My HandlerThread implementation for Threading exercise in Android-Academy SPb

CounterTask.java

package com.example.vitaliybv.threadingexercise;

import android.os.Handler;
import android.os.HandlerThread;
import android.os.Message;

import java.util.ArrayList;

public class CounterTask extends HandlerThread {

    private static final String WORKER_THREAD_NAME = CounterTask.class.getSimpleName();
    private Handler mWorkerHandler;
    private Handler mResponseHandler;
    private Callback mCallback;
    private static final int COUNTER = 1;

    public interface Callback {
        void onCountIncrease(int number);

        void onCountCompleted(String s);
    }

    public CounterTask(Handler responseHandler, Callback callback) {
        super(WORKER_THREAD_NAME);
        mResponseHandler = responseHandler;
        mCallback = callback;
    }

    public void queueTask(ArrayList<Integer> numbers) {
        mWorkerHandler.obtainMessage(COUNTER,numbers).sendToTarget();
    }

    public void prepareHandler() {
        mWorkerHandler = new Handler(getLooper(), new Handler.Callback() {
            @Override
            public boolean handleMessage(Message msg) {
                ArrayList<Integer> numbers = (ArrayList<Integer>) msg.obj;
                handleRequest(numbers);
                try {
                    msg.recycle();
                } catch (IllegalStateException e) {
                    mWorkerHandler.removeMessages(msg.what);
                }
                return true;
            }
        });
    }

    public void handleRequest(ArrayList<Integer> numbers) {

        for (final Integer number : numbers) {
            mResponseHandler.post(new Runnable() {
                @Override
                public void run() {
                    mCallback.onCountIncrease(number);
                }
            });

            try {
                Thread.sleep(500);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }

        mResponseHandler.post(new Runnable() {
            @Override
            public void run() {
                mCallback.onCountCompleted("DONE!");
            }
        });
    }

    public void cancelTask(){
        mWorkerHandler.removeMessages(COUNTER);
    }

}

ThreadsActivity.java

package com.example.vitaliybv.threadingexercise;

import android.app.Activity;
import android.content.Intent;
import android.os.Handler;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;

public class ThreadsActivity extends AppCompatActivity implements CounterTask.Callback {

    private Button mCreateButton;
    private Button mStartButton;
    private Button mCancelButton;
    private TextView mCounterTextView;
    private CounterTask mCounterTask;
    private Boolean isRunning = false;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_threads);

        mCreateButton = findViewById(R.id.thread_create);
        mStartButton = findViewById(R.id.thread_start);
        mCancelButton = findViewById(R.id.thread_cancel);
        mCounterTextView = findViewById(R.id.tv_thread_counter);


        mCreateButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (mCounterTask == null) {
                    mCounterTask = new CounterTask(new Handler(), ThreadsActivity.this);
                    mCounterTask.start();
                    mCounterTask.prepareHandler();
                    mCounterTextView.setText("HandlerThread is created");
                } else {
                    Toast.makeText(getApplicationContext(),
                            "HandlerThread is already created ",
                            Toast.LENGTH_SHORT)
                            .show();
                }

            }
        });

        mStartButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (mCounterTask != null && isRunning) {
                    Toast.makeText(getApplicationContext(),
                            "CounterTask is already running",
                            Toast.LENGTH_SHORT)
                            .show();
                } else if (mCounterTask != null) {
                    mCounterTask.queueTask(MainActivity.numbers);
                    isRunning = true;
                } else {
                    Toast.makeText(getApplicationContext(),
                            "You need to create CounterTask first",
                            Toast.LENGTH_SHORT)
                            .show();
                }
            }
        });

        mCancelButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (mCounterTask != null) {
                    mCounterTask.cancelTask();
                    if (mCounterTask.getState() == Thread.State.RUNNABLE) {
                        Toast.makeText(getApplicationContext(),
                                "Message removed, but task is still running",
                                Toast.LENGTH_SHORT)
                                .show();
                    } else {
                        mCounterTextView.setText("Task is canceled");
                    }
                } else {
                    Toast.makeText(getApplicationContext(),
                            "There is nothing to cancel",
                            Toast.LENGTH_SHORT)
                            .show();
                }
            }
        });
    }

    @Override
    protected void onDestroy() {
        mCounterTask.quit();
        super.onDestroy();
    }

    public static void start(Activity activity) {
        Intent intent = new Intent(activity, ThreadsActivity.class);
        activity.startActivity(intent);
    }

    @Override
    public void onCountIncrease(int number) {
        mCounterTextView.setText(String.valueOf(number));
    }

    @Override
    public void onCountCompleted(String s) {
        mCounterTextView.setText(s);
        isRunning = false;
    }
}