HEELP

[suprohub]

10-31 19:45:41.736 10253 10253 F DEBUG : Abort message: 'JNI DETECTED ERROR IN APPLICATION: JNI NewGlobalRef called with pending exception java.lang.ClassNotFoundException: Didn't find class "org.astonbitecode.j4rs.api.dtos.InvocationArg"

[suprohub]

i get this error on android

[suprohub]

i use jni onload and attach thread but if i try create instance i get this error

[astonbitecode]

Something seems to be wrong with your classpath. It seems the j4rs classes are not found and cannot be loaded.

How do you setup your Android app? Is it a Java application that calls Rust native code?
If so, have you checked the example project here?

There should not be any classloading issues if:

1. You specify the j4rs dependency in the Gradle (or Maven).
2. You have a JNI_OnLoad where you set the JavaVM.
3. You load the native library in Java.
4. You attach the thread and create the InvocationArg.

[suprohub]

Something seems to be wrong with your classpath. It seems the j4rs classes are not found and cannot be loaded.

How do you setup your Android app? Is it a Java application that calls Rust native code? If so, have you checked the example project here?

There should not be any classloading issues if:

1. You [specify](https://github.com/astonbitecode/j4rs-android-test/blob/58fb959dc83e8fa3d1dbfb3f073e2ee4c5c1c493/app/build.gradle#L37) the `j4rs` dependency in the Gradle (or Maven).

2. You have a `JNI_OnLoad` where you [set the `JavaVM`](https://github.com/astonbitecode/j4rs-android-test/blob/58fb959dc83e8fa3d1dbfb3f073e2ee4c5c1c493/j4rstestnative/src/lib.rs#L9).

3. You [load](https://github.com/astonbitecode/j4rs-android-test/blob/58fb959dc83e8fa3d1dbfb3f073e2ee4c5c1c493/app/src/main/java/com/example/j4rstest/RustFunctionCalls.java#L15) the native library in Java.

4. You [attach](https://github.com/astonbitecode/j4rs-android-test/blob/58fb959dc83e8fa3d1dbfb3f073e2ee4c5c1c493/j4rstestnative/src/lib.rs#L25) the thread and [create](https://github.com/astonbitecode/j4rs-android-test/blob/58fb959dc83e8fa3d1dbfb3f073e2ee4c5c1c493/j4rstestnative/src/lib.rs#L29) the `InvocationArg`.

not works

[suprohub]

i attach tread, add this to dependencies, load libary and only crashes

[suprohub]

                    if textedit.gained_focus() {
                        let jvm = Jvm::attach_thread().unwrap();
                        let instance = jvm.create_instance(
                            "pumpkin_egui_android.MainActivity",
                            InvocationArg::empty()
                        ).unwrap();
                        jvm.invoke(
                            &instance,
                            "openKeyboard",
                            InvocationArg::empty()
                        ).unwrap();
                    }

[suprohub]

  public void openKeyboard() {
    InputMethodManager imm =
            (InputMethodManager) getSystemService(Context.INPUT_METHOD_SERVICE);
    if (imm != null) {
        imm.toggleSoftInput(InputMethodManager.SHOW_FORCED, 0);
    }
  }```

[suprohub]

plugins {
    id 'com.android.application'
}

android {
    namespace "local.pumpkin_egui_android"
    compileSdk 33

    defaultConfig {
        applicationId "local.pumpkin_egui_android"
        minSdk 28
        targetSdk 33
        versionCode 1
        versionName "1"
    }

    buildTypes {
        debug
    }
    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }
}

dependencies {
    implementation 'com.google.android.material:material:1.5.0'
    implementation "androidx.games:games-activity:2.0.2"
    implementation 'io.github.astonbitecode:j4rs:0.20.0'
}

[astonbitecode]

I have just tested the example using the latest j4rs without issues.

When do you call the System.loadLibrary?
At the time it is called, the JNI_OnLoad is called and you should have there:

j4rs::set_java_vm

[suprohub]

I have just tested the example using the latest j4rs without issues.

When do you call the System.loadLibrary?
At the time it is called, the JNI_OnLoad is called and you should have there:

j4rs::set_java_vm

I call it from static in class, its needed for egui, set java vm i call too

[astonbitecode]

Do you maybe have some code to share?

[suprohub]

https://github.com/suprohub/Pumpkin/tree/android

[suprohub]

Go to pumpkin egui

[astonbitecode]

I am having difficulties to understand the setup of the project.

I see that you define a MainActivity in your AndroidManifest, but using also game-activity.

How do you build your project, create the apk and run it?

EDIT: One more question: Have you verified that JNI_OnLoad is indeed called?

[suprohub]

Cargo ndk then gradle build

[suprohub]

Cargo ndk then gradle build
How verify what jni on load is called?

[suprohub]

And i want help: what the bestethod: construct main activity for call method or inline method?

[suprohub]

Like call all method code in rust

[suprohub]

See makefile

[astonbitecode]

How verify what jni on load is called?

Using some logging I guess

construct main activity for call method or inline method?

As you see in the example project mentioned above, currently, the supported way is to implement the main activity in Java, use JNI_OnLoad and call the native method from Java to Rust.

I am also investigating "rust-only" ways, using native-activity, but there are currently classloading issues we need to overcome...

[suprohub]

Yeah its setted

[suprohub]

[suprohub]

I dont know what its wrong

[suprohub]

[suprohub]

But gradle build works

[suprohub]

Any updates?

[suprohub]

Helo?

[astonbitecode]

How does the app load the activity? Is the native activity used, or the activity you implemented?

You can open the apk and inspect:

1. Which Activity is it used? (android:name element)
2. Do j4rs classes exist inside .dex files? If the classes are not there, check if code shrinking is enabled. You should configure which code to keep in that case. Configuring proper keep rules is important because the code shrinker might otherwise remove classes, methods, or fields that are only used from JNI. (source)

[astonbitecode]

Implemented the ability to use j4rs along with android-activity.
I will soon update the README with instructions how to do it. In a nutshell, you should be able to pass to j4rs the JavaVM and the NativeActivity jobject and overcome the classloading issues:

let jvm = JvmBuilder::new()
        .with_java_vm(java_vm.clone())
        .with_classloader_of_activity_(activity_obj.clone())
        .build()?;

[astonbitecode]

For more details, please see this example project.