android - 距离计算bug android

Question

您好，我一直在开发计算行驶距离和速度的应用程序。所有获得速度和距离的功能都工作正常，但是在测试期间我看到了只有当速度为 19 Km/h + 时才开始测量距离的错误 +

有人知道为什么会发生这种情况吗？

谢谢

//initialize location listener
    locationListener = new LocationListener() {
        @Override
        public void onLocationChanged(Location location) {
            getSpeed(location);
            getDistance(location);
        }

        @Override
        public void onStatusChanged(String s, int i, Bundle bundle) {

        }

        @Override
        public void onProviderEnabled(String s) {

        }

        @Override
        public void onProviderDisabled(String s) {
        }

        //get the speed from the given location updates
        public void getSpeed(Location location) {
            currentSpeed = (location.getSpeed() * 3600 / 1000);
            String convertedSpeed = String.format("%.2f", currentSpeed);
            speedTxt.setText(convertedSpeed + "Km/h");
        }

        private void getDistance(Location location) {

            //to capture current location and keep as starting position of person
            if (pLat == 500.0 && pLng == 500.0 ){
                pLat = location.getLatitude();
                pLng = location.getLongitude();
            }

            if (cLat == 500.0 && cLng == 500.0){
                cLat = location.getLatitude();
                cLng=location.getLongitude();
            }

            //to check is the person has changed location
            if (pLat != cLat && pLng != cLng) {
                pLat = cLat;
                pLng = cLng;
            }

            //update the current location
            cLat = location.getLatitude();
            cLng = location.getLongitude();

            //call the calculation method
            distance += getDistanceBetweenGeoPoints(cLat, cLng, pLat, pLng);
            String convertedDistance = String.format("%.2f", distance);
            distanceTxt.setText(" " + convertedDistance);
        }

        public double getDistanceBetweenGeoPoints(Double cLat, Double cLng, Double pLat, Double pLng) {
            // CALCULATE DISTANCE BETWEEN TWO POINTS
            double earthRadius = 6367; //meters
            double dLat = Math.toRadians(cLat - pLat);
            double dLng = Math.toRadians(cLng - pLng);
            double a = Math.sin(dLat / 2) * Math.sin(dLat / 2) +
                    Math.cos(Math.toRadians(cLat)) * Math.cos(Math.toRadians(pLat)) *
                            Math.sin(dLng / 2) * Math.sin(dLng / 2);
            double c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
            double dist = (double) (earthRadius * c);
            dist = Math.round(dist * 100) / 100.0;

            return dist;
        }
    };

Answer 1

由于这条线，您的 getDistanceBetweenGeoPoints 函数将准确返回 0，因为位置存在微小差异:

dist = Math.round(dist * 100) / 100.0;

仅出于在 GetDistance() 中显示的目的尝试四舍五入总距离:

//call the calculation method
distance += getDistanceBetweenGeoPoints(cLat, cLng, pLat, pLng);
String convertedDistance = String.format("%.2f", Math.round(dist * 100) / 100.0);
distanceTxt.setText(" " + convertedDistance);