将keylistener或键绑定添加到使用ActionListener的JButton

Question

我需要一些帮助，从下一个例子中添加keylistener或键绑定到按钮。当我按下键盘上的A或B时，我想要做同样的操作，就像我用鼠标按下它一样。

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;

public class NetTest {

    static JButton btnA = new JButton("A");
    static JButton btnB = new JButton("B");
    static JPanel jp = new JPanel();
    static JFrame jf = new JFrame("Test APP");
    static JLabel jl = new JLabel("Which button was clicked ?");

    static ActionListener action = new ActionListener() {
        public void actionPerformed(ActionEvent e) {
            jl.setText(((JButton)e.getSource()).getText());
        }
    };

    public static void main(String[] args) {
        jf.setVisible(true);
        jf.setSize(400, 400);
        jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        jp.add(btnA);
        jp.add(btnB);
        jp.add(jl);
        jf.add(jp);

        btnA.addActionListener(action);
        btnB.addActionListener(action);
    }
}

Answer 1

为了听KeyEvents你需要使用JComponent#getInputMap()和JComponent#getActionMap()方法来输入你想要听的输入事件和相应的动作。试试这个例子：

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{

    private void initGUI(){
        AbstractAction buttonPressed = new AbstractAction() {
            @Override
            public void actionPerformed(ActionEvent e) {
                System.out.println(e.getActionCommand());
            }
        };

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

        /*
         * Get the InputMap related to JComponent.WHEN_IN_FOCUSED_WINDOW condition
         * to put an event when A key is pressed
         */
        submit.getInputMap(javax.swing.JComponent.WHEN_IN_FOCUSED_WINDOW).
                put(javax.swing.KeyStroke.getKeyStroke(java.awt.event.KeyEvent.VK_A,0), "A_pressed");
        /*
         * Add an action when the event key is "A_pressed"
         */
        submit.getActionMap().put("A_pressed", buttonPressed);

        /*
         * Same as above when you press B key
         */
        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);

        JPanel content = new JPanel(new FlowLayout());
        content.add(new JLabel("Test:"));
        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);
    }

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {

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

    }
}

注意：此示例在按下AbstractAction或A / B键时使用相同的JButton，但输出将取决于谁是事件源。

注2：如果你使用JComponent.WHEN_IN_FOCUSED_WINDOW条件，你的动作将在按下A或B键时执行。如果您有文本输入组件（如JTextfield或JTextArea），并且最终用户几乎肯定会按A或B键多次，则不需要此行为。如果是这种情况，那么你将不得不使用JComponent.WHEN_ANCESTOR_OF_FOCUSED_COMPONENT条件。

Answer 2

如果我理解你想要实现的目标，基本上你想要听两个特定的键盘事件（按下“A”或“B”键），并切换标签，就好像你点击了两个JButton中的一个。

您只需要将KeyListener添加到帧中，并实现其回调以仅响应“A”或“B”类型。还记得在JFrame对象上调用setFocusable（false）

    jf.setFocusable(true);
    jf.addKeyListener( new KeyListener() {

        @Override
        public void keyTyped( KeyEvent evt ) {
        }

        @Override
        public void keyPressed( KeyEvent evt ) {
        }

        @Override
        public void keyReleased( KeyEvent evt ) {
        }
    } );