Jak zatrzymać ten wątek w Androidzie?

W mojej aplikacji używam tego wątku do obracania drugiej ręki na zegarze. Ale problem polega na tym, że kiedy zamykam działanie, wątek nadal działa. Chcę zatrzymać wątek, aby nie mógł mieć wpływu na Bettry urządzenia.

Poniżej znajduje się mój kod aktywności, w którym obracam drugą ręką zegara:

<code> public class ClockActivity extends Activity implements OnClickListener{
    private Button chimeBtn;
    private ImageView img;
    private Thread myThread = null;

    @Override
    public void onCreate(Bundle savedInstanceState){
        super.onCreate(savedInstanceState);
        setContentView(R.layout.clock_layout);


        Runnable runnable = new CountDownRunner();
        myThread = new Thread(runnable);
        myThread.start();

        chimeBtn = (Button) findViewById(R.id.chimeBtn);
        chimeBtn.setOnClickListener(this);
    }
    @Override
    public void onClick(View v) {
        switch(v.getId()){
            case R.id.chimeBtn:
                playSound(R.raw.one_bell);
                break;
        }
    }
    public void playSound(int resources){

         MediaPlayer mp = MediaPlayer.create(getApplicationContext(), resources);
            mp.start();


    }

    private void doPlay(){
        new Thread(new Runnable() {

            @Override
            public void run() {
                // TODO Auto-generated method stub

                Log.v("log_tag", "this is seocond thread");

            }
        }).start();
    }
    public void doRotate() {

        runOnUiThread(new Runnable() {
            public void run() {
                try {

                    Date dt = new Date();
                    int hours = dt.getHours();
                    int minutes = dt.getMinutes();
                    int seconds = dt.getSeconds();
                    String curTime = hours + ":" + minutes + "::" + seconds;
                    Log.v("log_tag", "Log is here Time is now" + curTime);
                    img = (ImageView) findViewById(R.id.imgsecond);
                    RotateAnimation rotateAnimation = new RotateAnimation((seconds - 1) * 6, seconds * 6,
                            Animation.RELATIVE_TO_SELF, 0.5f,Animation.RELATIVE_TO_SELF, 0.5f);

                    rotateAnimation.setInterpolator(new LinearInterpolator());
                    rotateAnimation.setFillAfter(true);

                    img.startAnimation(rotateAnimation);
                } catch (Exception e) {
                    Log.e("log_tag", "Error msg is " + e.toString());

                }
            }
        });
    }

    @Override
    public boolean onKeyDown(int keyCode, KeyEvent event) { 

        if (keyCode == KeyEvent.KEYCODE_BACK) {       
            System.out.println("Back Key Press");
            if (myThread != null) {

                   myThread.interrupt(); //says that the myThread should stop 
                   try{ 
                           myThread.join(); //make this myThread wait for the other myThread to  finish before returning
                           myThread = new Thread();
                           myThread = null;
                   }catch(InterruptedException ie){ 
                           //handle the case if the thread.join is interrupt 
                           //don't know if this will ever happen, if it can... throw a runtime exception?, or reinterrupt? 
                           Thread.currentThread().interrupt(); 
                           //   reinterrupt because thrown exception cleared interrupt and hope it's handled elsewhere 
                   } 

            }
            System.out.println("Back Key Press");
            return true;       
        }       
        return super.onKeyDown(keyCode, event);     
    } 

    @Override
    public void onDestroy(){

        System.out.println("OnDestroy");

        super.onDestroy();

    }

    class CountDownRunner implements Runnable {
        // @Override
        public void run() {
            while (!Thread.currentThread().isInterrupted()) {
                try {
                    // Log.v("log_tag", "Roate is going");
                    doRotate();
                    Thread.sleep(1000);
                    //doPlay();
                    } catch (InterruptedException e) 
                    {
                    // Thread.currentThread().interrupt();
                } catch (Exception e) {
                    Log.e("log_tag", "Error is " + e.toString());
                }
            }
        }
    }
}
</code>

Z góry dziękuję.

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