February 7, 2014 / IST / Software Development, Tips & Tricks.

In this sample application we will create a countdown timer in android using the CountDownTimer class .This is an example of showing a 30 second countdown in a TextView . We will update the TextView on every tick of the timer.The option to stop and restart the timer is also provided.
So let us start:
1.Create a new project File ->New -> Project ->Android ->Android Application Project. While creating the new project, name the activity as TimerActivity(TimerActivity.java) and layout as activity_timer.xml.
2.Now let us design the UI for the TimerActivity i.e activity_timer.xml with a textview and a button.

activity_timer.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical"
    android:background="@drawable/bgi" >

    <TextView
    android:id="@+id/timer"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_centerHorizontal="true"
    android:layout_centerVertical="true"
    android:paddingRight="10dip"
    android:textSize="50dp" />

    <Button
    android:id="@+id/button"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:layout_alignParentBottom="true"
    android:layout_alignParentLeft="true"
    android:text="Start" />
</RelativeLayout>

3.Now in the TimerActivity we implement the count down timer by extending the CountDownTimer class.Press Ctrl+Shift+O for missing imports after typing the code.

TimerActivity.java

public class TimerActivity extends Activity implements OnClickListener {

	 private CountDownTimer countDownTimer;
	 private boolean timerHasStarted = false;
	 private Button startB;
	 public TextView text;
	 private final long startTime = 30 * 1000;
	 private final long interval = 1 * 1000;

	 @Override
	 public void onCreate(Bundle savedInstanceState) {
	  super.onCreate(savedInstanceState);
	  setContentView(R.layout.activity_timer);
	  startB = (Button) this.findViewById(R.id.button);
	  startB.setOnClickListener(this);
	  text = (TextView) this.findViewById(R.id.timer);
	  countDownTimer = new MyCountDownTimer(startTime, interval);
	  text.setText(text.getText() + String.valueOf(startTime / 1000));
	 }

	 @Override
	 public void onClick(View v) {
	  if (!timerHasStarted) {
	   countDownTimer.start();
	   timerHasStarted = true;
	   startB.setText("STOP");
	  } else {
	   countDownTimer.cancel();
	   timerHasStarted = false;
	   startB.setText("RESTART");
	  }
	 }

	 public class MyCountDownTimer extends CountDownTimer {
	  public MyCountDownTimer(long startTime, long interval) {
	   super(startTime, interval);
	  }

	  @Override
	  public void onFinish() {
	   text.setText("Time's up!");
	  }

	  @Override
	  public void onTick(long millisUntilFinished) {
	   text.setText("" + millisUntilFinished / 1000);
	  }
	 }

	}

4.Run the project by rightclicking project Run as → android project.

Output:
The output of this example would be similar to the one as follows:
android