Introduction to ABAP event-driven programming in SAP ALV and its examples

In this day and age, with the advent of the Internet and all that it brings, program code must be able to interact and communicate with the end user. This is done in ABAP/4 using events invoked by user actions. Processing blocks are defined by the event keyword and thus executed when some related event is invoked. By default, events start-of-selectionare attached to all events in ABAP/4. In a program, you can define a processing block and attach this block to an event keyword. For generally easy-to-read code, it's best to define sequential processing blocks in order that are most likely to fire during select screen execution. It is also good practice to program selection screens with the most important events. These events are as follows: initial event initialization. Select screen events at selection-screen. user command event at user-command.

Use the initialization eventinitialization

For example, in the ALV report, if the user needs to select the screen event by default, the following code can be used:

When this program executes and a selection screen is defined for it, this processing block is executed initialization, setting the parameter field to the current date of the system at execution time s_crdat-high, s_crdat-lowto sales orders since January 1, 2022. In this event block, you can specify initial defaults for the selection screen, based on whatever conditions are needed to maintain the integrity of the data entered by the user. Some examples include setting title bars, assigning text elements to graphical user interface (GUI) elements, and function code states.

Select screen events at selection-screen

at selection-screen Events are handled after user input on the activity selection screen. This can happen when the user presses a function key or clicks a button, among many other elements that the user can interact with. In addition to data validation checks, at selection-screenevents can be used to invoke warning messages, GUI state changes, and even popups. For example the following code: Using user command events at user-command Buttons, along with many other event-driven selection screen options, are useful in maintaining user interaction and validating user input. In the next section, you'll explore how to use a button to invoke at user-commandthe event and see an example of how to use a button to handle user input. The following code shows selection-screen pushbutton the syntax for the event: selection-screen pushbutton example1 user-command 1234. This statement, at selection-screen when used with the command, is a great way to interact with the user as they enter data. The syntax is similar selection-screen comment, just passing the data when the user presses the button. The button press at selection-screen fires in the event sccrfields-ucomm, and imports the input field. This data can then be validated and a message can be emitted depending on the purpose of the button. The following example shows how to use two buttons to determine the language in which the selected data is reported.

In this example, you can use a case statement to check which of the two buttons the user pressed. When the user fires at user-command the event, the field sy-ucommholds the unique four-byte name of the item the user selected. This way you can code various data validations or command user input based on a combination of data entered and the item the user selects (in this case a button).