自定义Gluon Attach插件中Java Runnable的JNI传递调用异常

背景 #

开发自定义Gluon Attach插件时，尝试将Java Runnable对象作为native方法showSaveAlert3的参数从Java层传递到JNI层，Native侧调用该Runnable时持续报错：

JNI DETECTED ERROR IN APPLICATION: JNI ERROR (app bug):  
jobject is an invalid JNI transition frame reference: 0x8000000000000008  

代码概览 #

Java类1（AndroidAlertDialogService） #

package com.gluonhq.attachextended.alertdialog.impl;

import com.gluonhq.attachextended.alertdialog.AlertDialogService;

public class AndroidAlertDialogService implements AlertDialogService {

    static {
        System.loadLibrary("alertdialog");
    }

    @Override
    public void showSaveAlert(String title, String content, Runnable r) {
        showSaveAlert3(title, content, r);
    }

    private native static void showSaveAlert3(String title, String content, Runnable r);
}

JNI代码（alertdialog.c） #

#include "util.h"

static jclass jAlertDialogServiceClass;
static jobject jDalvikAlertDialogService;

static jmethodID jAlertDialogServiceShowSaveAlert3Method;

static void initializeAlertDialogDalvikHandles() {
    jAlertDialogServiceClass = GET_REGISTER_DALVIK_CLASS(jAlertDialogServiceClass, "com/gluonhq/helloandroid/DalvikAlertDialogService");
    
    ATTACH_DALVIK();
    jmethodID jAlertDialogServiceInitMethod = (*dalvikEnv)->GetMethodID(dalvikEnv, jAlertDialogServiceClass, "<init>", "(Landroid/app/Activity;)V");

    jAlertDialogServiceShowSaveAlert3Method = (*dalvikEnv)->GetMethodID(dalvikEnv, jAlertDialogServiceClass, "showSaveAlert3", "(Ljava/lang/String;Ljava/lang/String;Ljava/lang/Runnable;)V");
    
    jobject jActivity = substrateGetActivity();
    jobject jObj = (*dalvikEnv)->NewObject(dalvikEnv, jAlertDialogServiceClass, jAlertDialogServiceInitMethod, jActivity);
    jDalvikAlertDialogService = (*dalvikEnv)->NewGlobalRef(dalvikEnv, jObj);
    DETACH_DALVIK();
}

//////////////////////////
// From Graal to native //
//////////////////////////

JNIEXPORT jint JNICALL
JNI_OnLoad_alertdialog(JavaVM *vm, void *reserved)
{
    JNIEnv* graalEnv;
    ATTACH_LOG_INFO("JNI_OnLoad_alertdialog called");
#ifdef JNI_VERSION_1_8
    if ((*vm)->GetEnv(vm, (void **)&graalEnv, JNI_VERSION_1_8) != JNI_OK) {
        ATTACH_LOG_WARNING("Error initializing native AlertDialog from OnLoad");
        return JNI_FALSE;
    }
    ATTACH_LOG_FINE("[AlertDialog Service] Initializing native AlertDialog from OnLoad");
    initializeAlertDialogDalvikHandles();
    return JNI_VERSION_1_8;
#else
    #error Error: Java 8+ SDK is required to compile Attach
#endif
}

// from Java to Android

JNIEXPORT void JNICALL Java_com_gluonhq_attachextended_alertdialog_impl_AndroidAlertDialogService_showSaveAlert3  
(JNIEnv *env, jclass jClass, jstring jtitle, jstring jcontent, jobject jr) {  
    const char *titleChars = (*env)->GetStringUTFChars(env, jtitle, NULL);  
    const char *contentChars = (*env)->GetStringUTFChars(env, jcontent, NULL);  

    ATTACH_DALVIK();  
    jstring jTitleString = (*dalvikEnv)->NewStringUTF(dalvikEnv, titleChars);  
    jstring jContentString = (*dalvikEnv)->NewStringUTF(dalvikEnv, contentChars);  

    jobject globalRunnable = (*dalvikEnv)->NewGlobalRef(dalvikEnv, jr);  
    jclass rClass = (*dalvikEnv)->GetObjectClass(dalvikEnv, globalRunnable);  

    jmethodID midMyCustomMethod = (*dalvikEnv)->GetMethodID(dalvikEnv, rClass, "run", "()V");  
    (*dalvikEnv)->CallVoidMethod(dalvikEnv, jDalvikAlertDialogService, jAlertDialogServiceShowSaveAlert3Method, jTitleString, jContentString, midMyCustomMethod);  

    DETACH_DALVIK();  
    (*env)->ReleaseStringUTFChars(env, jtitle, titleChars);  
    (*env)->ReleaseStringUTFChars(env, jcontent, contentChars);  
}

Java类2（DalvikAlertDialogService） #

package com.gluonhq.helloandroid;

import android.app.AlertDialog;
import android.content.DialogInterface;
import android.app.Activity;

public class DalvikAlertDialogService {

    private final Activity activity;

    public DalvikAlertDialogService(Activity activity) {
        this.activity = activity;
    }

    public void showSaveAlert3(String title, String content, Runnable r) {
        activity.runOnUiThread(() -> {
            if (!activity.isFinishing()) {
                AlertDialog.Builder dialog = new AlertDialog.Builder(activity);
                dialog.setCancelable(false);
                dialog.setTitle(title);
                dialog.setMessage(content);
                dialog.setPositiveButton("Ok", (DialogInterface dialog1, int id) -> {
                    dialog1.dismiss();
                    r.run();
                });

                AlertDialog alert = dialog.create();
                alert.show();
            }
        });
    }
}

已尝试方案 #

• 使用NewGlobalRef创建Runnable对象的持久引用后再调用其run方法。
• 检查Dalvik环境（dalvikEnv）的有效性。
• 查阅Gluon Attach现有插件（如DisplayService、StorageService）源码，但这些示例主要关注字符串、基本类型或数组的传递，未涉及Runnable这类复杂Java对象。

问题说明 #

尽管做了上述尝试，仍无法调用Runnable的run()方法，jobject引用在JNI环境中似乎失效，导致上述错误。

疑问 #

• 在此场景下，将Java Runnable对象传递到JNI并调用其run()方法的正确方式是什么？
• 处理Gluon Attach中的Runnable对象是否有遗漏的特定步骤？
• 该问题是否与Dalvik环境中引用管理（NewGlobalRef、Detach等）不当有关？

内容的提问来源于stack exchange，提问作者CTO - Abid Maqbool