额外的按钮不断出现

问题描述：

我是一种新的Java，并且我在每台运行我的程序的计算机上遇到这个小问题。我的代码是额外的按钮不断出现

import javax.swing.*; 
import java.awt.*; 
import java.awt.event.ActionListener; 
import java.awt.event.ActionEvent; 

public class FrameTest2 { 


    public static void main(String[] args){ 
    String s = "Catch Torchic"; 

    MainMenu m = new MainMenu(s); 
    } 
} 

class MainMenu extends JFrame { 

    JButton autoa, manualb, createc, exitd; 

    public MainMenu(String s){ 
     super(s); 
     setBackground(new Color(247,247,111)); 
     setSize(640,600); 
     setVisible(true); 
     setResizable(false); 
     setLocationRelativeTo(null); 
     setDefaultCloseOperation(EXIT_ON_CLOSE); 
     Container contentPane = getContentPane(); 
     setLayout(new BoxLayout(contentPane, BoxLayout.Y_AXIS)); 
     CustomPanel panel = new CustomPanel(); 
     panel.setAlignmentX(Component.CENTER_ALIGNMENT); 
     panel.setMinimumSize(new Dimension(600,365)); 
     panel.setPreferredSize(new Dimension(600,365)); 
     panel.setMaximumSize(new Dimension(600,365)); 
     panel.setBackground(new Color(247,247,111)); 
     contentPane.add(panel); 
     JPanel btnPanel = new JPanel(); 
     btnPanel.setLayout(new BoxLayout(btnPanel, BoxLayout.Y_AXIS)); 
     btnPanel.setBackground(new Color(247,247,111)); 
     autoa = new JButton("AutoPlay"); 
     autoa.setAlignmentX(Component.CENTER_ALIGNMENT); 
     btnPanel.add(autoa); 

     manualb = new JButton("Manual Play"); 
     manualb.setAlignmentX(Component.CENTER_ALIGNMENT); 
     btnPanel.add(manualb); 

     createc = new JButton("Create Maze"); 
     createc.setAlignmentX(Component.CENTER_ALIGNMENT); 
     btnPanel.add(createc); 

     exitd = new JButton("Exit"); 
     exitd.setAlignmentX(Component.CENTER_ALIGNMENT); 
     btnPanel.add(exitd); 

     btnPanel.setAlignmentX(Component.CENTER_ALIGNMENT); 
     contentPane.add(btnPanel); 
     setContentPane(contentPane); 

     ButtonHandler handler = new ButtonHandler(this); 
     autoa.addActionListener(handler); 
     manualb.addActionListener(handler); 
     createc.addActionListener(handler); 
     exitd.addActionListener(handler); 
} 

} 

class ButtonHandler implements ActionListener{ 
    MainMenu mm; 

    public ButtonHandler(MainMenu mm){ 
     this.mm = mm; 
    } 

    public void actionPerformed(ActionEvent e){ 
     if(e.getSource() == mm.autoa) 
     System.out.println("Clicked on Auto"); 
     else if(e.getSource() == mm.manualb) 
     System.out.println("Clicked on Manual"); 
     else if(e.getSource() == mm.createc) 
     System.out.println("Clicked on Create"); 
     else 
     System.exit(0); 
    } 

} 

class CustomPanel extends JPanel{ 
    public void paintComponent (Graphics painter){ 

    Image pic = Toolkit.getDefaultToolkit().getImage("logo.png"); 
    if(pic != null) painter.drawImage(pic, 105, 30, this); 

    } 
}

该代码产生到这一点：http://a3.sphotos.ak.fbcdn.net/hphotos-ak-ash4/318155_424290814251286_100000111130260_1871937_131988334_n.jpg

那里总是在左上角的额外按钮，我的问题是，我该如何去除呢？该按钮以随机间隔显示，有时不显示。

1）*“This code results into ..”* Compilation errors。为了更快地获得更好的帮助，请发布[SSCCE]（http://sscce.org/）。 2）请为代码块使用一致的逻辑缩进。 – 2012-04-07 00:20:50

我试过你的代码没有改变，它的工作很好，就像你可以在这张图中看到的一样：http://hpics.li/acc7d7d。 – 2012-04-07 00:21:29

我编辑了代码并放置了所有的类。我没有使用Eclipse，netbeans之类的东西。我只用了Notepad ++。 – 2012-04-07 00:59:00

答

试试这个变种。许多评论，最重要的是SHOUTING。请注意，当我把它变成工作代码（或者更确切地说，代码在这里用于加载图像）时，我从来没有看到过你描述的问题。

import javax.swing.*; 
import javax.swing.border.*; 
import java.awt.*; 
import java.awt.event.ActionListener; 
import java.awt.event.ActionEvent; 

import java.net.URL; 
import javax.imageio.ImageIO; 

public class FrameTest2 { 

    public static void main(String[] args) throws Exception { 
     final String s = "Catch Torchic"; 
     URL url = new URL("http://pscode.org/media/stromlo2.jpg"); 
     final Image image = ImageIO.read(url); 

     //Create the frame on the event dispatching thread 
     SwingUtilities.invokeLater(new Runnable(){ 

      @Override 
      public void run() { 
       new MainMenu(s, image); 
      } 

     }); 
    } 
} 

class MainMenu extends JFrame { 

    JButton autoa, manualb, createc, exitd; 

    public MainMenu(String s, Image image) { 
     super(s); 
     // do this after pack (if at all) 
     //setSize(640,600); 
     // do this after pack/setSize 
     //setVisible(true); 
     // don't do this in broken code 
     //setResizable(false); 
     // If you're going to spend space on GUI position.. 
     // setLocationRelativeTo(null); 
     // ..do it like this. 
     setLocationByPlatform(true); 

     setDefaultCloseOperation(EXIT_ON_CLOSE); 
     Container contentPane = getContentPane(); 
     contentPane.setLayout(new BorderLayout()); 
     CustomPanel panel = new CustomPanel(image); 
     panel.setAlignmentX(Component.CENTER_ALIGNMENT); 
     //panel.setMinimumSize(new Dimension(600,365)); 
     //panel.setPreferredSize(new Dimension(600,365)); 
     //panel.setMaximumSize(new Dimension(600,365)); 
     contentPane.add(panel); 
     JPanel btnPanel = new JPanel(); 
     btnPanel.setBorder(new EmptyBorder(5,5,100,5)); 
     btnPanel.setLayout(new BoxLayout(btnPanel, BoxLayout.Y_AXIS)); 
     // not needed for an SSCCE 
     //btnPanel.setBackground(new Color(247,247,111)); 
     autoa = new JButton("AutoPlay"); 
     autoa.setAlignmentX(Component.CENTER_ALIGNMENT); 
     btnPanel.add(autoa); 

     manualb = new JButton("Manual Play"); 
     manualb.setAlignmentX(Component.CENTER_ALIGNMENT); 
     btnPanel.add(manualb); 

     createc = new JButton("Create Maze"); 
     createc.setAlignmentX(Component.CENTER_ALIGNMENT); 
     btnPanel.add(createc); 

     exitd = new JButton("Exit"); 
     exitd.setAlignmentX(Component.CENTER_ALIGNMENT); 
     btnPanel.add(exitd); 

     // you already said that 
     //btnPanel.setAlignmentX(Component.CENTER_ALIGNMENT); 
     contentPane.add(btnPanel, BorderLayout.SOUTH); 
     setContentPane(contentPane); 

     ButtonHandler handler = new ButtonHandler(this); 
     autoa.addActionListener(handler); 
     manualb.addActionListener(handler); 
     createc.addActionListener(handler); 
     exitd.addActionListener(handler); 

     // CAUSE THE COMPONENTS TO BE PROPERLY LAID OUT. 
     pack(); 
     setSize(640,600); 
     setVisible(true); 
    } 

} 

class ButtonHandler implements ActionListener{ 
    MainMenu mm; 

    public ButtonHandler(MainMenu mm){ 
     this.mm = mm; 
    } 

    public void actionPerformed(ActionEvent e){ 
     // for clarity, even single line statements 
     // in these should be enclosed in {} 
     if(e.getSource() == mm.autoa) 
      System.out.println("Clicked on Auto"); 
     else if(e.getSource() == mm.manualb) 
      System.out.println("Clicked on Manual"); 
     else if(e.getSource() == mm.createc) 
      System.out.println("Clicked on Create"); 
     else 
      System.exit(0); 
    } 

} 

class CustomPanel extends JPanel{ 

    Image pic; 

    CustomPanel(Image pic) { 
     this.pic = pic; 
    } 

    public void paintComponent (Graphics painter){ 
     // DO NOT TRY TO READ IMAGES IN PAINT! 
     //Image pic = Toolkit.getDefaultToolkit().getImage("logo.png"); 
     if(pic != null) painter.drawImage(pic, 105, 30, this); 
    } 
}

另外'Toolkit.getDefaultToolkit（）。getImage（“logo.png”）;'很可能会在部署时失败，因为代码试图访问（大概是什么）一个'嵌入式'的应用程序。资源就好像它是一个'File'一样。这些必须由'URL'访问。 – 2012-04-07 07:06:15

非常感谢您的先生！问题：为什么要从URL中获取图片？我不能和班级一起吗？ pack（）获取要正确布局的组件？ – 2012-04-07 07:25:44

1）'URL'可以指向Jar文件中的条目 - 实际上，它是访问Jar中的资源（使用Java）的唯一方式。使用File.toURI（）。toURL（）'，你本地文件系统上的任何'File'路径也可以变成一个URL。简而言之，URL更加通用。 2）它也应该这样工作。使用'Class.getResource（String）'获取URL。 3）是的。我认为这可能是导致布局问题，但在绘制方法中读取图像从来不是一个好主意。 – 2012-04-07 07:32:24

答

我认为这是缺少contentPane.：

//setLayout(new BoxLayout(contentPane, BoxLayout.Y_AXIS)); 
    contentPane.setLayout(new BoxLayout(contentPane, BoxLayout.Y_AXIS));//

还有就是内容窗格中的多余设置。

//setContentPane(contentPane);

后 “没了：”

困难。 将setVisible(true)移动到最后，仅调用一个布局。尝试在内容窗格中没有两个面板（仅一个）：

Container contentPane0 = getContentPane(); 
    Container contentPane = new JPanel(); 
    contentPane0.add(contentPane);

nope，额外的按钮仍然以随机间隔出现 – 2012-04-07 02:07:12

额外的按钮不断出现

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