Virtual List Views
Original Publication Date: 2004-Dec-25
Included in the Prior Art Database: 2004-Dec-25
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The Traffic Control Application (Client Server) has to display/load from the Data Base large amount of data in an acceptable time for the operator. This operation is very time consuming and, due to the amount of data to be processed, the necessary time to display the requested data is not acceptable. Up to now, the operator has to wait until all the data to display is processed, the view with the requested data is only available when all the data is loaded. A new concept of a virtual list has been created. The virtual list view uses a mechanism that works on a virtual load policy. This means that only the items that are be seen at the moment are loaded. Through user's navigation, additional items are loaded as they are made visible. With this policy, having few or large amounts of items, it will not constrain the time for display a subset of items. By using the virtual list, the filter is set defined at the time view if a view is opened or is refreshed by pressing the F5 key. With this information only the items, which satisfy the filter requirements are visualized. Before retrieving the items, it calculates the number of items necessary to fill the visible part of the view and the total number of existing items. Then, the items are inserted in the view and the vertical scroll bar is adjusted based on the total number of existing items. The user can drag the scrollbar thumb up or down or press on the arrow buttons of the scroll bar to navigate through the items. When the operator drops the scrollbar thumb or presses the arrow buttons, the system calculates the new items that have to be loaded. Next, the view is cleaned and the new visible items are inserted. Finally, the view state member variables - total number of items and the index of the last item loaded - are updated and the scroll bar position is adjusted.