JNIHelper didn't find class that is there

[paulocoutinhox]

Hi,

Im trying call a static void method from Java class, but it throw error:

2024-04-28 16:22:08.929 27052-27145 JniHelper               com.game.app                   E  Failed to find static method id of performAction
2024-04-28 16:22:08.929 27052-27145 JniHelper               com.game.app                   E  Failed to find static java method. Class name: org.axmol.platform.PlatformDelegate, method name: performAction, signature: (Ljava/lang/String;Ljava/lang/String;J)V 

Java Class:

package org.axmol.platform;

import android.util.Log;

public class PlatformDelegate {

    public static void performAction(final String action, final long contextAddress) {
        Log.e("GAME", "Action: " + action);

        new Thread(() -> {
            String result = handleAction(action);
            nativeOnActionComplete(result, contextAddress);
        }).start();
    }

    private static String handleAction(String action) {
        try {
            Thread.sleep(1000);
        } catch (InterruptedException e) {
            Thread.currentThread().interrupt();
        }

        if (action.equals("checkSubscription")) {
            return "Subscribed";
        }

        return "Unknown Action";
    }

    public static native void nativeOnActionComplete(String result, long contextAddress);
}

C++ code:

void PlatformHelper::performAction(const std::string &action, std::function<void(std::string)> callback) {
    auto context = std::make_shared<PlatformHelperContext>(callback);
    auto contextAddress = new std::shared_ptr<PlatformHelperContext>(context);

    JniHelper::callStaticVoidMethod(
            "org.axmol.platform.PlatformDelegate",
            "performAction", "(Ljava/lang/String;J)V",
            action.c_str(),
            reinterpret_cast<jlong>(contextAddress)
    );
}

I use javap too to debug and it is there:

javap -s proj.android/app/build/intermediates/javac/debug/compileDebugJavaWithJavac/classes/org/axmol/platform/PlatformDelegate.class
Compiled from "PlatformDelegate.java"
public class org.axmol.platform.PlatformDelegate {
  public org.axmol.platform.PlatformDelegate();
    descriptor: ()V

  public static void performAction(java.lang.String, long);
    descriptor: (Ljava/lang/String;J)V

  public static native void nativeOnActionComplete(java.lang.String, long);
    descriptor: (Ljava/lang/String;J)V

What im doing wrong?

Thanks.

[smilediver]

Failed to find static java method. Class name: org.axmol.platform.PlatformDelegate, method name: performAction, signature: (Ljava/lang/String;Ljava/lang/String;J)V seems like the signature doesn't match, it's looking up with two string arguments (Ljava/lang/String;Ljava/lang/String;J)V.

[rh101]

The signature of callStaticVoidMethod is this:
static void callStaticVoidMethod(const char* className, const char* methodName, Ts&&... xs)

where Ts&&... xs should be the parameters that need to be received by the target method, so for performAction, it should just be a string, long, yet the code posted shows this:

JniHelper::callStaticVoidMethod(
        "org.axmol.platform.PlatformDelegate",
        "performAction", "(Ljava/lang/String;J)V",
        action.c_str(),
        reinterpret_cast<jlong>(contextAddress)
);

which is JniHelper::callStaticVoidMethod(className, string, string, string, long). You've accidentally added the java method performAction signature in the call, so change it to this and try again:

JniHelper::callStaticVoidMethod(
        "org.axmol.platform.PlatformDelegate",
        "performAction",
        action.c_str(),
        reinterpret_cast<jlong>(contextAddress)
);

If you review the implementation of callStaticVoidMethod, you will see that it automatically builds the type signature of the java method based on the passed in parameter types.

[paulocoutinhox]

My mistake :(

I don't know where i see that i need the signature.

Thanks.