Question

我正在尝试制作一个计算器，但是有问题。当我多次显示答案时，程序会将答案一遍又一遍，如 here 下图所示。

这是我的代码，任何人都可以帮我解决这个问题（在显示下一个答案之前清空标签）。谢谢！

   package Räknare;

        import javax.swing.JOptionPane;
        import javax.swing.JPanel;
        import javax.swing.JTextField;
        import javax.swing.ImageIcon;
        import javax.swing.JButton;

        import java.awt.BorderLayout;
        import java.awt.Component;
        import java.awt.Dimension;
        import java.awt.FlowLayout;
        import java.awt.Frame;
        import java.awt.Graphics;
        import java.awt.GraphicsConfiguration;
        import java.awt.LayoutManager;
        import java.awt.TextField;
        import java.awt.event.ActionEvent;
        import java.awt.event.ActionListener;

        import javax.swing.JFrame;
        import javax.swing.JLabel;


        public class huvudklassen extends JFrame {
            static GraphicsConfiguration gc = null;

        // Variables 
            static JLabel welcome = new JLabel("Welcome to my calculator");
            static JLabel theequation = new JLabel("what do you want to caculate?");




            static JFrame frame1 = new JFrame(gc);
            static JFrame frame2 = new JFrame(gc);

            static JTextField s = new JTextField();

            static JButton start = new JButton("start");
            static JButton calculate = new JButton("Calculate");
        //
                public static void frame() {

                frame1.setResizable(false);
                frame1.setVisible(true);
                frame1.setSize(400, 500);
                frame1.setTitle("My Calculatur");
                frame1.setLayout(null);
                frame1.setDefaultCloseOperation(EXIT_ON_CLOSE);
                frame1.setLocationRelativeTo(null);


                welcome.setBounds(120, 155, 200, 50);;
                start.setBounds(150,200,100,50);

                frame1.add(welcome);
                frame1.add(start);

                start.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                frame1.setVisible(false);
                frame2.setSize(400, 500);
                frame2.setResizable(false);
                frame2.setVisible(true);
                frame2.setDefaultCloseOperation(EXIT_ON_CLOSE);
                frame2.setLayout(null);
                frame2.setTitle("Caculation");
                frame2.setLocationRelativeTo(null);

                s.setBounds(150,200,100,30);
                theequation.setBounds(120,155,200,50);
                calculate.setBounds(120, 235, 150, 40);

                frame2.add(s);
                frame2.add(theequation);
                frame2.add(calculate);


                calculate.addActionListener(new ActionListener() {

                    public void actionPerformed1(ActionEvent a) {


                    String theequation2 = s.getText();

                    String left = "";
                    String tecken = "";
                    String right = "";

        //          if (theequation2 == null || theequation2.equals(""))


                    if (theequation2.contains("+")) {
                        left = left + theequation2.substring(0, theequation2.indexOf("+"));
                        right = right + theequation2.substring(theequation2.indexOf("+") + 1);
                        tecken = tecken + "+";
                        }

                    if (theequation2.contains("-")) {
                        left = left + theequation2.substring(0, theequation2.indexOf("-"));
                        right = right + theequation2.substring(theequation2.indexOf("-") + 1);
                        tecken = tecken + "-";
                        }

                    if (theequation2.contains("*")) {
                        left = left + theequation2.substring(0, theequation2.indexOf("*"));
                        right = right + theequation2.substring(theequation2.indexOf("*") + 1);
                        tecken = tecken + "*";
                        }

                    if (theequation2.contains("/")) {
                        left = left + theequation2.substring(0, theequation2.indexOf("/"));
                        right = right + theequation2.substring(theequation2.indexOf("/") + 1);
                        tecken = tecken + "/";
                        }

                    if (theequation2.contains("^")) {
                        left = left + theequation2.substring(0, theequation2.indexOf("^"));
                        right = right + theequation2.substring(theequation2.indexOf("^") + 1);
                        tecken = tecken + "^";
                        }

                    left = left.trim();
                    right = right.trim();   
                    double left1 = Double.parseDouble(left);
                    double right1 = Double.parseDouble(right);

                    double svar = 0;

                    if (tecken.equals("+"))
                        svar = svar + left1 + right1;

                    if (tecken.equals("-"))
                        svar = svar + (left1 - right1);

                    if (tecken.equals("*"))
                        svar = svar + left1 * right1;

                    if (tecken.equals("/"))
                        svar = svar + left1 * right1;

                    if (tecken.equals("%"))
                        svar = svar + left1 % right1;

                    if (tecken.equals("^")) {
                            svar = Math.pow(left1, right1); 
                    }

                    String answer1 = Double.toString(svar);
        //          JOptionPane.showMessageDialog(null, answer1);

                    JLabel answer = new JLabel();
                    answer.setBounds(180, 300, 150, 40);
                    answer.setText(answer1);


                    frame2.add(answer);
                    frame2.revalidate();
                    frame2.repaint();



                    }

                    @Override
                    public void actionPerformed(ActionEvent e) {
                        ActionEvent ActionEvent = null;
                        actionPerformed1(ActionEvent);

                    }

                });

            }
                });
                }


            public static void main(String[] args) {
                frame();
            }

        }



    JLabel answer = new JPanel();
    //          answer.setBounds(180, 300, 150, 40);

Answer 1

您应该使用相同的标签，而不是每次都使用新标签。

                JLabel answer = new JLabel();
                answer.setBounds(180, 300, 150, 40);
                answer.setText(answer1);

如何在再次显示之前清空标签？在Java

1 个答案: