如何获得地理围栏的停留时间？

我为这个问题找到了一个解决方案。为了确定地理围栏的停留时间，我必须获得用户触发地理围栏的时间，然后我使用这种数学方法来计算用户是否离开地理围栏

 Handler handler = new Handler();
    getCurrentLatLng();
    final Runnable myRunnable = new Runnable() {
        public void run() {
            GeofenceFinished myFinishedGeofence = db.getGeofenceFinishedByID("Finished" + id);
            if (!isUserInRegion(latitude, longitude, myLatLng.latitude, myLatLng.longitude, rd)
                    || myFinishedGeofence == null) {
                String time = convertTime(endTime - startTime);
                // get the finishedGeofence and set the duration of stay time
                if (myFinishedGeofence != null)
                    setDurationOfStay("Finished" + id, time, getCurrentTime(System.currentTimeMillis()));
                Toast.makeText(mContext, "Finish to determine duration of stay of " + myFinishedGeofence.getAddress(), Toast.LENGTH_SHORT).show();
                handler.removeCallbacks(this);
            } else {
                getCurrentLatLng();
                endTime += Constants.DELAY;
                handler.postDelayed(this, Constants.DELAY);
            }
        }

        private void setDurationOfStay(String geofenceid, String time, String endTime) {
            if (db == null) db = GeofenceDatabaseHelper.getInstance(mContext);
            if (!db.setDurationOfFinishedGeofence(geofenceid, time, endTime)) {
                Log.i("setDurationOfStay", "fail");
            }
        }
    };
    handler.postDelayed(myRunnable, Constants.DELAY);

private boolean isUserInRegion(double firstLat, double firstLog, double curLat, double curLog, float radius) {
    double distance = calculateDistance(firstLat, firstLog, curLat, curLog);
    return distance <= radius;
}

为了计算用户和地理围栏中心的距离，我需要以米为单位转换当前的纬度和经度，这样我就可以用圆的参数方程来计算

所以我使用github的这种方法

    // https://github.com/mgavaghan/geodesy
private double calculateDistance(double firstLat, double firstLog, double curLat, double curLog) {
    GeodeticCalculator geoCalc = new GeodeticCalculator();
    Ellipsoid reference = Ellipsoid.WGS84;
    GlobalPosition pointA = new GlobalPosition(firstLat, firstLog, 0.0); // Point A
    GlobalPosition userPos = new GlobalPosition(curLat, curLog, 0.0); // Point B
    // Distance between Point A and Point B
    double distance = geoCalc.calculateGeodeticCurve(reference, userPos, pointA).getEllipsoidalDistance();
    return distance;
}

希望它可以帮助某人：D