碎片化newInstance保存到捆绑的太多数据-android.os.TransactionTooLargeException

Question

I have created fragment standard way (skeleton generated by Android Studio). So I have newInstance static method:

public static EventsMapFragment newInstance(List<Event> eventList, String accessToken, String tokenType, String cityId, boolean isMessage)
{
     Bundle args = new Bundle();
     args.putString("events", new Gson().toJson(eventList));
     EventsMapFragment fragment = new EventsMapFragment();

     ///...........
     fragment.setArguments(args);
     return fragment;
}

Then in, onCreate override I need to retrieve my collection, quite standard way:

 @Override
 public void onCreate(Bundle savedInstanceState)
 {
    super.onCreate(savedInstanceState);
    if (getArguments() != null)
    {
        String json = getArguments().getString("events");
        Type type = new TypeToken<List<Event>>(){}.getType();
        mEventList = new Gson().fromJson(json, type);
   }

The problem is that eventList collection is very large, so I'm getting exception:

java.lang.RuntimeException: android.os.TransactionTooLargeException: data parcel size 592196 bytes

somewhere else in my app (weird, json is passed correctly, but system does not allow to pass anything more to bundle, it was not ease to track where exact problem is).

Because newInstance() method is static, I am unable to create retain fragment and pass data into it (I actually have no idea how to do that in this case).

My solution is to use WeakReference to pass data, something like that:

public class DataHolder
{
    private static final DataHolder holder = new DataHolder();
    Map<String, WeakReference<Object>> data = new HashMap<>();

    public static DataHolder getInstance() {return holder;}

    public void save(String id, Object object)
    {
        data.put(id, new WeakReference<>(object));
    }

    public Object retrieve(String id)
    {
        WeakReference<Object> objectWeakReference = data.get(id);
        return objectWeakReference.get();
    }
}

Then, to store data (instead of using bundle):

DataHolder.getInstance().save("eventList", eventList);

And to retrieve data:

mEventList = (List<Event>) DataHolder.getInstance().retrieve("eventList");

However, this does not work on KitKat (it seems to be working fine on 5.1 and newer). Main trouble I am unable to debug on KitKat, because of multidex, so debug compilation won't even run on KitKat (release has minifyEnabled=true and no multi dex). But it seems, on KitKat, this:

mEventList = (List<Event>) DataHolder.getInstance().retrieve("eventList");

is always null.

Do you have any ideas? My current solution is to check build version and pass json to bundle on KitKat (it works on KitKat, problem is 7.0 and newer) and use WeakReference on newer Android versions.

But I'm actually not happy with this.

[edit] So my last try is to get events collection from parent activity. In main activity, I have following code (one app drawer menu click):

if (menuId == R.id.nav_events_map)
{
  eventsToDraw =  Lists.newArrayList(Collections2.filter(events,x->!Utils.isGeojsonEmpty(x.getGeojson())));
  //....................
  if(eventsToDraw.size() >0)
  {
    mFragment = EventsMapFragment.newInstance();
    ReplaceFragment(mFragment);
  }
  else
  {
   mFragment = NoDataFragment.newInstance(getString(R.string.message_no_events));
   ReplaceFragment(mFragment);
 }
}

eventsToDraw is private field, I have simply created getter:

public List<Event> getEventsToDraw()
{
  return eventsToDraw;
}

Then, inside my map fragment:

@Override
 public View onCreateView(@NonNull LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
 {
  //Map initialization stuff
  //....................

   mEventList = ((MainActivity)getActivity()).getEventsToDraw();

  //Draw on map stuff etc
 }

The problem is that I'm always getting mEventList null. After some debugging, I noticed, that getEventsToDraw() is called to early, so it won't return my collection, it returns null, because there are no data available yet.

Answer 1

it works on KitKat

No, it does not. The 1MB IPC transaction limit has existed for many years. However, that limit is for all simultaneous IPC transactions for your process, and so failures will be probabilistic. For example, 592196 is less than 1MB, so what crashed for you may actually make it through OK sometimes, because there happens to be little else going on with IPC at that moment in time.

So I have newInstance static method

Don't pass a collection of events. Pass the barest minimum information necessary for the fragment to get back that collection of events. Use a process-level POJO cache to minimize redundant I/O, but support hitting the database/network/whatever again if needed, so you handle both configuration changes (process cache is still around) and process termination (but where the user returns to your task fairly quickly, so the instance stat is still used).