Java 为什么我的日本人最初看起来是白色的？

我制作了一个JApplet应用程序，它由九个按钮组成

• 当小程序第一次启动时，它是完全白色的。如果单击按钮所在的区域，按钮将变为可见并起作用

• 启动小程序30秒后，按钮变为可见，但背景仍为白色

• 主菜单应该是这样的

为什么小程序不能正确加载？ 小程序的代码如下所示：

ConverterApplet.java:

public class ConverterApplet extends JApplet {

    public void init()
    {
        try{
            SwingUtilities.invokeAndWait(new Runnable(){

                @Override
                public void run() 
                {
                    createGUI();

                }

            });
        }catch(Exception e)
        {
            System.err.println("GUI could not be created.");
        }
    }

    public void start(){}
    public void stop(){}

    public void destroy(){}

    public void paint(java.awt.Graphics g){
        resize(400,400);   
    };

    private void createGUI()
    {
        MainPanel m = new MainPanel();
        getContentPane().add(m,BorderLayout.CENTER); 
    }

}

public class MainPanel extends JPanel implements ActionListener {

    private final static String UNIT_SELECTION_PANEL = "UNIT_SELECTION_CARD";
    private final static String UNIT_CONVERSION_PANEL = "UNIT_CONVERSION_PANEL";    

    JPanel cardPanel;
    private JButton[] UnitButtons;
    private JButton backButton; 
    private CardLayout cardLayout;
    private UnitConversionPanel unitConversionPanel;

    public MainPanel()
    {
        super(new GridBagLayout());

        cardPanel = new JPanel();
        JPanel unitSelectionPanel = new JPanel();

        backButton = new JButton("<-");
        backButton.addActionListener(this);
        backButton.setVisible(false);

        UnitButtons = new JButton[9];
        UnitButtons[0] = new JButton("Length");
        UnitButtons[1] = new JButton("Time");
        UnitButtons[2] = new JButton("Mass");
        UnitButtons[3] = new JButton("Speed");
        UnitButtons[4] = new JButton("Volume");
        UnitButtons[5] = new JButton("Area");
        UnitButtons[6] = new JButton("Pressure");       
        UnitButtons[7] = new JButton("Temperature");
        UnitButtons[8] = new JButton("Energy");

        for(int i=0;i<UnitButtons.length;i++)
        {
            UnitButtons[i].addActionListener(this);
        }

        GridLayout layout = new GridLayout(0,3,20,20);
        unitSelectionPanel.setLayout(layout);

        for(JButton buttons: UnitButtons)
        {
            unitSelectionPanel.add(buttons);
        }

        unitConversionPanel = new UnitConversionPanel();

        cardLayout = new CardLayout();
        cardPanel.setLayout(cardLayout);
        cardPanel.add(UNIT_SELECTION_PANEL, unitSelectionPanel);
        cardPanel.add(UNIT_CONVERSION_PANEL, unitConversionPanel);
        cardLayout.show(cardPanel, UNIT_SELECTION_PANEL);

        GridBagConstraints c = new GridBagConstraints();
        //c.fill = GridBagConstraints.VERTICAL;
        c.gridx = 0;
        c.gridy = 0;
        //c.insets = new Insets(5,5,5,5);
        add(backButton,c); 

        c.fill = GridBagConstraints.BOTH;
        c.weightx = 1;
        c.weighty = 1;
        c.gridx = 0;
        c.gridy = 1;
        c.gridwidth=2;
        c.gridheight=1;
        add(cardPanel,c);       
    }

}

MainPanel.java:

public class ConverterApplet extends JApplet {

    public void init()
    {
        try{
            SwingUtilities.invokeAndWait(new Runnable(){

                @Override
                public void run() 
                {
                    createGUI();

                }

            });
        }catch(Exception e)
        {
            System.err.println("GUI could not be created.");
        }
    }

    public void start(){}
    public void stop(){}

    public void destroy(){}

    public void paint(java.awt.Graphics g){
        resize(400,400);   
    };

    private void createGUI()
    {
        MainPanel m = new MainPanel();
        getContentPane().add(m,BorderLayout.CENTER); 
    }

}

public class MainPanel extends JPanel implements ActionListener {

    private final static String UNIT_SELECTION_PANEL = "UNIT_SELECTION_CARD";
    private final static String UNIT_CONVERSION_PANEL = "UNIT_CONVERSION_PANEL";    

    JPanel cardPanel;
    private JButton[] UnitButtons;
    private JButton backButton; 
    private CardLayout cardLayout;
    private UnitConversionPanel unitConversionPanel;

    public MainPanel()
    {
        super(new GridBagLayout());

        cardPanel = new JPanel();
        JPanel unitSelectionPanel = new JPanel();

        backButton = new JButton("<-");
        backButton.addActionListener(this);
        backButton.setVisible(false);

        UnitButtons = new JButton[9];
        UnitButtons[0] = new JButton("Length");
        UnitButtons[1] = new JButton("Time");
        UnitButtons[2] = new JButton("Mass");
        UnitButtons[3] = new JButton("Speed");
        UnitButtons[4] = new JButton("Volume");
        UnitButtons[5] = new JButton("Area");
        UnitButtons[6] = new JButton("Pressure");       
        UnitButtons[7] = new JButton("Temperature");
        UnitButtons[8] = new JButton("Energy");

        for(int i=0;i<UnitButtons.length;i++)
        {
            UnitButtons[i].addActionListener(this);
        }

        GridLayout layout = new GridLayout(0,3,20,20);
        unitSelectionPanel.setLayout(layout);

        for(JButton buttons: UnitButtons)
        {
            unitSelectionPanel.add(buttons);
        }

        unitConversionPanel = new UnitConversionPanel();

        cardLayout = new CardLayout();
        cardPanel.setLayout(cardLayout);
        cardPanel.add(UNIT_SELECTION_PANEL, unitSelectionPanel);
        cardPanel.add(UNIT_CONVERSION_PANEL, unitConversionPanel);
        cardLayout.show(cardPanel, UNIT_SELECTION_PANEL);

        GridBagConstraints c = new GridBagConstraints();
        //c.fill = GridBagConstraints.VERTICAL;
        c.gridx = 0;
        c.gridy = 0;
        //c.insets = new Insets(5,5,5,5);
        add(backButton,c); 

        c.fill = GridBagConstraints.BOTH;
        c.weightx = 1;
        c.weighty = 1;
        c.gridx = 0;
        c.gridy = 1;
        c.gridwidth=2;
        c.gridheight=1;
        add(cardPanel,c);       
    }

}

public类主面板扩展JPanel实现ActionListener{
专用最终静态字符串单位选择面板=“单位选择卡”；
私有最终静态字符串UNIT\u CONVERSION\u PANEL=“UNIT\u CONVERSION\u PANEL”；
JPanel cardPanel；
私有JButton[]单元按钮；
私有JButton backButton；
私人卡布局卡布局；
专用单元转换面板单元转换面板；
公共主面板（）
{
超级（新GridBagLayout（））；
cardPanel=新的JPanel（）；
JPanel unitSelectionPanel=newjpanel（）；
backButton=新的JButton（“
不要调用在paint中更改GUI的方法，这样做通常会触发重新绘制，而重新绘制又会调用paint，而paint又会设置大小，进而

另外，不要试图从Java代码中调整小程序的大小（永远）。应在HTML中设置小程序的大小。删除整个方法。确保在添加组件后调用
validate（）

…希望制作这个..可执行jar。我应该使用JFrame吗

是的，当然

然后使用链接启动
JFrame
。创建一个“双击-启动”应用程序。为最终用户提供了一个不错的体验，但JWS让它变得非常流畅和专业。
抱歉，我养成了一个坏习惯。我试图更改主面板的大小，但没有效果。还有其他方法吗？删除该方法解决了问题BLIM，但是Applet窗口太小了。我有点希望把这个小程序变成一个可执行的jar。我应该使用JFrice吗？对不起，如果这是一个愚蠢的问题。谢谢Web启动提示：）@ W.K.S.：也考虑一个空的边框在代码>主板< /代码> + 1。