Issues using android studio to get time of travel between two points

Question

For the last week, I have been using Android Studio to write code that achieves the following goals:

1. Wait for the user to be within a certain distance of the start waypoint
2. Once at start waypoint, begin a timer that logs gps data and current time
3. Stops timer when the end waypoint is crossed

At the moment, I have the start and end waypoints hard coded but I seem to run into an error that I have been trying to trace with the step through function on my IDE but can't seem to find it. Below is the code I have been using:

void StartTimer (View view){
        //Location l = null;
        boolean hasLoc = false; //are we at the start?
        float speed = 0;
        float topSpeed = 0;


        while(hasLoc == false && cancel == false){
            float d = l.distanceTo(t);

            if(d < 2.0)
                hasLoc = true;

            //if(!l.equals(lm.getLastKnownLocation("")))
            String msg = "Latitude: " + l.getLatitude() + "\nLongitude: "+ l.getLongitude();
            Toast.makeText(getBaseContext(), msg, Toast.LENGTH_LONG).show();
        }

        hasLoc = false;

        Handler handler = new Handler();
        handler.postDelayed(new Runnable() {
            public void run() {
                // Actions to do after 10 seconds
                buzzer();
            }
        }, 10000);

        while(l.distanceTo(tf) > 2.0 && cancel == false){
            float cSpeed = l.getSpeed();

            if(cSpeed>topSpeed)
                topSpeed = cSpeed;

            String msg = "Current Speed: "+cSpeed+"Top Speed: "+topSpeed;
            Toast.makeText(getBaseContext(), msg, Toast.LENGTH_LONG).show();
        }

        cancel = false;
    }

When I run the code, the phone I test it one will run it but it won't respond, which leads me to believe there is an unsatisfied loop that I have not considered.

Any suggestions would be helpful, thank you in advance for advice!

Answer 1

Your while loops are clogging up the CPU's execution which is what is causing it to not respond. Instead you should place your code inside a thread and call Thread.sleep(1000); inside the thread, this way the the while loop is paused for 1 second after every execution of the code inside it.

Something like this:

  new Thread(new Runnable() {
        @Override
        public void run() {

            while (hasLoc == false && cancel == false) {
                float d = l.distanceTo(t);
                if (d < 2.0)
                    hasLoc = true;
                String msg = "Latitude: " + l.getLatitude() + "\nLongitude: " + l.getLongitude();

                try {
                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                runOnUiThread(new Runnable() {
                    @Override
                    public void run() {
                        Toast.makeText(getBaseContext(), msg, Toast.LENGTH_LONG).show();
                    }
                });
            }

            hasLoc = false;

            new Handler().postDelayed(new Runnable() {
                public void run() {
                    // Actions to do after 10 seconds
                    buzzer();
                }
            }, 10000);

            while (l.distanceTo(tf) > 2.0 && cancel == false) {
                float cSpeed = l.getSpeed();

                if (cSpeed > topSpeed)
                    topSpeed = cSpeed;

                String msg = "Current Speed: " + cSpeed + "Top Speed: " + topSpeed;
                try {
                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                runOnUiThread(new Runnable() {
                    @Override
                    public void run() {
                        Toast.makeText(getBaseContext(), msg, Toast.LENGTH_LONG).show();
                    }
                });
            }

            cancel = false;

        }
    }).start();