键事件侦听器中的多个键

Question

我想知道如何在键事件中按下所有键。例如，我想为 ctrl + f 编写一个侦听器来切换全屏。如何检查在一个事件中是否同时按下了 ctrl和f？

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编辑 1：

我尝试打印KeyEvent.getModifiersExText(e.getModifiersEx())并键入ctrl + f，但这只产生了?.

Answer 1

老实说，KeyListener有很多限制并且使用起来很麻烦（恕我直言），相反，我会简单地利用键绑定 API，它通常为您提供更大的灵活性和重用能力。

import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.GridBagLayout;
import java.awt.event.ActionEvent;
import java.awt.event.InputEvent;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import javax.swing.AbstractAction;
import javax.swing.ActionMap;
import javax.swing.InputMap;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.KeyStroke;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class KeyListenerTest {
    public static void main(String[] args) {
        new KeyListenerTest();
    }
    public KeyListenerTest() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                }
                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setLayout(new BorderLayout());
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }
    public class TestPane extends JPanel {
        private JLabel lbl;
        private boolean fullScreen = false;
        public TestPane() {
            lbl = new JLabel("Normal");
            setLayout(new GridBagLayout());
            add(lbl);
            InputMap im = getInputMap(WHEN_IN_FOCUSED_WINDOW);
            ActionMap am = getActionMap();
            im.put(KeyStroke.getKeyStroke(KeyEvent.VK_F, InputEvent.CTRL_DOWN_MASK), "FullScreen");
            am.put("FullScreen", new AbstractAction() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    if (fullScreen) {
                        lbl.setText("Normal");
                    } else {
                        lbl.setText("Full Screen");
                    }
                    fullScreen = !fullScreen;
                }
            });
        }
    }
}

只是为了不让你认为我完全有偏见，这里有一个使用 KeyListener 的例子......

import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.GridBagLayout;
import java.awt.event.ActionEvent;
import java.awt.event.InputEvent;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import javax.swing.AbstractAction;
import javax.swing.ActionMap;
import javax.swing.InputMap;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.KeyStroke;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class KeyListenerTest {
    public static void main(String[] args) {
        new KeyListenerTest();
    }
    public KeyListenerTest() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                }
                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setLayout(new BorderLayout());
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }
    public class TestPane extends JPanel {
        private JLabel lbl;
        private boolean fullScreen = false;
        public TestPane() {
            lbl = new JLabel("Normal");
            setLayout(new GridBagLayout());
            add(lbl);
            setFocusable(true);
            addMouseListener(new MouseAdapter() {
                @Override
                public void mouseClicked(MouseEvent e) {
                    requestFocusInWindow();
                }
            });
            addKeyListener(new KeyAdapter() {
                @Override
                public void keyPressed(KeyEvent e) {
                    if (e.getKeyCode() == KeyEvent.VK_F && e.isControlDown()) {
                        if (fullScreen) {
                            lbl.setText("Normal");
                        } else {
                            lbl.setText("Full Screen");
                        }
                        fullScreen = !fullScreen;
                    }
                }
            });
        }
    }
}

Answer 2

这样的事情应该这样做：

public MyListener extends KeyListener {
    @Override
    public void keyTyped(KeyEvent e) {
    }
    @Override
    public void keyPressed(KeyEvent e) {
        if ((e.getKeyCode() == KeyEvent.VK_F) && ((e.getModifiers() & KeyEvent.CTRL_DOWN_MASK) != 0)) {
            System.out.println("Keys ctrl+F pressed!");
        }
    }
    @Override
    public void keyReleased(KeyEvent e) {
    }
});

Answer 3

我发现了一些在这种情况下有效的很酷的方法：

e.isAltDown();

e.isAltGraphDown()

e.isControlDown()

e.isShiftDown()

Answer 4

如果按两个键，"keyPressed（KeyEvent e）"将被调用两次。您可以将按下的键存储在布尔数组中，并检查它们是否都被按下。

private boolean control_pressed = false;
public void keyPressed(KeyEvent e) {
    if (e.getKeyCode() == KeyEvent.VK_CONTROL) {
      control_pressed = true;
    }
    if (e.getKeyCode() == KeyEvent.VK_F && control_pressed) {
        /* do something */
    }
}
public void keyReleased(KeyEvent e) {
    if (e.getKeyCode() == KeyEvent.VK_CONTROL) {
      control_pressed = false;
    }
}

释放

必须再次释放控制变量。