在onbackpressed()之后notifydatasetchanged()无法正常工作 [英] notifydatasetchanged() not working after onbackpressed()

问题描述

• 返回按钮后，我的recyclerview无法正确更新 按下.
• 在按下后退按钮之前，recyclerview可以正常工作
• 数据已正确更新(在日志中可见)，但是recyclerview不能反映更改
• 处理程序的目的是轮询数据库以获取通知(工作正常)
• 每次都会显示通知吐司
• 我没有收到任何错误

• 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

如果我可以提供任何其他信息以帮助您，请不要犹豫.

If I can provide any other information to help do not hesitate to ask.

主要

 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
 }

适配器:

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();
    }
}

我没有解决以下问题:

• notifyDataSetChanged在RecyclerView上不起作用
• smoothScrollToPosition(在notifyDataSetChanged无法在android中工作后)
• adapter.notifyDataSetChange()从onResume()调用后不起作用

• notifyDataSetChanged not working on RecyclerView
• smoothScrollToPosition after notifyDataSetChanged not working in android
• adapter.notifyDataSetChange() not working after called from onResume()

推荐答案

在您的代码中进行一些更改

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

然后在此处进行一些更改

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
 }

代码中的另一个问题，您正在使用receive_live_message_async AsyncTask 将更新代码放入onPostExecute

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);
        }
    }

类似地，当您调用receive_live_message_async.execute();在onPostExecute中更新您的recyclerView

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);
    }

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