Google Maps Api V2-如何在移動時移動標記

Question

美好的一天，我有一個谷歌地圖api v2的問題我想移動標記您的位置的標記。但我想每10秒更新一次標記的位置，你有什麼想法如何做到這一點？

public class MapsActivity extends BaseMap { 

private final static String LINE = "cfngCjzqtQXgBp@HlFao@oAh@yCdBit@wFpf@wc@~RaQlKgJtH}GjEcE~IuLpFmH`DwHrD_IxDqFbFmFjIsHnCaA`IgBjMmCdHkA`H_AvLoDvAK~B?dNfAvUrExHhB`KpBhFjA~GtAlFjAnJzBtJjBdFhAvGxAbPbDxOlDjPpDrF|@pHm@`IsD`OgIbGeDtKeGjM_HpKyFdGeDtGyFpBGnB~@xGtClHpBxD~@~Ds@|IoD`Uf@`]xGpG\\bKuDxPGxFlA`DtA~FlAtQvCfPdCzHj@rNq@tKeCtIkBbJoCxGgCtI}DnGkChS_H`OuExKaEtUaHfRsFdIyBpF_BhHoBzJ}C|N{@hCI`EeBpF{NpAqD|CuIrEnBxFfCaAlC"; 
double ula, ulo, ula2 ,ulo2; 
final Context context1 = this; 
private MarkerOptions a = new MarkerOptions(); 
private Marker m; 
@Override 
protected void startDemo() { 
    List<LatLng> decodedPath = PolyUtil.decode(LINE); 

    getMap().addPolyline(new PolylineOptions().addAll(decodedPath).color(Color.RED)); 
    LocationManager lManager = (LocationManager) getSystemService(LOCATION_SERVICE); 

    if (ActivityCompat.checkSelfPermission(context1, android.Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(context1, android.Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) { 
     return; 
    } 
    Location lastKnownLocation = lManager.getLastKnownLocation(LocationManager.NETWORK_PROVIDER); 


    ula= lastKnownLocation.getLatitude(); 
    ulo=lastKnownLocation.getLongitude(); 
    Log.v("Lactitud", String.valueOf(ula)); 
    Log.v("Longitud", String.valueOf(ulo)); 


    MarkerOptions a = new MarkerOptions().position(new LatLng(ula,ulo)); 
    a.title("Tú"); 


    getMap().moveCamera(CameraUpdateFactory.newLatLngZoom(new LatLng(22.293139, -97.88466440000002), 12)); 

    getMap().addMarker(new MarkerOptions().position(new LatLng(22.360463,-97.908935)).icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_ORANGE))).setTitle("Urban Azteca"); 
    getMap().addMarker(new MarkerOptions().position(new LatLng(22.21510,-97.85956)).icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_ORANGE))).setTitle("Urban Tampico"); 
    getMap().addMarker(new MarkerOptions().position(new LatLng(ula,ulo))).setTitle("Tú"); 


    int delay = 1000; 
    final Handler handler = new Handler(); 
    handler.postDelayed(new Runnable() { 
     @Override 
     public void run() { 

      LocationManager lManager = (LocationManager) getSystemService(LOCATION_SERVICE); 
      if (ActivityCompat.checkSelfPermission(context1, android.Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(context1, android.Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) { 
       return; 
      } 
      Location lastKnownLocation = lManager.getLastKnownLocation(LocationManager.NETWORK_PROVIDER); 


      ula= lastKnownLocation.getLatitude(); 
      ulo=lastKnownLocation.getLongitude(); 

      m.setPosition(new LatLng(ula2, ulo2)); 

     }}, 10000); 

} 

} 

而當我運行它會給出這個錯誤。

12-16 11:02:05.984 26736-26736/com.example.maygea.pruebamaps E/AndroidRuntime: FATAL EXCEPTION: main 
                      Process: com.example.maygea.pruebamaps, PID: 26736 
                      java.lang.NullPointerException: Attempt to invoke virtual method 'void com.google.android.gms.maps.model.Marker.setPosition(com.google.android.gms.maps.model.LatLng)' on a null object reference 
                       at com.example.maygea.pruebamaps.MapsActivity$1.run(MapsActivity.java:85) 
                       at android.os.Handler.handleCallback(Handler.java:739) 
                       at android.os.Handler.dispatchMessage(Handler.java:95) 
                       at android.os.Looper.loop(Looper.java:211) 
                       at android.app.ActivityThread.main(ActivityThread.java:5389) 
                       at java.lang.reflect.Method.invoke(Native Method) 
                       at java.lang.reflect.Method.invoke(Method.java:372) 
                       at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1020) 
                       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:815) 

我認爲它是我的m.setPosition（new LatLng（ula2，ulo2））;

Answer 1

您應該使用location manager和requestLocationUpdates方法。此方法在每次位置更改時觸發onLocationChanged事件，然後您可以移動標記：

public class MainActivity extends FragmentActivity implements OnMapReadyCallback, LocationListener { 

    private GoogleMap mGoogleMap; 
    private Location mLocation; 

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

     MapFragment mapFragment = (MapFragment) getFragmentManager().findFragmentById(R.id.map); 
     mapFragment.getMapAsync(this); 

     LocationManager locationManager = new LocationManager(this); 
     locationManager.requestLocationUpdates (LocationManager.NETWORK_PROVIDER, 10, 10, this); 

     mLocation = locationManager.getLastKnownLocation(LocationManager.NETWORK_PROVIDER); 
     addMarker(); 

    } 

    @Override 
    public void onMapReady(GoogleMap map) { 
     mGoogleMap = map; 
     addMarker(); 

    } 

    @Override 
    public void onLocationChanged(Location location) { 
     mLocation = location; 
     addMarker(); 
    } 

    private void addMarker(){ 
     if (mGoogleMap == null){ 
      return; 
     } 
     mGoogleMap.clear(); 
     mGoogleMap.addMarker(new MarkerOptions() 
         .position(new LatLng(mLlocation.getLatitude(), mLocation.getLongitude())); 
    } 

}