如何让GUI按钮正确响应？

Question

我已经写了下面的代码，它似乎工作顺利，除了信息框中的“退出信息”按钮和信息框中的文本。首先，信息框中的文本（这在标签上）拒绝出现。其次，“退出信息”按钮不会出现在我设置的位置。有什么建议我可以做些什么来使其正常运行？ 感谢

注：我非常缺乏经验与Java，因此可能不会完全理解的答案，除非它们被写入，虽然他们是幼稚园的学生:)

import java.awt.*; 
    import javax.swing.*; 

    public class CombineInputWindow { 

public static void main(String[] args) { 
    // TODO Auto-generated method stub 

    // Create the frame 
    JFrame frame = new JFrame("New GUI");// Title the frame 
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);// add close function 

    // Create the label: 
    JLabel textLabel = new JLabel("");// No text is added 
    textLabel.setPreferredSize(new Dimension(320,240));// Set the size of the label 
    frame.getContentPane().add(textLabel, BorderLayout.CENTER);// Add the label to the frame 

    // The following three lines set the frame up further 
    frame.setLocationRelativeTo(null); 
    frame.pack(); 
    frame.setVisible(true); 

    // Create the panel 
    JPanel panel = new JPanel(); 
    frame.add(panel);// Add panel to frame 

    // Create lbutton (size, text, etc.) 
    JButton lbutton = new JButton("Move Left"); 
    panel.add(lbutton); 
    lbutton.setSize(128,32); 
    lbutton.setVisible(true); 
    lbutton.setLocation(0,208); 

    // Create rbutton (size, text, etc.) 
    JButton rbutton = new JButton("Move right"); 
    panel.add(rbutton); 
    rbutton.setSize(128,32); 
    rbutton.setVisible(true); 
    rbutton.setLocation(192,208); 

    // Create dodge button (size, text, etc.) 
    JButton btndodge = new JButton("Duck"); 
    panel.add(btndodge); 
    btndodge.setSize(64,32); 
    btndodge.setVisible(true); 
    btndodge.setLocation(128,208); 

    // Create exit button (size, text, etc.) 
    JButton btnexit = new JButton("Exit"); 
    panel.add(btnexit); 
    btnexit.setSize(64,32); 
    btnexit.setVisible(true); 
    btnexit.setLocation(256,0); 

    // Create info button (size, text, etc.) 
    JButton btninfo = new JButton("Info"); 
    panel.add(btninfo); 
    btninfo.setSize(64,32); 
    btninfo.setVisible(true); 
    btninfo.setLocation(192,0); 

    // Add function to the lbutton for mouse event 
    lbutton.addMouseListener(new java.awt.event.MouseAdapter() { 
     int vbtnclicks = 0; 
     public void mouseClicked(java.awt.event.MouseEvent evt) { 
      vbtnclicks = vbtnclicks + 1; 

      //The following code prints out the number of times the user has clicked the button 
      if (vbtnclicks > 2) { 
       System.out.println("You moved left " + vbtnclicks + " times!"); 
       } 

      else if (vbtnclicks == 1) { 
       System.out.println("You moved left once!"); 
       } 

      else if (vbtnclicks == 2){ 
       System.out.println("You moved left twice!"); 
      } 

      else { 
       // The following code should not have to show up 
       System.out.println("I get the sense this code has been meddled with..."); 
      } 

     } 
    }); 

    // Add mouse event for rbutton 
    rbutton.addMouseListener(new java.awt.event.MouseAdapter() { 
     int cbtnclicks = 0; 
     public void mouseClicked(java.awt.event.MouseEvent evt) { 
      cbtnclicks = cbtnclicks + 1; 

      //The following code prints out the number of times the user has clicked the button 
      if (cbtnclicks > 2) { 
       System.out.println("You moved right " + cbtnclicks + " times!"); 
       } 

      else if (cbtnclicks == 1) { 
       System.out.println("You moved right once!"); 
       } 

      else if (cbtnclicks == 2){ 
       System.out.println("You moved right twice!"); 
      } 

      else { 
       // The following code should not have to show up 
       System.out.println("I get the sense this code has been meddled with..."); 
      } 

     } 
    }); 

    // Add mouse event for btndodge 
      btndodge.addMouseListener(new java.awt.event.MouseAdapter() { 
       int dbtnclicks = 0; 
       public void mouseClicked(java.awt.event.MouseEvent evt) { 
        dbtnclicks = dbtnclicks + 1; 

        //The following code prints out the number of times the user has clicked the button 
        if (dbtnclicks > 2) { 
         System.out.println("You ducked " + dbtnclicks + " times!"); 
         } 

        else if (dbtnclicks == 1) { 
         System.out.println("You ducked once!"); 
         } 

        else if (dbtnclicks == 2){ 
         System.out.println("You ducked twice!"); 
        } 

        else { 
         // The following code should not have to show up 
         System.out.println("I get the sense this code has been meddled with..."); 
        } 

       } 
      }); 

    // Add mouse event and exit command to the exit button 
    btnexit.addMouseListener(new java.awt.event.MouseAdapter() { 
     public void mouseClicked(java.awt.event.MouseEvent evt) { 


      System.exit(0); 
    } 
    }); 

    // Add function to the "Info" button 
    btninfo.addMouseListener(new java.awt.event.MouseAdapter() { 
     public void mouseClicked(java.awt.event.MouseEvent evt) { 

      // Open an Info Window with specific settings 
      JFrame inframe = new JFrame("Info"); 

      JLabel inlabel = new JLabel("This is the info text."); 
      inlabel.setPreferredSize(new Dimension(300,100)); 
      inframe.getContentPane().add(inlabel, BorderLayout.CENTER); 

      inframe.setLocationRelativeTo(null); 
      inframe.pack(); 
      inframe.setVisible(true); 

      JPanel inpanel = new JPanel(); 
      inframe.add(inpanel); 

      JButton inextbtn = new JButton("Exit Info"); 
      inpanel.add(inextbtn); 

      inextbtn.setSize(96,24); 
      inextbtn.setVisible(true); 
      inextbtn.setLocation(0,0); 

      inextbtn.addMouseListener(new java.awt.event.MouseAdapter() { 
       public void mouseClicked(java.awt.event.MouseEvent evt) { 

        inframe.dispose(); 
        } 
      }); 
     } 
    }); 
    } 

}

Answer 1

你的主要问题，为什么infoLabel没有显示，是由于您在添加将其保存到contentPane中的JPanel之前在其JFrame上调用了setVisible(true)。在之后总是呼叫setVisible(true)将所有组件添加到您的JFrame中。由于inFrame使用BorderLayout，因此您还需要在JFrame之后添加JPanel以覆盖JLabel。

其他问题：

• 是，使用的ActionListeners为Jbutton将不MouseListeners。如果按钮具有焦点并按下空格键，则ActionListener将响应 - 这是预期的和正确的行为。 MouseListener不会。此外，如果您禁用JButton，则ActionListener将不起作用，这也是预期的并且是正确的，并且MouseListener再次出现在此处。
• 不要设置GUI组件的绝对大小或位置，而应让组件默认首选大小，容器布局管理器为您完成这些繁重工作。
• 信息窗口应该是一个JDialog而不是一个JFrame，因为可见应用程序应该只有一个主框架窗口，一个JFrame。

例如：

import java.awt.BorderLayout; 
import java.awt.Component; 
import java.awt.Dialog.ModalityType; 
import java.awt.Dimension; 
import java.awt.Window; 
import java.awt.event.ActionEvent; 
import java.awt.event.KeyEvent; 

import javax.swing.*; 

public class CombineInput2 { 

    public static void main(String[] args) { 
     SwingUtilities.invokeLater(() -> { 
      MainPanel mainPanel = new MainPanel(); 
      JFrame frame = new JFrame("Main GUI"); 
      frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE); 
      frame.add(mainPanel); 
      frame.pack(); 
      frame.setLocationRelativeTo(null); 
      frame.setVisible(true); 
     }); 
    } 

} 

class MainPanel extends JPanel { 
    public MainPanel() { 
     setPreferredSize(new Dimension(400, 400)); 
     add(new JButton(new InfoAction("Info", this))); 
     add(new JButton(new ExitAction())); 
    } 
} 

class InfoAction extends AbstractAction { 
    private MainPanel mainPanel; 
    private JDialog dialog; 

    public InfoAction(String name, MainPanel mainPanel) { 
     super(name); 
     this.mainPanel = mainPanel; 
    } 

    @Override 
    public void actionPerformed(ActionEvent e) { 
     if (dialog == null) { 
      Window win = SwingUtilities.getWindowAncestor(mainPanel); 
      dialog = new JDialog(win, "Info", ModalityType.APPLICATION_MODAL); 
      dialog.add(new DialogPanel()); 
      dialog.pack(); 
      dialog.setLocationRelativeTo(win); 
     } 
     dialog.setVisible(true); 
    } 
} 

class DialogPanel extends JPanel { 
    private static final int DP_WIDTH = 250; 
    private static final int DP_HEIGHT = 100; 
    private String text = "This is the info text."; 
    private JLabel infoLabel = new JLabel(text, SwingConstants.CENTER); 

    public DialogPanel() { 
     JPanel btnPanel = new JPanel(); 
     Action exitAction = new ExitAction(); 
     exitAction.putValue(Action.NAME, "Exit Info"); 
     btnPanel.add(new JButton(exitAction)); 

     setLayout(new BorderLayout()); 
     add(infoLabel, BorderLayout.CENTER); 
     add(btnPanel, BorderLayout.PAGE_START); 
    } 

    @Override 
    public Dimension getPreferredSize() { 
     Dimension prefSz = super.getPreferredSize(); 

     if (isPreferredSizeSet()) { 
      return prefSz; 
     } 
     int width = Math.max(prefSz.width, DP_WIDTH); 
     int height = Math.max(prefSz.height, DP_HEIGHT); 
     return new Dimension(width, height); 
    } 
} 

class ExitAction extends AbstractAction { 
    public ExitAction() { 
     super("Exit"); 
     putValue(MNEMONIC_KEY, KeyEvent.VK_X); 
    } 

    @Override 
    public void actionPerformed(ActionEvent e) { 
     Component c = (Component) e.getSource(); 
     if (c == null) { 
      return; 
     } 
     Window win = SwingUtilities.getWindowAncestor(c); 
     if (win != null) { 
      win.dispose(); 
     } 
    } 
}