How to convert Hashmap to String to save in SQLite data base?

I need to find a way of saving a HashMap to string to save in my SQLite database to retrieve on a later stage.

Here is my HashMap:

private Map<String, Bitmap> myMarkersHash new HashMap<String, Bitmap>();

Then when saving to the SQlite database:

contentValues.put(LocationsDB.FIELD_HASH, myMarkersHash);

But the problem is i get an error under put at contentValues.put with this error:

The method put(String, String) in the type ContentValues is not applicable for the arguments (String, Map<String,Bitmap>)

So my question is how can i convert that to a string so that i can save it into my sqlite database?

Thanks