Java 如何在swing中自动减去JText字段的输入值

我想自动减去

jt输出值，并希望减去的值出现在另一个文本字段中

我怎样才能做到这一点

这是我的jtextfield代码：

public class Showdata1 extends JFrame
{
public Showdata1()
  {

 this.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
Container c = getContentPane();
  c.setLayout( new FlowLayout());
    //  setUndecorated(true);
      Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
      setBounds(0,0,screenSize.width, screenSize.height);

       opening_km= new JLabel("Opening Km");
       opening_km.setBounds(0,280,258,30);
       opening_km.setFont(new java.awt.Font("Times New Roman", 1,25)); // NOI18N
       c.add(opening_km);

       opening_kms= new JTextField("");
       opening_kms.setBounds(200,280,258,30);
       opening_kms.setFont(new java.awt.Font("Times New Roman", 1,25)); // NOI18N
       c.add(opening_kms);

       closing_km= new JLabel("Closing Km");
       closing_km.setBounds(500,280,258,30);
       closing_km.setFont(new java.awt.Font("Times New Roman", 1,25)); // NOI18N
       c.add(closing_km);

       closing_kms= new JTextField("");
       closing_kms.setBounds(700,280,258,30);
       closing_kms.setFont(new java.awt.Font("Times New Roman", 1,25)); // NOI18N
       c.add(closing_kms);

       totalkm= new JLabel("Total Km");
       totalkm.setBounds(0,330,258,30);
       totalkm.setFont(new java.awt.Font("Times New Roman", 1,25)); // NOI18N
       c.add(totalkm);

       totalkms= new JTextField("");
       totalkms.setBounds(200,330,258,30);
       totalkms.setFont(new java.awt.Font("Times New Roman", 1,25)); // NOI18N
       c.add(totalkms);
 setLayout(null);
  }

  public static void main( String[] args )
  {
      final Showdata1 frame = new Showdata1();
      frame.setVisible(true);

}
}

试试这个

int val = Integer.parseInt(textField1.getText()) - Integer.parseInt(textField2.getText());

详情请参阅

创建这样一个类

public class MyTextField extends JTextField {
    // whaterver you want...
    public Integer getValue(){
        if(getText().length()  == 0)
            return 0;
        return Integer.parseInt(getText());
    }
}

然后你可以通过调用
getValue（）
method
来获取int值。这将自动更新我的答案。。