与长轮询的Android聊天

Question

I am having trouble implementing a chat application using long polling in an android App. The search for new messages works fine, it runs in an async task with HttpUrlConnection. The problem is with sending messages. I use another async task also with HttpUrlConnection but according to the logs I've been printing the message is sent only when the search for new messages is finished, that is after 30 seconds of long polling. Here is the async tast that I'm using:

HttpPost.java

package com.roscosoft.taxifast;

import android.os.AsyncTask;
import android.util.Log;

import org.json.JSONException;
import org.json.JSONObject;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.UnsupportedEncodingException;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLEncoder;
import java.util.HashMap;
import java.util.Map;

import javax.net.ssl.HttpsURLConnection;

/**
 * Created by titin on 7/12/16.
 */

public class HttpPost extends AsyncTask<Void, Void, Boolean> {
Exception error;

public interface HttpPostInterface {
    void termino(JSONObject obj);
    void cancelo(String error);
}


public static String getPostDataString(HashMap<String, String> params) throws UnsupportedEncodingException {
    StringBuilder result = new StringBuilder();
    boolean first = true;
    for(Map.Entry<String, String> entry : params.entrySet()){
        if (first)
            first = false;
        else
            result.append("&");

        result.append(URLEncoder.encode(entry.getKey(), "UTF-8"));
        result.append("=");
        result.append(URLEncoder.encode(entry.getValue(), "UTF-8"));
    }

    return result.toString();
}

private StringBuilder response;
private String postDataString;
private String url;
private HttpPostInterface delegate;
private int timeout;

HttpPost(String urlx, String postDataStringx, HttpPostInterface del) {
    url = urlx;
    postDataString = postDataStringx;
    delegate = del;
    timeout = 30000;
}
HttpPost(String urlx, String postDataStringx, HttpPostInterface del, int timeoutx) {
    url = urlx;
    postDataString = postDataStringx;
    delegate = del;
    timeout = timeoutx;
}


@Override
protected Boolean doInBackground(Void... params) {
    response = new StringBuilder();
    URL urlc = null;
    HttpURLConnection con = null;
    try{
        urlc = new URL(url);
    }catch (MalformedURLException e){
        Log.i("rosco", e.getMessage());
        error = e;
        return false;
    }
    try {
        con = (HttpURLConnection)urlc.openConnection();
        con.setReadTimeout(timeout);
        con.setConnectTimeout(timeout);
        con.setRequestMethod("POST");
        con.setDoInput(true);
        con.setDoOutput(true);

        OutputStream os = con.getOutputStream();
        BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(os, "UTF-8"));
        writer.write(postDataString);

        writer.flush();
        writer.close();
        os.close();

        int responseCode = con.getResponseCode();
        if (responseCode == HttpsURLConnection.HTTP_OK){
            String line;
            BufferedReader br = new BufferedReader(new InputStreamReader(con.getInputStream()));
            while ((line = br.readLine()) != null){
                response.append(line);
            }
        }else{
            error = new Exception("Error:"+responseCode);
            return false;
        }
    } catch (Exception e) {
        Log.i("rosco", "Hubo un error al hacer el request:"+e.getMessage());
        error = e;
        return false;
    }finally {
        con.disconnect();
    }
    return true;
}

@Override
protected void onPostExecute(final Boolean success) {

    if (success) {
        try{
            if (response.toString().length() == 0){
                if(delegate != null) delegate.cancelo("No hay respuesta del servidor");
            }else{
                //Log.i("rosco", response.toString()); // solo en desarrollo
            }
            JSONObject obj = new JSONObject(response.toString());
            if(delegate != null) delegate.termino(obj);
        }catch (JSONException e){
            Log.i("rosco", "Json malformado:"+e.getMessage()+":
"+response.toString());
            if(delegate != null) delegate.cancelo(response.toString());
        }
    } else {
        if(delegate != null) delegate.cancelo(error.getMessage());
    }
}

@Override
protected void onCancelled() {
    if(delegate != null) {
        if (error == null)
            delegate.cancelo("Se cancelo el request");
        else
            delegate.cancelo(error.getMessage());
    }
}
}

The web service is made in PHP is it possible that the server waits for the first connection to finish to accept the 'send message' connection? If so, do you have any idea how to fix it? Thanks very much in advance.

Answer 1

You need to use a THREAD_POOL_EXECUTOR to execute AsyncTask. Default implementation uses a serial executor running on a single thread

new MyAsyncTask().executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);