java - Java 中的 KeyBinds 在按住 Shift 时会中断

Question

当我使用按键绑定(bind)时，它们工作得很好。但是当我按住 Shift 并尝试使用按键绑定(bind)时，我的计算机没有检测到按键被按下/更改。另外，当尝试检测是否按下/释放 Shift 时，似乎什么也没有发生。

package main;
import java.awt.event.ActionEvent;
import java.awt.event.KeyEvent;

import javax.swing.AbstractAction;
import javax.swing.ActionMap;
import javax.swing.InputMap;
import javax.swing.JComponent;
import javax.swing.KeyStroke;

public class Input 
{

    private InputMap im;
    private ActionMap am;

    public Input(JComponent component)
    {
        im = component.getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW);
        am = component.getActionMap();

        im.put(KeyStroke.getKeyStroke("released ESCAPE"), "exitGame");
        am.put("exitGame", new AbstractAction()
                {
                    private static final long serialVersionUID = 1L;

                    @Override
                    public void actionPerformed(ActionEvent e)
                    {
                        System.exit(0);
                    }
                });
    }

    public void createKey(String key, AbstractAction action)
    {
        String command = key + "Action";
        im.put(KeyStroke.getKeyStroke(key), command);
        am.put(command, action);
    }

    public void createKey(int key, boolean released, AbstractAction action)
    {
        String command = key + "Action";
        im.put(KeyStroke.getKeyStroke(key, 0, released), command);
        am.put(command, action);
    }

}

public void keyInput(Input input)
    {
        input.createKey("A", new MoveAction(Direction.LEFT, false));
        input.createKey("released A", new MoveAction(Direction.LEFT, true));
        input.createKey("D", new MoveAction(Direction.RIGHT, false));
        input.createKey("released D", new MoveAction(Direction.RIGHT, true));

//Added this for testing purposes, but without it, holding shift down seems to stop all other inputs.
        input.createKey(KeyEvent.VK_SHIFT, false, new AbstractAction()
            {
                @Override
                public void actionPerformed(ActionEvent e) {
                    sprint = true;
                    System.out.println("Test!"); //THIS LINE NEVER APPEARS.
                }
            });
        input.createKey(KeyEvent.VK_SHIFT, true, new AbstractAction()
            {
                @Override
                public void actionPerformed(ActionEvent e) {
                    sprint = false;
                }
            });
    }

(keyInput 方法是单独类的一部分。)

Answer 1

击键由多个部分组成。生成事件的按键代码，零个或多个修饰符，可以更改按键代码的含义以及是否按下或释放。

根据修饰符的不同，单个击键可能具有不同的含义，例如 Shift 会将 a 更改为 A 或 1 到 !。

这使得 Shift+a 与仅 a 不同。当您还认为您还有 Ctrl、Alt、Wnd 和 Cmd 并且它们可以组合在一起时，这为每个键赋予了大量额外的可能含义。

按键绑定(bind)很有趣。您可以定义单个操作并将其应用于多个击键配置

例如，我们可以从...开始

InputMap im = getInputMap(WHEN_IN_FOCUSED_WINDOW);
ActionMap am = getActionMap();

am.put("left", new AbstractAction() {
    @Override
    public void actionPerformed(ActionEvent arg0) {
        label.setText("left");
    }
});
am.put("right", new AbstractAction() {
    @Override
    public void actionPerformed(ActionEvent arg0) {
        label.setText("right");
    }
});
am.put("released", new AbstractAction() {
    @Override
    public void actionPerformed(ActionEvent arg0) {
        label.setText("---");
    }
});

这定义了三个可以执行的 Action ，左、右、释放。每个都只是将 JLabel 的文本更改为某种状态，但您明白了。

然后您可以将这些操作应用于多个击键，例如...

im.put(KeyStroke.getKeyStroke(KeyEvent.VK_A, 0, false), "left");
im.put(KeyStroke.getKeyStroke(KeyEvent.VK_A, KeyEvent.SHIFT_DOWN_MASK, false), "left");

因此，按 a 或 Shift+a 将触发向左操作

im.put(KeyStroke.getKeyStroke(KeyEvent.VK_D, 0, false), "right");
im.put(KeyStroke.getKeyStroke(KeyEvent.VK_D, KeyEvent.SHIFT_DOWN_MASK, false), "right");

按d或Shift+d将触发右操作

im.put(KeyStroke.getKeyStroke(KeyEvent.VK_A, 0, true), "released");
im.put(KeyStroke.getKeyStroke(KeyEvent.VK_A, KeyEvent.SHIFT_DOWN_MASK, true), "released");

im.put(KeyStroke.getKeyStroke(KeyEvent.VK_D, 0, true), "released");
im.put(KeyStroke.getKeyStroke(KeyEvent.VK_D, KeyEvent.SHIFT_DOWN_MASK, true), "released");

释放其中任何四个键将生成released操作

可运行示例...

import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.GridBagLayout;
import java.awt.event.ActionEvent;
import java.awt.event.KeyEvent;
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;

public class Test {

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

    public Test() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                JFrame frame = new JFrame();
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        private JLabel label = new JLabel("---");

        public TestPane() {
            setLayout(new GridBagLayout());
            add(label);

            InputMap im = getInputMap(WHEN_IN_FOCUSED_WINDOW);
            ActionMap am = getActionMap();

            am.put("left", new AbstractAction() {
                @Override
                public void actionPerformed(ActionEvent arg0) {
                    label.setText("left");
                }
            });
            am.put("right", new AbstractAction() {
                @Override
                public void actionPerformed(ActionEvent arg0) {
                    label.setText("right");
                }
            });
            am.put("released", new AbstractAction() {
                @Override
                public void actionPerformed(ActionEvent arg0) {
                    label.setText("---");
                }
            });

            im.put(KeyStroke.getKeyStroke(KeyEvent.VK_A, 0, false), "left");
            im.put(KeyStroke.getKeyStroke(KeyEvent.VK_A, KeyEvent.SHIFT_DOWN_MASK, false), "left");

            im.put(KeyStroke.getKeyStroke(KeyEvent.VK_D, 0, false), "right");
            im.put(KeyStroke.getKeyStroke(KeyEvent.VK_D, KeyEvent.SHIFT_DOWN_MASK, false), "right");

            im.put(KeyStroke.getKeyStroke(KeyEvent.VK_A, 0, true), "released");
            im.put(KeyStroke.getKeyStroke(KeyEvent.VK_A, KeyEvent.SHIFT_DOWN_MASK, true), "released");

            im.put(KeyStroke.getKeyStroke(KeyEvent.VK_D, 0, true), "released");
            im.put(KeyStroke.getKeyStroke(KeyEvent.VK_D, KeyEvent.SHIFT_DOWN_MASK, true), "released");
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(200, 200);
        }

    }

}