There was a surprisingly acrimonious discussion about this, in the Android Developer’s Google Group, recently. Apparently the topic can be confusing.
The issue is that developers occasionally find themselves in need of a singleton. As a pattern, I would say that use of singletons has pretty well been discredited (see, e.g., WhySingletonsAreControversial ). Still, in Android, in a muli-activity application, it is entirely likely that there will be shared data and the desire to store that shared data in some place that is accessible to all application activities.
The problem with Singletons is that they really don’t exist. An instance of some kind of state is only a singleton within some context. A “singleton” on your phone is, clearly, not the same as the instance of the same singleton on my phone. It is even possible that the instance of the singleton on my phone this morning isn’t the same…
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