Question

关于Rxjava作为EventBus的使用情况，我已经阅读了this和this等几个教程。但是，它们并没有解决我的问题。

我正在使用自己的自定义nodejs服务器和socket.io制作聊天应用。授权通过改造（使用gson）完成。即使应用程序已关闭，用户也应该收到消息，因此与socket.io的连接通过常年服务进行维护，该服务将信息转发给活动，如果它显示给用户，否则它只显示通知并写入到SQL db（TODO）。我的Service接收来自socket.io的呼叫并解析有效负载。当发生这种情况时，它需要向活动发送一条消息以及收到的有效负载。

MyEventBus.class

public class MyRxBus {

    private static MyRxBus instance;

    private PublishSubject<Object> subject = PublishSubject.create();

    public static MyRxBus instanceOf() {
        if (instance == null) {
            instance = new MyRxBus();
        }
        return instance;
    }

    /**
     * Pass any event down to event listeners.
     */
    public void setString(Object object) {
        subject.onNext(object);
    }

    /**
     * Subscribe to this Observable. On event, do something 
     * e.g. replace a fragment
     */
    public Observable<Object> getEvents() {
        return subject;
    }
}

SocketService类

public class SocketService extends Service {
    private Socket mSocket;
    public SocketService() {
    }

    @Override
    public void onCreate() {
        super.onCreate();
        Log.d("SERVICE ","SOCKET SERVICE WAS CALLED");
        mSocket=SocketSingleton.getSocket("8080");
        mSocket.on(Socket.EVENT_CONNECT,onConnect);
        mSocket.on("new_message",onNewMessage);
        mSocket.connect();
    }


    private Emitter.Listener onNewMessage = new Emitter.Listener() {
        @Override
        public void call(Object... args) {
            Log.d("Received from socket ",args[0].toString());
            try {
                final JSONObject object = new JSONObject((String) args[0]);
                //Send this object to all subscribers
                //TODO: add rxjava eventbus to 1)add info to db, 2)update activity IF it is displayed
                MyRxBus.instanceOf()
                    .setEvent(object);

            } catch (JSONException e) {
                e.printStackTrace();
            }
        }
    };
  //some other functions (not related at all)

}

MainActivity.class

   public class MainActivity extends VesicaActivity {
    private Socket mSocketOne;
    private Gson gson = new Gson();
    private List<ChatMessage> mMessages = new ArrayList<ChatMessage>();
    private List<String> mListOfUsers = new ArrayList<String>();
    Boolean isNodeOne;
    String username;
    private JSONArray arrayOfUsers=null;
    private RecyclerView mRecyclerView;
    private RecyclerView.Adapter mAdapter;
    private RecyclerView.LayoutManager mLayoutManager;
    private Boolean _isConnected=false;
    private String socketIdtoSend;

    @BindView(R.id.et_text)EditText etText;
    @BindView(R.id.tv_user_list)TextView tvListUsers;
    @BindView(R.id.tv_status)TextView tvStatus;
    @BindView(R.id.toolbar)Toolbar toolbar;
    @BindView(R.id.et_self_destruct_time)EditText etSelfDestructTimer;
    @BindView(R.id.cb_self_destruct)CheckBox cbSelfDestruct;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        ButterKnife.bind(this);
        setSupportActionBar(toolbar);
        if (getSupportActionBar()!=null){
            getSupportActionBar().setDisplayHomeAsUpEnabled(true);
        }
        tvStatus.setText("checking connection...");
        username = Constants.getUsername();
        Integer portNumber = Constants.getPortNumber();
        socketIdtoSend = getIntent().getStringExtra("socketId");
        mMessages.add(createMessage("Sample Name","Sample Text",0));
        mRecyclerView = (RecyclerView) findViewById(R.id.recycler_view);
        mLayoutManager = new LinearLayoutManager(this);
        mRecyclerView.setLayoutManager(mLayoutManager);
        mAdapter = new ChatAdapter(mMessages, username);
        mRecyclerView.setAdapter(mAdapter);


        //-----------------------------------------------------------------

        MyRxBus.instanceOf()
                .getEvents()
                .subscribe(new Action1<Object>() {
                    @Override
                    public void call(Object o) {
                       final JSONObject object = new JSONObject((String) o)
                       ChatMessage message = createMessage(object.getString("user")
                               ,Encryption.Decrypt(object.getString("message"))
                               ,object.getInt("selfDestructTime"));
                       mMessages.add(message);
                       mAdapter.notifyDataSetChanged();
                        Toast.makeText(MainActivity.this," new message received ", Toast.LENGTH_SHORT).show();
                    }
                });

    }


    public ChatMessage createMessage(String user, String message, Integer time){
        return new ChatMessage.ChatMessageBuilder()
                .message(message)
                .user(user)
                .type("newMessage")
                .selfDestructTime(time)
                .sendToSocketId(socketIdtoSend)
                .build();
    }


    public void showDialogBoxToClearHistory(){
        new AlertDialog.Builder(MainActivity.this)
                .setTitle("Wipe Chat History")
                .setMessage("This will delete the entire chat history of this thread. It is irreversible. Do you want to continue?")
                .setPositiveButton(android.R.string.yes, new DialogInterface.OnClickListener() {
                    public void onClick(DialogInterface dialog, int which) {
                        // continue with delete
                        mMessages.clear();
                        mAdapter.notifyDataSetChanged();
                        Toast.makeText(MainActivity.this, "Cleared entire history", Toast.LENGTH_LONG).show();
                    }
                })
                .setNegativeButton("Skip", new DialogInterface.OnClickListener() {
                    public void onClick(DialogInterface dialog, int which) {
                       try{
                           dialog.dismiss();
                       }catch (Exception e){e.printStackTrace();}
                    }
                })
                .setCancelable(false)
                .show();
    }

    private void ScrollToBottom(){
        mRecyclerView.smoothScrollToPosition(mAdapter.getItemCount());
    }
}

当我运行此代码时，出现以下错误 rx.exceptions.OnErrorNotImplementedException: Can't create handler inside thread that has not called Looper.prepare()

指向 at com.example.varun.vesica.eventbus.MyRxBus.setEvent(MyRxBus.java:26)

我知道可以将observables和观察者设置为发出/观察不同的线程，但经过大量的反复试验后，我已经放弃并需要一些帮助。

任何帮助/链接将不胜感激。谢谢！

Answer 1

维持连接所有时间都会耗尽用户的电池电量。您应该考虑在设备被阻止或应用程序最小化时使用推送通知。在活动中订阅Observable时，保存订阅并在onPause中关闭它，否则将会出现设备轮换导致的延迟连接。考虑使用GreenRobot事件总线而不是重新发明轮子，它是非常方便的连接服务和活动的库：http://www.andreas-schrade.de/2015/11/28/android-how-to-use-the-greenrobot-eventbus/

Answer 2

您试图在调用adapter.notifyDataSetChanged() / Toast.makeText()的任意线程上调用setEvent()和setString()。当您以更新Android UI为目标订阅getEvents() observable时，您需要在主线程调度程序上观察：

    MyRxBus.instanceOf()
            .getEvents()
            .observeOn(AndroidSchedulers.mainThread())
            .subscribe(new Action1<Object>() {
                @Override
                public void call(Object o) {
                   final JSONObject object = new JSONObject((String) o)
                   ChatMessage message = createMessage(object.getString("user")
                           ,Encryption.Decrypt(object.getString("message"))
                           ,object.getInt("selfDestructTime"));
                   mMessages.add(message);
                   mAdapter.notifyDataSetChanged();
                    Toast.makeText(MainActivity.this," new message received ", Toast.LENGTH_SHORT).show();
                }
            });

RxJava作为服务和活动之间的Eventbus

2 个答案: