How to set a fixed CountDownTimer in a recyclerview element?

Question

I have the following recyclerview:

When I press Start button a CountDownTimer starts to countdown,but the problem is,that if I start the countdown on question example 1 (or any other question element) the countdown starts, but if I scroll down to the bottom of the recyclerview the timer resets.

The second problem is, that when I switch from this fragment to another(for example:going back to previous fragment with backpress) the timer resets.

I don't know, how to fix this problems, please help me.

My adapter for the recyclerview is the following:


import android.content.Context;
import android.os.CountDownTimer;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.TextView;

import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;

import java.text.MessageFormat;
import java.util.ArrayList;

public class QuestionsAdapter extends RecyclerView.Adapter<QuestionsAdapter.QuestionsViewHolder>
{
    Context context;
    ArrayList<Question> questions;

    public static class QuestionsViewHolder extends RecyclerView.ViewHolder
    {
        public TextView questionname;
        public TextView status;
        public TextView timereamining;
        public Button start;

        public QuestionsViewHolder(View v)
        {
            super(v);

            questionname=v.findViewById(R.id.questiontext);
            status=v.findViewById(R.id.statusstr);
            timereamining=v.findViewById(R.id.time);
            start=v.findViewById(R.id.startbutton);
        }
    }

    public QuestionsAdapter(Context context,ArrayList<Question> dataset)
    {
        this.context=context;
        this.questions=dataset;
    }

    @NonNull
    @Override
    public  QuestionsViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType)
    {
        View v= LayoutInflater.from(parent.getContext()).inflate(R.layout.listofquestions,parent,false);

        return new QuestionsViewHolder(v);
    }

    @Override
    public void onBindViewHolder(@NonNull final QuestionsViewHolder holder, final int position)
    {
        holder.questionname.setText(questions.get(position).getQuestionname());
        holder.status.setText(questions.get(position).getStatus());
        holder.timereamining.setText(String.valueOf(questions.get(position).getTimelimit())+":00");

        holder.start.setOnClickListener(new View.OnClickListener()
        {
            @Override
            public void onClick(View v)
            {
                new CountDownTimer(questions.get(position).getTimelimit()*60000, 1000)
                {
                    public void onTick(long millisUntilFinished)
                    {
                        long minutes=millisUntilFinished/60000;
                        long seconds=millisUntilFinished%60000/1000;

                        String timeleft;

                        timeleft=""+minutes;
                        timeleft+=":";
                        if(seconds<10)
                        {
                            timeleft+="0";
                        }

                        timeleft+=seconds;
                        holder.timereamining.setText(timeleft);

                    }

                    public void onFinish()
                    {
                        holder.timereamining.setText("done!");
                    }

                }.start();
            }
        });
    }

    @Override
    public int getItemCount()
    {
        return questions.size();
    }
}

So, a timer for each question can be started only once, can't it? Even if a user leaves your `Fragment` and then comes back? — Anatolii, Nov 20 '19 at 21:19

Richard Dapice · Answer 1 · 2019-11-20T22:32:37.083

0

The problem you are encountering is due to the inherent nature of RecyclerView. This is a good resource that explains what is happening: Understanding RecyclerView.

When the RecyclerView recycles your item row, you will lose any state that you are holding in that row. A few ideas that might help you accomplish what you are after would be starting each counter uniquely outside of your item row and maintaining a relationship inside your adapter, so when you scroll back to that item position, the row can reconnect to its counter. You could also possibly use a list view, as it will not (always) recycle your rows, but after thinking about this I wouldn't recommend it. List View Recycling

edited Nov 20 '19 at 22:32

answered Nov 20 '19 at 22:00

Richard Dapice

838
5
10

Thank you,I will try to use list view. – lambozsolty Nov 20 '19 at 22:27
I would do that only as your last resort, the list view will still be prone to recycling when your data gets too large. I would first try implementing another pattern than putting your timers in each row. – Richard Dapice Nov 20 '19 at 22:33

score 0 · Answer 2 · answered Nov 21 '19 at 04:15

When a item scrolled out of screen, recyclerview will recycle this item.

That means, onBindViewHolder for same positon will into several times, and a particular viewHolder will present for different data depends depends scroll state.

Consider onTick method should change data, and call adapter's notifyItemChagne method rather than change viewHolder directly.

more detail

How to set a fixed CountDownTimer in a recyclerview element?

2 Answers2