如何让两个JPanel听同一个事件

Question

我有一个JFrame，在这个JFrame里面有两个JPanel。当我按下一个键时，它们都必须监听这个键事件并采取行动。我想把所有的键盘事件都交给两个JPanel。你知道怎么做吗？

编辑：由于他们必须做不同的事情，我需要两个不同的听众，很抱歉没有具体说明。

第二版：我做了一个简单的代码来告诉你这个问题。当我按下向上键时，显示的两个JPanel都必须更改其字符串；在这段代码中，只有一个真正做出了反应！

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.event.ActionEvent;
import java.awt.event.KeyEvent;
import javax.swing.AbstractAction;
import javax.swing.ActionMap;
import javax.swing.InputMap;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.KeyStroke;
/**
*
 * @author antonioruffolo
 */
public class TwoPanelsTest extends JFrame {
public TwoPanelsTest() {
    setDefaultCloseOperation(EXIT_ON_CLOSE);
    setResizable(false);
    setSize(800, 600);
    PanelTest panelTest1= new PanelTest();
    PanelTest panelTest2= new PanelTest();
    GridBagLayout layout= new GridBagLayout();
    this.setLayout(layout);
    GridBagConstraints c = new GridBagConstraints();
    c.ipadx = 220;
    c.ipady = 390;
    c.insets.right= 0;
    c.insets.left=30;
    layout.setConstraints(panelTest1, c);
    this.add(panelTest1);
    layout.setConstraints(panelTest2, c);
    c.ipadx = 220;
    c.ipady = 390;
    c.insets.right=250;
    c.insets.left=50;
    this.add(panelTest2);

    setVisible(true);
    setLocationRelativeTo(null);
    setTitle("Test");
    setFocusable(false);
}
private class PanelTest extends JPanel{
    private String string="I'm not called by the event";
    private InputMap inputmap;
    private ActionMap actionmap;
    public PanelTest(){
        setFocusable(false);
        setDoubleBuffered(true);
        this.setBackground(Color.WHITE);
        inputmap = getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW);
        inputmap.put(KeyStroke.getKeyStroke(KeyEvent.VK_UP, 0), "up");
        actionmap = getActionMap();
        actionmap.put("up", new ActionController(this));
    }
    public void setString(String string){
        this.string=string;
    }
    @Override
    public void paintComponent( Graphics g){
        super.paintComponent(g);
        Font infoFont= new Font("OCR A Std", Font.BOLD, 10);
        g.setFont(infoFont);
        g.drawString(string, 10, 50);
    }
}//PanelTest
private class ActionController extends AbstractAction{
    private PanelTest panel;
    public ActionController (PanelTest panel){
        this.panel=panel;
    }
    @Override
    public void actionPerformed(ActionEvent ae) {
        panel.setString("Action performed");
        panel.repaint();
    }
}
public static void main(String[] args) {
    TwoPanelsTest t = new TwoPanelsTest();
}
}

Answer 1

使用密钥绑定而不是KeyListener，并且每个面板都有不同的Action实现。通过使用WHEN_ANCESTOR_OF_FOCUSED_COMPONENT输入映射，两个面板都可以响应。

附录：因为搜索在找到键的有效绑定后结束，下面的示例将事件转发到List<MyPanel>的元素，每个元素可以通过可用的Action做出不同的响应。

import java.awt.EventQueue;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.KeyEvent;
import java.util.Arrays;
import java.util.List;
import javax.swing.AbstractAction;
import javax.swing.Action;
import javax.swing.BorderFactory;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.KeyStroke;
/** @see http://stackoverflow.com/q/10011564/230513 */
public class TwoPanelsTest extends JFrame {
    private MyPanel one = new MyPanel("One");
    private MyPanel two = new MyPanel("Two");
    private List<MyPanel> list = Arrays.asList(one, two);
    public TwoPanelsTest() {
        super("TwoPanelsTest");
        this.setDefaultCloseOperation(EXIT_ON_CLOSE);
        JPanel panel = new JPanel(new GridLayout(0, 1, 10, 10));
        panel.setBorder(BorderFactory.createEmptyBorder(10, 10, 10, 10));
        panel.add(one);
        panel.add(two);
        panel.getInputMap(JComponent.WHEN_ANCESTOR_OF_FOCUSED_COMPONENT)
            .put(KeyStroke.getKeyStroke(KeyEvent.VK_UP, 0), "up");
        panel.getActionMap().put("up", new AbstractAction() {
            @Override
            public void actionPerformed(ActionEvent e) {
                for (MyPanel panel : list) {
                    panel.getAction().actionPerformed(e);
                }
            }
        });
        this.add(panel);
        this.pack();
        this.setLocationRelativeTo(null);
        this.setVisible(true);
    }
    private static class MyPanel extends JPanel {
        private String string = " will be updated though its action.";
        private Action action = new UpdateAction(this);
        private String name;
        private JLabel label;
        public MyPanel(String name) {
            this.name = name;
            this.label = new JLabel(name + string, JLabel.CENTER);
            this.setLayout(new GridLayout());
            this.setFocusable(true);
            this.add(label);
        }
        public Action getAction() {
            return action;
        }
        private void update() {
            label.setText(name + ": " + System.nanoTime());
        }
        private static class UpdateAction extends AbstractAction {
            private MyPanel panel;
            public UpdateAction(MyPanel panel) {
                this.panel = panel;
            }
            @Override
            public void actionPerformed(ActionEvent ae) {
                panel.update();
            }
        }
    }
    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                TwoPanelsTest t = new TwoPanelsTest();
            }
        });
    }
}

Answer 2

其中一种方法是使用SwingUtilities for Java6的方法（注意SwingUtilities for Java7有一些更改，但在这种情况下并不重要）可以重定向、分发来自标准Swing监听器的多个事件，将鼠标事件从一个容器重定向到另一个容器的简单示例

Answer 3

您应该创建一个XXListener实现，并通过.addXXListener将该侦听器添加到所需的所有组件中。

Answer 4

您可以为此使用观察者模式。http://en.wikipedia.org/wiki/Observer_pattern

MyKeyEventListener listener = new MyKeyEventListener();
JPanel one = new JPanel();
one.addKeyListener(listener);//method might be wrong
JPanel two = new JPanel();
two.addKeyListener(listener);
listener.addObserver(one);
listener.addObserver(two);