比如我要在TEXT1中输入50, 在 TEXT2  中输入100,那么text3的值会自动变为150

这要如何写代码.是什么事件.

呵,本人菜鸟.不会!
帮你顶

import javax.swing.UIManager;
import javax.swing.event.DocumentEvent;
import javax.swing.event.DocumentListener;

/*

 * Main.java

 *

 * Created on 2007年12月7日, 下午1:14

 */
/**

 *

 * @author  Eastsun

 */
public class Main extends javax.swing.JFrame {

    /** Creates new form Main */
    public Main() {
        initComponents();
    }
    
    private void initComponents() {

        bField = new javax.swing.JTextField();
        aField = new javax.swing.JTextField();
        summerField = new javax.swing.JTextField();
        jLabel1 = new javax.swing.JLabel();
        jLabel2 = new javax.swing.JLabel();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
        setTitle("加法计算器");
        setResizable(false);

        summerField.setEditable(false);
        summerField.setFont(new java.awt.Font("宋体", 1, 12));

        jLabel1.setText(" + ");

        jLabel2.setText(" = ");

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addContainerGap()
                .addComponent(bField, javax.swing.GroupLayout.PREFERRED_SIZE, 105, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addPreferredGap(javax.swing.)
                .addComponent(jLabel1)
                .addPreferredGap(javax.swing.)
                .addComponent(aField, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addPreferredGap(javax.swing.)
                .addComponent(jLabel2)
                .addPreferredGap(javax.swing.)
                .addComponent(summerField, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
        );

        layout.linkSize(javax.swing.SwingConstants.HORIZONTAL, new java.[] {aField, bField, summerField});

        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addContainerGap()
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(aField, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(summerField, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(jLabel1)
                    .addComponent(jLabel2)
                    .addComponent(bField, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
        );

        bField.getDocument().addDocumentListener(listener);
        aField.getDocument().addDocumentListener(listener);

        pack();
    }// </editor-fold>//GEN-END:initComponents

    private void updateSummer() {
        try {
            double a = Double.parseDouble(aField.getText());
            double b = Double.parseDouble(bField.getText());
            summerField.setText(String.valueOf(a + b));
        } catch (NumberFormatException ex) {
            summerField.setText("");
        }
    }

    /**
     * @param args the command line arguments
     */
    public static void main(String args[]) {
        try{
            UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
        }catch(Exception ex){
            //do nothing
        }
        java.awt.EventQueue.invokeLater(new Runnable() {

            public void run() {
                new Main().setVisible(true);
            }
        });
    }
    // Variables declaration - do not modify//GEN-BEGIN:variables
    private javax.swing.JTextField aField;
    private javax.swing.JTextField bField;
    private javax.swing.JLabel jLabel1;
    private javax.swing.JLabel jLabel2;
    private javax.swing.JTextField summerField;
    // End of variables declaration//GEN-END:variables
    private DocumentListener listener = new DocumentListener() {

        public void insertUpdate(DocumentEvent e) {
            updateSummer();
        }

        public void removeUpdate(DocumentEvent e) {
            updateSummer();
        }

        public void changedUpdate(DocumentEvent e) {
            updateSummer();
        }
    };


}

用JDK1.6编译运行.

谢谢!

没想到这么复杂

为什么我把代码复制到我那边就出错了呢?

搞一个让我下载.

[[italic] 本帖最后由 jiasen2007 于 2007-12-7 16:51 编辑 [/italic]]

代码是自动生成的,有点乱,来个手工修改过的:

import javax.swing.UIManager;
import javax.swing.event.DocumentEvent;
import javax.swing.event.DocumentListener;
/**

 *

 * @author  Eastsun

 */
public class Main extends javax.swing.JFrame {
    public Main() {
        bField = new javax.swing.JTextField(16);
        aField = new javax.swing.JTextField(16);
        summerField = new javax.swing.JTextField(16);
        javax.swing.JLabel jLabel1 = new javax.swing.JLabel(" + ");
        javax.swing.JLabel jLabel2 = new javax.swing.JLabel(" = ");
        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
        setTitle("加法计算器");
        summerField.setEditable(false);
        bField.getDocument().addDocumentListener(listener);
        aField.getDocument().addDocumentListener(listener);
        javax.swing.JPanel panel =new javax.swing.JPanel(new java.awt.BorderLayout());
        panel.add(aField,java.awt.BorderLayout.WEST);
        panel.add(jLabel1,java.awt.BorderLayout.CENTER);
        panel.add(bField,java.awt.BorderLayout.EAST);
        javax.swing.JPanel content =new javax.swing.JPanel(new java.awt.BorderLayout());
        content.add(panel,java.awt.BorderLayout.WEST);
        content.add(jLabel2,java.awt.BorderLayout.CENTER);
        content.add(summerField,java.awt.BorderLayout.EAST);
        content.setBorder(new javax.swing.border.EmptyBorder(4,16,4,16));
        getContentPane().add(content);
        pack();
        setResizable(false);
    }
    private void updateSummer() {
        try {
            double a = Double.parseDouble(aField.getText());
            double b = Double.parseDouble(bField.getText());
            summerField.setText(String.valueOf(a + b));
        } catch (NumberFormatException ex) {
            summerField.setText("");
        }
    }
    public static void main(String args[]) {
        try{
            UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
        }catch(Exception ex){
            //do nothing
        }
        new Main().setVisible(true);
    }
    private javax.swing.JTextField aField;
    private javax.swing.JTextField bField;
    private javax.swing.JTextField summerField;
    private DocumentListener listener = new DocumentListener() {
        public void insertUpdate(DocumentEvent e) {
            updateSummer();
        }
        public void removeUpdate(DocumentEvent e) {
            updateSummer();
        }
        public void changedUpdate(DocumentEvent e){
        }
    };

}

谢谢版主

对了，能不能把你做的那个jpx一起发给我。
我主要是要看事件和做法。

private DocumentListener listener = new DocumentListener()
这句话是什么意思

[[italic] 本帖最后由 jiasen2007 于 2007-12-7 19:22 编辑 [/italic]]

jpx是嘛?

private DocumentListener listener = new DocumentListener() {}
就是得到一个DocumentListener

对,我要看一下事件。
对了，你QQ多少呀！我加你。好不好。谢谢了。

Q:67035999

[[italic] 本帖最后由 jiasen2007 于 2007-12-7 19:43 编辑 [/italic]]