只有最后一个JPanel ActionListeners在工作

Question

我正在为游戏创建一个菜单，并试图创建4个JPanel，每个JPanel都可以滚动浏览玩家可以使用的化身。

它与JPanel的一个实例一起工作，但不能超过一个，并且只有最后一个JPanel才能工作。我认为这一定与JPanels中每个组件的创建有关，但我无法理解。

我会把课贴在下面。

@SuppressWarnings("serial")
public class Menu extends JPanel implements ActionListener {
  JLabel playerAvatar;
  JLabel playerTxt;
  JButton playerPlus;
  JButton playerMinus;
  Font font_1 = new Font("calibri", Font.BOLD, 55);
  Font font_2 = new Font("calibri", Font.BOLD, 30);
  int playerAvatarCount = -1;
  public Menu() {
    init();
  }
  public void init() {
    setOpaque(false);
    setLayout(new FlowLayout());
    setPreferredSize(new Dimension(1000, 800));
    JPanel[] players = new JPanel[4];
    players[0] = playerChoose(1);
    players[1] = playerChoose(2);
    players[2] = playerChoose(3);
    players[3] = playerChoose(4);
    for (int i = 0; i < 4; i++) {
      add(players[i]);
    }
  }
  private JPanel playerChoose(int i) {
    JPanel plyrPanel = new JPanel();
    plyrPanel.setPreferredSize((new Dimension(240, 200)));
    plyrPanel.setOpaque(false);
    playerAvatar = new JLabel("", SwingConstants.CENTER);
    playerAvatar.setIcon(new ImageIcon("C:\Users\Travis\workspace\BoardGame\none.png"));
    playerAvatar.setBackground(Color.WHITE);
    playerAvatar.setOpaque(true);
    playerAvatar.setBorder(BorderFactory.createLineBorder(Color.decode("#5B5C5C"), 3));
    playerAvatar.setPreferredSize(new Dimension(105, 155));
    playerPlus = new JButton(">");
    playerPlus.setPreferredSize(new Dimension(60, 155));
    playerPlus.setFont(font_1);
    playerPlus.setForeground(Color.decode("#5B5C5C"));
    playerPlus.setBorder(BorderFactory.createLineBorder(Color.decode("#5B5C5C"), 1));
    playerPlus.setBackground(Color.decode("#B2DBA4"));
    playerPlus.addActionListener(this);


    playerMinus = new JButton("<");
    playerMinus.setPreferredSize(new Dimension(60, 155));
    playerMinus.setFont(font_1);
    playerMinus.setForeground(Color.decode("#5B5C5C"));
    playerMinus.setBorder(BorderFactory.createLineBorder(Color.decode("#5B5C5C"), 1));
    playerMinus.setBackground(Color.decode("#B2DBA4"));
    playerMinus.addActionListener(this);
    playerTxt = new JLabel("Player " + i + "", SwingConstants.CENTER);
    playerTxt.setFont(font_2);
    playerTxt.setOpaque(false);
    playerTxt.setForeground(Color.WHITE);
    plyrPanel.add(playerMinus);
    plyrPanel.add(playerAvatar);
    plyrPanel.add(playerPlus);
    plyrPanel.add(playerTxt);
    validate();
    return plyrPanel;
  }
  @Override
  public void actionPerformed(ActionEvent e) {
      if (e.getSource() == playerPlus) {
        playerAvatar
            .setIcon(new ImageIcon("C:\Users\Travis\workspace\BoardGame\frog" + ++playerAvatarCount + ".png"));
      }
      if (e.getSource() == playerMinus) {
        playerAvatar
            .setIcon(new ImageIcon("C:\Users\Travis\workspace\BoardGame\frog" + --playerAvatarCount + ".png"));
      }
      if (playerAvatarCount < 0) {
        playerAvatar.setIcon(new ImageIcon("C:\Users\Travis\workspace\BoardGame\none.png"));
        playerAvatarCount = -1;
      } else if (playerAvatarCount > 3) {
        playerAvatar.setIcon(new ImageIcon("C:\Users\Travis\workspace\BoardGame\frog3.png"));
        playerAvatarCount = 3;
      }
    }
  }

Answer 1

您确实需要面向对象。这4个菜单元素中的每一个都是一种类型的类，它们都应该有自己的playerPlus和playerMinus按钮的实例。

public class MenuElement extends JPanel {
    JLabel playerAvatar;
    JLabel playerTxt;
    JButton playerPlus;
    JButton playerMinus;
    public void initComponent() {
        //lay out your elements here
    }
    public void addListeners() {
        //setUpYour listeners here
    }
}

如果您编写这样的类，那么您的菜单元素将引用其自己的播放器加号和减号按钮实例。你遇到的问题是，你有一个playerPlus和playerMinus的实例，它们在四个不同的组件中共享。

Answer 2

在您的方法中，您可以重新创建按钮playerPlus = new JButton(">");

但是在actionPerformed（）中，您可以通过与字段进行比较来检查源

if (e.getSource() == playerPlus)

该字段仅包含上次创建的按钮，因此条件

if (e.getSource() == playerPlus)
if (e.getSource() == playerMinus)

总是错误的。

最简单的方法是定义按钮的名称，并在检查中使用该名称

playerPlus = new JButton(">");
playerPlus .setName(">");

然后检查

if (e.getSource() instanceof JButton && ">".equals(((JButton)e.getSource()).getName()) ) {
  //do your logic here
}

Answer 3

这是因为您将JButtons定义为类中的字段。当您调用playerChoose(int)时，您将playerPlus and playerMinus分配给新JButton的引用。每次调用playerChoose时都会发生这种情况。因此，当ActionListener将事件源（e.getSource()）与存储在playerPlus或playerMinus中的引用进行比较时，只有最后定义的引用有效，因为这是最后一次设置playerPlus/playerMinus。