朋友们，怎么让textarea显示其他类的值，我写的老报空指针错误。谢拉

[phil1947]

public class try_disappare {
TextArea tf;
public void init() {
final Frame f= new Frame("synchronism_tongbu");
f.setSize(600,400);
f.setLocation(100,100);
tf=new TextArea();
f.add(tf);
f.addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent e) {
System.exit(0);
}
});

MenuBar bar= new MenuBar();
Menu send= new Menu("send");
Menu recive= new Menu("recive");
MenuItem start_s = new MenuItem("start");
start_s.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
appear_tf at = new appear_tf();
}
});

MenuItem end_s = new MenuItem("end");

MenuItem start_r = new MenuItem("start");
MenuItem end_r = new MenuItem("end");
send.add(start_s);
send.add(end_s);
recive.add(start_r);
recive.add(end_r);
bar.add(send);
bar.add(recive);
f.setMenuBar(bar);
f.setVisible(true);
//String t = vd.datetime;
//System.out.println(t);

}
public static void main(String[] args) {
try_disappare try_disappare = new try_disappare();
try_disappare.init();
}

}
class appear_tf{
try_disappare td;
public appear_tf(){
this.td = td;
td = new try_disappare();
td.tf.append("ssss");
//System.out.println("ssss");
}

}

如果写成内部类textarea能显示，这样写老报空指针错误。谢谢大家的帮忙

[pangxie]

import java.awt.Frame;
import java.awt.Menu;
import java.awt.MenuBar;
import java.awt.MenuItem;
import java.awt.TextArea;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;

public class try_disappare {

TextArea tf;

public void init() {
final Frame f = new Frame("synchronism_tongbu");
f.setSize(600, 400);
f.setLocation(100, 100);
tf = new TextArea();
f.add(tf);
f.addWindowListener(new WindowAdapter() {

public void windowClosing(WindowEvent e) {
System.exit(0);
}
});

MenuBar bar = new MenuBar();
Menu send = new Menu("send");
Menu recive = new Menu("recive");
MenuItem start_s = new MenuItem("start");
start_s.addActionListener(new ActionListener() {

public void actionPerformed(ActionEvent e) {
appear_tf at = new appear_tf(tf);//修改过的
}

});

MenuItem end_s = new MenuItem("end");

MenuItem start_r = new MenuItem("start");
MenuItem end_r = new MenuItem("end");
send.add(start_s);
send.add(end_s);
recive.add(start_r);
recive.add(end_r);
bar.add(send);
bar.add(recive);
f.setMenuBar(bar);
f.setVisible(true);
//String t = vd.datetime;
//System.out.println(t);

}

public static void main(String[] args) {
try_disappare try_disappare = new try_disappare();
try_disappare.init();
}
}
//修改过的(开始)
class appear_tf {

TextArea tf;

public appear_tf(TextArea tf) {
this.tf = tf;
tf.append("ssss");
//System.out.println("ssss");
}
}
//修改过的(结束)

[phil1947]

谢谢，朋友的帮助。