title: why Android Activity retain their state automatically?
body: <p>I have activity where I am running a CountDownTimer,if a calls comes or I rotate the screen the timers is still working continuously in some phone but in others phone the timers is not working,and I haven't done anything to retain the state.</p>
  
  <p>So I want to know is there any special feature to these phone to retain the activity state?</p>
  
  <p>here is the code :</p>
  
  <pre><code> new CountDownTimer(30000, 1000) {
  
       public void onTick(long millisUntilFinished) {
            mTextField.setText("seconds remaining: " + millisUntilFinished / 1000);
       }
  
       public void onFinish() {
           mTextField.setText("done!");
       }
  }.start();
  </code></pre>