-3

我运行此脚本，当我单击添加时，它可以工作并添加 2 个框，但是当我单击任何其他按钮时，它不会打开带有答案的框。我不知道为什么消息框没有打开其中任何一个的答案，但添加的任何人都可以解释并告诉我修复。编码：

import javax.swing.JFrame;
import javax.swing.JButton;
import javax.swing.Icon;
import javax.swing.ImageIcon;
import javax.swing.JOptionPane;
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JTextField;

public class Gui extends JFrame{

    private JButton reg;
    private JButton reg2;
    private JButton reg3;
    private JButton reg4;
    private JTextField text;
    private JTextField text2;
    private JTextField text3;
    private JTextField text4;
    private JTextField text5;
    private JTextField text6;
    private JTextField text7;
    private JTextField text8;


    public Gui(){
        super("Buttons");
        setLayout(new FlowLayout());



        text = new JTextField(20);
        text2 = new JTextField(20);
        text3 = new JTextField(20);
        text4 = new JTextField(20);
        text5 = new JTextField(20);
        text6 = new JTextField(20);
        text7 = new JTextField(20);
        text8 = new JTextField(20);
        reg = new JButton("Add");
        reg2 = new JButton("Divide");
        reg3 = new JButton("Multiply");
        reg4 = new JButton("Subtract");

        add(text);
        add(text2);
        add(reg);
        add(text3);
        add(text4);
        add(reg2);
        add(text5);
        add(text6);
        add(reg3);
        add(text7);
        add(text8);
        add(reg4);



        handlerClass handler = new handlerClass();
        reg.addActionListener(handler);
        reg2.addActionListener(handler);
        reg3.addActionListener(handler);
        reg4.addActionListener(handler);






    }

    public class handlerClass implements ActionListener{
        public void actionPerformed(ActionEvent event){
            String st = text.getText();
            String st2 = text.getText();
            String st3 = text.getText();
            String st4 = text.getText();
            String st5 = text.getText();
            String st6 = text.getText();
            String st7 = text.getText();
            String st8 = text.getText();

            int txt1 = Integer.parseInt(st);
            int txt2 = Integer.parseInt(st2);
            int txt3 = Integer.parseInt(st3);
            int txt4 = Integer.parseInt(st4);
            int txt5 = Integer.parseInt(st5);
            int txt6 = Integer.parseInt(st6);
            int txt7 = Integer.parseInt(st7);
            int txt8 = Integer.parseInt(st8);


            if(event.getActionCommand()=="Add"){
                int add=txt1+txt2;
                JOptionPane.showMessageDialog(null, String.format("Answer: %s", add));
            }

            if(event.getActionCommand()=="Divide"){
                if(txt4>0){
                    int add2=txt3/txt4;
                        JOptionPane.showMessageDialog(null, String.format("Answer: %s", add2));
                }else{
                JOptionPane.showMessageDialog(null, String.format("Cannot divide by zero"));
                }
            }

            if(event.getActionCommand()=="Multiply"){
                int add3=txt5*txt6;
                JOptionPane.showMessageDialog(null, String.format("Answer: %s", add3));
            }

            if(event.getActionCommand()=="Subtract"){
                int add4=txt7-txt8;
                JOptionPane.showMessageDialog(null, String.format("Answer: %s", add4));
            }
        }
    }
}
4

2 回答 2

2

不要使用==. 请改用equals(...)orequalsIgnoreCase(...)方法。了解 == 检查两个对象是否相同，这不是您感兴趣的。另一方面，这些方法检查两个字符串是否具有相同顺序的相同字符，这在这里很重要。所以而不是

if (fu == "bar") {
  // do something
}

做，

if ("bar".equals(fu)) {
  // do something
}

或者，

if ("bar".equalsIgnoreCase(fu)) {
  // do something
}
于 2012-06-02T14:52:05.123 回答
1

==比较引用的相等性。

.equals()比较字符串的值。

if("Multiply".equals(event.getActionCommand()))
{

}
于 2012-06-02T14:58:48.607 回答