android - 仅在谷歌地图中显示当前用户位置一次

Question

我的应用程序显示 map ，并自动将用户带到他们当前的位置。有一个文本框，允许用户键入他们的位置以在文本栏中键入的地址处显示标记。

当我启动该应用程序时，它会正确地向用户显示他们所在的位置。当我在 map 上输入新地址时，它会在新输入的位置显示一个标记。但是，此后它会自动将用户带回他们所在的位置，并从用户键入的位置中删除标记。

我想 onLocationChnaged 会触发多次。有谁知道在应用启动时只找到一次用户位置的解决方案是什么？

这是我的代码:

public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) 
       { 
         if (view != null) 
         {
             ViewGroup parent = (ViewGroup) view.getParent();
             if (parent != null)
                 parent.removeView(view); }
         try 
         { 
             view = inflater.inflate(R.layout.fragment_map_view, container, false);
         }
         catch (InflateException e)
         { /* map is already there, just return view as it is */ }

         LocationManager lm = (LocationManager)getActivity().getSystemService(Context.LOCATION_SERVICE);
         lm.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 0, 0, this);

         map = ((SupportMapFragment)getFragmentManager().findFragmentById(R.id.map_fragment)).getMap();
         map.setMyLocationEnabled(true);



         FragmentManager fm = getFragmentManager();
         FragmentTransaction ft = fm.beginTransaction();
         DateTimeFragment datetime=new DateTimeFragment();
         ft.add(R.id.datetime_container_map, datetime);
         //SupportMapFragment mapFragment=null;
         //if(mapFragment==null)
            // mapFragment= (SupportMapFragment)fm.findFragmentById(R.id.map_fragment);

         ft.commit();

         AutoCompleteTextView location= (AutoCompleteTextView)view.findViewById(R.id.location_map);
         location.setAdapter(new PlacesAutoCompleteAdapter(getActivity(),R.layout.list_layout));
         location.setOnItemClickListener(this);

         Spinner category=(Spinner)view.findViewById(R.id.category_query_map);
         ArrayAdapter<CharSequence> adapterCategory = ArrayAdapter.createFromResource(this.getActivity().getBaseContext(),R.array.category_names, android.R.layout.simple_spinner_item);
         adapterCategory.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
         category.setAdapter(adapterCategory);
         category.setOnItemSelectedListener(this);

         return view;
       }

     public void onItemClick(AdapterView<?> adapterView, View view, int position, long id)
     {
         String address_text = (String) adapterView.getItemAtPosition(position);
         Geocoder geocoder = new Geocoder(getActivity().getBaseContext());
         List<Address> addresses=null;
         LatLng latlng;
         MarkerOptions markerOptions;

         try {
             // Getting a maximum of 3 Address that matches the input text
            addresses = geocoder.getFromLocationName(address_text, 3);
         } catch (IOException e) {
             e.printStackTrace();
         }

         if(addresses==null || addresses.size()==0){
             Toast.makeText(getActivity().getBaseContext(), "No Location found", Toast.LENGTH_SHORT).show();
         }

         // Clears all the existing markers on the map
         map.clear();

         // Adding Markers on Google Map for each matching address
         for(int i=0;i<addresses.size();i++){

             Address address = (Address) addresses.get(i);

             // Creating an instance of GeoPoint, to display in Google Map
             latlng = new LatLng(address.getLatitude(), address.getLongitude());

             String addressText = String.format("%s, %s",
             address.getMaxAddressLineIndex() > 0 ? address.getAddressLine(0) : "",
             address.getCountryName());


             markerOptions = new MarkerOptions();
             markerOptions.position(latlng);
             markerOptions.title(addressText);

             map.addMarker(markerOptions);

             // Locate the first location
             if(i==0)
                 map.animateCamera(CameraUpdateFactory.newLatLng(latlng));
         }

     }

     @Override
     public void onLocationChanged(Location location) {

       map.clear();
       MarkerOptions mp = new MarkerOptions();
       mp.position(new LatLng(location.getLatitude(), location.getLongitude()));
       mp.title("my position");
       map.addMarker(mp);
       map.animateCamera(CameraUpdateFactory.newLatLngZoom(
        new LatLng(location.getLatitude(), location.getLongitude()), 16));

      }

      @Override
      public void onProviderDisabled(String provider) {
      // TODO Auto-generated method stub

       }

      @Override
      public void onProviderEnabled(String provider) {
      // TODO Auto-generated method stub

       }

      @Override
      public void onStatusChanged(String provider, int status, Bundle extras) {
      // TODO Auto-generated method stub

      }

      public void onItemSelected(AdapterView<?> arg0, View arg1, int arg2,
                long arg3) {
            // TODO Auto-generated method stub  
      }

      public void onNothingSelected(AdapterView<?> arg0) {
            // TODO Auto-generated method stub  
      }

有谁知道为什么在用户输入的地址中显示标记后，标记会自动更新到用户位置？

PS:我还想知道在旁注中，使用 Geocoder 将字符串转换为地址是否是一个好习惯，如图所示......或者我应该将它放在 AsyncTask 中

Answer 1

会不会是您的 onLocationChanged() 正在触发并将标记更新到当前位置？

你可以防止多次更新:

 private Location mLocation = null;

 @Override
 public void onLocationChanged(Location location) {

   if (mLocation == null) {
       mLocation = location;
       map.clear();
       MarkerOptions mp = new MarkerOptions();
       mp.position(new LatLng(location.getLatitude(), location.getLongitude()));
       mp.title("my position");
       map.addMarker(mp);
       map.animateCamera(CameraUpdateFactory.newLatLngZoom(
        new LatLng(location.getLatitude(), location.getLongitude()), 16));
    }
  }