Java密钥绑定不起作用

Question

我试图在JPanel上用Java创建键绑定.当我按下"w"按钮时,我想要执行某个动作.我遵循关于进行绑定的Java教程,但是actionPerformed方法没有执行(即没有文本打印出来).以下是我的测试GUI的全部代码,相关部分突出显示:

import java.awt.BorderLayout;
import java.awt.event.ActionEvent;

import javax.swing.AbstractAction;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.KeyStroke;

@SuppressWarnings("serial")
public class Test extends JFrame{

private JPanel panel;

public Test(){
    super();
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setSize(500,500);
    setLayout(new BorderLayout());
    setVisible(true);        
    panel = new JPanel();

    // HERE ARE THE KEY BINDINGS
    panel.getInputMap().put(KeyStroke.getKeyStroke('w'),"forward");
    panel.getActionMap().put("forward", new AbstractAction(){
        @Override
        public void actionPerformed(ActionEvent e){
            System.out.println("test");
        }
    });
    // END OF KEY BINDINGS

    add(panel, BorderLayout.CENTER);
}

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

}

永远不会打印文本"test".我尝试过多次使用许多不同的变体,不同的键,我确保面板是焦点,但没有运气.我究竟做错了什么？

Answer 1

问题是你正在查找的方式KeyStroke. KeyStroke.getKeyStroke('w')将返回typed w,由于某种原因,不会触发关键事件.这就是为什么我倾向于避免这种方法.而是使用

panel.getInputMap().put(KeyStroke.getKeyStroke("W"),"forward");

要么

panel.getInputMap().put(KeyStroke.getKeyStroke(KeyEvent.VK_W, 0),"forward");

此外,您可能想要定义焦点约束InputMap,例如

panel.getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW)...

会更安全......但你需要决定你想要从哪个级别触发击键

有关更多详细信息,请参阅JComponent和如何使用键绑定

更新了示例

import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.event.ActionEvent;
import java.awt.event.KeyEvent;
import javax.swing.AbstractAction;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.KeyStroke;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class Test extends JFrame {

    private JPanel panel;

    public Test() {
        super();
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setSize(500, 500);
        setLayout(new BorderLayout());
        setVisible(true);
        panel = new JPanel();

        // HERE ARE THE KEY BINDINGS
        panel.getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW).put(KeyStroke.getKeyStroke(KeyEvent.VK_W, 0), "forward");
        panel.getActionMap().put("forward", new AbstractAction() {
            @Override
            public void actionPerformed(ActionEvent e) {
                System.out.println("test");
            }
        });
        // END OF KEY BINDINGS

        add(panel, BorderLayout.CENTER);
    }

    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                }

                new Test();
            }
        });
    }
}