Android JNI 应用程序在从另一个 native 方法调用 CallObjectMethod 时崩溃

Question

我正在尝试使用 Node.js 和 socket.io 为 Android 应用程序和桌面浏览器创建一个社交应用程序。

在浏览器客户端上，一切正常，问题是 android 客户端。实际上我使用了 socket.io java 客户端，我希望在 native c++ 中这样做。我已经成功调用了 socket.io java 客户端类，使用jni 并成功连接到我的 node.js 服务器。两个发射器回调客户端接收来自服务器的消息，该消息从桌面浏览器 javascript 客户端发送。

当我添加发送的这一行时，android 客户端向服务器发送消息时出现问题给服务器的消息

env->CallObjectMethod(globalSocketObj,emit,lo,o);

...应用程序崩溃。-崩溃信息-

11-21 10:10:58.417 9310-9310/com.example.nyari.advancenative E/dalvikvm: JNI ERROR (app bug): attempt to use stale local reference 0x1df00025 11-21 10:10:58.417 9310-9310/com.example.nyari.advancenative E/dalvikvm: VM aborting 11-21 10:10:58.418 9310-9310/com.example.nyari.advancenative A/libc: Fatal signal 6 (SIGABRT) at 0x0000245e (code=-6), thread 9310 (i.advancenative) 11-21 10:10:58.418 9310-9310/com.example.nyari.advancenative A/libc: Send stop signal to pid:9310 in void debuggerd_signal_handler(int, siginfo_t*, void*)

---

必须用 native 代码完成这件事已经花了我三天时间。感谢您的帮助。

本地代码:

//METHOD CONNECTING WITH NODE SERVER
JNIEXPORT void JNICALL Java_com_example_nyari_advancenative_MainActivity_count
                (JNIEnv* env, jobject obj){
            //LOCAL VARIABLES TO INSTANCES/////////////////////////////////////////////////
            Main_class=env->GetObjectClass(obj);//GETTING MAINACTIVITY OBJECT
            jstring f=env->NewStringUTF("http://192.168.43.113:8081");
            jstring il=env->NewStringUTF("hello");
            jstring ili=env->NewStringUTF("message");
        jclass my_socket=env->FindClass("io/socket/client/Socket");//GETTING SOCKET CLASS OF SOCKETIO
        jclass my_IO=env->FindClass("io/socket/client/IO");//GETTING IO LOCAL CLASS
            jobject socketObj=env->AllocObject(my_socket);//socketIO object
           jobject my_IOobj=env->AllocObject(my_IO);//GETTING IO OBJECT FROM IO CLASS
            //GETTING SOCKET STATIC METHOD FROM IO
           jmethodID static_socket=env->GetStaticMethodID(my_IO,"socket","(Ljava/lang/String;)Lio/socket/client/Socket;");
            //GLOBAL VARIABLES INSTANCES
            globalSocket= (jclass) env->NewGlobalRef(my_socket);//GLOBAL REFERENCE OF SOCKET CLASS
            globalSocketObj=env->NewGlobalRef(socketObj);//GLOBAL SOCKETIO REFERENCE OBJECT
        ///
            //INSTANTIATING GLOBAL REFERENCE OF SOCKET OBJECT
        globalSocketObj=env->CallObjectMethod(my_IOobj, static_socket, f);
            //LOCAL REFERENCES VARIABLES
            //GETTING CONNECT METHOD OF SOCKET CLASS
            jmethodID socket_connect=env->GetMethodID(my_socket,"connect","()Lio/socket/client/Socket;");
            //GETTING THE RECEIVE EMMITER CLASS FROM MAINACTIVITY
            receiveField=env->GetFieldID(Main_class,"receive","Lio/socket/emitter/Emitter$Listener;");
            //GETTING OBJECT FROM RECEIVEFIELD EMITTER FROM IN MAINACTIVITY
            receiveObj=env->GetObjectField(obj,receiveField);
            ///METHOD FROM SOCKET CLASS on FOR HELLO MESSAGE WITH SERVER
            onReceive=env->GetMethodID(my_socket,"on","(Ljava/lang/String;Lio/socket/emitter/Emitter$Listener;)Lio/socket/emitter/Emitter;");
            /////////////////
            //GETTING CHAT EMITTER FIELD FROM  MAINACTIVITY
            receiveMessage=env->GetFieldID(Main_class,"chats","Lio/socket/emitter/Emitter$Listener;");
            //GETTING OBJECT FROM CHATFIELD EMITTER FROM IN MAINACTIVITY
            receiveMessageObj=env->GetObjectField(obj,receiveMessage);
            ///METHOD FROM SOCKET CLASS on FOR MESSAGES SENT AND RECEIVED
            onReceiveMessage=env->GetMethodID(my_socket,"on","(Ljava/lang/String;Lio/socket/emitter/Emitter$Listener;)Lio/socket/emitter/Emitter;");
        ////////////////////////////
            env->CallObjectMethod(globalSocketObj,onReceive,il,receiveObj);
            env->CallObjectMethod(globalSocketObj,onReceiveMessage,ili,receiveMessageObj);
        env->CallObjectMethod(globalSocketObj,socket_connect);

          }

    ///PROBLEMATIC METHOD USED TO SEND MESSAGE TO SERVER
JNIEXPORT void JNICALL Java_com_example_nyari_advancenative_MainActivity_vari(JNIEnv* env, jobject obj){
        jstring il=env->NewStringUTF("hello");//message to be sent to the server
        jstring ili=env->NewStringUTF("message");//for callback method in server
        jclass ob=env->GetObjectClass(globalSocketObj);
        jmethodID emit=env->GetMethodID(ob,"emit","(Ljava/lang/String;[Ljava/lang/Object;)Lio/socket/emitter/Emitter;");
        env->CallObjectMethod(globalSocketObj,emit,ili,il);//PROBLEMATIC CALL

    }

JAVA CODE :


    public class MainActivity extends AppCompatActivity {
    static{
    /*try{
        System.loadLibrary("louts");
    }catch(Error | Exception ignore){

    }*/
        System.loadLibrary("louts");
    }
        TextView text,tex;

        public native void connect();
        public native void count();
        public native void vari();
        public native Socket network();
    public native void send();
        String message;
    Emitter.Listener receive,chats;
    String jo= io.socket.client.Socket.EVENT_CONNECT;
        ArrayList<String> items;
        ArrayAdapter<String> adapter;
        ListView list;
        EditText texter;
        Button button;
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);

            setContentView(R.layout.activity_main);
            text=(TextView)findViewById(R.id.numb);
            tex=(TextView)findViewById(R.id.num);
    //LISTVIEW TO ADD MESSAGES FROM NODE SERVER
            items=new ArrayList<String>();
         adapter=new ArrayAdapter<String>(getApplicationContext(),android.R.layout.simple_list_item_1,items);

            list=(ListView)findViewById(R.id.list);
            list.setAdapter(adapter);
    //EDITTEXT TO GET MESSAGES
            texter=(EditText)findViewById(R.id.texter);
    //CONTAINS THE EMITTER CALLBACKS METHODS TO RECEIVE MESSAGES FROM NODE SERVER
            emit();
    //THREAD THAT CONTAINS  NATIVE METHOD count() that connects to NODE SERVER
    Thread y=new Thread(new Runnable(){

        @Override
        public void run() {
            count();
        }
    });
            y.start();
    //BUTTON THAT MESSAGE TO NODE SERVER
            button=(Button)findViewById(R.id.button);
            button.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                    String j=null;
                    j=texter.getText().toString();
                    JSONObject reg2=new JSONObject();
                    try {
                        reg2.put("ki",j);
                        /*socket.emit("message",reg2);*/
                        vari();
                        texter.setText("");
                    } catch (JSONException e) {
                        e.printStackTrace();
                    }
                }
            });

        }

        @Override
        protected void onDestroy() {
            super.onDestroy();
            connect();
        }

        private void emit(){
            receive= new Emitter.Listener() {
                @Override
                public void call(Object... args) {//CALLBACK METHOD FOR HELLO MESSAGE FROM SERVER
                    final JSONObject obj = (JSONObject)args[0];
                    MainActivity.this.runOnUiThread(new Runnable(){

                        @Override
                        public void run() {
                            try {
                                message=obj.getString("ki");
                                text.setText(message);
                            } catch (JSONException e) {
                                e.printStackTrace();
                            }
                        }
                    });

                }
            };
            chats= new Emitter.Listener() {
                @Override
                public void call(Object... args) {//CALLBACK METHOD TO RECEIVE CHAT MESSAGES FROM SERVER
                    final JSONObject obj = (JSONObject)args[0];
                    MainActivity.this.runOnUiThread(new Runnable(){

                        @Override
                        public void run() {
                            try {
                                message=obj.getString("mess");
                              //  items.add(message);
                                adapter.add(message);
                                adapter.notifyDataSetChanged();
                                //tex.setText(message);
                                //list.setVerticalScrollbarPosition(list.getHeight());
                            } catch (JSONException e) {
                                e.printStackTrace();
                            }
                        }
                    });
                }
            };

        }
    }

Answer 1

你在这里做的有几个问题:

       globalSocketObj=env->NewGlobalRef(socketObj);//GLOBAL SOCKETIO REFERENCE OBJECT
    ///
        //INSTANTIATING GLOBAL REFERENCE OF SOCKET OBJECT
    globalSocketObj=env->CallObjectMethod(my_IOobj, static_socket, f);

首先，您创建一个对 socketObj 引用的 Socket 实例的全局引用。创建全局引用的要点在于，与本地引用不同，当您返回 Java 时它不会被删除。到目前为止一切顺利，假设您希望防止 Socket 实例被垃圾收集。

第一个问题是您在下一行直接覆盖了 globalSocketObj 的值，因此您刚刚创建的全局引用现在处于不确定状态。这意味着一旦从当前方法返回，您将无法再引用该 Socket 对象，这首先违背了创建全局引用的目的。由于您将无法删除您创建的全局引用，因此您刚刚为自己赢得了内存泄漏。

第二个潜在的问题是您没有为使用env->CallObjectMethod(my_IOobj, static_socket, f) 创建的对象创建全局引用，这意味着您不会一旦您从当前方法返回，就可以再引用该对象。