How to count speed based on steps

Akshat :

I have a step counter app in which I am running a service which counts steps taken and then sends a broadcast to the fragment which is then updated on the fragment. The step counting is working fine but I want to calculate speed based on the steps. Here is what I am trying right now.

The receiver to get step count:

receiver = new BroadcastReceiver() {
    @Override
    public void onReceive(Context context, Intent intent) {
        int steps = intent.getIntExtra(StepCounterService.STEP_INCREMENT_KEY, 0);
        if (firstStepTime.equals("0")) {
            firstStepTime = intent.getStringExtra(StepCounterService.TIME_STAMP_KEY);
        } else if (secondStepTime.equals("0")) {
            secondStepTime = intent.getStringExtra(StepCounterService.TIME_STAMP_KEY);
        } else {
            firstStepTime = secondStepTime;
            secondStepTime = intent.getStringExtra(StepCounterService.TIME_STAMP_KEY);
        }

        updateAllUI(steps);
    }
};

So what I am doing is as soon as I start getting steps, I see if the variable firstStepTime is empty. If it is, I save the time in firstStepTime variable. The in the next step I see if secondStepTime is empty, and if it is, I save that time in secondStepTime variable. Now for the next steps both these are updated.

public void updateAllUI(int numberOfSteps) {

    if (!(firstStepTime.equals("0")) && !(secondStepTime.equals("0"))) {
        try {
            Calendar c = Calendar.getInstance();
            SimpleDateFormat timeFormat = new SimpleDateFormat("HH:mm:ss.SSS");
            timeDifference = timeFormat.parse(secondStepTime).getTime() - timeFormat.parse(firstStepTime).getTime();

            speed = (float) ((0.0254 / (timeDifference * 0.001)) * 3.6);
        } catch (Exception e) {
            timeDifference = 0;
            speed = 0;
        }

        textview.settext(speed +"Km/h);
    }
}

So in this I just check if both are not empty, I take the values and calculate the difference in times. The problem here is sometimes it doesn't count speed properly. And a bigger problem is if the user stops, the speed remains constant and doesn't drop to zero.

Is there any better way to do the speed calculation?

Ankit Arora :

As you're only counting steps and would like to calculate speed with steps taken only i am assuming that you would not like to use GPS for counting speed or you would like to provide backup speed counter if GPS is not there.

You can start a new thread by doing

    int interval=1*1000; //specifying interval to check steps
    Handler.postDelayed(mySpeedChecker(),1000);

You'll need to do this for every step taken

public void mySpeedChecker(){
// assuming steps taken stored in a global variable
// and there is one more variable which is updated by this function 
// to store number of steps before as global variable to calculate number of steps in time interval. 
// this should check if another step has been taken in the interval to check
// if stepsTaken>0 then speed is not zero and you'll know how much steps are taken
// if zero steps are taken then speed is zero 
// also it will tell you number of steps taken in last second 
// so you can use this to calculate and update speed 
// increase the interval for high accuracy but lower frequency of updates 
}

Also, it's a good idea to calculate user stride length when GPS is available so, whenever user is using GPS the step length can be calculated by finding out the distance covered/number of steps taken with the help of GPS, this will help your system calculate accurately the distance covered by user with the help of number of steps taken.