CODEWITHSUNDEEP
androidperformanceandroid-layoutandroid-intentandroid-widget
user2092317
user2092317

Reputation: 3348

Android Google Maps. Calculate the traveled distance onLocationchange and display in textview.?

I am working on a Android Google Map activity Project. I should calculate the traveled distance onLocationchange. Here i am facing a problem when calculatin the distance. Actual point here is to display the distance traveled in the textview when ever the onlocationchange is triggered. Here is the code what i have tried.

 @Override
            public void onLocationChanged(Location location) {
                // TODO Auto-generated method stub
                GeoPoint point = new GeoPoint((int)(location.getLatitude()*1E6),(int)(location.getLongitude() *1E6));
                path.add(point);
                controller.animateTo(point);
                mapview.invalidate();
                distance();
            }

            public void distance(){
                start = path.get(0);
                stop = path.get(path.size()-1);
                double lat1 = start.getLatitudeE6() / 1E6;
                double lat2 = stop.getLatitudeE6() / 1E6;
                double lon1 = start.getLongitudeE6() / 1E6;
                double lon2 = stop.getLongitudeE6() / 1E6;
                double dLat = Math.toRadians(lat2 - lat1);
                double dLon = Math.toRadians(lon2 - lon1);
                double a = Math.sin(dLat / 2) * Math.sin(dLat / 2) +
                Math.cos(Math.toRadians(lat1)) * Math.cos(Math.toRadians(lat2)) *
                Math.sin(dLon / 2) * Math.sin(dLon / 2);
                double c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
                double d = c * 6378.1;
                d =Double.parseDouble(new DecimalFormat("####.###").format(d));
                text.setText(" distance :" + d + "km");
            }

And I am passing four locations through DDMS Manual Decimal Here are those locations.

1)lat    -122.084095  This is the start point. and the text view is set to 0kms
                  long     37.422006

                2)lat    -122.085095    The textview distance is set to 0.088kms 
                  long     37.422006  

                3)lat    -122.085095    The textview distance is set to 0.142kms  wroks fine till here
                  long     37.423006    

                4)lat    -122.084095    The text view distance is set to 0.111kms    WTF. now why is that my distance is decreased from 0.142kms to 0.111kms
                  long     37.423006  

                5)4)lat    -122.084095    The text view distance is set to 0.0kms    OMG.. Now the textview shows 0.0kms whats wrong. 
                  long     37.422006

Is this the correct way to calculate distance. What is the mistake i am doing. I think we should for loop for the array of points. But How?? I dont know... PLEASE HELP.THANKS IN ADVANCE

Upvotes: 1

Views: 956

Answers (1)

Halogen
Halogen

Reputation: 541

The fact that it's saying your distance is 0 when you get back to the original point should set off a lightbulb: What you're actually calculating is the distance from your original point to whatever new point you're emulating, instead of a total distance along the path.

Instead of measuring the distance from point 1 to every other point, you should measure the distance from the last point you were at to the next point and add that to a distance variable you create to hold the total distance.

For example, changing the following should solve your problem:

start = path.get(path.size()-2);
//Be sure to check that there's at least 2 points in your array with an if statement!!

Then later:

totalDistance += d;
textView.setText("Text" + totalDistance);

where totalDistance is some double you define earlier.

Upvotes: 1

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