如何计算旅行的总距离? [英] How to calculate the total distance traveled?

问题描述

我有一个数组列表ArrayList()，用于保存lat和lng.当有新的点时，将画一条线.我想获取此数组中的元素，以便计算总距离.但是我以某种方式使用calculateDistance方法来计算总距离，结果是不正确的.所以我想知道我做错了什么.

I have an array list, ArrayList(), which is used to save lat and lng. And then a line will be drawn when there is a new point. I want to get the element inside this array, in order to calculate the total distance. But somehow i use the calculateDistance Method to calculate the total distance, the result is not correct. So i want to know if i had do something wrong.

private void whereAmI(){

    Location location = manager.getLastKnownLocation(LocationManager.GPS_PROVIDER);
    updateWithNewLocation(location);

    //GPS Listener
    manager.addGpsStatusListener(gpsListener);

    //Location Listener
    int minTime = 0;//ms
    int minDist = 0;//meter
    manager.requestLocationUpdates(LocationManager.GPS_PROVIDER, minTime, minDist, locationListener);
}

GpsStatus.Listener gpsListener = new GpsStatus.Listener() {
    @Override
    public void onGpsStatusChanged(int event) {
        switch (event) {
            case GpsStatus.GPS_EVENT_STARTED:
                Log.d("x=", "GPS_EVENT_STARTED");
                Toast.makeText(MapsActivity.this, "GPS_EVENT_STARTED", Toast.LENGTH_SHORT).show();
                break;
            case GpsStatus.GPS_EVENT_STOPPED:
                Log.d("x=", "GPS_EVENT_STOPPED");
                Toast.makeText(MapsActivity.this, "GPS_EVENT_STOPPED", Toast.LENGTH_SHORT).show();
                break;
            case GpsStatus.GPS_EVENT_FIRST_FIX:
                Log.d("x=", "GPS_EVENT_FIRST_FIX");
                Toast.makeText(MapsActivity.this, "GPS_EVENT_FIRST_FIX", Toast.LENGTH_SHORT).show();
                break;
            case GpsStatus.GPS_EVENT_SATELLITE_STATUS:
                Log.d("x=", "GPS_EVENT_SATELLITE_STATUS");
                break;
        }
    }
};

LocationListener locationListener = new LocationListener(){
    @Override
    public void onLocationChanged(Location location) {
        updateWithNewLocation(location);
    }

    @Override
    public void onProviderDisabled(String provider) {
        updateWithNewLocation(null);
    }

    @Override
    public void onProviderEnabled(String provider) {

    }

    @Override
    public void onStatusChanged(String provider, int status, Bundle extras) {
        switch (status) {
            case LocationProvider.OUT_OF_SERVICE:
                Log.v("x=", "Status Changed: Out of Service");
                Toast.makeText(MapsActivity.this, "Status Changed: Out of Service", Toast.LENGTH_SHORT).show();
                break;
            case LocationProvider.TEMPORARILY_UNAVAILABLE:
                Log.v("x=", "Status Changed: Temporarily Unavailable");
                Toast.makeText(MapsActivity.this, "Status Changed: Temporarily Unavailable", Toast.LENGTH_SHORT).show();
                break;
            case LocationProvider.AVAILABLE:
                Log.v("x=", "Status Changed: Available");
                Toast.makeText(MapsActivity.this, "Status Changed: Available", Toast.LENGTH_SHORT).show();
                break;
        }
    }

};

private void showMarkerMe(double lat, double lng){
    if (markerMe != null) {
        markerMe.remove();
    }

    MarkerOptions markerOpt = new MarkerOptions();
    markerOpt.position(new LatLng(lat, lng));
    markerOpt.title("I am here!");
    markerMe = mMap.addMarker(markerOpt);

    //Toast.makeText(this, "lat:" + lat + ",lng:" + lng, Toast.LENGTH_SHORT).show();
}

private void cameraFocusOnMe(double lat, double lng){
    CameraPosition camPosition = new CameraPosition.Builder()
            .target(new LatLng(lat, lng))
            .zoom(16)
            .build();

    mMap.animateCamera(CameraUpdateFactory.newCameraPosition(camPosition));
}

private void trackToMe(double lat, double lng){
    if (traceOfMe == null) {
        traceOfMe = new ArrayList<LatLng>();
    }
    traceOfMe.add(new LatLng(lat, lng));

    calculateDistance(traceOfMe);

    PolylineOptions polylineOpt = new PolylineOptions();
    for (LatLng latlng : traceOfMe) {
        polylineOpt.add(latlng);
    }

    polylineOpt.color(Color.RED);

    Polyline line = mMap.addPolyline(polylineOpt);
    line.setWidth(10);
}

private void calculateDistance(ArrayList<LatLng> points) {

    for (int i =0; i < points.size() -1; i++) {
        LatLng pointA =  points.get(i);
        LatLng pointB = points.get(i + 1);
        float[] results = new float[3];
        Location.distanceBetween (pointA.latitude, pointA.longitude, pointB.latitude, pointB.longitude, results);
        totalD +=  results[0];
    }
}

private void updateWithNewLocation(Location location) {

    String where = "";
    if (location != null) {

        double lng = location.getLongitude();

        double lat = location.getLatitude();

        float speed = location.getSpeed();

        long time = location.getTime();
        String timeString = getTimeString(time);

        speedList.add(""+ speed);

        where = "Lng: " + lng +
                "  Lat: " + lat +
                "  Speed: " + speed +
                "\nTime: " + timeString +
                "  Provider: " + "gps" +
                "  Distance: " + totalD ;


        showMarkerMe(lat, lng);
        cameraFocusOnMe(lat, lng);
        trackToMe(lat, lng);

    }else{
        where = "No location found.";
    }


    txt.setText(where);
}

推荐答案

我不确定在 totalD 变量的声明位置，但是似乎它是在每个点添加值时累积值列表.假设您从A点步行到B点的距离为10米，因此您的初始ArrayList仅包含2个点，并且当您计算距离时，它正确地计算为10米并分配给totalD变量.现在，您从B点到C点走的更远，再说5米，您的ArrayList现在包含3个点A，B和C，总距离应该为15米(10 + 5).函数的编写方式是遍历点列表，并将其全部添加到totalD中，而无需重新设置.因此，您的totalD已经从先前的计算中获得了10的值，现在通过再次遍历ArrayList并获得15的总和，您可以将15与之前的第一次计算所获得的10相加.您的totalD现在为25(10 + 15，以前所有计算的结果之和)，而不是简单的15(仅最后一次计算的结果).因此，在您的 calculateDistance()方法而不是

I'm not sure where the totalD variable is declared, but it seems like it is accumulating values with each point you add to the list. Say you walk from point A to point B with a distance of 10 meters, so your initial ArrayList contains only 2 points and when you calculate the distance it is correctly calculated as 10 meters and assigned to totalD variable. Now you walk further, from point B to point C, say another 5 meters, and your ArrayList now contains 3 points A, B, and C, with a total distance that's supposed to be 15 meters (10 + 5). The way your function was written, you go through the list of points, and add it all to totalD without ever re-setting it. So, your totalD already had a value of 10 from the previous calculation, and now by going through the ArrayList again and getting a total of 15, you add that 15 to the previous 10 that you had there from the first calculation. Your totalD is now 25 (10 + 15, the results of all previous calculations combined), instead of simply 15 (the result of only the last calculation). So in your calculateDistance() method instead of

totalD +=  results[0];

您应该有一个局部变量，例如 tempTotalDistance ，然后将所有点之间的距离相加，然后将其最终值分配给全局 totalD .您的新 calculateDistance()看起来可能像这样:

you should have a local variable, say tempTotalDistance, and then add all distances between points into it, and then assign its final value to your global totalD. Your new calculateDistance() can look something like this:

private void calculateDistance(ArrayList<LatLng> points) {

    float tempTotalDistance;

    for (int i =0; i < points.size() -1; i++) {
        LatLng pointA =  points.get(i);
        LatLng pointB = points.get(i + 1);
        float[] results = new float[3];
        Location.distanceBetween (pointA.latitude, pointA.longitude, pointB.latitude, pointB.longitude, results);
        tempTotalDistance +=  results[0];
    }

    totalD = tempTotalDistance;
}

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