Restoring MapView's state on rotate and on back
Solution 1
Here is my fix to the first problem:
It seems that Map
is trying to unparcel all the bundle, not just it's own information when I call mMap.onCreate(savedInstanceState)
and it has problem with it if I'm using my custom Parcelable
class. The solution that worked for me was removing my extras from savedInstanceState
as soon as I used them - before I call Map's onCreate()
. I do it with savedInstanceState.remove(MY_KEY)
. Another thing I had to do was to call mMap.onSaveInstanceState()
before adding my own information to outState
in Fragment's
onSaveInstanceState(Bundle outState)
function.
And here's how I handled the second one:
I simplified the example project to the bare bones. I was adding raw Markers
to the map and if I replace the Fragment
with map with another one then after clicking "back" I still got "nulled" map.
So I did two things:
- saving
CameraPosition
inonPause()
function to restore it inonResume()
- setting
mMap
to null inonPause()
so when theFragment
comes back, theMarkers
are added again by theaddMapPoints()
function (I had to change it a little bit since I was saving and checkingMarkers
id's).
Here are code samples:
private CameraPosition cp;
...
public void onPause() {
mMapView.onPause();
super.onPause();
cp = mMap.getCameraPosition();
mMap = null;
}
...
public void onResume() {
super.onResume();
setUpMapIfNeeded();
mMapView.onResume();
if (cp != null) {
mMap.moveCamera(CameraUpdateFactory.newCameraPosition(cp));
cp = null;
}
}
And to update the camera position in onResume()
I had to manually initialize maps. I did it in setUpMap()
:
private void setUpMap() {
try {
MapsInitializer.initialize(getActivity());
} catch (GooglePlayServicesNotAvailableException e) {
}
mMap.setOnInfoWindowClickListener(this);
mMap.setOnMapLongClickListener(this);
addMapPoints();
}
I realize that those aren't real solutions - just overrides but it's the best I can do for now and the project must go on. If anyone finds cleaner fixes I'll be grateful for letting me know about them.
Solution 2
Came here in search of any hints regarding onSaveInstance
and NullPointerException
. I have tried various workarounds including the one mentioned by @Izydorr but have had no luck. The issue was with FragmentPagerAdapter
- the adapter of the ViewPager
that was hosting my fragments that were embedding the MapView
s. After having it changed to FragmentStatePagerAdapter
the NPEs have gone away. Whew!
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Izydorr
Updated on July 09, 2022Comments
-
Izydorr almost 2 years
Background
I have a larger application in which I had/have several problems with new Google Maps API. I tried to describe it in a different question but since it seems too complex I decided to start a new project, as simple as possible and try to reproduce problems. So here it is.
The situation
I'm using
Fragments
and want to putMapView
inside. I don't want to useMapFragment
. The sample project I prepared may be not very beautiful but I tried to make it as simple as possible and it had to contain some elements (again simplified) from the original app. I have oneActivity
and my customFragment
withMapView
in it, added programatically. TheMap
contains some points/Markers
. After clicking on aMarker
theInfoWindow
is shown and clicking on it causes nextFragment
being shown (withreplace()
function) in content.The problems
There are two issues I have:
When the
Map
withMarkers
is displayed screen rotation causesClass not found when unmarshalling
error with my customMyMapPoint
class - I have no idea why and what it means.I click the
Marker
and thenInfoWindow
. After this I press hardware back button. Now I can see theMap
but with noMarkers
and centered in0,0
point.
The code
MainActivity
public class MainActivity extends FragmentActivity { private ArrayList<MyMapPoint> mPoints = new ArrayList<MyMapPoint>(); @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); if (savedInstanceState == null) { mPoints.add(new MyMapPoint(1, new LatLng(20, 10), "test point", "description", null)); mPoints.add(new MyMapPoint(2, new LatLng(10, 20), "test point 2", "second description", null)); Fragment fragment = MyMapFragment.newInstance(mPoints); getSupportFragmentManager().beginTransaction() .add(R.id.contentPane, fragment).commit(); } } }
activity_main.xml
<?xml version="1.0" encoding="utf-8"?> <FrameLayout xmlns:android="http://schemas.android.com/apk/res/android" android:id="@+id/contentPane" android:layout_width="fill_parent" android:layout_height="fill_parent" />
map_fragment.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" > <com.google.android.gms.maps.MapView xmlns:map="http://schemas.android.com/apk/res-auto" android:id="@+id/map" android:layout_width="match_parent" android:layout_height="match_parent" /> </LinearLayout>
MyMapFragment
public class MyMapFragment extends Fragment implements OnInfoWindowClickListener { public static final String KEY_POINTS = "points"; private MapView mMapView; private GoogleMap mMap; private HashMap<MyMapPoint, Marker> mPoints = new HashMap<MyMapPoint, Marker>(); public static MyMapFragment newInstance(ArrayList<MyMapPoint> points) { MyMapFragment fragment = new MyMapFragment(); Bundle args = new Bundle(); args.putParcelableArrayList(KEY_POINTS, points); fragment.setArguments(args); return fragment; } @Override public void onSaveInstanceState(Bundle outState) { super.onSaveInstanceState(outState); mMapView.onSaveInstanceState(outState); MyMapPoint[] points = mPoints.keySet().toArray( new MyMapPoint[mPoints.size()]); outState.putParcelableArray(KEY_POINTS, points); } @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); if (savedInstanceState == null) { Bundle extras = getArguments(); if ((extras != null) && extras.containsKey(KEY_POINTS)) { for (Parcelable pointP : extras.getParcelableArrayList(KEY_POINTS)) { mPoints.put((MyMapPoint) pointP, null); } } } else { MyMapPoint[] points = (MyMapPoint[]) savedInstanceState .getParcelableArray(KEY_POINTS); for (MyMapPoint point : points) { mPoints.put(point, null); } } } @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { View layout = inflater.inflate(R.layout.map_fragment, container, false); mMapView = (MapView) layout.findViewById(R.id.map); return layout; } @Override public void onActivityCreated(Bundle savedInstanceState) { super.onActivityCreated(savedInstanceState); mMapView.onCreate(savedInstanceState); setUpMapIfNeeded(); addMapPoints(); } @Override public void onPause() { mMapView.onPause(); super.onPause(); } @Override public void onResume() { super.onResume(); setUpMapIfNeeded(); mMapView.onResume(); } @Override public void onDestroy() { mMapView.onDestroy(); super.onDestroy(); } public void onLowMemory() { super.onLowMemory(); mMapView.onLowMemory(); }; private void setUpMapIfNeeded() { if (mMap == null) { mMap = ((MapView) getView().findViewById(R.id.map)).getMap(); if (mMap != null) { setUpMap(); } } } private void setUpMap() { mMap.setOnInfoWindowClickListener(this); addMapPoints(); } private void addMapPoints() { if (mMap != null) { HashMap<MyMapPoint, Marker> toAdd = new HashMap<MyMapPoint, Marker>(); for (Entry<MyMapPoint, Marker> entry : mPoints.entrySet()) { Marker marker = entry.getValue(); if (marker == null) { MyMapPoint point = entry.getKey(); marker = mMap.addMarker(point.getMarkerOptions()); toAdd.put(point, marker); } } mPoints.putAll(toAdd); } } @Override public void onInfoWindowClick(Marker marker) { Fragment fragment = DetailsFragment.newInstance(); getActivity().getSupportFragmentManager().beginTransaction() .replace(R.id.contentPane, fragment) .addToBackStack(null).commit(); } public static class MyMapPoint implements Parcelable { private static final int CONTENTS_DESCR = 1; public int objectId; public LatLng latLng; public String title; public String snippet; public MyMapPoint(int oId, LatLng point, String infoTitle, String infoSnippet, String infoImageUrl) { objectId = oId; latLng = point; title = infoTitle; snippet = infoSnippet; } public MyMapPoint(Parcel in) { objectId = in.readInt(); latLng = in.readParcelable(LatLng.class.getClassLoader()); title = in.readString(); snippet = in.readString(); } public MarkerOptions getMarkerOptions() { return new MarkerOptions().position(latLng) .title(title).snippet(snippet); } @Override public int describeContents() { return CONTENTS_DESCR; } @Override public void writeToParcel(Parcel dest, int flags) { dest.writeInt(objectId); dest.writeParcelable(latLng, 0); dest.writeString(title); dest.writeString(snippet); } public static final Parcelable.Creator<MyMapPoint> CREATOR = new Parcelable.Creator<MyMapPoint>() { public MyMapPoint createFromParcel(Parcel in) { return new MyMapPoint(in); } public MyMapPoint[] newArray(int size) { return new MyMapPoint[size]; } }; } }
If you need to take a look at any other file - let me know. Here you can find a complete project, you just have to put your own Maps API KEY in
AndroidManifest.xml
file.EDIT
I managed to make the example even more simple and updated the code above.
-
darnmason almost 10 yearsCheers for your answer re the Map attempting to unparcel the whole Bundle, I implemented your suggestion ages ago, but recently added a
ViewPager
to my Fragment which caused theBadParcelableException
again. Turns out theViewPager
's saved state can't be unparcelled either as it's from the Support Library so I opted to copy the map state into a new Bundle instead of removing all the parcels I knew about, my answer is here: stackoverflow.com/a/24651246/1007151 -
Ruben2112 almost 7 yearsThis Interface is now deprecated. See here: stackoverflow.com/questions/38727517/…