Android Context not serializable dilemma for class that implements Iteratable

问题

Here is my situation. I have written a Playlist class that stores a context. Playlist has 9 child classes. Unfortunately, to pass Playlist between intents, it must implement Serializable. This is a problem because Playlist stores a context, so that the Iterator can work, as the Iterator method that must be Overridden from Iterator can not accept any parameters. Therefore, I must store Context somewhere as it is needed to determine the size of the Playlist. Here is the (simplified) code.

public abstract class Playlist implements Serializable, Iterable<Song>
    {
        private static final long serialVersionUID = 0L;

        private Context context;
        public Context getContext() { return context; }

        public Playlist(Context context)
        {
            this.context = context;
        }

        public abstract int size(); //getContext() referenced in all currently written children
        public abstract Song getSong(int index); //getContext() referenced in all currently written children

        @Override
        public PlaylistIterator iterator()
        {
            return new PlaylistIterator();
        }

        public class PlaylistIterator implements Iterator<Song>
        {
            private int current;

            PlaylistIterator()
            {
                current = 0;
            }

            @Override
            public boolean hasNext()
            {
                return current < size(); //SIZE HERE needs access to a context, but this method certainly can not take one, and neither can the constructor above.**
            }

            @Override
            public Song next()
            {
                if (!hasNext())
                    throw new NoSuchElementException();

                return getSong(current++);
            }

            @Override
            public void remove()
            {
                throw new UnsupportedOperationException();
            }
        }
    }

I have read that you can store a static context, but that this is poor design. I can not seem to find a way around this.

I have considered adding a static context reference that is assigned in writeObject, and then accessed in readObject, as the transition should be nearly instant because the Serialization implementation is only so that Playlist can be passed in an intent. But even this feels hacky.

Is there a common work around to dealing with the fact that we cannot serialize context? Is my solution acceptable in terms of stability? It might be against the rules, but what is your recommendation in this situation?

回答1:

I have written a Playlist class that stores a context

That's probably not a good idea.

Unfortunately, to pass Playlist between intents, it must implement Serializable

It could be Parcelable, but that does not solve your problem. A Context cannot go into either a Serializable or a Parcelable.

because Playlist stores a context, so that the Iterator can work,

That's probably not a good idea.

Therefore, I must store Context somewhere as it is needed to determine the size of the Playlist.

Or, the Playlist could hold the size of the playlist. An int is readily able to be used with Serializable or Parcelable.

Or, get rid of the Iterator, as that is not going to work well with Serializable or Parcelable either.

I can not seem to find a way around this.

Have Playlist be a pure model object, with no Context.

Or, depending on the use case, have Playlist be a singleton, using the Application as the Context. It is unclear whether there is only one Playlist or several.

but what is your recommendation in this situation?

Playlist should not hold a Context and should not have an Iterator.

来源：https://stackoverflow.com/questions/37231573/android-context-not-serializable-dilemma-for-class-that-implements-iteratable

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serialization