ActionEvent - KeyEvent问题？

Question

不知道为什么，但当我尝试使用KeyEvents进行ImageIcon移动时，它不起作用。我想，当我按下"A“键时，我的形象会向左移动。

这是我的代码，由一个助手完成：

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


public class MainClass extends AbstractAction {
    JLabel label;

    int x = 300;
    int y = 300;

    public MainClass() {
        final JPanel panel = new JPanel();
        final ImageIcon image = new ImageIcon("Character Face Left - Bronze.png");

        label = new JLabel(image,JLabel.CENTER );

        label.setSize(500,500);
        label.setLocation(x, y); 

        final JFrame frame = new JFrame( "Rover: Bound to Earth" );
        frame.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
        frame.setLayout(null);
        frame.add(label);
        frame.setSize(500, 500);
        frame.setVisible(true);

        InputMap inputMap = panel.getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW);
        ActionMap actionMap = panel.getActionMap();

        inputMap.put(KeyStroke.getKeyStroke(KeyEvent.VK_A, 0), "LEFT");
        actionMap.put("LEFT", this);
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        x -= 10;
        label.setLocation(x, y);
    }

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

Answer 1

    InputMap inputMap = panel.getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW);
    ActionMap actionMap = panel.getActionMap();

将键绑定添加到面板，但从不使用面板。

应该将键绑定添加到要操作的组件中：

    InputMap inputMap = label.getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW);
    ActionMap actionMap = label.getActionMap();

或者，如果确实希望设置面板上的绑定，则需要将标签添加到面板中，然后将面板添加到框架中。因此，框架将使用默认的BorderLayout，面板将使用空布局。

不要随意设置组件的大小：

label.setSize(500,500);

相反，您可以根据首选的大小来确定大小：

label.setSize( label.getPreferredSize() );

另外，为什么要扩展AbstracAction？

public class MainClass extends AbstractAction {

该类中的代码用于创建GUI，您不应该仅为此扩展AbstractAction。

阅读有关如何使用动作的Swing教程中的部分。ActionDemo.java源代码将向您展示如何更好地构造代码，并将动作作为单独的内部类使用。

Answer 2

尝试以下代码(左箭头图像，分别是右箭头图像，嵌入到Base64格式的代码中)：

import javax.swing.*;
import java.awt.*;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;
import java.util.Base64;

public class MainClass extends JFrame {

    private static final String LEFT_ARROW = "iVBORw0KGgoAAAANSUhEUgAAAEAAAABACAMAAACdt4HsAAAAA3NCSVQICAjb4U/gAAAACXBIWXMAAAbsAAAG7AEedTg1AAAAGXRFWHRTb2Z0d2FyZQB3d3cuaW5rc2NhcGUub3Jnm+48GgAAAVNQTFRF////AAAAAAAAVVVVQEBAMzMzKysrJCQkQEBAYGBgLi4uKysrNzc3SUlJMzMzLS0tNjY2aGhoQ0NDMzMzNzc3MzMzPDw8MjIyXFxcNzc3TExMNTU1XV1dZWVlMTExampqPDw8ZmZmSkpKNDQ0Xl5eQUFBPDw8VFRUaGhoQUFBOzs7SkpKYWFhR0dHREREWFhYampqR0dHQUFBUVFRZWVlSEhIUVFRXV1dbm5uSkpKUFBQWFhYaGhoUFBQWFhYZGRkdHR0UlJSWFhYXl5eb29vWVlZYWFhbGxseXl5W1tbY2Njd3d3ZmZmbW1tdXV1gICAZ2dnb29vh4eHf39/cnJyfX19h4eHc3Nzenp6h4eHj4+PfHx8hoaGjo6Ofn5+hYWFjo6OlZWVfHx8goKChoaGiIiIioqKjIyMjo6OkJCQkpKSk5OTlJSUlpaWl5eXmJiYmZmZ40GS6gAAAGJ0Uk5TAAECAwQFBgcICAsMDg4PERMWFxkcHiIkJC4vMDQ1OTo8PD5AQUtNT1ZeX2BkcHF0e4SFh4uYmJyiqqqusbu8wMbLy87R19jc4eLj6Ovs7vHy8vT19/j5+vv7/P39/f7+/v7HrT76AAABKUlEQVRYw+3XxVIDQQCE4YYQCBAI7hbcHYJbcPfgDoENw/T7n3Ldwy4F1Reoyn+e/mpuUwNk+hc1ifvehLYffTbKPGf6jQoQXnaoABVbhgpQf2ipAJ0JUgEG76gAWROvVIDQ/AcVoGTNUAGqdy1dQJt3Id99yynd2SfvGvz2Pdf8UVGf/cgLFSAw804FKFz5pAKUb1sqQO0RqQAdF5SAgXtKwGSSCpC7kKICRNYtFaByj7+v2QUUxA2lGyAw62gAMJYUAfTdiABaz0QAVfsigOINqwEILhoNAGKOCGDoQQTQdSkCqDsRAZTtiADyVt0HTdS7/O8e9zntcQUwnhIB9N+KANrPRQA1ByKAok0RQPaSCABTXyKA4UcRQPeVCKDxWP3ylGZ+fX++NPvqVHl2jq5HAAAAAElFTkSuQmCC";
    private static final String RIGHT_ARROW = "iVBORw0KGgoAAAANSUhEUgAAAEAAAABACAYAAACqaXHeAAADzklEQVR4Xu2bX0jaaxjHX/8s+2NIQnFOjqYyi7YMbFLSzMqyYrk2DiWMbvbnMOjAgg1h29W2mwOHwc6hiLStdoi2RuDO8aJdNMvWoX8rDTMPTpsEugRZJqyGJup5vPCuiyNkSI9fePndKe+X930/z+/7vD9KLBYjmEUlyJUxIGMAcmUMyBhwzKqpqeFVV1f/gNYAmLyyoqLCVlVVdQ6lARQKhSaRSNhSqdQMq0GOlgKwChhNTU3vZTLZz2gpwOVyqa2trc8VCsVTtBQoLCwkbW1taqVS+bdYLD6FEoP5+flxE67weLxlMIGFsg7IysoicCaIgBD/ggklKAshKpVKamtri4ESNhgX0FaClZWVzIaGhiUgxFW0pTCfz6e3tLS8BVSq0eYBRUVFFCDEUyDECwqIpEB0cohg/52ORCJnSQpUXl6e1O+yWCwCtcKt3NxcfmNj4yWj0RhMuQFCofARuJ+SCi07O5skKwaDQRpBi4uLFiDExdXV1a/kiHRoKKpWq/8qLS29StJQa2tr/qWlJQk8nSjzAJFIxG5ubrbW19fL0AYiAoGAATvCCJS4jjYRKi4upgIiX7a3t/+KNhIrKCggsAoednV16VQqFQ1lJpiTk0PkcvlP8C7xETIGJspQlEajkbq6uipImeyAyR9RpsLxQhFyRg7QwQEpUyXaWLysrIwJhDDBAXkZbV+Aw+HQIWbTd3R03EXbGGGz2RRYCc86Ozu1aDtDeXl5BEy43d3dbYhjEmVrLBgMxodpYmIigs6AnZ2d6MzMzE2dTncf3RbweDwhyA7kk5OTL9FRwOl0Bqanp89PTU19QEWBeLaxvr7uMhgMvPn5+c//LxE6IYIIj5jN5n8gKGmCESYgNAaEQiGysrLy5+jo6A10L0P7+/uxhYWFB4nJozLA7/dHYPKd4+Pjv5FDdKK3wPb29nfY61K9Xr+GLhFyuVw+KHDOJiaPyoCNjQ3b8vLymbm5OW8KGiPpq2g0SiwWyzuNRqOMgVLaGOnp6eHAH/JICsRkMlUQWtwhSejg4CBe4Pw+NDR071h6g4ODg1/gAePo1dvbK04Wc3DY/QKY06DrDu/u7oZNJpMiMXlUBni93m8weeHY2Ng0uvsBW1tbntnZ2RIIMT6huyHicDhWNjc3ufAuHyDHIHo6Yc5ms73p7++/hu6aXDgcJlar9Uli8qgMAMxFgfHdAwMDj9FdlQ0EAiEobaVarfY1urvCPp/Pb7fbBcPDw4vobou73e7PcNqXjIyMuEkSOhEU2Nvbe9XX1/cHSRNlPp0lyJUxIGMAcv0HB8VtSN5KVe4AAAAASUVORK5CYII=";
    private JLabel label;
    private ImageIcon leftArrow;
    private ImageIcon rightArrow;

    MainClass() {
        loadResources();
        buildUI();
        registerListeners();
    }

    private void loadResources() {
        leftArrow = new ImageIcon(Base64.getDecoder().decode(LEFT_ARROW));
        rightArrow = new ImageIcon(Base64.getDecoder().decode(RIGHT_ARROW));
    }

    private void buildUI() {
        label = new JLabel("test");
        label.setIcon(leftArrow);
        label.setSize(100, 64);
        label.setOpaque(true);
        label.setBackground(Color.CYAN);
        label.setLocation(0, 0);

        JPanel panel = new JPanel();
        panel.setOpaque(true);
        panel.setLayout(null);
        panel.add(label);

        this.setContentPane(panel);
    }

    private void registerListeners() {
        this.addKeyListener(new KeyAdapter() {

            @Override
            public void keyPressed(KeyEvent e) {
                int x = 0;
                int y = 0;
                ImageIcon newImageIcon = null;
                switch (e.getKeyCode()) {
                    case KeyEvent.VK_LEFT:
                        newImageIcon = leftArrow;
                        x -= 10;
                        break;
                    case KeyEvent.VK_RIGHT:
                        newImageIcon = rightArrow;
                        x += 10;
                        break;
                    case KeyEvent.VK_UP:
                        y -= 10;
                        break;
                    case KeyEvent.VK_DOWN:
                        y += 10;
                        break;
                }
                if (x != 0 || y != 0) {
                    Point location = label.getLocation();
                    label.setLocation(location.x + x, location.y + y);
                    if (newImageIcon != null) {
                        label.setIcon(newImageIcon);
                    }
                }
            }

        });
    }

    public static void main(String[] args) {
        JFrame frame = new MainClass();
        frame.setSize(500, 500);
        frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }
}