How To Structure Android Timer App With Thread

I'm trying to create a simple Workout Timer for Android. The user creates a WorkoutPlan containing info such as total duration, total rest time, etc, the app will display a timer that updates every second.

Pretty simple to begin with, but I'm trying to build the app as properly as possible, i.e. separation of concern, correct techniques, responsive UI, ensure the timer will be accurate, etc.

Here's a simplification of what I have so far:

WorkoutPlan, the user can load/save different workout plans to the timer

Code:
public class WorkoutPlan {
public long duration;
}
TimerThread, this class implements `Runnable`, it takes in a `WorkoutPlan` in the constructor, start/stop, shows elapsed time.

Code:
public class TimerThread implements Runnable {
public boolean running = false;

[Code]....

TimerView, the custom view that displays the elapsed time

Code:
public class TimerView extends View {
private final Paint mBg;
private final Paint mText;
private WorkoutPlan plan;
private TimerThread timer;
private Thread thread;
private Handler handler = new TimerHandler();

[Code]...

Finally, WorkoutTimer, the activity that starts it off

Code:
public class WorkoutTimer extends Activity {
private TimerView mTimer;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {

[Code]....

A couple of questions:

Where's the best place to create the `WorkoutPlan` object? Currently it's done in `TimerView`. Should it be done in the `WorkoutTimer` activity instead? If yes, how do I pass the `WorkoutPlan` object to `TimerView`?

The app works fine the first time, but crashes when I go to the home screen then back to the app the second time. What's causing it to crash? Is it the theading?

Currently I'm using a `Handler` in a new `Thread`. Is this ok or would a `TimerTask` be better? Where's the best place to start the thread? Am I correct to put all the threading code in `TimerView`?

Am I correct to add synchronized to all the methods in `TimerThread`?