# android – How can I get the distance between two point by latlng?-ThrowExceptions

Exception or error:

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（30.6055980,114.3603140),the result is about 3111km.but the right distance is about 134km.
My code is:

``````    class btnListener implements OnClickListener{

public void onClick(View v) {
lat_a=lat_A.getText().toString();
lng_a=lng_A.getText().toString();
lat_b=lat_B.getText().toString();
lng_b=lng_B.getText().toString();
double a1,n1,a2,n2;
a1=30.6055980;
a2=Double.parseDouble(lat_b);
n2=Double.parseDouble(lng_b);
double R=6371;
double D=Math.acos(Math.sin(a1)*Math.sin(a2)+Math.cos(a1)*Math.cos(a2)*Math.cos(n2-n1));
Toast.makeText(getApplication(), "the distance is"+String.valueOf(D*R)+"km from A to B", Toast.LENGTH_SHORT).show();
}

}
``````
How to solve:

Try below code.

``````public float distance (float lat_a, float lng_a, float lat_b, float lng_b )
{
double a = Math.sin(latDiff /2) * Math.sin(latDiff /2) +
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.

###

There is an api provided by android itself to get distance between two points. Use:

``````Location.distanceBetween(
startLatitude,
startLongitude,
endLatitude,
endLongitude,
results);
``````

which returns distance in meters.

###

``````LatLng startLatLng = new LatLng(startLatitude, startLongitude);
LatLng endLatLng = new LatLng(endLatitude, endLongitude)
double distance = SphericalUtil.computeDistanceBetween(startLatLng, endLatLng);
``````

``````compile 'com.google.android.gms:play-services-maps:15.0.1'