A suite of function modules that can be called effectively build and process the ALV-ed report output whichs allows a variety of functions to be included. Sorting, download, swapping around fields on the display and recording the layout settings are only a few of the possibilities. But don't start with the function module stuff when you're starting with ALV's. Skip function modules and step onto the Object Oriented train right away.
Once you are familiar with the basic ALV strength, you can build on it using Abap Objects. Screens can be composed as flight simulation cockpits, where the sky is the limit. Functionality such as hierarchy trees, context-sensitive functions and drag & drop can make your application turn heads..
So how does this work? The concept of Abap Objects with it's classes, methods and events is utilized to the level of true object oriented programming. This is a good way to get into Abap Objects... An ALV list can be set up quite easily, simply by instantiating a class for the ALV. The result will be a variabele defined as type ref to which needs to be placed somewhere. For every detail you would like to arrange, a local class definition can be set up (definition) and implemented (implementation) with minimum effort. The methods you like to define are set up as handler for the event you want to act on, such as user_command or double_click.
But these articles take things further than just the ALV list - several of these lists can be set up using a splitter - which devides the screen into area's for which seperate ALV's, tree's or web pages can be set up. Dragging and dropping stuff between the panels can also be done - which is something that is quite hard to establish in ABAP otherwise...