Java JCombobox 不会更改 JPanel 中的图像

Question

>我有一个问题。我有一个元素会 JPanel。在这个JPanel将是四个JButton和图像。此图像是"绿色LED灯"，会根据按下哪个JButton而变化。效果很好。但我也希望JComboBox改变这个参数。

这就是问题所在。尽管参数（从 1 到 4）正在发生变化（这显示了 LED 附近的 JLabel），但是图片（LED灯）不想将其更改为正确的图片。

截图

该计划分为3个班级。

MyFrame.class这个主类。

public class MyFrame extends JFrame {
int ctrlTriggers = 1;
private JLabel label = new JLabel();
private Triggers triggers;
private String[] typeTrig = {"1", "2", "3", "4"};
public MyFrame() {
  JFrame frame = new JFrame("JComboBox Problem");
  frame.setBounds(50, 0, 800, 240);
  frame.setLayout(new BorderLayout());

  int tvalue = 1;
  String tstr = Integer.toString(tvalue);
  JPanel panelTrig = new JPanel(new BorderLayout());
  label = new JLabel(tstr, 4);
  panelTrig.add(label);
  final JLabel et = label;
  triggers = new Triggers(typeTrig, "trigger " + Integer.toString(1));
  triggers.addChangeListener(new ChangeListener() {
     public void stateChanged(ChangeEvent e) {
        Triggers tr = (Triggers) e.getSource();
        int vol;
        vol = (int) tr.getValue();
        et.setText(Integer.toString(vol));
     }
  });
  panelTrig.add(triggers, BorderLayout.LINE_START);

  // JCOMBOBOX
  JPanel pCombo = new JPanel();
  pCombo.setLayout(new FlowLayout());
  Presets combo = new Presets();
  combo.addChangeListener(new ChangeListener() {
     public void stateChanged(ChangeEvent e) {
        Presets presetcombo = (Presets) e.getSource();
        int tval;
        tval = (int) presetcombo.getValue(ctrlTriggers);
        label.setText(Integer.toString(tval));
        triggers.setValue(tval);
     }
  });
  pCombo.add(combo, BorderLayout.CENTER);
  frame.add(pCombo, BorderLayout.CENTER);
  frame.add(panelTrig, BorderLayout.LINE_START);

  frame.addWindowListener(new WindowAdapter() {
     public void windowClosing(WindowEvent e) {
        System.exit(0);
     }
  });
  setDefaultCloseOperation(DISPOSE_ON_CLOSE);
  frame.show();
}
public static void main(String[] args) {
  SwingUtilities.invokeLater(new Runnable() {
     public void run() {
        new MyFrame();
     }
  });
 }
}

触发器.class这个类是 JPanel，其中有 4 个 JButton 和"类似 LED 的图像"

public class Triggers extends JPanel
    implements ActionListener, ItemListener {
public Triggers(String s[], String name) {
  JPanel panel = new JPanel(new BorderLayout());
  this.value = Integer.parseInt(s[selected]);
  for (int i = 0; i < s.length; i++) {

     ImageIcon cup = new ImageIcon();
     button[i] = new JButton(z[i], cup);
     button[i].setPreferredSize(new Dimension(70, 25));
     Font font = button[i].getFont();
     button[i].setFont(new Font(font.getFontName(), font.getStyle(), 10));
     button[i].setActionCommand(s[i]);
     if (i == selected) {
        button[i].setSelected(true);
     } else {
        button[i].setSelected(false);
     }
  }

  ButtonGroup group = new ButtonGroup();
  for (int i = 0; i < s.length; i++) {
     group.add(button[i]);
     button[i].addActionListener(this);
     button[i].addItemListener(this);
  }

  diody = new JLabel(createImageIcon("/resources/diody/"
          + this.value
          + ".png"));

  diody.setPreferredSize(new Dimension(20, 100));
  JPanel triggs = new JPanel(new FlowLayout());
 triggs.setPreferredSize(new Dimension(80, 120));
  for (int i = 0; i < s.length; i++) {
     triggs.add(button[i]);
  }
  panel.add(triggs, BorderLayout.LINE_START);
  panel.add(diody, BorderLayout.LINE_END);
  add(panel);

}
public void actionPerformed(ActionEvent e) {
  cmd = e.getActionCommand();
  diody.setIcon(createImageIcon("/resources/diody/"
          + cmd
          + ".png"));

  if (cmd.equals("1")) {
     setValue(1);
  } else if (cmd.equals("2")) {
     setValue(2);
  } else if (cmd.equals("3")) {
     setValue(3);
  } else if (cmd.equals("4")) {
     setValue(4);
  }
}
public static ImageIcon createImageIcon(String path) {
  java.net.URL imgURL = Triggers.class.getResource(path);
  if (imgURL != null) {
     return new ImageIcon(imgURL);
  } else {
     System.err.println("Couldn't find file: " + path);
     return null;
  }
}
public int setController() {
  return value;
}
public void setValue(int k) {
  this.value = k;
  cmd = Integer.toString(this.value);
  repaint();
  fireChangeEvent();
}
public int getValue() {
  return this.value;
}
public void setSel(int k) {
  selected = k;
  repaint();
  fireChangeEvent();
}
public void itemStateChanged(ItemEvent ie) {
  String s = (String) ie.getItem();
}
public void addChangeListener(ChangeListener cl) {
  listenerList.add(ChangeListener.class, cl);
}
public void removeChangeListener(ChangeListener cl) {
  listenerList.remove(ChangeListener.class, cl);
}
protected void fireChangeEvent() {
  Object[] listeners = listenerList.getListenerList();
  for (int i = listeners.length - 2; i >= 0; i -= 2) {
     if (listeners[i] == ChangeListener.class) {
        if (changeEvent == null) {
           changeEvent = new ChangeEvent(this);
        }
        ((ChangeListener) listeners[i + 1]).stateChanged(changeEvent);
     }
  }
}
private ChangeEvent changeEvent = null;
private EventListenerList listenerList = new EventListenerList();
private JLabel diody;
private int x = 1;
private int y = 4;
private JButton button[] = new JButton[y];
double border = 4;
double vborder = 1;
int controller[] = new int[4];
String z[] = {"1", "2", "3", "4"};
private int selected;
private int value;
private String cmd;
}

类预设 这是JCombobox。

public class Presets extends JPanel
       implements ActionListener {
  private int value;
  private int[] ctrlIdx = new int[27];
  private int controller;
  private ChangeEvent changeEvent = null;
  private EventListenerList listenerList = new EventListenerList();
  private JLabel label;
  private String[][] presets = {
     {"0", "3"},
     {"1", "2"},
     {"2", "3"},
     {"3", "1"},
     {"4", "4"},
     {"5", "2"},};
  String[] ctrlName = {"preset 1 (value 3)", "preset 2 (value 2)", "preset 3 (value 3)", "preset 4 (value 1)", "preset 5 (value 4)", "preset 5 (value 2)"};
  public Presets() {

     JPanel panel = new JPanel();
     panel.setLayout(new BorderLayout());
     panel.setPreferredSize(new Dimension(600, 30));
     JComboBox combolist = new JComboBox(ctrlName);
     combolist.setSelectedIndex(2);
     combolist.addActionListener(this);
     combolist.setPreferredSize(new Dimension(300, 30));
     label = new JLabel();
     label.setFont(label.getFont().deriveFont(Font.ITALIC));
     label.setHorizontalAlignment(JLabel.CENTER);
     int indeks = combolist.getSelectedIndex();
     updateLabel(ctrlName[combolist.getSelectedIndex()], indeks);
     label.setBorder(BorderFactory.createEmptyBorder(10, 0, 0, 0));
     label.setPreferredSize(new Dimension(300, 30));

     panel.add(combolist, "East");
     add(panel);
     setPreferredSize(new Dimension(600, 40));
  }
  public void setSelectedItem(int a) {
  }
  public void setValue(int c, int v) {
     controller = c;
     value = v;
     ctrlIdx[controller] = value;
     repaint();
     fireChangeEvent();
  }
  public int getController() {
     return controller;
  }
  public int getValue(int c) {
     int w = (int) ctrlIdx[c];
     return (int) w;
  }
  public void actionPerformed(ActionEvent e) {
     JComboBox cb = (JComboBox) e.getSource();
     String pres = (String) cb.getSelectedItem();
     int indeks = cb.getSelectedIndex();
     updateLabel(pres, indeks);

     for (int i = 0; i < ctrlName.length; i++) {
        for (int j = 0; j < 2; j++) {
           setValue(j, Integer.parseInt(presets[indeks][j]));
        }
     }

  }
  protected void updateLabel(String name, int ii) {
     label.setToolTipText("A drawing of a " + name.toLowerCase());
  }
  protected static ImageIcon createImageIcon(String path) {
     java.net.URL imgURL = Presets.class.getResource(path);
     if (imgURL != null) {
        return new ImageIcon(imgURL);
     } else {
        System.err.println("Couldn't find file: " + path);
        return null;
     }
  }
  public void addChangeListener(ChangeListener cl) {
     listenerList.add(ChangeListener.class, cl);
  }
  public void removeChangeListener(ChangeListener cl) {
     listenerList.remove(ChangeListener.class, cl);
  }
  protected void fireChangeEvent() {
     Object[] listeners = listenerList.getListenerList();
     for (int i = listeners.length - 2; i >= 0; i -= 2) {
        if (listeners[i] == ChangeListener.class) {
           if (changeEvent == null) {
              changeEvent = new ChangeEvent(this);
           }
           ((ChangeListener) listeners[i + 1]).stateChanged(changeEvent);
        }
     }
  }
}

有人可以帮助我，我做错了什么？

Answer 1

图像仅在 Triggers 类的 actionPerformed 方法中开始加载，这意味着当您调用 setValue 以响应 Presets 类引发的 stateChanged 事件时，不会开始加载新图像。

移动图像加载逻辑，使其位于setValue方法中或由setValue方法触发