秋千组合框

Question

好了，所以我简单地定义，像这样的组合框...

JComboBox yearSelect = new JComboBox(); 

现在，我还没有将此添加到面板或任何东西，我刚才定义它。当我运行该应用程序时，没有任何显示..当我注释掉这条线......该应用程序显示其他面板，就像我想要的那样..是否有什么我做错了？也许我忘记了一些与组合框有关的事情？我想这可能是我错过的一些愚蠢的东西。

这是我的整个内容构造函数。

private Container pane;   // content pane 
private JPanel calendarPanel; // where our calendar will go 
private JPanel datePanel;  // where "todays date" will go 
private JPanel pnlToolbar;  // tool bar for moving in the year 
private JPanel bottomPanel; 
private JPanel yearPanel; 
private JLabel lbCurrentMonth; 
private JLabel dateLabel; 
private JButton monthBack; 
private JButton monthForward; 
private JComboBox yearSelect; 

private Date today = new Date(); 
private int currentMonth = today.getMonth(); 
private int currentYear = today.getYear(); 
final private String [] days = {"Sunday", "Monday", "Tuesday", 
           "Wednesday", "Thursday", "Friday", 
           "Saturday"}; 

final private String [] months = {"January", "Febuary", "March", "April", 
            "May", "June", "July", "August", 
            "September", "October", "November", 
            "December"}; 


public Calendar() { 

    // call the calendar frame class constructor (Window class) 
    // this function will setup our basic window 
    super(); 

    // define the current date of the calendar as today 



    // below are attributes to our window. They define what content 
    // is on them. 


    // define our window 
    pane = window.getContentPane(); 
    pane.setLayout(new BorderLayout()); 

    calendarPanel = new JPanel(new FlowLayout()); 
    calendarPanel.setBorder(BorderFactory.createTitledBorder("Calendar")); 

    pnlToolbar = new JPanel(new FlowLayout(FlowLayout.CENTER, 40, 5)); 
    pnlToolbar.setSize(300, 45); 


    ////////////////////////////////////////////////////////////////////// 
    /* setup our lower date panel, that displays todays date 
    and the year drop down menu */ 

    // for "todays date" 
    dateLabel = new JLabel(returnDateString()); 
    dateLabel.setFont(new Font(null, Font.BOLD, 12)); 

    datePanel = new JPanel(new FlowLayout(FlowLayout.LEFT, 5, 5)); 
    datePanel.add(new JLabel("Todays Date: "), BorderLayout.WEST); 
    datePanel.add(dateLabel, BorderLayout.EAST); 

    // for "year select" 
    // yearSelect = new JComboBox(); 

    yearPanel = new JPanel(new FlowLayout(FlowLayout.RIGHT, 5, 5)); 
    //yearPanel.add(yearSelect); 

    bottomPanel = new JPanel(new BorderLayout()); 
    bottomPanel.add(datePanel, BorderLayout.WEST); 
    //bottomPanel.add(yearPanel, BorderLayout.EAST); 

    // setup the tool bar panel 
    lbCurrentMonth = new JLabel(months[currentMonth]); 
    monthBack = new JButton("<<"); 
    monthForward = new JButton(">>"); 
    monthForward.setEnabled(true); 
    monthBack.setEnabled(true); 

    pnlToolbar.add(monthBack); 
    pnlToolbar.add(lbCurrentMonth); 
    pnlToolbar.add(monthForward); 



    // add everything to the content panel 
    pane.add(calendarPanel, BorderLayout.CENTER); 
    pane.add(bottomPanel, BorderLayout.SOUTH); 
    pane.add(pnlToolbar, BorderLayout.NORTH); 

Answer 1

您需要添加模型才能显示数据。见JComboBox.setModel。

Answer 2

没什么，我附上了我上面的代码的其余部分。即使我没有将该对象添加到面板，它也会这样做。我只是实例化对象，仅此而已。有任何想法吗？此外，我创建了一个单独的应用程序来确保我正确地执行组合框，这里是我注意到的。它不中sperate应用同样的事情..下面..（很脏）

public class Main { 


public static void main(String[] args) { 
    String [] selectFill = {"Cat", "Dog"}; 
    JFrame window = new JFrame("Window"); 
    window.setBounds(0, 0 , 800, 600); 
    window.setVisible(true); 
    window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
    window.setLayout(null); 

    //JComboBox selectBox = new JComboBox(selectFill); 
    JLabel check = new JLabel("Select: "); 
    JPanel contentPanel = new JPanel(new FlowLayout()); 
    Container pane = window.getContentPane(); 
    pane.add(contentPanel); 
    pane.setLayout(new FlowLayout()); 
    contentPanel.add(check); 
    //contentPanel.add(selectBox); 
} 

} 

由于一些奇怪的原因，当我调整窗口的大小，或minmize它加载的内容。或者..如果我注释掉组合框对象的行，它也显示内容。