java - 通过实现 KeyBindings 使用键入的 key

Question

能否请您帮助我如何将 KeyBinding 和 Consume 一起用于键入的 Chars ，与演示我的 SSCCE 的方式相同 通过使用 KeyListener

import java.awt.*;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import javax.swing.*;

public class Login {

    private static final long serialVersionUID = 1L;
    /* PassWord for unlock*/
    private PswChecker checker = new PswChecker("pass");

    public Login() {
        JTextField firstField = new JTextField(10);
        firstField.addKeyListener(passwordKeyListener);
        JLabel firstLabel = new JLabel("Password is 'pass' ", JLabel.RIGHT);
        firstLabel.setLabelFor(firstField);
        JPanel p = new JPanel();
        p.setLayout(new GridLayout(0, 2, 5, 5));
        p.add(firstLabel);
        p.add(firstField);
        JFrame f = new JFrame("login");
        f.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
        f.setContentPane(p);
        f.setLocationByPlatform(true);
        f.pack();
        f.setVisible(true);
    }
    //
    private KeyListener passwordKeyListener = new KeyListener() {

        private boolean enabled = true;

        @Override
        public void keyTyped(KeyEvent e) {
            if (!enabled) {
                return;
            }
            if (e.getKeyChar() != KeyEvent.CHAR_UNDEFINED) {
                boolean b = checker.accept(e.getKeyChar());
                e.consume();
                if (b) {
                    enabled = false;
                    if (e.getComponent() != null) {
                        e.getComponent().removeKeyListener(this);
                    }
                    unlock();
                }
            }
        }

        @Override
        public void keyReleased(KeyEvent e) {
        }

        @Override
        public void keyPressed(KeyEvent e) {
        }
    };

    void unlock() {
        JOptionPane.showMessageDialog(null, "unlocked");
    }

    public static void main(String[] args) {
        javax.swing.SwingUtilities.invokeLater(new Runnable() {

            public void run() {
                Login log = new Login();
            }
        });
    }

    class PswChecker {

        private String password = null;
        private boolean unlocked = false;
        private long lastInputTimestamp = 0L;
        private int index = 0;

        public PswChecker(String password) {
            if (password == null) {
                throw new IllegalArgumentException("Null password");
            }
            if (password.trim().length() == 0) {
                throw new IllegalArgumentException("Empty password");
            }
            this.password = password;
        }

        public boolean accept(char c) {
            if (unlocked) {
                return true;
            }
            long timestamp = System.currentTimeMillis();
            if (timestamp - lastInputTimestamp > 700) {
                index = 0;
            }
            lastInputTimestamp = timestamp;
            if (password.charAt(index) == c) {
                index++;
            } else {
                if (password.charAt(0) == c) {
                    index = 1;
                } else {
                    index = 0;
                }
            }
            unlocked = (index == password.length());
            return unlocked;
        }

        public boolean isUnlocked() {
            return unlocked;
        }

        public boolean isLocked() {
            return !unlocked;
        }

        @Override
        public String toString() {
            return unlocked ? "UNLOCKED" : "LOCKED";
        }

        /*private boolean check(String keystrokes, String password, boolean expectUnLocked) {
        PswChecker checker = new PswChecker(password);
        for (int i = 0; i < keystrokes.length(); i++) {
        checker.accept(keystrokes.charAt(i));
        }
        return checker.isUnlocked();
        }*/
    }
}

Answer 1

为了安全，考虑JPasswordField ，图文并茂here .这将允许使用 DocumentFilter , 讨论 here .

附录:即使对于更一般的情况，我也会使用 DocumentFilter ， 如下所示。我会用 key bindings用于在组件之间共享 Action，如 keypad example 所示.

附录:为了说明@kleopatra 的评论，我更新了代码以将ESC 绑定(bind)到Reset。实际上，我只会使用尚未绑定(bind)到文本字段操作或正常使用所需的键。

import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.KeyEvent;
import javax.swing.*;
import javax.swing.text.*;

/** @see https://stackoverflow.com/q/9610386/230513 */
public class Login {

    private static final String PWD = "pass";
    private static final String RESET = "Reset";
    private PlainDocument doc = new PlainDocument();
    private JTextField text = new JTextField(doc, "", 10);

    public Login() {
        doc.setDocumentFilter(new FieldFilter(PWD));
        JLabel label = new JLabel("Password is '" + PWD + "'", JLabel.RIGHT);
        label.setLabelFor(text);
        text.setToolTipText("Press ESC to reset.");
        text.getInputMap().put(
            KeyStroke.getKeyStroke(KeyEvent.VK_ESCAPE, 0), RESET);
        text.getActionMap().put(RESET, new Reset());
        JPanel p = new JPanel();
        p.setLayout(new GridLayout(0, 2, 5, 5));
        p.add(label);
        p.add(text);
        JFrame f = new JFrame("Login");
        f.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
        f.setContentPane(p);
        f.setLocationByPlatform(true);
        f.pack();
        f.setVisible(true);
    }

    private static class FieldFilter extends DocumentFilter {

        private String password;
        private boolean unlocked;
        private StringBuilder sb = new StringBuilder();

        public FieldFilter(String password) {
            this.password = password;
        }

        @Override
        public void replace(FilterBypass fb, int offset, int length,
            String text, AttributeSet attrs) throws BadLocationException {
            if (unlocked) {
                super.replace(fb, offset, length, text, attrs);
            } else {
                sb.append(text);
                unlocked = password.equals(sb.toString());
            }
        }

        public void reset() {
            sb.delete(0, sb.length());
            unlocked = false;
        }
    }

    private static class Reset extends AbstractAction {

        @Override
        public void actionPerformed(ActionEvent e) {
            JTextField jtf = (JTextField) e.getSource();
            PlainDocument doc = (PlainDocument) jtf.getDocument();
            try {
                doc.remove(0, doc.getLength());
            } catch (BadLocationException ex) {
                ex.printStackTrace(System.err);
            }
            FieldFilter filter = (FieldFilter) doc.getDocumentFilter();
            filter.reset();
        }
    }

    public static void main(String[] args) {
        javax.swing.SwingUtilities.invokeLater(new Runnable() {

            @Override
            public void run() {
                Login log = new Login();
            }
        });
    }
}