How to serialize a Bundle?

Question

I'd like to serialize a Bundle object, but can't seem to find a simple way of doing it. Using Parcel doesn't seem like an option, since I want to store the serialized data to file.

Any ideas on ways to do this?

The reason I want this is to save and restore the state of my activity, also when it's killed by the user. I already create a Bundle with the state I want to save in onSaveInstanceState. But android only keeps this Bundle when the activity is killed by the SYSTEM. When the user kills the activity, I need to store it myself. Hence i'd like to serialize and store it to file. Of course, if you have any other way of accomplishing the same thing, i'd be thankful for that too.

Edit: I decided to encode my state as a JSONObject instead of a Bundle. The JSON object can then be put in a Bundle as a Serializable, or stored to file. Probably not the most efficient way, but it's simple, and it seems to work ok.

Answer 1

I use SharedPreferences to get around that limitation, it uses the same putXXX() and getXXX() style of storing and retrieving data as the Bundle class does and is relatively simple to implement if you have used a Bundle before.

So in onCreate I have a check like this

if(savedInstanceState != null)
{
    loadGameDataFromSavedInstanceState(savedInstanceState);
}
else
{
    loadGameDataFromSharedPreferences(getPreferences(MODE_PRIVATE));
}

I save my game data to a Bundle in onSaveInstanceState(), and load data from a Bundle in onRestoreInstanceState()

AND

I also save game data to SharedPreferences in onPause(), and load data from SharedPreferences in onResume()

onPause()
{
    // get a SharedPreferences editor for storing game data to
    SharedPreferences.Editor mySharedPreferences = getPreferences(MODE_PRIVATE).edit();

    // call a function to actually store the game data
    saveGameDataToSharedPreferences(mySharedPreferences);

   // make sure you call mySharedPreferences.commit() at the end of your function
}

onResume()
{
    loadGameDataFromSharedPreferences(getPreferences(MODE_PRIVATE));
}

I wouldn't be surprised if some people feel this is an incorrect use of SharedPreferences, but it gets the job done. I have been using this method in all my games (nearly 2 million downloads) for over a year and it works.

Answer 2

storing any Parcelable to a file is very easy:

FileOutputStream fos = context.openFileOutput(localFilename, Context.MODE_PRIVATE);
Parcel p = Parcel.obtain(); // i make an empty one here, but you can use yours
fos.write(p.marshall());
fos.flush();
fos.close();

enjoy!