代码贴上,有点多,但是简单:
package xiaobenben.muticast;import java.io.IOException;
import java.net.DatagramPacket;
import java.net.InetAddress;
import java.net.MulticastSocket;
import java.util.Scanner;import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;public class Muticast extends Activity {
/** Called when the activity is first created. */
private Button button_send;
private TextView textview;
private Button button_begin;
private EditText edittext;
private static final String BROADCAST_IP = "224.0.0.1";
public static final int BROADCAST_PORT = 4545;
private static final int DATA_LEN = 4096;
private MulticastSocket socket ;
private InetAddress broadcastAddress = null;
private Scanner scan = null;
byte[] inBuff = new byte[DATA_LEN];
private DatagramPacket inPacket = new DatagramPacket(inBuff , inBuff.length);
private DatagramPacket outPacket = null;
private String str;
public void ini(){
try{
socket = new MulticastSocket(BROADCAST_PORT);
System.out.println("1111111111111111111");
broadcastAddress = InetAddress.getByName(BROADCAST_IP);
socket.joinGroup(broadcastAddress);
socket.setLoopbackMode(false);
outPacket = new DatagramPacket(new byte[0] , 0 ,broadcastAddress , BROADCAST_PORT);
}catch (Exception e){
e.printStackTrace();
}
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
button_send = (Button)findViewById(R.id.button_ok);
button_begin = (Button)findViewById(R.id.button_begin);
textview = (TextView)findViewById(R.id.textview_text);
edittext = (EditText)findViewById(R.id.editview);
textview.setText("hi,xiaobenben!");
button_begin.setText("开始");
ini();
button_begin.setOnClickListener(new Button.OnClickListener(){ public void onClick(View v) {
// TODO Auto-generated method stub
try {
System.out.println("init() start");
button_begin.setText("结束");
Runnable ping = new Multicast();
new Thread(ping).start();
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
});
button_send.setOnClickListener(new Button.OnClickListener(){ public void onClick(View v) {
// TODO Auto-generated method stub
try{
//scan = new Scanner(Muticast.this.edittext.getText().toString());
str = edittext.getText().toString();
//byte[] buff = scan.next().getBytes();
byte[] buff = str.getBytes();
outPacket.setData(buff);
socket.send(outPacket);
edittext.setText("");
}catch (Exception e){
e.printStackTrace();
}
}
});
}
class Multicast implements Runnable{ //内部类
Multicast(){
}
public void run(){
try
{
while(true)
{
socket.receive(inPacket);
System.out.println(new String(inBuff , 0 , inPacket.getLength()));
str = new String(inBuff , 0 , inPacket.getLength());
textview.setText("聊天信息:" + str);
//textview.setText("聊天信息:" + new String(inBuff , 0 , inPacket.getLength()));
//System.out.println(inPacket.getAddress().getHostAddress());
}
}
catch (IOException ex)
{
ex.printStackTrace();
try
{
if (socket != null)
{
socket.leaveGroup(broadcastAddress);
socket.close();
}
System.exit(1);
}
catch (IOException e)
{
e.printStackTrace();
}
}
}
}
}其实就是实现 局域网聊天的小程序罢了
package xiaobenben.muticast;import java.io.IOException;
import java.net.DatagramPacket;
import java.net.InetAddress;
import java.net.MulticastSocket;
import java.util.Scanner;import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;public class Muticast extends Activity {
/** Called when the activity is first created. */
private Button button_send;
private TextView textview;
private Button button_begin;
private EditText edittext;
private static final String BROADCAST_IP = "224.0.0.1";
public static final int BROADCAST_PORT = 4545;
private static final int DATA_LEN = 4096;
private MulticastSocket socket ;
private InetAddress broadcastAddress = null;
private Scanner scan = null;
byte[] inBuff = new byte[DATA_LEN];
private DatagramPacket inPacket = new DatagramPacket(inBuff , inBuff.length);
private DatagramPacket outPacket = null;
private String str;
public void ini(){
try{
socket = new MulticastSocket(BROADCAST_PORT);
System.out.println("1111111111111111111");
broadcastAddress = InetAddress.getByName(BROADCAST_IP);
socket.joinGroup(broadcastAddress);
socket.setLoopbackMode(false);
outPacket = new DatagramPacket(new byte[0] , 0 ,broadcastAddress , BROADCAST_PORT);
}catch (Exception e){
e.printStackTrace();
}
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
button_send = (Button)findViewById(R.id.button_ok);
button_begin = (Button)findViewById(R.id.button_begin);
textview = (TextView)findViewById(R.id.textview_text);
edittext = (EditText)findViewById(R.id.editview);
textview.setText("hi,xiaobenben!");
button_begin.setText("开始");
ini();
button_begin.setOnClickListener(new Button.OnClickListener(){ public void onClick(View v) {
// TODO Auto-generated method stub
try {
System.out.println("init() start");
button_begin.setText("结束");
Runnable ping = new Multicast();
new Thread(ping).start();
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
});
button_send.setOnClickListener(new Button.OnClickListener(){ public void onClick(View v) {
// TODO Auto-generated method stub
try{
//scan = new Scanner(Muticast.this.edittext.getText().toString());
str = edittext.getText().toString();
//byte[] buff = scan.next().getBytes();
byte[] buff = str.getBytes();
outPacket.setData(buff);
socket.send(outPacket);
edittext.setText("");
}catch (Exception e){
e.printStackTrace();
}
}
});
}
class Multicast implements Runnable{ //内部类
Multicast(){
}
public void run(){
try
{
while(true)
{
socket.receive(inPacket);
System.out.println(new String(inBuff , 0 , inPacket.getLength()));
str = new String(inBuff , 0 , inPacket.getLength());
textview.setText("聊天信息:" + str);
//textview.setText("聊天信息:" + new String(inBuff , 0 , inPacket.getLength()));
//System.out.println(inPacket.getAddress().getHostAddress());
}
}
catch (IOException ex)
{
ex.printStackTrace();
try
{
if (socket != null)
{
socket.leaveGroup(broadcastAddress);
socket.close();
}
System.exit(1);
}
catch (IOException e)
{
e.printStackTrace();
}
}
}
}
}其实就是实现 局域网聊天的小程序罢了
Multicast的run中
textview.setText("聊天信息:" + str);这个要放在主线程里可以这样:
activity中创建一个handler,然后在Multicast的run中,str接收完了,然后通过handler发消息来通知UI更新。改成这样:
socket.receive(inPacket);
System.out.println(new String(inBuff , 0 , inPacket.getLength()));
str = new String(inBuff , 0 , inPacket.getLength());//这个str最好定义一个全局的,不然还要通过bundle来传递
handler.sendEmptyMessage(1);//ID自己定义然后handler里handlemessage中根据msg的id==1来做
textview.setText("聊天信息:" + str);的工作
// TODO Auto-generated method stub
try{
//scan = new Scanner(Muticast.this.edittext.getText().toString());
str = edittext.getText().toString();
//byte[] buff = scan.next().getBytes();
byte[] buff = str.getBytes();
outPacket.setData(buff);
socket.send(outPacket);
edittext.setText("");
}catch (Exception e){
e.printStackTrace();
}
}
});
}
我先在EditText输入8个字节的消息,然后点击发送按钮发送后,然后第二次即使在EditText输入10个字节,但是也只是发送了前8个字节,也就是说每次发送的字节数最多就是上次发送消息的字节数,这是为什么呢?代码有什么问题吗?该怎么改呢?
正解android中确实需要这种Handler机制来处理在其他线程中控制主线程的UI.