Check if a latitude and longitude is within a circle

问题

See this illustration:

What I would like to know is:

1. How to create an area (circle) when given a latitude and longitude and the distance (10 kilometers)
2. How to check (calculate) if a latitude and longitude is either inside or outside the area

I would prefer if you can give me code example in Java or specifically for Android with Google Maps API V2

回答1:

What you basically need, is the distance between two points on the map:

float[] results = new float[1];
Location.distanceBetween(centerLatitude, centerLongitude, testLatitude, testLongitude, results);
float distanceInMeters = results[0];
boolean isWithin10km = distanceInMeters < 10000;

If you have already Location objects:

Location center;
Location test;
float distanceInMeters = center.distanceTo(test);
boolean isWithin10km = distanceInMeters < 10000;

Here is the interesting part of the API used: https://developer.android.com/reference/android/location/Location.html

回答2:

Have you gone through the new GeoFencing API. It should help you. Normal implementation takes a lot of time. This should help you implementing it easily.

回答3:

see https://developer.android.com/reference/android/location/Location.html

Location areaOfIinterest = new Location;
Location currentPosition = new Location;

areaOfIinterest.setLatitude(aoiLat);
areaOfIinterest.setLongitude(aoiLong);

currentPosition.setLatitude(myLat);
currentPosition.setLongitude(myLong);

float dist = areaOfIinterest.distanceTo(currentPosition);

return (dist < 10000);

回答4:

If you mean by "How to create an area", that you want to draw the area on the map, you will find an example right in the map V2 reference doc for the class Circle.

For checking whether the distance between the center of the circle and your point is greater than 10 km I would suggest to use the static method Location.distanceBetween(...) as it avoids unnecessary object creations.

See also here (at the very end of the answer) for a code example in case the area is a polygon rather than a circle.

回答5:

Check this:

 private boolean isMarkerOutsideCircle(LatLng centerLatLng, LatLng draggedLatLng, double radius) {
    float[] distances = new float[1];
    Location.distanceBetween(centerLatLng.latitude,
            centerLatLng.longitude,
            draggedLatLng.latitude,
            draggedLatLng.longitude, distances);
    return radius < distances[0];
}

来源：https://stackoverflow.com/questions/22063842/check-if-a-latitude-and-longitude-is-within-a-circle