java - 根据按下的键更改标签文本

Question

在下面的程序中，我试图根据按下的键更改标签的文本，但我不知道该怎么做。按下键时要执行的语句在 TimerListener InnerClass 的 actionPerformed() 方法中定义。但我不明白如何从那里访问标签。

package aircraftPackage;

import java.awt.*;
import java.awt.event.*;
import java.awt.geom.AffineTransform;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.net.*;
import java.util.HashMap;
import java.util.Map;
import javax.imageio.ImageIO;
import javax.swing.*;

public class Controller extends JPanel {

    private static final long serialVersionUID = 1L;
    public static final int STEP = 3;
    private static final int TIMER_DELAY = STEP * 8;
    private BufferedImage playerImage = null;
    private Map<Direction, Boolean> directionMap = new HashMap<Direction, Boolean>();



    enum Direction {

        UP(KeyEvent.VK_UP, 0, -1), DOWN(KeyEvent.VK_DOWN, 0, 1),
        LEFT(KeyEvent.VK_LEFT, -1, 0), RIGHT(KeyEvent.VK_RIGHT, 1, 0);
        private int keyCode;
        private int xDirection;
        private int yDirection;

        private Direction(int keyCode, int xDirection, int yDirection) {
            this.keyCode = keyCode;
            this.xDirection = xDirection;
            this.yDirection = yDirection;
        }

        public int getKeyCode() {
            return keyCode;
        }

        public int getXDirection() {
            return xDirection;
        }

        public int getYDirection() {
            return yDirection;
        }
    }

    public Controller() {

        for (Direction direction : Direction.values()) {
            directionMap.put(direction, false);
        }
        setKeyBindings();
        Timer timer = new Timer(TIMER_DELAY, new TimerListener());
        timer.start();
    }

    private void setKeyBindings() {
        InputMap inMap = getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW);
        ActionMap actMap = getActionMap();
        for (final Direction direction : Direction.values()) {
            KeyStroke pressed = KeyStroke.getKeyStroke(direction.getKeyCode(), 0, false);
            KeyStroke released = KeyStroke.getKeyStroke(direction.getKeyCode(), 0, true);
            inMap.put(pressed, direction.toString() + "pressed");
            inMap.put(released, direction.toString() + "released");
            actMap.put(direction.toString() + "pressed", new AbstractAction() {

                private static final long serialVersionUID = 1L;

                @Override
                public void actionPerformed(ActionEvent e) {
                    directionMap.put(direction, true);
                }
            });
            actMap.put(direction.toString() + "released", new AbstractAction() {

                private static final long serialVersionUID = 1L;

                @Override
                public void actionPerformed(ActionEvent e) {
                    directionMap.put(direction, false);
                }
            });
        }

    }



    private class TimerListener implements ActionListener {

        @Override
        public void actionPerformed(ActionEvent e) {
            boolean moved = false;
            for (Direction direction : Direction.values()) {
                if (directionMap.get(direction)) {
                    if (direction.keyCode == 37) {
                        System.out.println("go LEFT");

                    } else if (direction.getKeyCode() == 39) {
                        System.out.println("go RIGHT");
                    } else if (direction.getKeyCode() == 38) {
                        System.out.println("go UP");
                    }
                    else if (direction.getKeyCode()==40){
                        System.out.println("go DOWN");
                    }
                }
            }
        }
    }

    public static void createAndShowUI() {
        JFrame frame = new JFrame("MoveIcon");
        JPanel panel = new JPanel();
        JLabel jl = new JLabel();
        jl.setText("testing....");
        frame.add(jl);
        frame.add(panel);
        frame.getContentPane().add(new Controller());
        new Controller();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);

    }

    public static void main(String[] args) {

        java.awt.EventQueue.invokeLater(new Runnable() {

            @Override
            @SuppressWarnings("static-access")
            public void run() {
                createAndShowUI();
            }
        });
    }
}

实际上，我想做的是，在 Netbeans 中创建一个包含各种标签的漂亮表单(在 Netbeans 中更容易做到)并使用上面的代码只是为了知道按下了哪个键并更改每个键的值相应地标记。我试过了，但没用。请帮我解决这个问题。谢谢。

PS : 你会在一些问题或一些网站上找到上面的部分代码，因为它们不是我自己写的。我之前没有任何使用键绑定(bind)/keyListeners 等的经验。这只是我正在进行的项目的一部分。

Answer 1

我试图删除您现在不需要的所有内容，并添加了一个显示如下方向的 JLabel:

---

这应该可以帮助您入门。

import java.awt.event.*;
import java.util.HashMap;
import java.util.Map;
import javax.swing.*;

public class Controller extends JPanel {

    private static final long serialVersionUID = 1L;
    private static final int STEP = 3;
    private static final int TIMER_DELAY = STEP * 8;
    private Map<Direction, Boolean> directionMap = new HashMap<Direction, Boolean>();

    private JLabel lblDirection = new JLabel();

    enum Direction {

        UP(KeyEvent.VK_UP), DOWN(KeyEvent.VK_DOWN),
        LEFT(KeyEvent.VK_LEFT), RIGHT(KeyEvent.VK_RIGHT);

        private int keyCode;

        private Direction(int keyCode) {
            this.keyCode = keyCode;
        }

        public int getKeyCode() {
            return keyCode;
        }
    }

    public Controller() {

        add(lblDirection);

        for (Direction direction : Direction.values()) {
            directionMap.put(direction, false);
        }
        setKeyBindings();
        Timer timer = new Timer(TIMER_DELAY, new TimerListener());
        timer.start();
    }

    private void setKeyBindings() {
        InputMap inMap = getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW);
        ActionMap actMap = getActionMap();
        for (final Direction direction : Direction.values()) {
            KeyStroke pressed = KeyStroke.getKeyStroke(direction.getKeyCode(), 0, false);
            KeyStroke released = KeyStroke.getKeyStroke(direction.getKeyCode(), 0, true);
            inMap.put(pressed, direction.toString() + "pressed");
            inMap.put(released, direction.toString() + "released");
            actMap.put(direction.toString() + "pressed", new AbstractAction() {

                private static final long serialVersionUID = 1L;

                @Override
                public void actionPerformed(ActionEvent e) {
                    directionMap.put(direction, true);
                }
            });
            actMap.put(direction.toString() + "released", new AbstractAction() {

                private static final long serialVersionUID = 1L;

                @Override
                public void actionPerformed(ActionEvent e) {
                    directionMap.put(direction, false);
                }
            });
        }
    }

    private class TimerListener implements ActionListener {

        @Override
        public void actionPerformed(ActionEvent e) {
            StringBuilder s = new StringBuilder("go ");
            for (Direction direction : Direction.values()) {
                if (directionMap.get(direction)) {
                    s.append(direction.name() + " ");
                }
            }
            lblDirection.setText(s.toString());
        }
    }

    public static void createAndShowUI() {
        JFrame frame = new JFrame("KeyMapping");
        frame.getContentPane().add(new Controller());
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(400, 80);
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        java.awt.EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                createAndShowUI();
            }
        });
    }
}