android - 检查 GPS 可访问性

Question

我想检查设备是否从卫星获取数据。如果我得到我当前的位置，那么我会做一些事情。否则，如果我还没有任何坐标，我想 toast 给我留言。我怎么知道我是否已经得到坐标？

GeoPoint h = null;
double latitude = 10, longitude = 10;
public void onClick(View v) 
{
    switch (v.getId())
    {
      case R.id.get_GPS:
          final LocationManager manager = (LocationManager) getSystemService( Context.LOCATION_SERVICE );
          if(isInternetOn() && manager.isProviderEnabled(LocationManager.GPS_PROVIDER))
          {
//I want here to check, if I get latitude and longitude values, which differ from 10 x 10, I go to my map, otherwise I say, that there's no information received from satellite.
/*
              h = new GeoPoint((int) (latitude * 1000000), (int) (longitude * 1000000));

              if(h.getLatitudeE6()==h.getLongitudeE6() && h.getLongitudeE6()==10000000)
              {
                  Toast.makeText(this, "No information received from satellite yet.", Toast.LENGTH_LONG).show();
                  break;
              }
              */
              Intent i = new Intent (this,getGPS.class);
              startActivity(i);
          }
          else
          {   
              if(!isInternetOn() && !manager.isProviderEnabled( LocationManager.GPS_PROVIDER))
              {
                  buildAlertMessageNoGpsNoInternet();
                  break;
              }

              if(!isInternetOn())
              {
                  buildAlertMessageNoInternet();
                  break;
              }
              if(!manager.isProviderEnabled( LocationManager.GPS_PROVIDER))
              {
                  buildAlertMessageNoGps();
                  break;
              }
          }

        break;
      case R.id.about_button:
        Intent j = new Intent(this, About.class);
        startActivity(j);
        break;
      case R.id.exit_button:
        this.moveTaskToBack(true);
        break;
    }
}

Sam，我在“if”中得到空指针异常:

if(manager.isProviderEnabled(LocationManager.GPS_PROVIDER))
          {

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

              /*Here ->*/if(location.getTime() > ((Calendar.getInstance().getTimeInMillis()) - 10000))
              {
                  Intent i = new Intent (this, getGPS.class);
                  startActivity(i);
              }

              else 
              {
                    // Wait for new location
                    LocationListener locationListener = new myLocationListener();
                    manager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0,locationListener);
              }
}

日志

05-05 11:42:49.444: E/AndroidRuntime(300): java.lang.NullPointerException

Answer 1

我会尝试类似的方法:

public class Example extends Activity {

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        LocationManager manager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
        Location location = manager.getLastKnownLocation(LocationManager.GPS_PROVIDER);

        if(location.getTime() > Calendar.getInstance().getTimeInMillis() - 2 * 60 * 1000) {
            // Do something with the recent location fix
        }
        else {
            // Wait for new location
            LocationListener locationListener = new myLocationListener();
            manager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0,locationListener);
        }
    }

    private class myLocationListener implements LocationListener {
        public void onLocationChanged(Location location) {
            if (location != null) {
                Log.v("Location Changed", location.getLatitude() + " " + location.getLongitude());
                // Do something with current location
            }
        }

        // Must implement missing functions!
    }
}

添加

如果此处的位置为空，则可能意味着无论出于何种原因都没有最后已知的位置。简单修复:

if(location != null && location.getTime() > ((Calendar.getInstance().getTimeInMillis()) - 10000))