| 摘要 |
A navigation manager component cooperable with a user interface renderer is described. The navigation manager manages one or more navigation units and maintains a navigation unit cursor. Each navigation unit is associated with another navigation unit managed by the same navigation manager. The navigation manager provides a range of navigation services, which operate upon the navigation unit cursor. These services include a service to navigate forwards and a service to navigate backwards. These services take into account the associations between navigation units in order to determine the correct sequence of navigation units for forwards and backwards navigation. The services also determine whether the items represented by each navigation unit include eligible items or items for which data entry is incomplete. In this way, navigation units for which all the items represented by the navigation unit are ineligible can be passed over by the navigation services, to that they never become current. |
