Timer Utility for Android

We launched LenX last week and got a lot of feedback. One of them was to include a timer utility to set the exposure time. I looked up a bit and found out that the best way to do this was to use Handler and create a separate thread.

Usage of the TimerUtility class:

• Call a fixed method of my activity after certain time interval
• Pause the timer if pause button is pressed
• Resumer the timer when resume button is pressed

The first part was pretty easy. Create a Runnable which invokes the method. Use a Handler to process this Runnable instance using postDelayed method and provide the time interval in milliseconds.

For the second part, I looked around a bit and found out that I can remove the Runnable using ‘removeCallbacks’ method. Now, I was wondering what to do for the third part. I could simply use postDelayed again to process the Runnable, but I wanted the appropriate time interval. To overcome this, I started to save the system time when it started, paused, resumed etc and calculated elapsed time and used this elapsed time in postDelayed and processed the Runnable.

TimerUtility Class

public class TimerUtility {
    private int time_in_ms;
    private final Context context;
    private final MyActivity mAct;
    private Handler handler;
    private final Runnable runnable;
    private long startTime, pauseTime, elapsedTime, remainingTime, resumeTime;

    public TimerUtility(Context con) {
        context = con;
        mAct = (MyActivity)context;

        runnable = new Runnable() {
            @Override
            public void run() {
                mAct.onTimerStop();
            }
        };

    }

    public void setTime(int timeInMS) {
        time_in_ms = timeInMS;
    }
    
    public void startTimer() {
        startTime = System.currentTimeMillis();
        resumeTime = startTime;
        elapsedTime = 0;
        remainingTime = time_in_ms;

        handler = new Handler();
        handler.postDelayed(runnable, time_in_ms);
    }

    public void pauseTimer() {
        
        pauseTime = System.currentTimeMillis();
        elapsedTime = pauseTime - resumeTime + elapsedTime;
        remainingTime = time_in_ms - elapsedTime;
        handler.removeCallbacks(runnable);
    }

    public void resumeTimer() {
        resumeTime = System.currentTimeMillis();
        handler.postDelayed(runnable, remainingTime);
    }
}

We also added some animation with the timer, but that content is for some other post. I have added a simple working demo showing the usage of TimerUtility on GitHub. You can fork it here.

P.S. So much to do with LenX. I am overwhelmed, but it’s fun!

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