问题
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();
}
回答1:
Use mapview.clear() than mapview.invalidate() . After every UI change you should call invalidate() on mapview.
回答2:
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();
}
}
}
回答3:
setContentView(R.layout.activity_map_view);
//
SupportMapFragment fm = (SupportMapFragment)getSupportFragmentManager().findFragmentById(R.id.map);
map = fm.getMap();
//
来源：https://stackoverflow.com/questions/17354324/how-do-i-clear-the-map-of-all-points-and-markers-and-routes-when-switching-tabs