Question

我需要在自行车移动时使用GPS在Android中计算距离。而我在仿真器中为aprx提供纬度和经度值，给出正确的值，但是通过使用设备的数据包数据并且运行应用程序时，值会随着任何移动而改变。这是代码，请建议。

@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
        showCurrentLocation();
        b2=(Button)findViewById(R.id.button2);
        b2.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                clearButton();
            }
    });     
    }

    @SuppressWarnings("unused")
    protected void showCurrentLocation() {
        // Getting LocationManager object
        locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
        // Creating an empty criteria object
        Criteria criteria = new Criteria();
        // Getting the name of the provider that meets the criteria
        provider = locationManager.getBestProvider(criteria, false);

        if (provider != null && !provider.equals("")) {
            Location location = locationManager.getLastKnownLocation(provider);

            locationManager.requestLocationUpdates(provider, 20000, 1, this);
            clat = location.getLatitude();
            clon = location.getLongitude();
            a[0] = clat;
            a[1] = clon;

            if (location != null)
                onLocationChanged(location);
            else
                Toast.makeText(getBaseContext(), "Location can't be retrieved",
                        Toast.LENGTH_SHORT).show();

        } else {
            Toast.makeText(getBaseContext(), "No Provider Found",
                    Toast.LENGTH_SHORT).show();
        }
    }

    @Override
    public void onLocationChanged(Location location) {
        // Getting reference to TextView tv_longitude
        locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
        // Creating an empty criteria object
        Criteria criteria = new Criteria();
        // Getting the name of the provider that meets the criteria
        provider = locationManager.getBestProvider(criteria, false);

        if (provider != null && !provider.equals("")) {
            // Get the location from the given provider
            Location location1 = locationManager.getLastKnownLocation(provider);
            locationManager.requestLocationUpdates(provider, 20000, 1, this);
            plat = location.getLatitude();
            plon = location.getLongitude();
            a[2] = plat;
            a[3] = plon;
            if(a[0]!=a[2]||a[1]!=a[3])
        {
                dis += getDistance(a);
        }

            a[0] = plat;
            a[1] = plon;
            Log.e("aa", String.valueOf(dis));
            TextView tvDistance = (TextView) findViewById(R.id.textView1);
            tvDistance.setText(String.valueOf(dis) + " km");
        }
    }
   public double getDistance(double a[]) {
    double earthRadius = 6371; //kilometers
    double dLat = Math.toRadians(a[2] -a[0] );
    double dLng = Math.toRadians(a[3] -a[1]);
    double b = Math.sin(dLat/2) * Math.sin(dLat/2) +
               Math.cos(Math.toRadians(a[0])) * Math.cos(Math.toRadians(a[2])) *
               Math.sin(dLng/2) * Math.sin(dLng/2);
    double c = 2 * Math.atan2(Math.sqrt(b), Math.sqrt(1-b));
    float dist = (float) (earthRadius * c);

    return dist;
    }

    protected void clearButton(){
        dis=0;
        showCurrentLocation();
    }

Answer 1

你可以做一个步骤并且当位置不同时调用getDistance，但是当经过的时间与自行车速度（1s？）相关时。

private long timestamp = 0;

public double getDistance(double a[]) {
    timestamp = System.currentTimeMillis();
    (....)
}


public void onLocationChanged(Location location) {
     (...)
     if(System.currentTimeMillis() - timestamp > 1000){
          dis += getDistance(a);
     }

计算在android中行进的距离（移动时）

1 个答案: