How do I clear the map of All points and markers and routes when switching tabs with a tab host

Question

I created an App that uses Google Maps to get the users current location and draw routes. Recently I converted this app to a TabHost with five tabs. Because of this I now need a way to clear and restart the map whenever a user clicks on that tab. How can I do this. Below is the layout.xml and activity code for my map.

activity_map_view.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >


    <Button
        android:id="@+id/btn_draw"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text=" Get Directions"
        android:layout_alignParentBottom="true"
        android:layout_centerHorizontal="true" />

    <RelativeLayout
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal" >

        <Button
            android:id="@+id/btn_find"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/str_btn_find"
            android:layout_alignParentRight="true" />

        <EditText
            android:id="@+id/et_location"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:inputType="text"
            android:hint="@string/hnt_et_location"
            android:layout_toLeftOf="@id/btn_find" />

    </RelativeLayout>



    <fragment 
          android:id="@+id/map"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    class="com.google.android.gms.maps.SupportMapFragment"/>
</LinearLayout>

And below is my is my on create method for MapviewActivity.java

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    markerList = new ArrayList<Marker>();



    if (EvacRouteTableActivity.evacRouteStr !=null){
        fuelStopBundle = EvacRouteTableActivity.evacRouteStr;
        evacName = EvacRouteTableActivity.evacRouteStr;

    } else if (FuelStopActivity.type != null){
        fuelStopBundle = FuelStopActivity.type;
        shelorfuelAddress = FuelStopActivity.type;
    } else if (ShelterActivity.type != null){
        fuelStopBundle = ShelterActivity.type;
        shelorfuelAddress = ShelterActivity.type;
    }
    //List<EvacRoute> evacRouteList = new ArrayList<EvacRoute>(DALController.sharedInstance().getAllEvacRoutes());
    lm = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
    List<FuelStop> fuelStopList = new ArrayList<FuelStop>();
    List<Shelter> shelterList = new ArrayList<Shelter>();
    final boolean isGPS = lm.isProviderEnabled(LocationManager.GPS_PROVIDER); 
    setContentView(R.layout.activity_map_view);
    MapAsyncClass ac = new MapAsyncClass(MapViewActivity.this);
    ac.execute();
    Button btn_find = (Button) findViewById(R.id.btn_find);
    btn_directions = (Button) findViewById(R.id.btn_draw);
    // Getting reference to btn_find of the layout activity_main

    final EditText etLocation = (EditText) findViewById(R.id.et_location);
    if (isGPS){
        btn_find.setVisibility(View.GONE);
        etLocation.setVisibility(View.GONE);
    } else {
        btn_find.setVisibility(View.VISIBLE);

        etLocation.setVisibility(View.VISIBLE);     
        btn_directions.setVisibility(View.GONE);
    }


    //shelorfuelAddress = fuelStopBundle.getString("key");
    /**
     * This will make sure that if the user selects the 
     */

    if (fuelStopBundle != null && evacName != null){



        //showCurrentLocationOnMap();   


        // Defining button click event listener for the find button
        findClickListener = new OnClickListener() {
            @Override
            public void onClick(View v) {

                // Getting user input location
                String location = etLocation.getText().toString();


                if(location!=null && !location.equals("")){
                    currentLocation = getLocationFromAddress(location);

                    AsyncTask<String, Void, List<Address>> execute = new GeocoderTask().execute(location);
                    String latStr = String.valueOf(latitude);
                    String longStr = String.valueOf(longitude);

                    try {
                        evacRoute = DALController.sharedInstance().getEvacuationRoutewithoutgps(evacName, currentLocation, latStr, longStr);
                    } catch (ClientProtocolException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    } catch (URISyntaxException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    } catch (IOException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    } catch (ParserConfigurationException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    } catch (SAXException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                    showEvacuationRoute(evacRoute);
                }
            }
        };
  }
  showCurrentLocationOnMap();

  if (isGPS){
  // Defining button click event listener for the find button
      OnClickListener directionsClickListener = new OnClickListener() {
          @Override
          public void onClick(View v) {
              if (shelorfuelAddress!=null){
                  Intent intent = new Intent(android.content.Intent.ACTION_VIEW,    
                          Uri.parse("http://maps.google.com/maps?saddr=<"+latitude+">,<"+longitude+">&daddr=<"+currentFuelLat+">,<"+currentFuellong+">"));
                  startActivity(intent);
              } else {
                  LatLng destLatLng = DALController.sharedInstance().getDestPoint();        
                  Double latDouble = destLatLng.latitude;
                  Double longDouble = destLatLng.longitude;
                  Intent intent = new Intent(android.content.Intent.ACTION_VIEW,        
                          Uri.parse("http://maps.google.com/maps?saddr=<"+latitude+">,<"+longitude+">&daddr=<"+latDouble+">,<"+longDouble+">"));
                  startActivity(intent);                
              }


          }
      };
      btn_directions.setOnClickListener(directionsClickListener);
  }

  btn_find.setOnClickListener(findClickListener);

  /**
   * this ensures that if the user clicked on the Mapview from the MainActivity
   * that ten shelters and ten fueling points will show on the map
   */
  if (shelorfuelAddress==null && isGPS){


      // Setting button click event listener for the find button
      btn_find.setOnClickListener(findClickListener);
      fuelStopList = DALController.sharedInstance().getAllFuelStops();
      shelterList = DALController.sharedInstance().getAllShelters();
      if (fuelStopList == null){

      } else {
          for (FuelStop fuelStop : fuelStopList){


              try {
                  ShowFuelStop(fuelStop.getAddress());
              } catch (IOException e) {
                  e.printStackTrace();
              }
          }
      }

      for (Shelter shelter : shelterList){

          try {
              ShowShelters(shelter.getAddress());
          } catch (IOException e) {
              e.printStackTrace();
          }
      }      

  }

  mMenu = new CustomMenu(this, this, getLayoutInflater());
  mMenu.setHideOnSelect(true);
  mMenu.setItemsPerLineInPortraitOrientation(4);
  mMenu.setItemsPerLineInLandscapeOrientation(8);
  //load the menu items
  loadMenuItems();
}

Answer 1

I found with time the the map.clear() was working but objects where getting re added to the map because of the use of some of the global variables that I needed. So I had to do a map.clear() on the onResume() then do some object deallocation. Once I did this it worked, and actually deallocating the objects helped with garbage collection on the map as java has problems collecting items that still have a reference. See Code below.

@Override
public void onResume(){
    super.onResume();
    if (map != null){
        onCreateCalled += 1;
        if (onCreateCalled >=3){
            if (fuelPolyLine != null){
                fuelPolyLine.remove();
                fuelPolyLine = null;
                fuelStoprectLine = null;
            }
            if (shelterPolyLine != null){
                shelterPolyLine.remove();
                shelterPolyLine = null;
                shelterRectLine = null;
            }
            if (evacPolyLine != null){
                evacPolyLine.remove();
                evacPolyLine = null;
                evacRouteRectLine = null;
            }
            map.clear();
            currentLocation = null;
            map = null;
            markerOptions = null;
            evacRoute = null;
            lm = null;
            ll = null;
            mf = null;


            setupMap();

        }


    }
}

Answer 2

Use mapview.clear() than mapview.invalidate() . After every UI change you should call invalidate() on mapview.

Answer 3

       setContentView(R.layout.activity_map_view);

     //
       SupportMapFragment fm = (SupportMapFragment)getSupportFragmentManager().findFragmentById(R.id.map);
       map = fm.getMap();
       //