【求助】Java GUI 事件监听器的参数传递


我的思路错了吗？或者是我的代码有问题？

求大侠指点。
[解决办法]
我做了如下修改：

import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JTextField;

public class Frame1 {
static JButton button1;
public static void main(String []args){
button1 = new JButton("button1");
JFrame frame1 = new JFrame("frame1");
button1.addActionListener(new Listener1(button1, frame1)); 
frame1.add(button1);
frame1.setLayout(new FlowLayout());
frame1.setBounds(400, 100, 400, 300);
frame1.setVisible(true);
}
static JButton getbun(){
return button1; 
 
 
}
}

class Frame2{
JButton button2;
static JTextField tf;
public Frame2(JButton button1, JFrame frame1){
 tf = new JTextField(20);
JButton button2 = new JButton("修改");
button2.addActionListener(new Listener2(button1, tf.getText(),frame1));

JFrame frame2 = new JFrame("frame2");
frame2.setLayout(new FlowLayout());
frame2.setBounds(450, 150, 300, 200);
frame2.add(tf);
frame2.add(button2);
        frame2.setVisible(true);

}
static JTextField gettext(){
return tf;
}

}

class Listener1 implements ActionListener{
JButton button;
JFrame frame;
public Listener1(JButton button, JFrame frame){
this.frame = frame;
this.button = button;
}
public void actionPerformed(ActionEvent e){
        Frame2 frame2 = new Frame2(button,frame);
}
}


class Listener2 implements ActionListener{
String taskNameOld, taskNameNew;
JButton button;
JFrame frame;

public Listener2(JButton button, String stringNew, JFrame frame){
this.frame = frame;

this.taskNameOld = button.getText();
this.taskNameNew = taskNameNew;
}
public void actionPerformed(ActionEvent e){
if(taskNameNew != taskNameOld)
{
Frame1.getbun().setText(Frame2.gettext().getText().toString());//运行时Eclipse报错
frame.repaint();
}
}
}

[解决办法]
button空指针了。因为在Listener2的构造方法中少写了一句

this.button = button;

[解决办法]
很简单
你少了this.button=button;所以button是空，所以是空指针异常
然后
你获取tf内容应该是监听方法里面获取，如在actionPerformed里面
像你button2.addActionListener(new Listener2(button1, tf.getText(),frame1));这样的话
在初始化的时候就已经获取了，这时tf里面是没有内容的，应该写在监听方法里面，这样才是点击按钮时获取
改了如下
class Listener2 implements ActionListener{
String taskNameOld, taskNameNew;
JButton button;
JFrame frame;
JTextField tf;
public Listener2(JButton button,JTextField tf, JFrame frame){
this.frame = frame;
this.button = button;
this.taskNameOld = button.getText();
this.tf = tf;
}
public void actionPerformed(ActionEvent e){
if(taskNameNew != taskNameOld)
{taskNameNew = tf.getText();
button.setText(taskNameNew);//运行时Eclipse报错
frame.repaint();
}
}
}
然后上面的有一句button2.addActionListener(new Listener2(button1, tf,frame1));改成这样
另外还想跟你说，判断字符是不是一样是用equals方法，不是用==或者！=，这样是判断地址，而不是内容