在后台连续获取当前位置

Question

在我的项目中，我使用了一项服务来在后台连续检索位置。我的LocationService如下：

public class LocationService extends Service
{

    private static final int TWO_MINUTES = 1000 * 60 * 2;
    public LocationManager locationManager;
    public MyLocationListener listener;
    public Location previousBestLocation = null;

    Intent i;


    @Override
    public void onCreate()
    {
        super.onCreate();
    i = new Intent("LOCATION_CHANGED");

    }

    @Override
    public int onStartCommand(Intent intent,int flags, int startId)
    {
        locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
        listener = new MyLocationListener();
        locationManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 4000, 0, listener);
        locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 4000, 0, listener);
        return super.onStartCommand(intent, flags, startId);

    }

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

    protected boolean isBetterLocation(Location location, Location currentBestLocation) {
        if (currentBestLocation == null) {
            // A new location is always better than no location
            return true;

        }

        // Check whether the new location fix is newer or older
        long timeDelta = location.getTime() - currentBestLocation.getTime();
        boolean isSignificantlyNewer = timeDelta > TWO_MINUTES;
        boolean isSignificantlyOlder = timeDelta < -TWO_MINUTES;
        boolean isNewer = timeDelta > 0;

        // If it's been more than two minutes since the current location, use the new location
        // because the user has likely moved
        if (isSignificantlyNewer) {
            return true;
            // If the new location is more than two minutes older, it must be worse
        } else if (isSignificantlyOlder) {
            return false;
        }

        // Check whether the new location fix is more or less accurate
        int accuracyDelta = (int) (location.getAccuracy() - currentBestLocation.getAccuracy());
        boolean isLessAccurate = accuracyDelta > 0;
        boolean isMoreAccurate = accuracyDelta < 0;
        boolean isSignificantlyLessAccurate = accuracyDelta > 200;

        // Check if the old and new location are from the same provider
        boolean isFromSameProvider = isSameProvider(location.getProvider(),
                currentBestLocation.getProvider());

        // Determine location quality using a combination of timeliness and accuracy
        if (isMoreAccurate) {
            return true;
        } else if (isNewer && !isLessAccurate) {
            return true;
        } else if (isNewer && !isSignificantlyLessAccurate && isFromSameProvider) {
            return true;
        }
        return false;
    }



    /** Checks whether two providers are the same */
    private boolean isSameProvider(String provider1, String provider2) {
        if (provider1 == null) {
            return provider2 == null;
        }
        return provider1.equals(provider2);
    }



    @Override
    public void onDestroy() {
        // handler.removeCallbacks(sendUpdatesToUI);
        super.onDestroy();
        Log.v("STOP_SERVICE", "DONE");
        locationManager.removeUpdates(listener);
    }

    public static Thread performOnBackgroundThread(final Runnable runnable) {
        final Thread t = new Thread() {
            @Override
            public void run() {
                try {
                    runnable.run();
                } catch(Exception e) {
System.out.print(e);
                }
            }
        };
        t.start();
        return t;
    }




    public class MyLocationListener implements LocationListener
    {

        public void onLocationChanged(final Location loc)
        {
            Log.i("**************************************", "Location changed");
            if(isBetterLocation(loc, previousBestLocation)) {
                String newLocation = "Lat: " + loc.getLatitude() + " and Long: " + loc.getLongitude();
               i = new Intent("LOCATION_CHANGED");
                i.putExtra("location", newLocation);
                sendBroadcast(i);



            }
        }

        public void onProviderDisabled(String provider)
        {
            Toast.makeText( getApplicationContext(), "Gps Disabled", Toast.LENGTH_SHORT ).show();
        }


        public void onProviderEnabled(String provider)
        {
            Toast.makeText(getApplicationContext(), "Gps Enabled", Toast.LENGTH_SHORT).show();
        }


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

        }

    }
}

我在MainActivity 收到了广播意图，如下：

public class MainActivity extends Activity {


    TextView txt_location;



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

        txt_location = (TextView)findViewById(R.id.current_location);


        if (savedInstanceState == null) {
            getFragmentManager().beginTransaction()
                    .add(R.id.container, new PlaceholderFragment()).commit();


        }

   }



    public class LocationBroadcast extends BroadcastReceiver {
        @Override
        public void onReceive(Context ctx, Intent intent) {

            txt_location.setText(intent.getExtras().getString("location"));
        }

    }



       public static class PlaceholderFragment extends Fragment {


        public PlaceholderFragment() {

        }

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                Bundle savedInstanceState) {


            return inflater.inflate(R.layout.fragment_main, container,
                    false);

        }
    }

}

我要做的就是在txt_location 上设置位置的纬度和经度。此代码不起作用并按原样显示txt_location：

如您所见，它没有显示任何位置更新...Logcat 没有显示任何错误..谁能指导我是什么错误？

Answer 1

将此类用作服务。但在此之前在清单中定义服务类

<service android:name="com.example.androidservice.beckend.EndlessService" />

在活动类中使用

startService(new Intent ( this , EndlessService.class)) ;

import android.app.Service;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Handler;
import android.os.HandlerThread;
import android.os.IBinder;
import android.os.Looper;
import android.os.Message;
import android.os.Process;
import android.util.Log;
import android.widget.Toast;

public class EndlessService extends Service {
    private Looper mServiceLooper;
    private ServiceHandler mServiceHandler;

    // Handler that receives messages from the thread
    private final class ServiceHandler extends Handler {
        public ServiceHandler(Looper looper) {
            super(looper);
        }

        @Override
        public void handleMessage(Message msg) 
        {
            new HitToTheInternet().execute("");
        }
    }

    @Override
    public void onCreate() {
        // Start up the thread running the service. Note that we create a
        // separate thread because the service normally runs in the process's
        // main thread, which we don't want to block. We also make it
        // background priority so CPU-intensive work will not disrupt our UI.
        HandlerThread thread = new HandlerThread("ServiceStartArguments",Process.THREAD_PRIORITY_BACKGROUND);
        thread.start();

        // Get the HandlerThread's Looper and use it for our Handler
        mServiceLooper = thread.getLooper();
        mServiceHandler = new ServiceHandler(mServiceLooper);
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        Toast.makeText(this, "service starting", Toast.LENGTH_SHORT).show();

        // For each start request, send a message to start a job and deliver the
        // start ID so we know which request we're stopping when we finish the
        // job
        Message msg = mServiceHandler.obtainMessage();
        msg.arg1 = startId;
        mServiceHandler.sendMessage(msg);

        if ( intent == null )
        {
            Log.e("intentStatus", "intent is null");
        }

        // If we get killed, after returning from here, restart
        return START_STICKY;
    }

    @Override
    public IBinder onBind(Intent intent) {
        // We don't provide binding, so return null
        return null;
    }

    @Override
    public void onDestroy() {
        Toast.makeText(this, "service done", Toast.LENGTH_SHORT).show();
    }

    class HitToTheInternet extends AsyncTask<String, String, String>
    {

        @Override
        protected String doInBackground(String... params) {
            // TODO Auto-generated method stub

            Log.e("doInBackground", "Running") ;

            return null;
        }

        @Override
        protected void onPostExecute(String result) {
            // TODO Auto-generated method stub
            super.onPostExecute(result);

            new Handler().postDelayed(new Runnable() {
                public void run() {
                    Message msg = mServiceHandler.obtainMessage();
                    mServiceHandler.sendMessage(msg);
                }
            }, 10000);
        }
    }
}

Answer 2

在 5 秒后开始服务说：

AlarmManager alarm =(AlarmManager)context.getSystemService(context.ALARM_SERVICE);
        PendingIntent pi = PendingIntent.getService(context, 0, new Intent(context,MonitorService.class), 0);
        alarm.setRepeating(AlarmManager.ELAPSED_REALTIME_WAKEUP, SystemClock.elapsedRealtime(), 5*1000, pi);

停止报警：

AlarmManager mgr =(AlarmManager)getSystemService(ALARM_SERVICE);
        PendingIntent pi = PendingIntent.getService(context, 0, new Intent(this,MonitorService.class), 0);
        mgr.cancel(pi);
        pi.cancel();