Android hierarchical-list select/de-select popup activity

I need a user interface component launched as a popup activity (using call startActivityForResult() ) that takes a hierarchical data-structure and displays the hierarchy as a scrollable, selectable list with checkboxes. The hierarchical data structure is made up of a set of groups that themselves may have subgroups or items. Items and groups should be listed in depth-first order, and indented according to their level in the hierarchy (ie. siblings should all be indented by the same amount). Each group (parent) in the hierarchy should be expandable to show children or contractible to hide them. The user can select single leaves, or can select whole groups (which automatically checks all items under it). If a group does not have all its children selected, then the checkbox should be checked but displayed to show partial selection (see image_partial selection). The dialog should look like that shown below (see image_popup_listview) with the list displayed with checkboxes added. The expand/contract icon can be supplied as shown. None of the other dialog elements except the list itself are required. a simple ok button should be added to the bottom of the layout to test result return. When the user clicks 'Ok', the result that the popup activity returns should be the same hierarchical data structure with the 'selected' flag set on groups and leaves as selected by the user. The file [login to view URL] shows a bare-bones version of the datastructure to be supplied. getters and setters have been left out etc for brevity. You can code without getters/setters om the datastructure. These will be fixed on integration to the wider system.