Image gallery with "select folder" option

I have installed a number of apps that have their own image gallery functionality (not using another app via intents). The default view is usually a list of the folders in my SD card that contain images (usually with some kind of thumbnail representing the folder), and then when I drill down into one of these folders they display the thumbs of the images that the folder contains.

Is the folder list part of the MediaStore api, or are the developers doing this manually (query the 开发者_开发知识库file system for a list of folders, scan files in folder for common image extensions, etc)? The tutorials I'm finding online for creating an image gallery using the MediaStore api usually just query the whole SD card and fill a GridView with a Cursor returned from managedQuery. Are there better tutorials and documentation for making a custom image gallery?