Question

所以我尝试寻找解决方案，但一无所获，也不知道如何让我的搜索更准确。我有这个用于Java的家庭作业，我遇到了JComboBox，但并不总是改变我JPanel中的组件。这是我第一次发帖提问，对不起，如果我搞砸了这个问题。无论如何，这是代码（目的是为飞行公司创建GUI）。

问题在于，当我从选项1（“办公室”）转到选项2（“试用”）时，JComboBox执行它应该做的事情并将JPanel（jplType）更改为应该，但当我从选项3（“主机”）回到选项2时，它根本不会改变JPanel（jplType）。

问题是，我在

中添加了System.out.println()

if(index == 1)
{
  // ..
}

它会打印出来但由于某种原因它无法添加JCheckBox。

如果有人能弄清楚我在这里搞砸了什么，我会很感激，因为我已经在这里待了一个小时。

提前致谢。

public class abc {

public static void main(String[] args) {
    CompanyDialog abc = new CompanyDialog();

    }

}

class CompanyDialog extends JFrame {

    private String[] employee = {"office", "Pilot", "Host"};
    private String[] employeeTitles = {"Office options", "Pilot options", "Host options"};
    public final static int GAP = 3;
    // Frame Constants.
    public final static int FWIDTH = 605;
    public final static int FHEIGHT = 235;
    // Constant for the Combo Box.
    public final static int CBWIDTH = FWIDTH/3-4;
    public final static int CBHEIGHT = 20;
    // Width constant for TextField.
    public final static int TWIDTH = 20;

    private JPanel jplType = new JPanel(new FlowLayout(FlowLayout.LEFT, GAP, GAP));

    private JComboBox jcbType = new JComboBox(employee);
    private JLabel jlblOptions = new JLabel();
    private JTextField jtfOptions = new JTextField(TWIDTH);

public CompanyDialog(){
    super("Worker Dialog");

    //Combo box panel configurations
    JPanel jplWorker = new JPanel(new FlowLayout(FlowLayout.LEFT, GAP, GAP));

    JTextField nametxt = new JTextField(TWIDTH);
    jcbType.setPreferredSize(new Dimension(CBWIDTH,CBHEIGHT));
    jplWorker.add(jcbType);

    setDisplay(0);

    add(jplWorker, BorderLayout.NORTH);
    setAlwaysOnTop(true);
    setVisible(true);
    setSize(FWIDTH, FHEIGHT);
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setLocationRelativeTo(null);
    setResizable(false);

    jcbType.addItemListener(new ItemListener() { /**Handle item selection*/
        public void itemStateChanged(ItemEvent e) {
            jplType.removeAll();
            setDisplay(jcbType.getSelectedIndex());
        }
    }
            );
}
public void setDisplay(int index){
    jplType.add(jlblOptions);
    jplType.add(jtfOptions);
    jplType.setBorder(new TitledBorder(employeeTitles[index]));
    if(index == 0){
        jlblOptions.setText("Office:");
        jtfOptions.setText("");
    }
    else if(index == 1) {
        jlblOptions.setText("Air Time:");
        jtfOptions.setText("0");
        JCheckBox jcbCaptain = new JCheckBox("Is a Captain");
        jplType.add(jcbCaptain);
    }
    else if(index == 2){
        jlblOptions.setText("Air Time:");
        jtfOptions.setText("0");
    }

    add(jplType, BorderLayout.CENTER);
}
}

Answer 1

从

更改setDisplay（）方法

public void setDisplay(int index){
        jplType.add(jlblOptions);
        jplType.add(jtfOptions);
        jplType.setBorder(new TitledBorder(employeeTitles[index]));
        if(index == 0){
            jlblOptions.setText("Office:");
            jtfOptions.setText("");
        }
        else if(index == 1) {
            jlblOptions.setText("Air Time:");
            jtfOptions.setText("0");
            JCheckBox jcbCaptain = new JCheckBox("Is a Captain");
            jplType.add(jcbCaptain);
        }
        else if(index == 2){
            jlblOptions.setText("Air Time:");
            jtfOptions.setText("0");
        } 
        else
        {
            jlblOptions.setText("");
            jtfOptions.setText("");
        }
        add(jplType, BorderLayout.CENTER);

     }

到

public void setDisplay(int index){
        jplType.add(jlblOptions);
        jplType.add(jtfOptions);
        jplType.setBorder(new TitledBorder(employeeTitles[index]));
        if(index == 0){
            jlblOptions.setText("Office:");
            jtfOptions.setText("");
        }
        else if(index == 1) {
            jlblOptions.setText("Air Time:");
            jtfOptions.setText("0");
            JCheckBox jcbCaptain = new JCheckBox("Is a Captain");
            jplType.add(jcbCaptain);
        }
        else if(index == 2){
            jlblOptions.setText("Air Time:");
            jtfOptions.setText("0");
        } 
        else
        {
            jlblOptions.setText("");
            jtfOptions.setText("");
        }
        add(jplType, BorderLayout.CENTER);

        this.revalidate();
    }

Answer 2

    private JPanel jplType = new JPanel(new FlowLayout(FlowLayout.LEFT, GAP, GAP));
    ////////////////////////////
    ///////////////////////////
    public void setDisplay(int index){
       jplType.add(jlblOptions);
       jplType.add(jtfOptions);
       jplType.setBorder(new TitledBorder(employeeTitles[index]));
       if(index == 0){
           jlblOptions.setText("Office:");
           jtfOptions.setText("");
       }
       else if(index == 1) {
           jlblOptions.setText("Air Time :");
           jtfOptions.setText("0");
           JCheckBox jcbCaptain = new JCheckBox("Is a Captain");
           jplType.add(jcbCaptain);
       }
       else if(index == 2){
           jlblOptions.setText("Air Time :");
           jtfOptions.setText("0");
       }
       add(jplType, BorderLayout.CENTER); 
       // 
       //
       revalidate();
       repaint(); 
       //
   }

错误的想法是期望Layout会自己安排他的内容，特别是当你使用如FlowLayout这样简单的布局时

JComboBox仅在从第1个到第2个（不是第3个到第2个）时更改组件

2 个答案: