Question

我编写了以下代码，除了信息框中的“退出信息”按钮和信息框中的文本外，它似乎工作顺利。首先，信息框中的文本（这在标签上）拒绝显示。其次，“退出信息”按钮不会出现在我为其设置的位置。有关如何使其正常运行的任何建议？感谢

注意：我对Java非常缺乏经验，因此可能无法完全理解答案，除非它们写成幼儿园学生：）

    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

您的主要问题，即infoLabel未显示的原因，是由于您在将JFrame添加到其contentPane的JPanel之前在其JFrame上调用了setVisible(true)。在将所有组件添加到JFrame后，请始终致电setVisible(true) 。由于inFrame使用BorderLayout，你还可以通过将JPanel添加到JFrame来覆盖JLabel。

其他问题：

是的，使用ActionListeners for JButtons而不是MouseListeners。如果按钮具有焦点并且按下了空格键，则ActionListener将响应 - 这是预期的正确行为。 MouseListener不会。此外，如果你禁用一个JButton，一个ActionListener不会工作，再次这是预期的和正确的，并且MouseListener再次在这里行为不端。

不要设置GUI组件的绝对大小或位置，而是让组件默认首选大小，容器布局管理器为您做这件事。

信息窗口应该是JDialog而不是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(); } } }

如何让GUI按钮正确响应？

1 个答案: