Android客户端未正确向服务器发送消息

Question

I'm writing a code for a client on an android device to send messages to a server and the server is supposed to reply to it. the layout is composed of an edit text field, a button and a text view. When the button is pressed the message should be taken from the edit text field and sent to the server, when the server receives the message it should reply with a message stating that it has received it and then that reply message is to be received by the client and written on the text view. The problem is that the message is sent to the server when I press on button twice and then when I press the third time the server crashes. Any help on what's the problem would really be appreciated. Thanks in advance.

This is the logcat error that I get

02-04 04:18:38.065: I/Error51(32228): android.os.NetworkOnMainThreadException

MainActivity.java

package com.example.testclientandroid;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.InetAddress;
import java.net.Socket;
import java.net.UnknownHostException;

import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

public class MainActivity extends Activity {

    static Socket socket;
    static final int SERVERPORT = 50000;
    static final String SERVER_IP = "192.168.0.105";

    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        new Thread(new ClientThread()).start();

        Button button = (Button) findViewById(R.id.button1);

        button.setOnClickListener(new OnClickListener() {

            public void onClick(View v) {
                // TODO Auto-generated method stub
                EditText editText = (EditText) findViewById(R.id.editText1);
                TextView textView = (TextView) findViewById(R.id.textView2);
                try {
                    String str = editText.getText().toString();

                    PrintWriter out = new PrintWriter(socket.getOutputStream(), true);
                    out.println(str);

                    BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
                    textView.setText(in.readLine());

                } catch (UnknownHostException e) {
                    Log.i("Error47", e.toString());
                } catch (IOException e) {
                    Log.i("Error49", e.toString());
                } catch (Exception e) {
                    Log.i("Error51", e.toString());
                }
            }
        });
    }

    private static class ClientThread implements Runnable {

        public void run() {

            try {
                InetAddress serverAddr = InetAddress.getByName(SERVER_IP);

                socket = new Socket(serverAddr, SERVERPORT);

            } catch (UnknownHostException e) {
                Log.i("Error64", e.toString());
            } catch (IOException e) {
                Log.i("Error65", e.toString());
            }
        }

    }
}

activity_main.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MainActivity" >

    <EditText
        android:id="@+id/editText1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_alignParentTop="true"
        android:ems="10" >

        <requestFocus />
    </EditText>

    <Button
        android:id="@+id/button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/editText1"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="48dp"
        android:text="Send" />

    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_below="@+id/button1"
        android:layout_marginTop="53dp"
        android:text="Response:"
        android:textAppearance="?android:attr/textAppearanceLarge" />

    <TextView
        android:id="@+id/textView2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/textView1"
        android:layout_alignParentBottom="true"
        android:layout_alignParentRight="true"
        android:layout_below="@+id/textView1" />

</RelativeLayout>

Android Manifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.testclientandroid"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="10"
        android:targetSdkVersion="19" />
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>
    <uses-permission android:name="android.permission.INTERNET"/>

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.example.testclientandroid.MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

ServerClass.java

package mainPackage;
//Server
import java.net.*;
import java.io.*;

public class ServerClass
{

    static final int PORTNUMBER = 50000;

    public static void main(String[] args) throws IOException
    {
        new Thread(new ServerThread()).start();
    }

    public static class ServerThread implements Runnable {

        ServerSocket serverSocket;
        Socket clientSocket;
        public void run() {
            try {
                serverSocket = new ServerSocket(PORTNUMBER);
                clientSocket = serverSocket.accept();
                new Thread(new CommunicationThread(clientSocket)).start();

            } catch (IOException e1) {
                e1.printStackTrace();
            }
        }
    }

    public static class CommunicationThread implements Runnable {

        Socket socket;
        BufferedReader in;
        PrintWriter out;

        public CommunicationThread(Socket clientSocket) {

            socket = clientSocket;

            try {

                in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
                //out = new PrintWriter(clientSocket.getOutputStream(), true); 
            } catch (IOException e) {
                System.out.println(e.toString());
            }
        }

        public void run() {
            try {

                while(in.readLine() != null)
                {
                    System.out.println(in.readLine());
                    out.println(in.readLine() + " Received");
                }

            } catch (IOException e) {
                System.out.println(e.toString());
            }
        }
    }
}

Update I tried using asyncTask, I don't get a Logcat error anymore but now the server doesn't receive the message at all,

Here's the modified code:

package com.example.testclientandroid;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.InetAddress;
import java.net.Socket;
import java.net.UnknownHostException;

import android.app.Activity;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

public class MainActivity extends Activity {

    static Socket socket;
    static final int SERVERPORT = 50000;
    static final String SERVER_IP = "192.168.0.105";

    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        new Thread(new ClientThread()).start();

        Button button = (Button) findViewById(R.id.button1);

        button.setOnClickListener(new OnClickListener() {

            public void onClick(View v) {
                // TODO Auto-generated method stub
                new CommunicationTask().execute();
            }
        });
    }

    private static class ClientThread implements Runnable {

        public void run() {

            try {
                InetAddress serverAddr = InetAddress.getByName(SERVER_IP);

                socket = new Socket(serverAddr, SERVERPORT);

            } catch (UnknownHostException e) {
                Log.i("Error64", e.toString());
            } catch (IOException e) {
                Log.i("Error65", e.toString());
            }
        }
    }

    private class CommunicationTask extends AsyncTask<Void, Void, String> {

        @Override
        protected String doInBackground(Void... params) {
            // TODO Auto-generated method stub
            EditText editText = (EditText) findViewById(R.id.editText1);
            String result;
            try {
                String str = editText.getText().toString();

                PrintWriter out = new PrintWriter(socket.getOutputStream(), true);
                out.println(str);

                BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
                result = in.readLine();
                return result;
            } catch (UnknownHostException e) {
                Log.i("Error47", e.toString());
            } catch (IOException e) {
                Log.i("Error49", e.toString());
            } catch (Exception e) {
                Log.i("Error51", e.toString());
            }
            return "Error";
        }

        @Override
        protected void onPostExecute(String result) {
            // TODO Auto-generated method stub
            super.onPostExecute(result);

            TextView textView = (TextView) findViewById(R.id.textView2);
            textView.setText(result);
        }   
    }
}

Answer 1

Any operation that needs internet should be done on background. Try to read Asynctask to remove this error.

Answer 2

Try to use asynctask , its simple and easier.AsyncTask enables proper and easy use of the UI thread. This class allows to perform background operations and publish results on the UI thread without having to manipulate threads and/or handlers.

Here is an example private class DownloadFilesTask extends AsyncTask { protected Long doInBackground(URL... urls) { int count = urls.length; long totalSize = 0; for (int i = 0; i < count; i++) { totalSize += Downloader.downloadFile(urls[i]); publishProgress((int) ((i / (float) count) * 100)); // Escape early if cancel() is called if (isCancelled()) break; } return totalSize; }

 protected void onProgressUpdate(Integer... progress) {
     setProgressPercent(progress[0]);
 }

 protected void onPostExecute(Long result) {
     showDialog("Downloaded " + result + " bytes");
 }

}