借助 CommonsWare 和 Blackkara的 答案，我能够解决我的问题。

根据他们的建议，我更改了代码，并通过调试仔细检查了代码的每个步骤。

因此，我遇到了这样的问题：在棉花糖的情况下，我的onLocationChanged（）没有被解雇，但是令人惊讶的是，在低于Android
M或6.0的旧设备中，它却被解雇了。

为了解决这个问题，我更改了代码，如下所示，在此发布完整的代码，以便任何有相同问题的人都可以摆脱。

GPSTracker.java

public class GPSTracker extends Service{

    private  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 = 1000; // 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;

    Activity activity;

    public GPSTracker() {
    }

    public GPSTracker(Context context, Activity activity) {
        this.mContext = context;
        this.activity = activity;
        getLocation();
    }

    public Location getLocation() {
        try {


            locationManager = (LocationManager) mContext.getSystemService(LOCATION_SERVICE);

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

            // Getting network status
            isNetworkEnabled = locationManager
                    .isProviderEnabled(LocationManager.NETWORK_PROVIDER);

            if (!isGPSEnabled && !isNetworkEnabled) {
                // No network provider is enabled
            } else {
                this.canGetLocation = true;
                if (isNetworkEnabled) {
                    int requestPermissionsCode = 50;

                    locationManager.requestLocationUpdates(
                            LocationManager.NETWORK_PROVIDER,
                            MIN_TIME_BW_UPDATES,
                            MIN_DISTANCE_CHANGE_FOR_UPDATES, mLocationListener);
                    Log.d("Network", "Network");
                    if (locationManager != null) {
                        location = locationManager
                                .getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
                        if (location != null) {
                            latitude = location.getLatitude();
                            longitude = location.getLongitude();
                        }
                    }
                }
            }
            // If GPS enabled, get latitude/longitude using GPS Services
            if (isGPSEnabled) {
                if (location == null) {
                    if (ContextCompat.checkSelfPermission(activity, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(activity, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
                        ActivityCompat.requestPermissions(activity, new String[]{Manifest.permission.ACCESS_FINE_LOCATION}, 50);

                    } else {
                        locationManager.requestLocationUpdates(
                                LocationManager.GPS_PROVIDER,
                                MIN_TIME_BW_UPDATES,
                                MIN_DISTANCE_CHANGE_FOR_UPDATES, mLocationListener);
                        Log.d("GPS Enabled", "GPS Enabled");
                        if (locationManager != null) {

                            location = locationManager
                                    .getLastKnownLocation(LocationManager.GPS_PROVIDER);
                            if (location != null) {
                                latitude = location.getLatitude();
                                longitude = location.getLongitude();
                            }
                        }
                    }
                }

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

        return location;
    }


    /**
     * Stop using GPS listener
     * Calling this function will stop using GPS in your app.
     * */
    public void stopUsingGPS() {

    }


    private final LocationListener mLocationListener = new LocationListener() {
        @Override
        public void onLocationChanged(final Location location) {

            if (location != null) {
                latitude = location.getLatitude();
                longitude = location.getLongitude();
            }
        }

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

        }

        @Override
        public void onProviderEnabled(String provider) {

        }

        @Override
        public void onProviderDisabled(String provider) {

        }
    };

    /**
     * Function to get latitude
     * */
    public double getLatitude(){
        if(location != null){
            latitude = location.getLatitude();
        }

        // return latitude
        return latitude;
    }


    /**
     * Function to get longitude
     * */
    public double getLongitude(){
        if(location != null){
            longitude = location.getLongitude();
        }

        // return longitude
        return longitude;
    }

    /**
     * Function to check GPS/Wi-Fi enabled
     * @return boolean
     * */
    public boolean canGetLocation() {
        return this.canGetLocation;
    }


    /**
     * Function to show settings alert dialog.
     * On pressing the Settings button it will launch Settings Options.
     * */
    public void showSettingsAlert() {
        AlertDialog.Builder alertDialog = new AlertDialog.Builder(mContext);

        // Setting Dialog Title
        alertDialog.setTitle("GPS is settings");

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

        // On pressing the Settings button.
        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);
            }
        });

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

        // Showing Alert Message
        alertDialog.show();
    }


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

DashboardActivity.java

public class DashboardActivity extends Activity {

    Context mContext;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_dashboard);

        mContext = this;

        if (ContextCompat.checkSelfPermission(mContext, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(mContext, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
            ActivityCompat.requestPermissions(DashboardActivity.this, new String[]{Manifest.permission.ACCESS_FINE_LOCATION}, 1);

        } else {
            Toast.makeText(mContext,"You need have granted permission",Toast.LENGTH_SHORT).show();
            gps = new GPSTracker(mContext, DashboardActivity.this);

            // Check if GPS enabled
            if (gps.canGetLocation()) {

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

                // \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();
            }
        }           
    }


    @Override
    public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);

        switch (requestCode) {
            case 1: {
                // If request is cancelled, the result arrays are empty.
                if (grantResults.length > 0
                        && grantResults[0] == PackageManager.PERMISSION_GRANTED) {

                    // permission was granted, yay! Do the

                    // contacts-related task you need to do.

                    gps = new GPSTracker(mContext, DashboardActivity.this);

                    // Check if GPS enabled
                    if (gps.canGetLocation()) {

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

                        // \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();
                    }

                } else {

                    // permission denied, boo! Disable the
                    // functionality that depends on this permission.

                    Toast.makeText(mContext, "You need to grant permission", Toast.LENGTH_SHORT).show();
                }
                return;
            }
        }
    }
}

Manifest.xml：

添加的权限

    <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
    <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
    <uses-permission android:name="android.permission.INTERNET" />

在应用程序标签中声明服务：

 <service android:name=".utilities.GPSTracker"/>