Android Tutorial [B4X] #CustomBuildAction

The #CustomBuildAction attribute allows running external programs during the compilation process.
The syntax is:

#CustomBuildAction <compilation step>, command to run, zero or more arguments

It is related to the comment links and #Macro features https://www.b4x.com/android/forum/threads/b4x-comment-links.119897/. it uses a simpler syntax.

Example from B4XPages template, that copies the updated "shared files" to the platform specific Files folder during compilation, after the project folders are created if needed:

#CustomBuildAction: folders ready, %WINDIR%\System32\Robocopy.exe,"..\..\Shared Files" "..\Files"

The following compilation steps are available:

B4X

1 - no reason to use. Before the cleaning step. Use "folders ready" instead.
folders ready - after the code is parsed and the folders tree is ready.

B4A

2 - before the "Compiling resources (aapt2)" step
3 - before the "Signing AAB file" step
after packager - after the "Signing AAB file" step
4 - before the installation step
5- after the installation step

B4J

2 - before the compiled program is run
3 - after a library was compiled
before packager - before the standalone package process starts
after packager - after a standalone package was built

Command variables

The following variables can be used (same as with comment links and #Macro):
Environment variables (%WINDIR%, etc.)
%PROJECT% - project path, where the main project file is located.
%B4X% - IDE folder
%JAVABIN% - Java bin folder
%PROJECT_NAME% - project name based on the main project file.
%ADDITIONAL% - additional libraries folder
%B4J_PYTHON% (B4J only) - global Python folder, as set under Tools - Configure Paths

Notes

- The commands root path is the project's Objects folder.
- Multiple actions can be added during the same compilation step.
- CustomBuildActions are not executed when building from the command line.