered too)
return true;
}
}
}
Thank you for your time.
You shouldn't "control" views from outside the adapter. Instead, Override onSaveState and onRestoreState in your activity. Make same methods in your adapter with passing the bundle to the adapter in order to save state. save an integer array of positions that were selected into the bundle(that you passed into an adapter). In corresponding way, you can get the array of selected positions from the bundle of On restore state.
activity:
#Override
protected void onRestoreInstanceState(Bundle savedInstanceState){
adapter.onRestoreInstanceState(savedInstanceState);
}
in your adapter:
public void onRestoreInstanceState(Bundle state){
selectedItemsArray = state.getIntArray("my_array_key")
}
#Alessandro
You can handle the Runtime changes by yourself.
In your manifest, you can define the changes that your activity will handle by itself and it will not be restarted.
android:configChanges="orientation|keyboardHidden"
After that, you'll have to handle the Configuration changes that you declared in your manifest using this method in your activity:
#Override
public void onConfigurationChanged(Configuration newConfig) {
super.onConfigurationChanged(newConfig);
// Checks the orientation of the screen
if (newConfig.orientation == Configuration.ORIENTATION_LANDSCAPE) {
// Do your thing
}
}
SOLVED
Find out that for solving the problem I had to accomplish two little tasks:
saving and restoring the selected item selection state (for example via an array, as helpfully suggested by #Inkognito);
retrieving the views for applying the selection, based on the position inside the RecyclerView.
So, I had to modify some code.
Before proceeding, I would like to point out that the Activity class has a sub-class, which is the Adapter class (named ImageGalleryAdapter); the Adapter subclass, in turn, has its own subclass, which is the ViewHolder class (named MyViewHolder).
So: Activity class -> Adapter class -> ViewHolder class
Code modified in the parent class (the activity class, in which the RecyclerView is)
#Override
protected void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
adapter.onSaveInstanceState(outState);
}
#Override
protected void onRestoreInstanceState(Bundle savedInstanceState) {
super.onRestoreInstanceState(savedInstanceState);
adapter.onRestoreInstanceState(savedInstanceState);
}
In the onSaveInstanceState and onRestoreInstanceState methods, I added the references for saving and restoring instance states of the "adapter" sub-class.
Code added in the adapter class (which is inside the RecyclerView class)
private boolean [] selectedItemsArray;
private void onSaveInstanceState(Bundle outState) {
outState.putBooleanArray("my_array_key" , selectedItemsArray = mpsaPO.getItemsSelected());
}
private void onRestoreInstanceState(Bundle state) {
if (state != null) {
selectedItemsArray = state.getBooleanArray("my_array_key");
}
}
The selectedItemsArray is a boolean array in which the information of which elements of the RecyclerView are selected (true = selected; false = not selected) is contained.
Then, adding this element in the saved instance and retrieved via the activity class, makes the app able to know which are the views selected after that the activity is re-created.
Code added inside the onBindViewHolder method, which is inside the adapter class
if (selectedItemsArray != null) {
if (selectedItemsArray[position]) {
holder.itemView.setSelected(true);
holder.mPhotoCheckBox.setChecked(true);
holder.mPhotoCheckBox.setVisibility(View.VISIBLE);
}
}
With this last part of code, we are applying the selection to the corresponding views based on which items/views were selected before that the activity was saved.
The holer object contains the itemView and mPhotoCheckBox objectsm on which we can perform the selection.
I know there are lots of threads already on this topic, but none of the given solutions worked for me so far. I'm trying to add or update an item of a RecyclerView. Here's my code so far:
MainActivity
private MyListItemAdapter mAdapter;
private RecyclerView recyclerView;
// called on activity create
private void init() {
// initialize activity, load items, etc ...
mAdapter = new MyListItemAdapter(this, items);
recyclerView.setAdapter(mAdapter);
}
// called when I want to replace an item
private void updateItem(final Item newItem, final int pos) {
mAdapter.replaceItem(newItem, pos);
}
MyListItemAdapter
public class MyListItemAdapter extends RecyclerView.Adapter<MyListItemAdapter.MyListItemViewHolder> {
private List<Item> mItems;
public void replaceItem(final Item newItem, final int pos) {
mItems.remove(position);
mItems.add(position, newItem);
notifyItemChanged(position);
notifyDataSetChanged();
}
}
I tried to make this changes from the MainActivity aswell, but in every case I tried my list doesn't get updated. The only way it worked was when I reset the adapter to the recyclerView:
mAdapter.notifyDataSetChanged();
recyclerView.setAdapter(mAdapter);
which obviously is a bad idea. (aside from the bad side effects wouldn't even work when I'm using lazy loading on my lists).
So my question is, how can I make notifyDataSetChanged() work properly?
edit
I found a solution for replacing items. After mAdapter.replaceItem(newItem, pos); I had to call recyclerView.removeViewAt(position);
This works for replacing an item, but doesn't solve my problem when I want to add items (e.g. lazy loading) to my list
edit2
I found a working solution for adding items
Adapter:
public void addItem(final Item newItem) {
mItems.add(newItem);
notifyDataSetChanged();
}
Activity:
private void addItem(final Item newItem) {
mAdapter.addItem(newItem);
recyclerView.removeViewAt(0); // without this line nothing happens
}
For some reason this works (also: it doesn't remove the view at position 0), but I'm sure this isn't the correct way to add items to a recyclerView
This should work:
private ArrayList<Item> mItems;
public void replaceItem(final Item newItem, final int position) {
mItems.set(position, newItem);
notifyItemChanged(position);
}
ArrayList.set() is the way to go to replace items.
For adding items, just append them to mItems and then go notifyDatasetChanged(). Another way to go is to use notifyItemRangeInserted(). Depending on where/how are you adding new items and how many of them, it might be worth it.
Use
mItems.set(position, newItem);
instead of
mItems.add(position, newItem);
because .set method will replace your data to particular position.
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(...));