从JNI调用Java函数的最佳方法

如何解决从JNI调用Java函数的最佳方法

我是JNI的新手，我想知道从JNI调用Java函数的最佳方法是什么。 我的要求：

start中的
1. TestClass可以从不同的线程中调用
一段时间后，触发了onSomethingHappened中的
2. MyCallbackCass （不是立即）可以说是在触发启动30秒后

这是我的代码段：

NativeJNI.cpp文件

static JavaVM* g_JavaVM = NULL;
MyCallbackCass *callbackClass = new MyCallbackCass();

JNIEXPORT jint JNICALL JNI_OnLoad(JavaVM* vm,void* reserved) {
    g_JavaVM = vm;
    return JNI_VERSION_1_6;
}

// class to atach JNIEnv because method may be called from different Threads
class AttachedEnv final {
private:
    JNIEnv *mEnv;
    bool needDetach;

    int getEnv(JNIEnv **g_env) {
        int getEnvStat = g_JavaVM->GetEnv((void **) g_env,JNI_VERSION_1_6);
        if (getEnvStat == JNI_EDETACHED) {
            if (g_JavaVM->AttachCurrentThread(g_env,nullptr) != 0) {
                __android_log_print(ANDROID_LOG_ERROR,"GetEnvironmentRoutine","FAILED ATTACH THREAD");
                return 2; //Failed to attach
            }
            return 1; //Attached. Need detach
        }
        return 0;//Already attached
    }

public:
    AttachedEnv() {
        auto resCode = getEnv(&mEnv);
        if (resCode == 2)
            throw std::runtime_error("Cannot retrieve JNI environment");
        needDetach = (resCode == 1);
    }

    ~AttachedEnv() {
        if (needDetach) {
            g_JavaVM->DetachCurrentThread();
        }
    }

    JNIEnv *env() const noexcept {
        return mEnv;
    }
};


class MyCallbackCass : MyCustomCallback {
    private: 
        jobject m_Obj;

    MyCallbackCass() {

    }

    void setEnvVariables(jobject obj) {
        this->m_Obj = obj; // I really doubt about this line
    }

     virtual void onSomethingHappened() override {
        // Here I need to call Java method from JNI
          AttachedEnv attachedEnv;
         JNIEnv *env = attachedEnv.env();

         jclass objClass = env->GetObjectClass(m_Obj); // is it a good approach? Is a good idea to have m_Obj in my class?
         mFunctionId = env->GetMethodID(objClass,"callbackedCalled","(Z)V");

         env->CallVoidMethod(m_Obj,mFunctionId,true);
     }
}


void Java_com_playground_TestClass_start(JNIEnv *env,jobject dispatcher) {
    callbackClass->setEnvVariables(dispatcher) // I don't think this is a good approach
}

Koltin文件

@Keep
class TestClass {
    fun onStartClicked() {
        start()
    }

    external fun start()

    fun callbackedCalled(value: Boolean) {
        Timber.d("Callback from JNI was called with value $value")
    }

    companion object {
        init {
            System.loadLibrary("DemoJNI")
        }
    }
}

此代码有效。所以我主要担心： 将jobject调度程序传递给我的回调类真的是一种好方法吗？ 是否可以拥有全局jobject并以某种方式在JNI_OnLoad中对其进行初始化？ 您可能有什么建议或改进吗？ 谢谢您的答复和时间。