android客户端在多个界面切换时保持socket的链接的实例

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.net.Socket;
import java.net.UnknownHostException;

import android.app.Application;

public class ApplicationUtil extends Application{

    private Socket socket;
    private DataOutputStream out = null;
    private DataInputStream in = null;


    public void init() throws IOException, Exception{
        this.socket = new Socket("192.168.1.104",10202);
        this.out = new DataOutputStream(socket.getOutputStream());
        this.in = new DataInputStream(socket.getInputStream());
    }
    
    public Socket getSocket() {
        return socket;
    }

    public void setSocket(Socket socket) {
        this.socket = socket;
    }

    public DataOutputStream getOut() {
        return out;
    }

    public void setOut(DataOutputStream out) {
        this.out = out;
    }

    public DataInputStream getIn() {
        return in;
    }

    public void setIn(DataInputStream in) {
        this.in = in;
    }
    
}

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.login"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="10"
        android:targetSdkVersion="15" />

    <application
        android:name="com.util.ApplicationUtil"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
    
    <activity
            android:name=".LoginActivity"
            android:label="@string/title_activity_main" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
      <activity android:name=".MainActivity"/>
      
    </application>
   
    <!-- 振动需要的权限 -->
     <uses-permission android:name="android.permission.VIBRATE"/>
 <!-- 声明网络权限 -->
    <uses-permission android:name="android.permission.INTERNET"/>
</manifest>

import java.io.BufferedWriter;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.net.Socket;
import java.net.UnknownHostException;

import com.login.R;
import com.util.ApplicationUtil;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

public class LoginActivity extends Activity{

    private EditText usernameT;
    private EditText passwordT;
    private Button loginButton;
    private Socket socket;
    private DataOutputStream out;
    private DataInputStream in;

    @Override
    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
        setContentView(R.layout.login);
        
        usernameT = (EditText) findViewById(R.id.username);
        passwordT = (EditText) findViewById(R.id.password);
        loginButton = (Button) findViewById(R.id.login);
        
        
        
        loginButton.setOnClickListener(new OnClickListener(){
            public void onClick(View v) {
                
                ApplicationUtil appUtil =  (ApplicationUtil) LoginActivity.this.getApplication();
                try {
                    appUtil.init();
                    Socket socket = appUtil.getSocket();
                    out = appUtil.getOut();
                    in = appUtil.getIn();
                    
                } catch (IOException e1) {
                    e1.printStackTrace();
                } catch (Exception e1) {
                    e1.printStackTrace();
                }
                
                
                String username = usernameT.getText().toString();
                String password = passwordT.getText().toString();
                MD5 md5 = new MD5();
                String ss = md5.MD5(username+"|"+password);
    
                try {
                    //发送数据
                    String str = "[login]|"+ss;
                    out.writeBytes(str);
                    out.flush();
                    System.out.println("str ===> "+str);
                     //创建一个缓冲字节数
                    int r = in.available();  
                    while(r==0){  
                     r = in.available();  
                    }  
                    byte[] b = new byte[r];
                    in.read(b);
                    String result = new String(b,"utf-8");
                    System.out.println("result = "+result);
                    if(result.equals("登陆成功0")){
                        Intent intent = new Intent();
                        intent.setClass(LoginActivity.this, MainActivity.class);
                        startActivity(intent);
                    }
                    else
                    {
                        Intent intent = new Intent();
                        intent.setClass(LoginActivity.this, MainActivity.class);
                        startActivity(intent);
                    }
            
                } catch (UnknownHostException e) {
                    e.printStackTrace();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        });
        
    }
}

import java.io.BufferedReader;
import java.io.DataInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.Socket;

import com.image.TestActivity;
import com.login.R;
import com.util.ApplicationUtil;

import android.media.RingtoneManager;
import android.net.Uri;
import android.os.Bundle;
import android.os.Handler;
import android.os.Looper;
import android.os.Message;
import android.provider.MediaStore.Audio;
import android.app.Activity;
import android.app.Notification;
import android.app.NotificationManager;
import android.app.PendingIntent;
import android.content.Context;
import android.content.Intent;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

public class MainActivity extends Activity {

    private EditText mess; 
    private Socket socket;
    private Handler handler;
    private DataInputStream in;
    
     private NotificationManager nm;  
     private Notification n;  
     private int messageNotificationID = 0;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.success);
        mess = (EditText) findViewById(R.id.message);
        
        ApplicationUtil appUtil = (ApplicationUtil) MainActivity.this.getApplication();
        socket = appUtil.getSocket();
        in = appUtil.getIn();
  
        handler = new Handler(){
            @Override
            public void handleMessage(Message msg) {
                //如果来自子线程
                if(msg.what == 0x123){
                    mess.append(msg.obj.toString()+"\n");
                    //消息通知
                    mynoti();
                }
            }
        };
        //调用线程
        myThread();
      
   }
    //JAVA可以设置读写缓冲区的大小-setReceiveBufferSize(int size), setSendBufferSize(int size)。
    public void myThread(){
        Thread oneThread = new Thread(new Runnable(){
             public boolean isRunning = true;
            public void run() {     
                while(isRunning){
                try {
                    Thread.sleep(1000);
                     //创建一个缓冲字节数
                    int r = in.available();
                    while(r==0){  
                         r = in.available();  
                        }
                    byte[] b = new byte[r];
                    in.read(b);
                    String content = new String(b,"utf-8");
                        //每当读到来自服务器的数据后，发送消息通知程序页面显示数据  
                        Message msg = new Message();
                        msg.what = 0x123;
                        msg.obj = content;
                        Log.v("ho", content);
                        handler.sendMessage(msg);
                    
                } catch (IOException e) {
                    e.printStackTrace();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                } 
            }
            }
        });
        oneThread.start();
    }
    
    public void mynoti(){
             NotificationManager mNotificationManager = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
            // 创建一个通知  
            Notification mNotification = new Notification();  
            //用系统自带的铃声
            mNotification.sound = Uri.withAppendedPath(Audio.Media.INTERNAL_CONTENT_URI, "6"); 
            // mNotification.sound = Uri.parse("file:///sdcard/wen.mp3");
            //mNotification.defaults=Notification.DEFAULT_SOUND;  
            
            //Notification.FLAG_INSISTENT;      //让声音、振动无限循环，直到用户响应
            //Notification.FLAG_AUTO_CANCEL;    //通知被点击后，自动消失
            //Notification.FLAG_NO_CLEAR;  //点击‘Clear‘时，不清楚该通知(QQ的通知无法清除，就是用的这个)
            mNotification.flags = Notification.FLAG_NO_CLEAR; ;  
            
            //通知时发出的振动  
            //第一个参数: 振动前等待的时间  
            //第二个参数： 第一次振动的时长、以此类推  
            long[] vir = {0,100,200,300};  
            mNotification.vibrate = vir;  
            
            mNotificationManager.notify(messageNotificationID, mNotification);
            messageNotificationID++;
    }
}

import java.security.MessageDigest;

public class MD5 {

     // MD5加码。32位     
     public static String MD5(String inStr) {     
      MessageDigest md5 = null;     
      try {     
       md5 = MessageDigest.getInstance("MD5");     
      } catch (Exception e) {     
       System.out.println(e.toString());     
       e.printStackTrace();     
       return "";     
      }     
      char[] charArray = inStr.toCharArray();     
      byte[] byteArray = new byte[charArray.length];     
        
      for (int i = 0; i < charArray.length; i++)     
       byteArray[i] = (byte) charArray[i];     
        
      byte[] md5Bytes = md5.digest(byteArray);     
        
      StringBuffer hexValue = new StringBuffer();     
        
      for (int i = 0; i < md5Bytes.length; i++) {     
       int val = ((int) md5Bytes[i]) & 0xff;     
       if (val < 16)     
        hexValue.append("0");     
       hexValue.append(Integer.toHexString(val));     
      }         
      return hexValue.toString();     
     }     
}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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:orientation="vertical">
   
        <TableLayout 
         android:layout_width="fill_parent"
         android:layout_height="wrap_content"
            >
        <TableRow>
            <TextView 
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="账号："
                />
       <EditText
            android:id="@+id/username"
            android:layout_width="200dp"
            android:layout_height="wrap_content"
            android:layout_marginLeft="10dp"
            android:layout_marginTop="10dp"
            android:layout_marginRight="10dp"
            android:hint="账号"
        />
         </TableRow> 
         <TableRow>
            <TextView 
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="密码："
                />
        <EditText
            android:id="@+id/password"
            android:password="true"
            android:layout_width="200dp"
            android:layout_height="wrap_content"
            android:layout_marginLeft="10dp"
            android:layout_marginTop="10dp"
            android:layout_marginRight="10dp"
            android:hint="密码"
        />
         </TableRow>  
         
         
        </TableLayout>
         <Button
            android:id="@+id/login"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:layout_marginLeft="10dp"
            android:layout_marginTop="10dp"
            android:layout_marginRight="10dp"
            android:text="登录"
    />

</LinearLayout>

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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:orientation="vertical">
    
    <TextView 
        android:id="@+id/success"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="不断接受信息，并提示"
        />
    <EditText 
        android:id="@+id/message"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:cursorVisible="false"
        />
    </LinearLayout>