When to use a Content Provider

I would argue it is definitely a good idea to use a ContentProvider even if you don't intend to make it public.

It's good practice to provide the extra level of abstraction over your data to make it easier to change internally. What if you decide to change the underlying database structure at a later time? If you use a ContentProvider you can contain all the structural changes within it, where as if you don't use one, you are forced to change all areas of the code that are affected by the structural changes. Besides, it's nice to be able to re-use the same standard API for accessing data rather than littering your code with low-level access to the database.

Also, there is always the chance that you might want to expose your data in the future. If you don't use a ContentProvider up front, it will be much harder to retrofit it in at a later date.

Then, there's the other parts of the Android where ContentProvider's are required/recommended such as when using SyncAdapters and if you want an App Widget that involves data access for instance.

In summary, there is very little overhead involved in writing a ContentProvider up front (once you have learned the API which is a good idea anyway) so it makes sense to do so, even for private data.

If you are not planning to share data, don't think about Content Providers. They are powerful but hard to write and it will be just silly to implement them if you are going to use them internally.

However, I'm wondering if anyone has thoughts about making a Content Provider to use just within your own app.

Of course... for instance, for an old TODO list app I wrote, I had to write a content provider to allow other apps retrieve and access the tasks states. It was part of the requirements, but more than that it made sense and made the app nicer.

Take a look at the MOTODEV Studio for Eclipse. It is a development environment that extends Eclipse. They have a tool where you can automatically generate a content provider for a database. If a content provider makes it easier to access your data and it doesn't have a significant impact on performance go ahead and use it. In most scenarios this will be the case.