在GWT中保存活动状态

Question

I'm having hard times trying to figure out how the state of an activity can be saved in GWT, like in Android.

I mean, when an activity is going to be discarded how can we serialize its state somewhere and retrieve it when the activity is shown again ?

I've read the put into practice the following official guide
http://www.gwtproject.org/doc/latest/DevGuideMvpActivitiesAndPlaces.html
but it doesn't say anything about my problem.

Can you help ?

EDIT:

Now I'm wondering what's the use of Tokenizet getToken method is...

public static class Tokenizer implements PlaceTokenizer<HelloPlace> {
        @Override
        public String getToken(HelloPlace place) {

            return place.getHelloName();
        }

        @Override
        public HelloPlace getPlace(String token) {

            return new HelloPlace(token);
        }
    }

Answer 1

Activity should not have a state. A view has a state, and a view is not discarded when a user moves from place to place within an app.

For example, an activity can load the data and populate the corresponding view. It can also set a flag in a view, eg populated = true . Next time an activity starts it can check if the view is populated and act accordingly.

The need for such flags is dictated by your requirements. Sometimes users expect to see a refreshed data every time they visit a place. In other cases, it may not be necessary or practical.

EDIT:

Token is used to provide additional information to an activity about what a user expects to see in a view. For example, a view can display information about a blogger. Then a token may provide an id of a blogger that a user expects to see:

/#BloggerBio:12345

When BloggerBioActivity parses this token ("12345"), it knows to load the bio of a blogger with id=12345 and show it in the BloggerBioView.

When a user visits this view again, it is up to you what happens. You may refresh the view even if the token is the same, or you can compare the token to the id of a blogger shown in a view, and if it is the same, do nothing.