Java事件处理——按钮和按键映射到动作对象

野性酷女 2022-06-16 13:22 155阅读 0赞

目标：实现按下CTRL+Y、CTRL+B或CTRL+R来改变面板颜色  
Swing包的Action接口封装了命令，将它们连接到多个事件源。

java代码如下：  
ActionFrame.java

package simpleframe;
    
    import java.awt.*;
    import java.awt.event.*;
    import javax.swing.*;
    
    public class ActionFrame extends JFrame{ 
    
        private JPanel buttonPanel;
        private static final int DEFAULT_WIDTH = 300;
        private static final int DEFAULT_HEIGHT = 200;
    
        public ActionFrame(){
            setSize(DEFAULT_WIDTH,DEFAULT_HEIGHT);
    
            buttonPanel = new JPanel();
    
            //定义action
            Action yellowAction = new ColorAction("黄色", new ImageIcon("yellow-ball.gif"), Color.YELLOW);
            Action blueAction = new ColorAction("蓝色", new ImageIcon("blue-ball.gif"), Color.BLUE);
            Action redAction = new ColorAction("红色", new ImageIcon("red-ball.gif"), Color.RED);
    
            //给button添加动作
            buttonPanel.add(new JButton(yellowAction));
            buttonPanel.add(new JButton(blueAction));
            buttonPanel.add(new JButton(redAction));
    
            //把panel加到frame中
            add(buttonPanel);
    
            //关联Y,B,R 键和名字
            InputMap imap = buttonPanel.getInputMap(JComponent.WHEN_ANCESTOR_OF_FOCUSED_COMPONENT);
            imap.put(KeyStroke.getKeyStroke("ctrl Y"), "panel.yellow");
            imap.put(KeyStroke.getKeyStroke("ctrl B"), "panel.blue");
            imap.put(KeyStroke.getKeyStroke("ctrl R"), "panel.red");
    
            //关联名字和动作
            ActionMap amap = buttonPanel.getActionMap();
            amap.put("panel.yellow", yellowAction);
            amap.put("panel.blue", blueAction);
            amap.put("panel.red", redAction);
        }
    
        public class ColorAction extends AbstractAction{ //AbstractAction类实现了Action接口除actionPerformed方法之外的所有六个方法
            /** * 构造一个color action * @param name button显示的名字 * @param icon button显示的图标 * @param c 背景颜色 */
            public ColorAction(String name, Icon icon, Color c) {
                putValue(Action.NAME, name);
                putValue(Action.SMALL_ICON, icon);
                putValue(Action.SHORT_DESCRIPTION, "设置面板颜色为" + name.toLowerCase());
                putValue("color", c);
            }
    
            @Override
            public void actionPerformed(ActionEvent arg0) {
                Color c = (Color)getValue("color");
                buttonPanel.setBackground(c);
            }
        }
    
        public static void main(String[] args) {
            EventQueue.invokeLater(new Runnable()
            {
               public void run()
               {
                  JFrame frame = new ActionFrame();
                  frame.setTitle("ActionColor");
                  frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                  frame.setVisible(true);
               }
            });
    
        }
    
    }

运行结果如下图：  
![这里写图片描述][SouthEast]

[SouthEast]: /images/20220616/3aec0cc26a2a46128dc46c6c0c29ff00.png