当扫描仪等待用户输入时，java GUI冻结

6 月，1 周 Questions & Answers 707

我意识到，您需要使用事件调度线程来避免冻结和死锁，但现在我来讨论冻结问题。我怀疑我有这个问题是因为封装的EDT

这是一个包含主要静态方法的类：

@SuppressWarnings("serial")
public class WelcomeScreen extends JFrame implements ActionListener {

/*
 * initialize variables
 */
private JButton btnSubmit;
private JTextField nameInput;
private JLabel enterName;

public WelcomeScreen() {

    /*
     * build the welcome frame with all components
     */
    setAlwaysOnTop(true);
    setDefaultCloseOperation(EXIT_ON_CLOSE);
    setLocationRelativeTo(null);
    setResizable(false);
    setBounds(0, 0, 514, 256);
    getContentPane().setLayout(null);

    // welcome label
    JLabel label_welcome = new JLabel("<html>Welcome to <br/>Game</html>");
    label_welcome.setHorizontalAlignment(SwingConstants.CENTER);
    label_welcome.setBounds(159, 11, 190, 32);
    getContentPane().add(label_welcome);

    // create the warrior button
    btnSubmit = new JButton("Start");
    btnSubmit.setBounds(209, 129, 89, 23);
    btnSubmit.addActionListener(this);
    btnSubmit.setFocusable(false);
    getContentPane().add(btnSubmit);

    enterName = new JLabel("Enter Player Name:");
    enterName.setBounds(50, 60, 150, 50);
    getContentPane().add(enterName);

    nameInput = new JTextField();
    nameInput.setBounds(212, 70, 125, 25);
    getContentPane().add(nameInput);

    // set frame visible
    setVisible(true);

}

/*
 * action listener
 */
public void actionPerformed(ActionEvent evt) {

    if (evt.getSource().equals(btnSubmit)) {
        dispose();
        new Core();
    }

}

/*
 * <<<<<MAIN STATIC METHOD>>>>>
 */
public static void main(String[] args) {

    // safely start the welcome frame
    SwingUtilities.invokeLater(new Runnable() {
        public void run() {
            new WelcomeScreen();
        }
    });

}
}

这是扩展JFrame的第二个类。这是冻结的GUI。如果查看gameEngine（）方法，您会注意到字符串输入=键盘。next（），导致冰冻。如果这一行被注释掉，GUI将显示两个字符串“test1”和“test2”

@SuppressWarnings("serial")
public class Core extends JFrame {

/*
 * initialize variables
 */
private Scanner keyboard;
private JTextArea textArea;

public Core() {

    /*
     * create the frame that displays output messages
     */
    setBounds(0, 0, 800, 400);
    setResizable(false);
    setLocationRelativeTo(null);
    setAlwaysOnTop(true);
    setDefaultCloseOperation(EXIT_ON_CLOSE);
    getContentPane().setLayout(null);

    JPanel panel = new JPanel();
    panel.setBounds(10, 11, 774, 349);
    panel.setLayout(null);
    getContentPane().add(panel);

    textArea = new JTextArea();
    JScrollPane scroll = new JScrollPane(textArea);
    scroll.setBounds(0, 0, 774, 349);
    textArea.setBounds(10, 11, 443, 279);
    panel.add(scroll);

    // THIS ISN'T EVEN SHOWING UP
    appendMessage("test1");

    // set frame visible
    setVisible(true);

    // NEITHER IS THIS
    appendMessage("test2");

    /*
     * start game engine
     */
    gameEngine();

}

/*
 * start gameEngine
 */
public void gameEngine() {

    // instantiate scanner
    keyboard = new Scanner(System.in);

    // <<<<<<<<<<<<<<<THIS HERE IS CAUSING THE GUI TO FREEZE>>>>>>>>>>>>>>>
    String input = keyboard.next();

}

// append a message to the GUI
public void appendMessage(String s) {
    textArea.append("> " + s + "\n");
}

}

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共 (2) 个答案

# 1 楼答案

您的问题是，扫描仪正在阻止Swing事件线程，从而阻止GUI绘制和与用户交互。一个简单的解决方案是在后台线程中进行扫描仪交互。更好的解决方案是完全摆脱扫描仪（System.in），通过GUI实现所有用户交互。控制台I/O和GUI I/O不应混合使用

使用JTextField和布局管理器获取并响应输入的一个简单示例：

import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.KeyEvent;

import javax.swing.*;

@SuppressWarnings("serial")
public class Fu22GamePanel extends JPanel {
    private static final int COLS = 50;
    private static final int ROWS = 25;
    private static final int GAP = 3;
    private JTextField entryField = new JTextField(COLS);
    private JTextArea textArea = new JTextArea(ROWS, COLS);
    private String playerName;

    public Fu22GamePanel(String name) {
        this.playerName = name;
        textArea.setFocusable(false);
        textArea.setWrapStyleWord(true);
        textArea.setLineWrap(true);
        JScrollPane scrollPane = new JScrollPane(textArea);
        scrollPane.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);

        EntryAction entryAction = new EntryAction("Submit", KeyEvent.VK_S);
        entryField.setAction(entryAction);
        JPanel bottomPanel = new JPanel();
        bottomPanel.setLayout(new BoxLayout(bottomPanel, BoxLayout.LINE_AXIS));
        bottomPanel.add(entryField);
        bottomPanel.add(new JButton(entryAction));

        setBorder(BorderFactory.createEmptyBorder(GAP, GAP, GAP, GAP));
        setLayout(new BorderLayout(GAP, GAP));
        add(scrollPane);
        add(bottomPanel, BorderLayout.PAGE_END);
    }

    private class EntryAction extends AbstractAction {
        public EntryAction(String name, int mnemonic) {
            super(name);
            putValue(MNEMONIC_KEY, mnemonic);
        }

        @Override
        public void actionPerformed(ActionEvent e) {
            String text = entryField.getText();
            entryField.setText("");
            textArea.append("> " + text + "\n");
            entryField.requestFocusInWindow();
        }
    }

    private static class WelcomePanel extends JPanel {
        private JTextField playerNameField = new JTextField(10);

        public WelcomePanel() {
            int wpGap = 20;
            setBorder(BorderFactory.createEmptyBorder(wpGap, wpGap, wpGap, wpGap));
            add(new JLabel("Enter Player Name:"));
            add(playerNameField);
        }

        public String getPlayerName() {
            return playerNameField.getText();
        }
    }

    private static void createAndShowGui() {
        WelcomePanel welcomePanel = new WelcomePanel();
        int response = JOptionPane.showConfirmDialog(null, welcomePanel, "Welcome to the Game", JOptionPane.OK_CANCEL_OPTION);
        if (response != JOptionPane.OK_OPTION) {
            return;
        }

        String name = welcomePanel.getPlayerName();

        Fu22GamePanel mainPanel = new Fu22GamePanel(name);

        JFrame frame = new JFrame("Game   Player: " + name);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().add(mainPanel);
        frame.pack();
        frame.setLocationRelativeTo(null);


        frame.setVisible(true);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> {
            createAndShowGui();
        });
    }
}

# 2 楼答案

使用一个JTextField作为输入，再加上一个ActionListener，您可以对适当的事件做出响应，比如输入键

使用JTextArea作为输出

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.JTextField;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class NastyAdventure {

    public static void main(String[] args) {
        new NastyAdventure();
    }

    public NastyAdventure() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                    ex.printStackTrace();
                }

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        private JTextArea output;
        private JTextField input;

        private boolean isDead = false;

        public TestPane() {
            setLayout(new BorderLayout());
            output = new JTextArea(10, 30);
            input = new JTextField(20);
            add(new JScrollPane(output));
            add(input, BorderLayout.SOUTH);

            output.setEditable(false);
            output.append("A bear appears on the trial in front of you\n");
            output.append("What do you do?");

            input.addActionListener(new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    input.setText(null);
                    if (!isDead) {
                        output.append("\nThe bear eats you, you die\n");
                        output.append("The adventure is over, the bear wins\n");
                    } else {
                        output.append("You're dead, you can't do anything\nThe adventure is over, the bear wins\n");
                    }
                    isDead = true;
                }
            });
        }

    }

}

查看How to Use Text Fields、How to Use Text Areas、How to Write an Action Listeners和Writing Event Listeners了解更多详细信息

你可能还想看看Model-View-Controller，这将帮助你保持游戏的状态，使其与UI分离

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有 Java 编程相关的问题?

当扫描仪等待用户输入时，java GUI冻结

共 (2) 个答案

# 1 楼答案

# 2 楼答案