如何在actionListener(actionEvent e)中声明JLabels，以便在JButton被点击时设置Text。

Question

我正在编写一个石头剪刀布游戏，我试图让每一个JLabels在三个按钮（石头、纸、剪刀）被点击时更新。

问题是每个JLabels都是在createWindow()中定义的，我需要它们也在ActionListener(ActionEvent e)中定义。

我试着从createWindow()和JLabels更新中复制粘贴一些代码，但唯一的问题是，它创建了一个没有按钮的全新窗口（只包含文本）。如果我尝试在主方法之外实例化标签，JLabels根本就不会出现。

任何帮助都是值得感激的（无论我是否要重新编写整个程序），我是Java和Swing的新手，任何批评都会以某种方式帮助我。我是在Eclipse IDE中编写的）。

  import java.awt.*;
  import java.awt.event.ActionEvent;
  import java.awt.event.ActionListener;
  import javax.swing.*;

  public class RockPaperScissors extends JPanel implements ActionListener {
public static void main(String[] args) {
    RockPaperScissors sm = new RockPaperScissors();
    sm.createWindow();
}
private void createWindow() {
    // create JFrame/JPanel
    JFrame frame = new JFrame("Rock! Paper! Scissors!");
    JPanel panel = new JPanel();
    JLabel title = new JLabel("Rock! Paper! Scissors!");
    JLabel playerchoice = new JLabel("");
    JLabel computerdecision = new JLabel("");
    JLabel outcome = new JLabel("");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setLocationRelativeTo(null);
    frame.setVisible(true);
    frame.pack();
    frame.setExtendedState(JFrame.MAXIMIZED_BOTH);
    JButton button1 = new JButton("Rock");
    panel.add(button1);
    button1.addActionListener(this);
    button1.setBounds(480, 500, 100, 50);
    JButton button2 = new JButton("Paper");
    panel.add(button2);
    button2.addActionListener(this);
    button2.setBounds(590, 500, 100, 50);
    JButton button3 = new JButton("Scissors");
    panel.add(button3);
    button3.addActionListener(this);
    button3.setBounds(700, 500, 100, 50);
    frame.add(panel);
    panel.setLayout(new BorderLayout());
    GroupLayout layout = new GroupLayout(this);
    this.setLayout(layout);
    panel.add(title);
    panel.add(playerchoice);
    panel.add(computerdecision);
    panel.add(outcome);
    outcome.setBounds(571, 90, 260, 200);
    computerdecision.setBounds(571, 100, 260, 200);
    playerchoice.setBounds(571, 120, 260, 200);
    title.setBounds(571, 0, 260, 200);
}
     public void actionPerformed(ActionEvent e) {
    // JLabels
    int choice = 0;
    int computerchoice = 0;
    int min = -1;
    int max = -3;
    computerchoice = (int) (Math.random() * (max - min - 1) + min);
    if (computerchoice == -1) {
        panel.add(computerdecision);
        computerdecision.setText("The Computer Chose Rock!");
        // for checking
        System.out.println("The Computer Chose Rock!");
    } else if (computerchoice == -2) {
        panel.add(computerdecision);
        computerdecision.setText("The Computer Chose Paper!");
        // for checking
        System.out.println("The Computer Chose Paper!");
    } else if (computerchoice == -3) {
        panel.add(computerdecision);
        computerdecision.setText("The Computer Chose Scissors!");
        // for checking
        System.out.println("The Computer chose Scissors!");
    }
    if (e.getActionCommand().equals("Rock")) {
        choice = 1;
        panel.add(playerchoice);
        playerchoice.setText("You chose Rock!");
        // for checking
        System.out.println("You chose Rock!");
    } else if (e.getActionCommand().equals("Paper")) {
        choice = 2;
        panel.add(playerchoice);
        playerchoice.setText("You chose Paper!");
        // for checking
        System.out.println("You chose Paper!");
    } else if (e.getActionCommand().equals("Scissors")) {
        choice = 3;
        panel.add(playerchoice);
        playerchoice.setText("You chose Scissors!");
        // for checking
        System.out.println("You chose Scissors!");
    }
    if (choice + computerchoice == 0) {
        panel.add(outcome);
        outcome.setText("It is a Tie!");
        // for checking
        System.out.println("It is a Tie!");
    } else if (choice + computerchoice == 1 || choice + computerchoice == -2) {
        panel.add(outcome);
        outcome.setText("You Win!");
        // for checking
        System.out.println("You Win!");
    } else if (choice + computerchoice == 2 || choice + computerchoice == -1) {
        panel.add(outcome);
        outcome.setText("You Lose...");
        // for checking
        System.out.println("You Lose...");
    }
}}

Answer 1

你的问题的解决方法很简单，只需在你的应用程序中加入以下功能 panel, playerchoice, computerdecision 和 outcome 成员 RockPaperScissors 类，而不是像这样的局部变量

public class RockPaperScissors extends JPanel implements ActionListener {
     private JPanel panel;
     private JLabel computerdecision;
     private JLabel playerchoice;
     private JLabel outcome;

     ...

     private void createWindow() {
         JFrame frame = new JFrame("Rock! Paper! Scissors!");
         panel = new JPanel();
         playerchoice = new JLabel("");
         computerdecision = new JLabel("");
         outcome = new JLabel("");
         JLabel title = new JLabel("Rock! Paper! Scissors!");
         ...
     }
     ...
}