问题
- My recyclerview is not updating correctly after the back button is pressed.
- The recyclerview works fine before the back button is pressed
- The data is properly updated (seen in the log) but the recyclerview does not reflect the change
- The purpose of the handler is to poll the database for a notification (working fine)
- The notification toast is displayed everytime
- I am not receiving any errors
If I can provide any other information to help do not hesitate to ask.
Main:
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_chat_room);
recView = (RecyclerView) findViewById(R.id.recyclerViewMessages);
linearLayoutManager = new LinearLayoutManager(this) {};
linearLayoutManager.setReverseLayout(true);
recView.setLayoutManager(linearLayoutManager);
listData = (ArrayList) MessagingData.getMessageListData();
adapter = new RecyclerViewAdapterMessaging(listData, this);
recView.setAdapter(adapter);
adapter.setItemClickCallback(this);
final Handler h = new Handler();
final int delay = 2000; //milliseconds
h.postDelayed(new Runnable(){
public void run(){
Notify_Message_Async notify_message_async = new Notify_Message_Async(ctx);
notify_message_async.execute(NOTIFICATION, message_id);
System.out.println(global.getNotification());
if(global.getNotification()==1){
Toast.makeText(ctx, "Notified",
Toast.LENGTH_LONG).show();
try {
refresh_receive();
} catch (ExecutionException e) {
Toast.makeText(ctx, "catch",
Toast.LENGTH_LONG).show();
e.printStackTrace();
} catch (InterruptedException e) {
Toast.makeText(ctx, "catch",
Toast.LENGTH_LONG).show();
e.printStackTrace();
}
}
h.postDelayed(this, delay);
}
}, delay);
}
public void refresh_receive() throws ExecutionException, InterruptedException {
String method = "receive_message";
Receive_Live_Message_Async receive_live_message_async = new Receive_Live_Message_Async(this);
receive_live_message_async.execute(method, message_id).get();// Setup the message
adapter.setListData((ArrayList)MessagingData.getMessageListData());
adapter.notifyDataSetChanged();
global.setNotification(0);//reset notification
}
Adapter:
public class RecyclerViewAdapterMessaging extends RecyclerView.Adapter<RecyclerViewAdapterMessaging.Holder> {
private View v;
private List<List_Item_Messaging> listData;
private LayoutInflater inflater;
Global global = new Global();
private ItemClickCallback itemClickCallback;
Context context;
public interface ItemClickCallback {
void onItemClick(View v, int p);
void onSecondaryIconClick(int p);
}
public void setItemClickCallback(final ItemClickCallback itemClickCallback) {
this.itemClickCallback = itemClickCallback;
}
public RecyclerViewAdapterMessaging(List<List_Item_Messaging> listData, Context c) {
inflater = LayoutInflater.from(c);
context = c;
this.listData = listData;
}
@Override
public int getItemViewType(int position) {//0 for self... /1 for Other
List_Item_Messaging item = listData.get(position);
//ENSURE GLOBAL USERNAME NOT NULL
String other_username = item.getMessage_username();
if (other_username == null) {
((Activity) context).finish();
}
if (item.getMessage_username().trim().equals(global.getUserName())) {
System.out.println("The usernames are the same");
return 0;
} else {
System.out.println("The usernames are the NOT same");
return 1;
}
}
@Override
public Holder onCreateViewHolder(ViewGroup parent, int viewType) {
switch (viewType) {
case 0:
View view = inflater.inflate(R.layout.chat_thread, parent, false);// Self
v = view;
break;
case 1:
View view2 = inflater.inflate(R.layout.chat_thread_other, parent, false);// Not self
int width2 = global.getScreenWidth();
v = view2;
break;
}
return new Holder(v);
}
@Override
public void onBindViewHolder(Holder holder, int position) {
List_Item_Messaging item = listData.get(position);
holder.conversation.setText(item.getMessage_conversation());
}
public void setListData(ArrayList<List_Item_Messaging> exerciseList) {
this.listData.clear();
this.listData.addAll(exerciseList);
}
@Override
public int getItemCount() {
return listData.size();
}
class Holder extends RecyclerView.ViewHolder implements View.OnClickListener {
ImageView thumbnail;
//ImageView secondaryIcon;
TextView conversation;
View message_container;
public Holder(View itemView) {
super(itemView);
conversation = (TextView) itemView.findViewById(R.id.conversation_textview);
message_container = itemView.findViewById(R.id.message_container);
message_container.setOnClickListener(this);
}
@Override
public void onClick(View v) {
if (v.getId() == R.id.message_container) {
itemClickCallback.onItemClick(v, getAdapterPosition());
} else {
itemClickCallback.onSecondaryIconClick(getAdapterPosition());
}
}
}
public void clearItems() {
listData.clear();
this.notifyDataSetChanged();
}
}
I have referenced the following to no solution:
- notifyDataSetChanged not working on RecyclerView
- smoothScrollToPosition after notifyDataSetChanged not working in android
- adapter.notifyDataSetChange() not working after called from onResume()
回答1:
change a little in your code
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_chat_room);
recView = (RecyclerView) findViewById(R.id.recyclerViewMessages);
linearLayoutManager = new LinearLayoutManager(this) {};
linearLayoutManager.setReverseLayout(true);
recView.setLayoutManager(linearLayoutManager);
// change here
if (listData != null)
listData.clear();
else listData = new <> ArrayList();
listData.addAdd((ArrayList)MessagingData.getMessageListData());
adapter = new RecyclerViewAdapterMessaging(listData, this);
recView.setAdapter(adapter);
adapter.setItemClickCallback(this);
final Handler h = new Handler();
final int delay = 2000; //milliseconds
then make a small change here
public void refresh_receive() throws ExecutionException, InterruptedException {
String method = "receive_message";
Receive_Live_Message_Async receive_live_message_async = new Receive_Live_Message_Async(this);
receive_live_message_async.execute(method, message_id).get();// Setup the message
// changing here
dataList.clear();
dataList.addAdd((ArrayList)MessagingData.getMessageListData())
adapter.setListData(dataList);
adapter.notifyDataSetChanged();
global.setNotification(0);//reset notification
}
another problem in your code, you are using receive_live_message_async AsyncTask put your update code in onPostExecute
public class receive_live_message_async extends AsyncTask {
@Override
protected Object doInBackground(Object[] objects) {
return null;
}
@Override
protected void onPreExecute() {
super.onPreExecute();
}
@Override
protected void onPostExecute(Object o) {
// call your refresh_receive(); here
super.onPostExecute(o);
}
}
similarly when you are call receive_live_message_async.execute(); update your recyclerView in onPostExecute
@Override
protected void onPostExecute(Object o) {
dataList.clear();
dataList.addAll((ArrayList)MessagingData.getMessageListData());
adapter.notifyDataSetChanged();
super.onPostExecute(o);
}
来源：https://stackoverflow.com/questions/41432754/notifydatasetchanged-not-working-after-onbackpressed