ActionEvent 无法识别 CTRL 键绑定

Question

我正在尝试将键绑定集成到我正在制作的程序中，但由于该程序很长，我正在尝试学习我在 StackOverflow 上找到的一个较小的类似编码的程序。

这是我正在使用的代码：

import java.awt.Color;
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;

import javax.swing.AbstractAction;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;

public class Demo {

	@SuppressWarnings("serial")
	private void initGUI() {
		JPanel content = new JPanel(new FlowLayout());
		content.add(new JLabel("Test:"));

		AbstractAction buttonPressed = new AbstractAction() {
			@Override
			public void actionPerformed(ActionEvent e) {
				System.out.println(e.getActionCommand());
				System.out.println(e.getSource());
				if ("a".equals(e.getActionCommand()))
					content.setBackground(new Color(227, 19, 19));
				if ("b".equals(e.getActionCommand()))
					content.setBackground(new Color(0, 225, 19));
			}
		};

		JButton submit = new JButton("Submit");
		submit.addActionListener(buttonPressed);

		submit.getInputMap(javax.swing.JComponent.WHEN_IN_FOCUSED_WINDOW).put(
          javax.swing.KeyStroke.getKeyStroke(
            java.awt.event.KeyEvent.VK_A,
            java.awt.event.InputEvent.CTRL_DOWN_MASK),
          "A_pressed");
		submit.getActionMap().put("A_pressed", buttonPressed);
      
      submit.getInputMap(javax.swing.JComponent.WHEN_IN_FOCUSED_WINDOW).put(
        javax.swing.KeyStroke.getKeyStroke(
          java.awt.event.KeyEvent.VK_B, 0),
        "B_pressed");
		submit.getActionMap().put("B_pressed", buttonPressed);

		content.add(submit);

		JFrame frame = new JFrame("Demo");
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		frame.setContentPane(content);
		frame.pack();
		frame.setLocationRelativeTo(null);
		frame.setVisible(true);
	}

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

			@Override
			public void run() {
				new Demo().initGUI();
			}
		});
	}
}

我要做的是按 CTRL+A 并让背景改变颜色。但是，当我这样做时，System.out.println(e.getActionCommand()) 正在返回一个看起来像框中的问号的字符，就像它是未知字符或其他东西一样。如果您按 B，程序可以运行，但添加修饰符 CTRL 不能正常工作。

问题是我做错了吗？程序是否正常工作，我不知道如何比较e.getActionCommand() 和字符串 CTRL+A 作为 ActionEvent 返回的内容？请帮忙。

Answer 1

据我所知，如果一个 Action 没有明确设置其 actionCommand，它将在创建 ActionEvent 时设置。在您的代码中，actionCommmand 将是您的 keyStroke 的 charKey 的字符串表示形式（b 和 ctrl+a 不是 a） 所以我可以建议对每个动作采取不同的行动：

class simpleAction extends AbstractAction {

        public simpleAction ( String name ) {
            super ();
            putValue ( Action.ACTION_COMMAND_KEY, name );
        }

        @Override
        public void actionPerformed ( ActionEvent e ) {
            System.out.println ( "getActionCommand----->" + e.getActionCommand () );
            System.out.println ( "getSource----->" + e.getSource () );

            if ( "a".equals ( e.getActionCommand () ) ) {
                content.setBackground ( new Color ( 227, 19, 19 ) );
            }
            if ( "b".equals ( e.getActionCommand () ) ) {
                content.setBackground ( new Color ( 0, 225, 19 ) );
            }

        }
    }

    JButton submit = new JButton ( "Submit" );
    submit.addActionListener ( new simpleAction ( "Submit" ) );

    submit.getInputMap ( javax.swing.JComponent.WHEN_IN_FOCUSED_WINDOW ).put (
            javax.swing.KeyStroke.getKeyStroke ( java.awt.event.KeyEvent.VK_A, java.awt.event.InputEvent.CTRL_DOWN_MASK ), "A_pressed" );
    submit.getActionMap ().put ( "A_pressed", new simpleAction ( "a" ) );

    submit.getInputMap ( javax.swing.JComponent.WHEN_IN_FOCUSED_WINDOW ).put (
            javax.swing.KeyStroke.getKeyStroke (
                    java.awt.event.KeyEvent.VK_B, 0 ),
            "B_pressed" );
    submit.getActionMap ().put ( "B_pressed", new simpleAction ( "b" ) );

或第二种解决方案是检查 ctrl+a 的字符串表示形式

所以你改变

 if ( "a".equals ( e.getActionCommand () ) ) {
                content.setBackground ( new Color ( 227, 19, 19 ) );
            }

通过

 if ( "\u0001".equals ( e.getActionCommand () ) ) {
                content.setBackground ( new Color ( 227, 19, 19 ) );
            }