How can I get the distance between two point by latlng?

Question

I want to get the distance from A to B by latlng.When i run my app with the following code,it return a wrong result. Fx i tryed A( 31.172740,115.0081630) ,then B（30.6055980,

Answer 1

Try below code.

public float distance (float lat_a, float lng_a, float lat_b, float lng_b ) 
{
    double earthRadius = 3958.75;
    double latDiff = Math.toRadians(lat_b-lat_a);
    double lngDiff = Math.toRadians(lng_b-lng_a);
    double a = Math.sin(latDiff /2) * Math.sin(latDiff /2) +
    Math.cos(Math.toRadians(lat_a)) * Math.cos(Math.toRadians(lat_b)) *
    Math.sin(lngDiff /2) * Math.sin(lngDiff /2);
    double c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a));
    double distance = earthRadius * c;

    int meterConversion = 1609;

    return new Float(distance * meterConversion).floatValue();
}

If you didn't understood, please check this link, same code available here.