user2590541 - 1 year ago 472

Android Question

Hi i need to cal an event at onchangelocation(), by comparing current latitude and longitude with some saved latitude and longitude but i m getting an error. eclipse is not recognizing key word distance, and for correction error it is giving hint to crate method "distance" having 4 parameter ... how to fix it??? or some other way to do same work???

thanks and regards. code is attached below

`@Override`

public void onLocationChanged(Location location) {

double currentLat=location.getLatitude();

double currentLon=location.getLongitude();

if (distance(lat,lon,currentLat,currentLon)<2.0){

//do what you want to do...

}

}

Answer Source

You actually need to implement a function called distance that will calculate the distance between two locations. **Calculating the distance between two locations is one possible way of comparing the longitude and latitude values.**

An example of comparing them:

```
@Override
public void onLocationChanged(Location location) {
double lat2 = location.getLatitude();
double lng2 = location.getLongitude();
// lat1 and lng1 are the values of a previously stored location
if (distance(lat1, lng1, lat2, lng2) < 0.1) { // if distance < 0.1 miles we take locations as equal
//do what you want to do...
}
}
/** calculates the distance between two locations in MILES */
private double distance(double lat1, double lng1, double lat2, double lng2) {
double earthRadius = 3958.75; // in miles, change to 6371 for kilometer output
double dLat = Math.toRadians(lat2-lat1);
double dLng = Math.toRadians(lng2-lng1);
double sindLat = Math.sin(dLat / 2);
double sindLng = Math.sin(dLng / 2);
double a = Math.pow(sindLat, 2) + Math.pow(sindLng, 2)
* Math.cos(Math.toRadians(lat1)) * Math.cos(Math.toRadians(lat2));
double c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a));
double dist = earthRadius * c;
return dist; // output distance, in MILES
}
```