求助，自己编写聊天工具，报空指针异常。半天没找出在..... - 黑马程序员技术交流社区

import java.net.*;
import java.io.*;
import java.awt.*;
import java.awt.event.*;
class MyQQ
{
public static void main(String[] args) throws Exception
{
MyQQFrame myqq=new MyQQFrame();
}
}
class MyQQFrame
{
MyQQFrame()
{
init();
}
private Frame frame;
private TextArea ta_sender;
private TextArea ta_receiver;
private Button button;
private DatagramSocket ds_sender;
public void init()
{
frame=new Frame("MyQQ");
frame.setVisible(true);
frame.setBounds(30,30,500,400);
frame.setLayout(new FlowLayout());
ta_sender=new TextArea(3,35);
ta_receiver=new TextArea(16,60);
button=new Button("发送");
frame.add(ta_receiver);
frame.add(ta_sender);
frame.add(button);
try
{
DatagramSocket ds_sender=new DatagramSocket();
}
catch (Exception e)
{
e.printStackTrace();
}
setEvent();
startReceive();
}
public void startReceive()
{
new Thread(new Runnable(){
public void run()
{
try
{
DatagramSocket ds=new DatagramSocket(6777);
while(true)
{
byte[] buf=new byte[1024];
DatagramPacket dp=new DatagramPacket(buf,buf.length);
ds.receive(dp);
String ip=dp.getAddress().getHostAddress();
String data=new String(dp.getData(),0,dp.getLength());
ta_receiver.append(ip+"\r\n\t"+data+"\r\n");
}
}
catch (Exception e)
{
//System.out.println(e.toString());//把接受异常屏蔽，说明是发送出的问题
}
}
}).start();
}
public void setEvent()
{
button.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent e)
{
try
{
byte[] buf=ta_sender.getText().getBytes();
DatagramPacket dp=new DatagramPacket(buf,buf.length,InetAddress.getByName("192.168.1.3"),6777);
ds_sender.send(dp);
}
catch (Exception ex)
{
System.out.println(ex.toString());
}
}
});
frame.addWindowListener(new WindowAdapter()
{
public void windowClosing(WindowEvent e)
{
System.exit(0);
}
});
}
}

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