mobile-app/rust-adapter/build.rs

 use std::path::Path;
 use std::env;

 fn main() {
     env::set_var("RUST_LOG", "DEBUG");

     let source_folder = "/mnt/extramedia3/mbess/workspace/popequer/android_app/rust-adapter/src"; //use your projects folder
     let out_file = "/mnt/extramedia3/mbess/workspace/popequer/android_app/rust-adapter/glue.rs";
     rifgen::Generator::new(rifgen::TypeCases::CamelCase, rifgen::Language::Java,source_folder)
        .generate_interface(out_file);

    let swig_gen = flapigen::Generator::new(flapigen::LanguageConfig::JavaConfig(
        flapigen::JavaConfig::new(
            Path::new("../app")
                .join("src")
                .join("main")
                .join("java")
                .join("net")
                .join("mbess")
                .join("popequer"),
            "net.mbess.popequer".into(),
        )
        .use_null_annotation_from_package("androidx.annotation".into()),
    ))
    .rustfmt_bindings(true);

    let out_dir = env::var("OUT_DIR").unwrap();
    let in_src = Path::new("./").join("glue.rs");
    let out_src = Path::new(&out_dir).join("java_glue.rs");
    swig_gen.expand("android bindings", &in_src, &out_src);
 }