问题
I'm implementing an endless data loading for a RecyclerView. When software detects that last item is going to be shown, it downloads new items and call to the loadMoreData() function but new dataset is not showing.
When I called notifyDataSetChanged() so nothing to be happened.
I have only one solution that is refresh the view is to set again the adapter but problem is that the recyclerview returns to the first position then again recyclerview scrolled up from the first position to last position.
RecyclerViewActivity.java
RecyclerView rv;
DatabaseHelpr databaseHelpr;
RVAdapter adapter;
LocationFinder locationfinder;
Location currentLocation;
ArrayList<ServiceModel> childList, list;
private int MainService_ID, city_id;
String url2;
ActionBar actionBar;
JSONArray items = null;
Utility utility;
Double lat, longi;
LinearLayoutManager llm;
int counter=0;
ProgressBar progressBar;
private static final String TAG_ITEMS = "items";
private static final String TAG_LOCALITY = "Locality";
private static final String TAG_BUSINESS_ID = "Business_Id";
private static final String TAG_LONGITUDE = "Longitude";
private static final String TAG_BUSINESS_NAME = "Business_Name";
private static final String TAG_LATITUDE = "Latitude";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.recyclerview_activity);
list = new ArrayList<>();
utility = new Utility(this);
llm = new LinearLayoutManager(this);
Bundle bundle=getIntent().getExtras();
MainService_ID=bundle.getInt("service_id");
String mainService_Name = bundle.getString("service_name");
city_id = bundle.getInt("city_id");
lat= bundle.getDouble("lat");
longi=bundle.getDouble("longi");
rv=(RecyclerView)findViewById(R.id.rv);
rv.setLayoutManager(llm);
actionBar = getSupportActionBar();
assert actionBar != null;
actionBar.setDisplayHomeAsUpEnabled(true);
actionBar.setTitle(mainService_Name);
//Here city_id = 8, lat = 18.552954, longi = 73.897200, counter=0, MainService_ID = 5
String url="https://servicedata2-dot-indiacomapi.appspot.com/_ah/api/servicedata/v1/ServiceData?city_id=";
url2 =url+city_id+"&lat="+lat+"&lng="+longi+"&roll="+counter+"&service_id="+MainService_ID;
AsyncHttpClient client = new AsyncHttpClient();
progressBar=(ProgressBar) findViewById(R.id.progressBar1);
progressBar.setVisibility(View.VISIBLE);
client.get(url2, new AsyncHttpResponseHandler() {
@Override
public void onSuccess(int statusCode, Header[] headers, byte[] response) {
// called when response HTTP status is "200 OK"
String s = new String(response);
try {
JSONObject jsonObj = new JSONObject(s);
// Getting JSON Array node
items = jsonObj.getJSONArray(TAG_ITEMS);
// looping through All Contacts
for (int i = 0; i < items.length(); i++) {
JSONObject c = items.getJSONObject(i);
String locality = c.getString(TAG_LOCALITY);
String business_Id = c.getString(TAG_BUSINESS_ID);
String longitude = c.getString(TAG_LONGITUDE);
String latitude = c.getString(TAG_LATITUDE);
String business_Name = c.getString(TAG_BUSINESS_NAME);
locationfinder = new LocationFinder(RecyclerViewActivity.this);
// check if GPS enabled
if (locationfinder.canGetLocation()) {
double lat = locationfinder.getLatitude();
double longi = locationfinder.getLongitude();
currentLocation = new Location("");
currentLocation.setLatitude(lat);
currentLocation.setLongitude(longi);
} else {
locationfinder.showSettingsAlert();
}
Location savedLocation = new Location("databaseLocation");
savedLocation.setLatitude(Double.parseDouble(latitude));
savedLocation.setLongitude(Double.parseDouble(longitude));
Double difference = currentLocation.distanceTo(savedLocation) * (0.001);
difference = Double.parseDouble(new DecimalFormat("##.##").format(difference));
String newDifference = String.valueOf(difference) + " km";
ServiceModel serviceModel = new ServiceModel(business_Id, business_Name, newDifference, locality);
list.add(serviceModel);
}
} catch (JSONException e) {
e.printStackTrace();
}
progressBar.setVisibility(View.GONE);
adapter = new RVAdapter(RecyclerViewActivity.this, list);
rv.setAdapter(adapter);
rv.addOnScrollListener(new EndlessRecyclerOnScrollListener(llm) {
@Override
public void onLoadMore(int current_page) {
// counter= counter+1;
loadMoreData();
}
});
}
@Override
public void onFailure(int statusCode, Header[] headers, byte[] errorResponse, Throwable e) {
// called when response HTTP status is "4XX" (eg. 401, 403, 404)
//Toast.makeText(getApplicationContext(),""+statusCode,Toast.LENGTH_LONG).show();
}
});
}
private void loadMoreData() {
counter= counter+1;
//Here city_id = 8, lat = 18.552954, longi = 73.897200, counter=1, MainService_ID = 5
String url="https://servicedata2-dot-indiacomapi.appspot.com/_ah/api/servicedata/v1/ServiceData?city_id=";
url2 =url+city_id+"&lat="+lat+"&lng="+longi+"&roll="+counter+"&service_id="+MainService_ID;
AsyncHttpClient client = new AsyncHttpClient();
progressBar=(ProgressBar) findViewById(R.id.progressBar1);
progressBar.setVisibility(View.VISIBLE);
client.get(url2, new AsyncHttpResponseHandler() {
@Override
public void onSuccess(int statusCode, Header[] headers, byte[] response) {
// called when response HTTP status is "200 OK"
String s = new String(response);
try {
JSONObject jsonObj = new JSONObject(s);
// Getting JSON Array node
items = jsonObj.getJSONArray(TAG_ITEMS);
// looping through All Contacts
for (int i = 0; i < items.length(); i++) {
JSONObject c = items.getJSONObject(i);
String locality = c.getString(TAG_LOCALITY);
String business_Id = c.getString(TAG_BUSINESS_ID);
String longitude = c.getString(TAG_LONGITUDE);
String latitude = c.getString(TAG_LATITUDE);
String business_Name = c.getString(TAG_BUSINESS_NAME);
locationfinder = new LocationFinder(RecyclerViewActivity.this);
// check if GPS enabled
if (locationfinder.canGetLocation()) {
double lat = locationfinder.getLatitude();
double longi = locationfinder.getLongitude();
currentLocation = new Location("");
currentLocation.setLatitude(lat);
currentLocation.setLongitude(longi);
} else {
locationfinder.showSettingsAlert();
}
Location savedLocation = new Location("databaseLocation");
savedLocation.setLatitude(Double.parseDouble(latitude));
savedLocation.setLongitude(Double.parseDouble(longitude));
Double difference = currentLocation.distanceTo(savedLocation) * (0.001);
difference = Double.parseDouble(new DecimalFormat("##.##").format(difference));
String newDifference = String.valueOf(difference) + " km";
ServiceModel serviceModel = new ServiceModel(business_Id, business_Name, newDifference, locality);
list.add(serviceModel);
}
} catch (JSONException e) {
e.printStackTrace();
}
progressBar.setVisibility(View.GONE);
//adapter = new RVAdapter(RecyclerViewActivity.this, list);
//rv.setAdapter(adapter);
adapter.notifyDataSetChanged();
}
@Override
public void onFailure(int statusCode, Header[] headers, byte[] errorResponse, Throwable e) {
}
});
Toast.makeText(this, "Net is present", Toast.LENGTH_SHORT).show();
}
}
RVAdapter.java
public class RVAdapter extends RecyclerView.Adapter<RVAdapter.PersonViewHolder>{
private final LayoutInflater mInflater;
List<ServiceModel> persons ;
private Context mContext;
public RVAdapter(Context context,List<ServiceModel> persons){
this.mInflater = LayoutInflater.from(context);
this.persons = new ArrayList<>(persons);
this.mContext = context;
}
@Override
public void onAttachedToRecyclerView(RecyclerView recyclerView) {
super.onAttachedToRecyclerView(recyclerView);
}
@Override
public PersonViewHolder onCreateViewHolder(ViewGroup viewGroup, int i) {
View v = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.item, viewGroup, false);
PersonViewHolder pvh = new PersonViewHolder(v);
return pvh;
}
@Override
public void onBindViewHolder(PersonViewHolder personViewHolder, int i) {
ServiceModel person = persons.get(i);
personViewHolder.businessName.setOnClickListener(clickListener);
personViewHolder.image_url.setOnClickListener(clickListenerImage);
personViewHolder.businessName.setTag(personViewHolder);
personViewHolder.difference.setTag(personViewHolder);
personViewHolder.business_id.setTag(personViewHolder);
personViewHolder.image_url.setTag(personViewHolder);
personViewHolder.locality.setTag(personViewHolder);
personViewHolder.businessName.setText(Html.fromHtml(person.getBusinessname()));
String firstLetter = String.valueOf(person.getBusinessname().charAt(0));
ColorGenerators generator = ColorGenerators.MATERIAL; // or use DEFAULT
int color = generator.getColor(person.getBusinessname());
TextDrawable drawable = TextDrawable.builder().buildRound(firstLetter, color); // radius in px
personViewHolder.image_url.setImageDrawable(drawable);
personViewHolder.difference.setText(Html.fromHtml(person.getNewDiffer()));
personViewHolder.locality.setText(Html.fromHtml(person.getLocality()));
personViewHolder.bind(person);
}
View.OnClickListener clickListener = new View.OnClickListener() {
@Override
public void onClick(View view) {
PersonViewHolder holder = (PersonViewHolder) view.getTag();
int position = holder.getPosition();
ServiceModel person = persons.get(position);
String businessids = person.getBusinessid();
Intent intent = new Intent(mContext, BusinessInfoActivity.class);
intent.putExtra("businessids", businessids);
mContext.startActivity(intent);
}
};
View.OnClickListener clickListenerImage = new View.OnClickListener() {
@Override
public void onClick(View view) {
PersonViewHolder holder = (PersonViewHolder) view.getTag();
int position = holder.getPosition();
ServiceModel person = persons.get(position);
String businessids = person.getBusinessid();
Intent intent = new Intent(mContext, BusinessInfoActivity.class);
intent.putExtra("businessids", businessids);
mContext.startActivity(intent);
}
};
@Override
public int getItemCount() {
return persons.size();
}
public void animateTo(List<ServiceModel> models) {
applyAndAnimateRemovals(models);
applyAndAnimateAdditions(models);
applyAndAnimateMovedItems(models);
}
private void applyAndAnimateRemovals(List<ServiceModel> newModels) {
for (int i = persons.size() - 1; i >= 0; i--) {
final ServiceModel model = persons.get(i);
if (!newModels.contains(model)) {
removeItem(i);
}
}
}
private void applyAndAnimateAdditions(List<ServiceModel> newModels) {
for (int i = 0, count = newModels.size(); i < count; i++) {
final ServiceModel model = newModels.get(i);
if (!persons.contains(model)) {
addItem(i, model);
}
}
}
private void applyAndAnimateMovedItems(List<ServiceModel> newModels) {
for (int toPosition = newModels.size() - 1; toPosition >= 0; toPosition--) {
final ServiceModel model = newModels.get(toPosition);
final int fromPosition = persons.indexOf(model);
if (fromPosition >= 0 && fromPosition != toPosition) {
moveItem(fromPosition, toPosition);
}
}
}
public ServiceModel removeItem(int position) {
final ServiceModel model = persons.remove(position);
notifyItemRemoved(position);
return model;
}
public void addItem(int position, ServiceModel model) {
persons.add(position, model);
notifyItemInserted(position);
}
public void moveItem(int fromPosition, int toPosition) {
final ServiceModel model = persons.remove(fromPosition);
persons.add(toPosition, model);
notifyItemMoved(fromPosition, toPosition);
}
public static class PersonViewHolder extends RecyclerView.ViewHolder {
protected CardView cv;
protected TextView businessName, difference, business_id, locality;
protected ImageView image_url;
public PersonViewHolder(View itemView) {
super(itemView);
cv = (CardView)itemView.findViewById(R.id.cv);
businessName = (TextView)itemView.findViewById(R.id.business_name);
difference = (TextView)itemView.findViewById(R.id.txtDifferenece);
business_id = (TextView)itemView.findViewById(R.id.business_id);
image_url = (ImageView)itemView.findViewById(R.id.thumbnail);
locality= (TextView)itemView.findViewById(R.id.txtLocality);
}
public void bind(ServiceModel model) {
businessName.setText(model.getBusinessname());
}
}
}
Please help me, How to set notifyDataSetChanged() to the adapter. it is not working in my code. I already checked all answers which is posted on the stackoverflow.
回答1:
you are setting the new list to the RecyclerView Adapter , set the list in the Adapter:
make a method setItems(list) in adapter and call it before notifyDataSetChanged() and in adapter do
this.persons = new ArrayList<>(persons);
in setItems
add this method in adapter:
public void setItems(List<ServiceModel> persons) {
this.persons = persons;
}
and call it before notifyDataSetChanged() like this:
adapter.setItems(list);
adapter.notifyDataSetChanged();
回答2:
Issue is in these lines..
adapter = new RVAdapter(RecyclerViewActivity.this, list);
rv.setAdapter(adapter);
adapter.notifyDataSetChanged();
You are initialising your adapter every time. No need to reinitialize it.
Just update your arraylist and invoking to adapter.notifyDataSetChanged(); will make it work.
回答3:
Like @Beena mentioned, you are creating and setting new adapter ever time, in your success response.
One approach would be to create an adapter and set it to the recycler view only for the first time, and then onSuceess() of your api callback, call a method of your adapter.
In, them adapter method, just add that new data in your main arraylist and do notifyItemInserted() instead of notifyDataSetChanged, in this way you will also see the default adding animation of recyclerView.
回答4:
when you every fill your list call below method.
if (adapter != null) // it works second time and later
adapter.notifyDataSetChanged();
else { // it works first time
adapter = new AdapterClass(context,list);
listView.setAdapter(adapter);
}
回答5:
I solved this with added method in RVAdapter that call notifyDataSetChanged().
Simply in RVAdapter:
public void refreshList(){
notifyDataSetChanged();
}
and call this method in MainActivity when need:
rVAdapter.refreshList();
来源：https://stackoverflow.com/questions/35147466/set-notifydatasetchanged-on-recyclerview-adapter