Fixes: #3550 ; Add hello-world Android Java Example using Mill

[himanshumahajan138]

Description

This PR fixes #3550 by adding a "hello-world" Android Java example using Mill.

Changes:

• Created 1-hello-world folder inside example/javalib/android
  • This folder contains a src folder for sources and a build.mill file.
• Created two modules:
  • AndroidSdkModule.scala: This module handles the SDK setup.
  • AndroidAppModule.scala: This module extends both AndroidSdkModule and JavaModule to ensure proper functionality.
• In build.mill, extended the App module for building the Android application.
• android_examples.adoc created and referred in navbar.adoc, finally tested.
• Documentation done for android modules and build.mill and finally tested
• Code is fully documented with references taken from example/{javalib,kotlinlib,scalalib} and scalalib/{Modules...}.
• All the Documentation is checked locally (worlking as expected for scaladoc{AndroidAppModule, AndroidScalaModule})
• Documentation and explanation of the code are embedded as comments within the code.
• Included a screenshot of the application to demonstrate its functionality.

Type of Change

• New feature (non-breaking change which adds functionality)

Related Issues

issue #3550

Testing

Tested by building the Android app using Mill, ensuring that both the AndroidSdkModule and AndroidAppModule work together as expected. Successfully generated the APK and verified the "Hello World" functionality.

Checklist

• Created 1-hello-world folder with build.mill and sources
• Created two modules AndroidAppModule.scala and AndroidSdkModule.scala
• Created documentation file android_examples.adoc, above two modules also done.
• Code builds and passes all tests.
• Documentation Tested with local doc's creation
• I have added comments in the code where necessary, updated the documentation accordingly.
• Any dependent changes have been merged and published.

Additional Notes

Feel free to review the code and let me know if any further improvements are needed.

Screenshots

[himanshumahajan138]

@lihaoyi Sir please don't get irritated by my doubts(i am newbie) please clear my last doubt...

basically when i reviewed Json files(allSources.json, allSourceFiles.json .....so on) in the out folder:

allSources.json

{
    "value": [
        "ref:v0:c984eca8:/home/himanshu138/opensource/himanshu/mill/out/example/javalib/android/1-hello-world/local/testCached.dest/sandbox/run-1/app/src"
    ],
    "valueHash": -2002708993,
    "inputsHash": 1715811750
}

allSourceFiles.json

{
    "value": [],
    "valueHash": 1467096776,
    "inputsHash": 435515105
}

so after this i came to know that even JavaModule is unable to pick up my src files because it is also get path added with app becoz of which i am getting error of no source files and then i checked all previous examples/javalib/ and found this :

object `package` extends RootModule with JavaModule {...}

and when i tried this same thing then i got shocked this time it got the files and sources, see:

what i tired
object `package` extends RootModule with AndroidAppModule {...}

allSources.json
{
    "value": [
        "ref:v0:49c3a842:/home/himanshu138/opensource/himanshu/mill/out/example/javalib/android/1-hello-world/local/testCached.dest/sandbox/run-1/src"
    ],
    "valueHash": -1645131398,
    "inputsHash": 1044320490
}

allSourceFiles.json
{
    "value": [
        "ref:v0:60186141:/home/himanshu138/opensource/himanshu/mill/out/example/javalib/android/1-hello-world/local/testCached.dest/sandbox/run-1/src/main/java/com/helloworld/app/MainActivity.java"
    ],
    "valueHash": -249522556,
    "inputsHash": -470604943
}

Final Verdict: we also need to use package and make androidApp as a RootModule object

please share your thoughts and suggestions...

[lihaoyi]

Yes the filesystem hierarchy has to match the module hierarchy

[himanshumahajan138]

Yes the filesystem hierarchy has to match the module hierarchy

Thanks Alot Sir finally now i got answers to all of my doubts...

[himanshumahajan138]

@lihaoyi Thankyou Sir for the detailed feedback!

I’ve addressed all the requested changes and resolved the comments. Please let me know if anything else needs attention.

Please pardon me if I missed anything or made a mistake. Looking forward to your final review and any further suggestions!