JAVA: 如何监听事件handler/How 的调用以获取事件处理程序的返回结果?

JAVA: How to listen to calling of event handler/How to get returned result of an event handler?

我正在创建一个 Android 聊天应用程序,其中我使用 WebSockets,除此之外,我想创建应用程序协议的自定义实现。

我陷入了困境。

本质上,我想要的是一种知道事件处理程序方法已在另一个 class 中调用的方法,基于此在我的 class 中启动我自己的方法,然后获取我的 class.

中该事件处理程序方法的结果

这怎么可能?

我进行了很多研究,发现了一些类似绑定、事件发射器等的东西。有人能给我指出正确的方向并提供一些我可以学习这项技术的资源吗?

这是我到目前为止所做的:

public void connect(){

        try {

            setUpWebSocketHandler(handler);
           mConnection.connect(wsuri, handler);

        }
        catch (WebSocketException e) {

           Log.d("exception", e.toString());
        }


}


public void setUpWebSocketHandler(WebSocketHandler handler)
{
    handler = new WebSocketHandler(){

  //first method for websockethandler

        @Override
        public void onOpen() {


            //here i create a json format string to be sent to my         server that returns something afterwards
            String output = json.toString();
            Log.d("OUTPUT+" , output);
            Log.d("onOpen", "Status: Connected to " + wsuri);
            mConnection.sendTextMessage(output);
        }



//second method for websockethandler
        @Override
        public void onTextMessage(final String payload) {

            Log.d("onTextMessage", "Response: " + payload);
            JSONObject jsonObj = null;
            try {
                jsonObj = new JSONObject(payload);
            } catch (JSONException e1) {
                // TODO Auto-generated catch block
                e1.printStackTrace();
            }
            try {

                String type = jsonObj.getString("type");
                switch (type) {
                    case "xxx":
                        //authEvent
                        System.out.println("xxx");
                        break;
                    case "yyy":
                        //userOnlineEvent
                        System.out.println("yyy");
                        break;
                    case "zzz":
                        System.out.println("zzz");

                        break;
                    case "userListToken":

                        userList = getUserList(payload);

                        break;


                    default:
                        System.out.println("DefaultCase");
                        break;
                }
            } catch (JSONException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }



        }

//third method for websockethandler

        @Override
        public void onClose(int code, String reason) {
            Log.d("onClose", "Connection lost.");
        }

    };
}



public String getUserList(final String payload)
{
    final Thread connectthread;
    connectthread = new Thread(
            new Runnable()
            {
                public void run()
                {
                    try {
                        //here i create a URL, send post request to it and i get a response with userlist
                        HttpClient client = new DefaultHttpClient();

                        HttpGet post = new HttpGet(url);


                        HttpResponse response = client.execute(post);
                        BufferedReader rd = new BufferedReader(new InputStreamReader(response.getEntity().getContent()));


                        while ((userList = rd.readLine()) != null) {
                            System.out.println(userList);
                            Log.d("HTTP GET RESPONSE", "Response: " + userList);

                        }



                    } catch (JSONException | IOException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                }
            }
    );



    connectthread.start();
    try
    {
        connectthread.join();
    }
    catch (Exception e)
    {
        Log.i("error","Error!!");
    }

    System.out.println("userListToken");
    return userList;
}

我还有一个问题。我使用回调获得了用户列表....现在的问题是:

private class ProcessLogin extends AsyncTask<String, Void, String> {
    private ProgressDialog pDialog;
    String uname,password;
    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        uname = txtUsername.getText().toString();
        password = txtPassword.getText().toString();

        pDialog = new ProgressDialog(LoginActivity.this);
        pDialog.setTitle("Contacting Servers");
        pDialog.setMessage("Logging in ...");
        pDialog.setIndeterminate(false);
        pDialog.setCancelable(false);
        pDialog.show();
    }
    @Override
    protected String doInBackground(String... args) {

        String user = null;

        ifly.connect();


        user = userList;
        return user;
    }
    @Override
    protected void onPostExecute(String user) {
        try {

            if(user != null){






                //Intent i = new Intent("com.example.tabmainactivity");
                Log.d("Got it", "Response: " + userList);
                pDialog.dismiss();
                //startService(new Intent(getApplicationContext(),iFlyChatMessage.class));
                //startActivity(i);
                //finish();

            }else{
                // username / password doesn't match
                pDialog.dismiss();
                Toast.makeText(getApplicationContext(),
                        "Incorrect username/password", Toast.LENGTH_SHORT).show();

            }


        } catch (Exception e) {
            e.printStackTrace();
        }

    }
}


public void processMessage(String userList)
{
       this.userList = userList;
}

我想要 postExecute 中的 userList,以便我可以将此 userList 发送到另一个 activity。我如何停止 doinbackground() 以等待回调完成。如果我使用 thread.sleep,整个过程都会停止,连连接都不工作。

谢谢

您可以在某处声明一个接口,让您的事件处理程序接受此接口的一个实例,然后创建一个匿名 class 实现此接口,同时在您的处理程序向事件源的注册中传递该实例。

如下所示:

public class MyClass{ ... ... component.addXXXListener(new EventHandler(new MyInterface() { @Override public void doSomething() { callMethod(); } })); ... ... public void callMethod() { ... ... }

希望你明白了。

我不确定我是否理解正确。

您应该使用回调对象。

类似于:

public interface MessageProcesor{
         public void processMessage(String message);
     }

您的 activity 应该实现这个接口。 您的 "client" class 中应该有 MessageProcesor 字段。 您的代码应如下所示:

private MessageProcesor callback;

public void setUpWebSocketHandler(WebSocketHandler handler)
{
    handler = new WebSocketHandler(){

  //first method for websockethandler

        @Override
        public void onOpen() {


            //here i create a json format string to be sent to my         server that returns something afterwards
            String output = json.toString();
            Log.d("OUTPUT+" , output);
            Log.d("onOpen", "Status: Connected to " + wsuri);
            mConnection.sendTextMessage(output);
        }



//second method for websockethandler
        @Override
        public void onTextMessage(final String payload) {

            Log.d("onTextMessage", "Response: " + payload);
            JSONObject jsonObj = null;
            try {
                jsonObj = new JSONObject(payload);
            } catch (JSONException e1) {
                // TODO Auto-generated catch block
                e1.printStackTrace();
            }
            try {

                String type = jsonObj.getString("type");
                switch (type) {
                    case "xxx":
                        //authEvent
                        System.out.println("xxx");
                        break;
                    case "yyy":
                        //userOnlineEvent
                        System.out.println("yyy");
                        break;
                    case "zzz":
                        System.out.println("zzz");

                        break;
                    case "userListToken":

                        userList = getUserList(payload);
                        callback.processMessage(userList);

                        break;


                    default:
                        System.out.println("DefaultCase");
                        break;
                }
            } catch (JSONException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }



        }

//third method for websockethandler

        @Override
        public void onClose(int code, String reason) {
            Log.d("onClose", "Connection lost.");
        }

    };
}



public String getUserList(final String payload)
{
    final Thread connectthread;
    connectthread = new Thread(
            new Runnable()
            {
                public void run()
                {
                    try {
                        //here i create a URL, send post request to it and i get a response with userlist
                        HttpClient client = new DefaultHttpClient();

                        HttpGet post = new HttpGet(url);


                        HttpResponse response = client.execute(post);
                        BufferedReader rd = new BufferedReader(new InputStreamReader(response.getEntity().getContent()));


                        while ((userList = rd.readLine()) != null) {
                            System.out.println(userList);
                            Log.d("HTTP GET RESPONSE", "Response: " + userList);

                        }



                    } catch (JSONException | IOException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                }
            }
    );



    connectthread.start();
    try
    {
        connectthread.join();
    }
    catch (Exception e)
    {
        Log.i("error","Error!!");
    }

    System.out.println("userListToken");
    return userList;
}

您可以将 "callback" 作为构造函数参数或通过 setter 方法传递。

希望这对您有所帮助。