java - 无法获取纬度和经度值。应该更改什么？

Question

output screenshot with Toast

//这里是 homeactivity.java 上的按钮

 FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                gps = new GpsTracker(DrAppointHome.this);

                if(gps.canGetLocation()) {

                    double latitude = gps.getLatitude();
                    double longitude = gps.getLongitude();

                    FragmentTransaction fragmentTransaction = mFragmentManager.beginTransaction();
                    fragmentTransaction.replace(R.id.containerView,update).commit();
                    update.update(latitude, longitude);

                    // \n is for new line
                    Toast.makeText(getApplicationContext(), "Your Location is - \nLat: " + latitude + "\nLong: " + longitude, Toast.LENGTH_LONG).show();
                } else {
                    // Can't get location.
                    // GPS or network is not enabled.
                    // Ask user to enable GPS/network in settings.
                    gps.showSettingsAlert();
                }
            }
        });

//这里是GpsTracker.java的代码

public class GpsTracker extends Service implements LocationListener {

    private final Context mContext;

    // Flag for GPS status
    boolean isGPSEnabled = false;

    // Flag for network status
//    boolean isNetworkEnabled = false;

    // Flag for GPS status
    boolean canGetLocation = false;

    Location location; // Location
    double latitude; // Latitude
    double longitude; // Longitude

    // The minimum distance to change Updates in meters
    private static final long MIN_DISTANCE_CHANGE_FOR_UPDATES = 10; // 10 meters

    // The minimum time between updates in milliseconds
    private static final long MIN_TIME_BW_UPDATES = 1000 * 60 * 1; // 1 minute

    // Declaring a Location Manager
    protected LocationManager locationManager;

    public GpsTracker(Context context) {
        this.mContext = context;
        getLocation();
    }

    public Location getLocation() {
        try {
            locationManager = (LocationManager) mContext
                    .getSystemService(LOCATION_SERVICE);

            // Getting GPS status
            isGPSEnabled = locationManager
                    .isProviderEnabled(LocationManager.GPS_PROVIDER);



            if (!isGPSEnabled) {
                // No network provider is enabled
            } else {
                this.canGetLocation = true;

                if (isGPSEnabled) {
                    if (location == null) {
                        locationManager.requestLocationUpdates(
                                LocationManager.GPS_PROVIDER,
                                MIN_TIME_BW_UPDATES,
                                MIN_DISTANCE_CHANGE_FOR_UPDATES, this);
                        Log.d("TD", "GPS Enabled");
                        if (locationManager != null) {
                            location = locationManager
                                    .getLastKnownLocation(LocationManager.GPS_PROVIDER);
                            if (location != null) {
                                latitude = location.getLatitude();
                                longitude = location.getLongitude();
                                Log.e("TD", "Lat: "+latitude);
                            }
                        }
                    }
                }
            }
        }
        catch (SecurityException e) {
            e.printStackTrace();
        }
        catch (Exception e) {
            e.printStackTrace();
        }

        return location;
    }


    public void stopUsingGPS(){
        try {
            if (locationManager != null) {
                locationManager.removeUpdates(GpsTracker.this);
            }
        }
        catch (SecurityException e) {
            e.printStackTrace();
        }
    }




    public double getLatitude(){
        if(location != null){
            latitude = location.getLatitude();
        }

        // return latitude
        return latitude;
    }

    public double getLongitude(){
        if(location != null){
            longitude = location.getLongitude();
        }

        // return longitude
        return longitude;
    }


    public boolean canGetLocation() {
        return this.canGetLocation;
    }



    public void showSettingsAlert(){
        AlertDialog.Builder alertDialog = new AlertDialog.Builder(mContext);


        alertDialog.setTitle("GPS is settings");


        alertDialog.setMessage("GPS is not enabled. Do you want to go to settings menu?");


        alertDialog.setPositiveButton("Settings", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog,int which) {
                Intent intent = new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS);
                mContext.startActivity(intent);
            }
        });


        alertDialog.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int which) {
                dialog.cancel();
            }
        });


        alertDialog.show();
    }


    @Override
    public void onLocationChanged(Location location) {
    }


    @Override
    public void onProviderDisabled(String provider) {
    }


    @Override
    public void onProviderEnabled(String provider) {
    }


    @Override
    public void onStatusChanged(String provider, int status, Bundle extras) {
    }


    @Override
    public IBinder onBind(Intent arg0) {
        return null;
    }
}

//这里是 java 上的请求处理程序代码

public class RequestHandlerNearme {
    List<String> sb;
    List<DoctorNearMe> drList1 = new ArrayList<>();

    public List<String> sendPostRequest(String requestURL,
                                        HashMap<String, String> postDataParams) {

        URL url;



        try {
            url = new URL(requestURL);

            HttpURLConnection conn = (HttpURLConnection) url.openConnection();
            conn.setReadTimeout(5000);
            conn.setConnectTimeout(5000);
            conn.setRequestMethod("POST");
            conn.setDoInput(true);
            conn.setDoOutput(true);


            OutputStream os = conn.getOutputStream();
            BufferedWriter writer = new BufferedWriter(
                    new OutputStreamWriter(os, "UTF-8"));
            writer.write(getPostDataString(postDataParams));

            writer.flush();
            writer.close();
            os.close();
            int responseCode = conn.getResponseCode();

            if (responseCode == HttpsURLConnection.HTTP_OK) {
                BufferedReader br = new BufferedReader(new InputStreamReader(conn.getInputStream()));
                sb  = new ArrayList<>();
                String response = "";

                }
                for (int i = 0; i<sb.size()-7; i=i+7){

                    drList1.add(new DoctorNearMe(sb.get(i),sb.get(i+1),sb.get(i+2),sb.get(i+3),sb.get(i+4),Double.parseDouble(sb.get(i+5)),Double.parseDouble(sb.get(i+6))));

                }

            }

        } catch (Exception e) {
            e.printStackTrace();
        }
        return sb;
    }

    private String getPostDataString(HashMap<String, String> params) throws UnsupportedEncodingException {
        StringBuilder result = new StringBuilder();
        boolean first = true;
        for (Map.Entry<String, String> entry : params.entrySet()) {
            if (first)
                first = false;
            else
                result.append("&");

            result.append(URLEncoder.encode(entry.getKey(), "UTF-8"));
            result.append("=");
            result.append(URLEncoder.encode(entry.getValue(), "UTF-8"));
        }

        return result.toString();
    }

}

//这里是java上的 fragment 代码

public class DoctorNearYou extends Fragment {
    private static final String NEAR_YOU_URL = "http://doctorsportal.netne.net/nearme.php";
    private static final String KEY_LATITUDE = "latitude";
    private static final String KEY_LONGITUDE = "longitude";

    private List<String> result;
    ListView list;
    public RequestHandlerNearme rh = new RequestHandlerNearme();

    LayoutInflater inflater;

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        this.inflater = inflater;
        return inflater.inflate(R.layout.doctornearyoufragment,null);
    }

    public void update(final double latitude, final double longitude) {
        rh.drList1.clear();

        class TDsAdapter extends ArrayAdapter<DoctorNearMe> {
            public TDsAdapter(){
                super(getActivity().getApplicationContext(),R.layout.custom_list_view_near_me,rh.drList1);
            }

            @Override
            public View getView(int position, View convertView, ViewGroup parent) {
                View itemView = convertView;
                if (itemView == null) {
                    itemView = inflater.inflate(R.layout.custom_list_view_near_me, parent, false);
                }


                DoctorNearMe currentItem = rh.drList1.get(position);
                TextView dRName = (TextView) itemView.findViewById(R.id.dRName1);
                dRName.setText(currentItem.getDrName());

                TextView drSpeciality = (TextView) itemView.findViewById(R.id.drSpeciality1);
                drSpeciality.setText(currentItem.getDrSpeciality());

                TextView drJobTitle = (TextView) itemView.findViewById(R.id.drJobTitle1);
                drJobTitle.setText(currentItem.getDrJobTitle());

                ImageView drProPic = (ImageView) itemView.findViewById(R.id.drPropic1);
                Picasso.with(getContext()).load(currentItem.getDrProPic()).into(drProPic);



                double earthRadius = 6371000; //meters
                double dLat = Math.toRadians(currentItem.getlatitude()-latitude);
                double dLng = Math.toRadians(currentItem.getLongitude()-longitude);
                double a = Math.sin(dLat/2) * Math.sin(dLat/2) +
                        Math.cos(Math.toRadians(latitude)) * Math.cos(Math.toRadians(currentItem.getlatitude())) *
                                Math.sin(dLng/2) * Math.sin(dLng/2);
                double c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a));
               Double Distence = (Double) ((earthRadius * c)/1000);




                TextView distence = (TextView) itemView.findViewById(R.id.drdistence);
                distence.setText(Distence+"");

                return itemView;
            }
        }


        class LoadDoctors extends AsyncTask<Void, Void, List<String>>{
            ProgressDialog loading;
            @Override
            protected void onPreExecute() {
                super.onPreExecute();

            }

            @Override
            protected void onPostExecute(List<String> s) {
                super.onPostExecute(s);


                s.remove(s.size() - 1);
                s.remove(s.size() - 1);
                s.remove(s.size() - 1);


                Toast.makeText(getActivity(), ""+s.size(), Toast.LENGTH_SHORT).show();
                ArrayAdapter<DoctorNearMe> adapter = new TDsAdapter();

                list = (ListView) getActivity().findViewById(R.id.drlistforhome1);

                list.setAdapter(adapter);

            }

            @Override
            protected List<String> doInBackground(Void... params) {

                HashMap<String,String> param = new HashMap<String,String>();

                param.put(KEY_LATITUDE, latitude+"");
                param.put(KEY_LONGITUDE, longitude+"");
                result = rh.sendPostRequest(NEAR_YOU_URL, param);

                return result;
            }
        }

        new LoadDoctors().execute();



    }


}

//这里是代码

public class DoctorNearMe {
    public String drName;
    public String drSpeciality;
    public String drJobTitle;
    public String drProPic;
    public String drUname;
    public Double latitude;
    public Double longitude;
    public DoctorNearMe(String drName, String drSpeciality, String drJobTitle, String drProPic, String drUname, Double latitude, Double longitude) {
        this.drName = drName;
        this.drSpeciality = drSpeciality;
        this.drJobTitle = drJobTitle;
        this.drProPic = drProPic;
        this.drUname = drUname;
        this.latitude= latitude;
        this.longitude=longitude;
    }

    public String getDrName() {
        return drName;
    }

    public void setDrName(String drName) {
        this.drName = drName;
    }

    public String getDrSpeciality() {
        return drSpeciality;
    }

    public void setDrSpeciality(String drSpeciality) {
        this.drSpeciality = drSpeciality;
    }

    public String getDrJobTitle() {
        return drJobTitle;
    }

    public void setDrJobTitle(String drJobTitle) {
        this.drJobTitle = drJobTitle;
    }

    public String getDrProPic() {
        return drProPic;
    }

    public void setDrProPic(String drProPic) {
        this.drProPic = drProPic;
    }

    public String getDrUname() {
        return drUname;
    }

    public void setDrUname(String drUname) {
        this.drUname = drUname;
    }

    public Double getlatitude() {
        return latitude;
    }

    public void setLatitude(Double latitude) {
        this.latitude= latitude;
    }

    public Double getLongitude() {
        return longitude;
    }

    public void setLongitude(Double longitude) {
        this.longitude= longitude;
    }

}

我该如何解决这个问题？

Answer 1

if (!isGPSEnabled) {
    // No network provider is enabled
} else { .... }

首先，您仅使用 GPS 提供商来获取位置，如果未启用 GPS，您的代码将超出范围并且永远不会发出位置请求。请注意您的代码的这种情况。

其次，当你调用 getLocation() 方法时，它无法尽快获取新位置，也许你知道。然后，您仅获得 GPS 提供商的缓存位置。如果没有缓存的位置数据，您的方法将返回 null 并且位置参数将为 null，直到 gps 提供程序获得新位置

我看到一些事情，每当您单击 fab 按钮时，它都会创建 GpsTracker，那么之前请求的位置更新呢？

为什么不设置下面的位置参数呢？

@Override
public void onLocationChanged(Location location) {

}
....
double latitude = gps.getLatitude();
double longitude = gps.getLongitude();

如果不这样做，getLatitude 和 getLongitude 返回缓存值或 null(引用我的第二部分)