Tomorrow spent 30 points to study this:
If you know a BADI name, you can:
1) Use SE18, enter the Badi name, select Interface, and then check the corresponding interface embodiment code (Example Implementation Clasee)
2) Use SE19 to implement the BADI interface (the first time the interface must be created to create the create imagentation))
SE18 is used for creating BADI Definition
SE 19 is used for implementing BADI
i.e BADI Implementation
The definition can be created through SE18
Implementation will be done through SE19.
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BADI Definition.
1).Start transaction SE18 and give the BADI name.
2)Now you will see the methods and parameters used in that BADI.
3)Now you have to choose the appropriate method in the BADI.
4)The import parameters within the methods will contain the runtime values.
BADI Implementation
1)Now start transaction SE19 and give the implementation name.
2)Now you can see implementation linked with the BADI and also the class for the implementation will be displayed.
3)When you double click on the method it will take you to the editor where you will be coding.
4)Now the BADI should be activated.
5)Also the BADI can be deactivated using deactivate button.
Reprinted: https://www.cnblogs.com/rainysblog/p/6555788.html