201771010142张燕/杨蓉庆实验十三 图形界面事件处理技术

实验十三  图形界面事件处理技术

实验时间 2018-11-22

 

基础知识：

 ⚫ 事件源（event source）：能够产生事件的对象都可 以成为事件源，如文本框、按钮等。一个事件源是一个 能够注册监听器并向监听器发送事件对象的对象。

⚫ 事件监听器（event listener）：事件监听器对象接 收事件源发送的通告（事件对象），并对发生的事件作 出响应。一个监听器对象就是一个实现了专门监听器接 口的类实例，该类必须实现接口中的方法，这些方法当 事件发生时,被自动执行。

⚫ 事件对象（event object）：Java将事件的相关信息 封装在一个事件对象中，所有的事件对象都最终派生于 java.util.EventObject类。不同的事件源可以产生不 同类别的事件

AWT事件处理机制的概要： ⚫ 监听器对象:是一个实现了特定监听器接口（ listener interface）的类实例。

⚫ 事件源:是一个能够注册监听器对象并发送事件对 象的对象。

⚫ 当事件发生时，事件源将事件对象自动传递给所 有注册的监听器。

⚫ 监听器对象利用事件对象中的信息决定如何对事 件做出响应。

GUI设计中，程序员需要对组件的某种事件进行响应和处理时，必须完成两个步骤：

1) 定义实现某事件监听器接口的事件监听器类，并具体化接口中声明的事件处理抽象方法。

2) 为组件注册实现了规定接口的事件监听器对象；

⚫ 注册监听器方法 eventSourceObject.addEventListener(eventListenerObject)

⚫ 下面是监听器的一个示例： ActionListener listener = …;

JButton button=new JButton(“Ok”); button.addActionListener(listener);

⚫ 动作事件（ActionEvent）:当特定组件动作（点 击按钮）发生时，该组件生成此动作事件。

⚫ 该 事 件 被 传 递 给 组 件 注 册 的 每 一 个 ActionListener 对象， 并 调 用 监 听 器 对 象 的 actionPerformed方法以接收这类事件对象。

⚫ 能够触发动作事件的动作，主要包括：

(1) 点击按钮

(2) 双击一个列表中的选项；

(3) 选择菜单项；

(4) 在文本框中输入回车。

11.1.1  监听器接口的实现

监听器类必须实现与事件源相对应的接口，即必须提供接口中方法的实现。

⚫ 监听器接口方法实现 class Mylistener implements ActionListener {  public void actionPerformed (ActionEvent event) {  …… }}

 private class ColorAction implements ActionListener

   {

     public ColorAction(Color c)

   {

      backgroundColor = c;

  }.

  public void actionPerformed(ActionEvent event)

   {

       buttonPanel.setBackground(backgroundColor);

   }.

    private Color backgroundColor;

 }

实验内容

1、实验目的与要求

(1) 掌握事件处理的基本原理，理解其用途；

(2) 掌握AWT事件模型的工作机制；

(3) 掌握事件处理的基本编程模型；

(4) 了解GUI界面组件观感设置方法；

(5) 掌握WindowAdapter类、AbstractAction类的用法；

(6) 掌握GUI程序中鼠标事件处理技术。

2、实验内容和步骤

实验1： 导入第11章示例程序，测试程序并进行代码注释。

测试程序1：

l 在elipse IDE中调试运行教材443页-444页程序11-1，结合程序运行结果理解程序；

原代码如下：

package button;

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

/**
 * A frame with a button panel
 */
public class ButtonFrame extends JFrame
{
    //属性的定义
   private JPanel buttonPanel;//内容窗格对象
   private static final int DEFAULT_WIDTH = 300;//窗口宽度
   private static final int DEFAULT_HEIGHT = 200;//窗口高度

   public ButtonFrame()
   {      
      setSize(DEFAULT_WIDTH, DEFAULT_HEIGHT);//更改了GUI界面的宽度和高度

      // 生成三个按钮对象
      JButton yellowButton = new JButton("yellow");
      JButton blueButton = new JButton("Blue");
      JButton redButton = new JButton("Red");

      buttonPanel = new JPanel();

      // 向buttonPanel内容窗格添加三个按钮组件
      buttonPanel.add(yellowButton);
      buttonPanel.add(blueButton);
      buttonPanel.add(redButton);

      // 添加内容窗格
      add(buttonPanel);

      // 注册监听器类对象
      ColorAction yellowAction = new ColorAction(Color.YELLOW);
      ColorAction blueAction = new ColorAction(Color.BLUE);
      ColorAction redAction = new ColorAction(Color.RED);

      // 监听器类对象和组件对应
      yellowButton.addActionListener(yellowAction);
      blueButton.addActionListener(blueAction);
      redButton.addActionListener(redAction);
   }

   /**
    * An action listener that sets the panel's background color.
    */
   private class ColorAction implements ActionListener//ColorAction为监听器类
   {
      private Color backgroundColor;

      public ColorAction(Color c)
      {
         backgroundColor = c;
      }
     
      public void actionPerformed(ActionEvent event)
      {
         buttonPanel.setBackground(backgroundColor);
      }
   }
}

ackage button;

import java.awt.*;
import javax.swing.*;

/**
 * @version 1.34 2015-06-12
 * @author Cay Horstmann
 */
public class ButtonTest
{
   public static void main(String[] args)
   {
      EventQueue.invokeLater(() -> {
         JFrame frame = new ButtonFrame();//生成GUI类对象frame
         frame.setTitle("ButtonTest");//设置程序的名字
         frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);//窗口的退出按钮起作用
         frame.setVisible(true);//可视化，使得程序可见
      });
   }
}

l 在事件处理相关代码处添加注释；

l 用lambda表达式简化程序；

简化程序ButtonFrame①

package shiyan;

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

/**
 * A frame with a button panel
 */
public class ButtonFrame extends JFrame {
    // 属性的定义
    private JPanel buttonPanel;// 内容窗格对象
    private static final int DEFAULT_WIDTH = 300;// 窗口宽度
    private static final int DEFAULT_HEIGHT = 200;// 窗口高度

    public ButtonFrame() {
        setSize(DEFAULT_WIDTH, DEFAULT_HEIGHT);// 更改了GUI界面的宽度和高度

        // 生成三个按钮对象
        /*
         * JButton yellowButton = new JButton("yellow"); JButton blueButton = new
         * JButton("Blue"); JButton redButton = new JButton("Red");
         */
        buttonPanel = new JPanel();

        // 向buttonPanel内容窗格添加三个按钮组件
        /*
         * buttonPanel.add(yellowButton); buttonPanel.add(blueButton);
         * buttonPanel.add(redButton);
         */
        // 添加内容窗格
        add(buttonPanel);

        // 注册监听器类对象
        /*
         * ColorAction yellowAction = new ColorAction(Color.YELLOW); ColorAction
         * blueAction = new ColorAction(Color.BLUE); ColorAction redAction = new
         * ColorAction(Color.RED);
         */

        // 监听器类对象和组件对应
        /*
         * yellowButton.addActionListener(yellowAction);
         * blueButton.addActionListener(blueAction);
         * redButton.addActionListener(redAction);
         */
        makeButton("yellow", Color.YELLOW);
        makeButton("blue", Color.BLUE);
        makeButton("red", Color.RED);
        makeButton("green", Color.GREEN);

    }

    public void makeButton(String name, Color backgroundColor) {
        JButton button = new JButton(name);
        buttonPanel.add(button);

        ColorAction action = new ColorAction(backgroundColor);
        button.addActionListener(action);
    }

    /**
     * An action listener that sets the panel's background color.
     */
    private class ColorAction implements ActionListener// ColorAction为监听器类
    {
        private Color backgroundColor;

        public ColorAction(Color c) {
            backgroundColor = c;
        }

        public void actionPerformed(ActionEvent event) {
            buttonPanel.setBackground(backgroundColor);
        }
    }
}

简化程序ButtonFrame②

package button;

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

/**
 * A frame with a button panel
 */
public class ButtonFrame extends JFrame {
    private JPanel buttonPanel;
    private static final int DEFAULT_WIDTH = 300;
    private static final int DEFAULT_HEIGHT = 200;

    public ButtonFrame() {
        setSize(DEFAULT_WIDTH, DEFAULT_HEIGHT);

        // create buttons
        /*
         * JButton yellowButton = new JButton("Yellow"); JButton blueButton = new
         * JButton("Blue"); JButton redButton = new JButton("Red");
         */
        buttonPanel = new JPanel();

        // add buttons to panel
        /*
         * buttonPanel.add(yellowButton); buttonPanel.add(blueButton);
         * buttonPanel.add(redButton);
         */
        // add panel to frame
        add(buttonPanel);

        // create button actions
        /*
         * ColorAction yellowAction = new ColorAction(Color.YELLOW); ColorAction
         * blueAction = new ColorAction(Color.BLUE); ColorAction redAction = new
         * ColorAction(Color.RED);
         */

        // associate actions with buttons
        /*
         * yellowButton.addActionListener(yellowAction);
         * blueButton.addActionListener(blueAction);
         * redButton.addActionListener(redAction);
         */
        makeButton("yellow", Color.YELLOW);
        makeButton("blue", Color.BLUE);
        makeButton("red", Color.RED);
        makeButton("green", Color.GREEN);

    }

    public void makeButton(String name, Color backgroundColor) {
        JButton button = new JButton(name);
        buttonPanel.add(button);
        /*
         * ColorAction action = new ColorAction(backgroundColor);
         * button.addActionListener(action);
         */
        button.addActionListener(new ActionListener() {

            public void actionPerformed(ActionEvent e) {
                buttonPanel.setBackground(backgroundColor);
            }
        });
    }
}

/**
 * An action listener that sets the panel's background color.
 */
/*
 * private class ColorAction implements ActionListener { private Color
 * backgroundColor;
 * 
 * public ColorAction(Color c) { backgroundColor = c; }
 * 
 * public void actionPerformed(ActionEvent event) {
 * buttonPanel.setBackground(backgroundColor); } } }
 */

l 掌握JButton组件的基本API；

l 掌握Java中事件处理的基本编程模型。

测试程序2：

l 在elipse IDE中调试运行教材449页程序11-2，结合程序运行结果理解程序；

l 在组件观感设置代码处添加注释；

package plaf;

import java.awt.*;
import javax.swing.*;

/**
 * @version 1.32 2015-06-12
 * @author Cay Horstmann
 */
public class PlafTest
{
   public static void main(String[] args)
   {
      EventQueue.invokeLater(() -> {
         JFrame frame = new PlafFrame();
         frame.setTitle("PlafTest");
         frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
         frame.setVisible(true);
      });
   }
}

package plaf;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
import javax.swing.UIManager;

/**
 * A frame with a button panel for changing look-and-feel
 */
public class PlafFrame extends JFrame
{
   private JPanel buttonPanel;

   public PlafFrame()
   {
      buttonPanel = new JPanel();

      UIManager.LookAndFeelInfo[] infos = UIManager.getInstalledLookAndFeels();
      for (UIManager.LookAndFeelInfo info : infos)
         makeButton(info.getName(), info.getClassName());

      add(buttonPanel);
      pack();
   }

   /**
    * Makes a button to change the pluggable look-and-feel.
    * @param name the button name
    * @param className the name of the look-and-feel class
    */
   private void makeButton(String name, String className)
   {
      // 窗格中添加按钮

      JButton button = new JButton(name);
      buttonPanel.add(button);

      // 设定按钮动作
      button.addActionListener(event -> {
         // 按钮动作: 切换到新的外观和感觉
         try
         {
            UIManager.setLookAndFeel(className);
            SwingUtilities.updateComponentTreeUI(this);
            pack();
         }
         catch (Exception e)
         {
            e.printStackTrace();
         }
      });
   }
}

l 了解GUI程序中观感的设置方法。

测试程序3：

l 在elipse IDE中调试运行教材457页-458页程序11-3，结合程序运行结果理解程序；

package action;

import java.awt.*;
import javax.swing.*;

/**
 * @version 1.34 2015-06-12
 * @author Cay Horstmann
 */
public class ActionTest
{
   public static void main(String[] args)
   {
      EventQueue.invokeLater(() -> {
         JFrame frame = new ActionFrame();
         frame.setTitle("ActionTest");
         frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
         frame.setVisible(true);
      });
   }
}

package action;

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

/**
 * A frame with a panel that demonstrates color change actions.
 */
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();

      // 定义动作
      Action yellowAction = new ColorAction("Yellow", new ImageIcon("yellow-ball.gif"),
            Color.YELLOW);
      Action blueAction = new ColorAction("Blue", new ImageIcon("blue-ball.gif"), Color.BLUE);
      Action redAction = new ColorAction("Red", new ImageIcon("red-ball.gif"), Color.RED);

      // 为这些动作添加按钮
      buttonPanel.add(new JButton(yellowAction));
      buttonPanel.add(new JButton(blueAction));
      buttonPanel.add(new JButton(redAction));

//将Y、B和R键与名称联系起来
      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");

      // 把名字和行动联系起来
      ActionMap amap = buttonPanel.getActionMap();
      amap.put("panel.yellow", yellowAction);
      amap.put("panel.blue", blueAction);
      amap.put("panel.red", redAction);
   }
   
   public class ColorAction extends AbstractAction
   {
      /**
       * Constructs a color action.
       * @param name the name to show on the button
       * @param icon the icon to display on the button
       * @param c the background color
       */
      public ColorAction(String name, Icon icon, Color c)
      {
         putValue(Action.NAME, name);
         putValue(Action.SMALL_ICON, icon);
         putValue(Action.SHORT_DESCRIPTION, "Set panel color to " + name.toLowerCase());
         putValue("color", c);
      }

      public void actionPerformed(ActionEvent event)
      {
         Color c = (Color) getValue("color");
         buttonPanel.setBackground(c);
      }
   }
}

l 掌握AbstractAction类及其动作对象；

l 掌握GUI程序中按钮、键盘动作映射到动作对象的方法。

测试程序4：

l 在elipse IDE中调试运行教材462页程序11-4、11-5，结合程序运行结果理解程序；

package mouse;

import java.awt.*;
import javax.swing.*;

/**
 * @version 1.34 2015-06-12
 * @author Cay Horstmann
 */
public class MouseTest
{
   public static void main(String[] args)
   {
      EventQueue.invokeLater(() -> {
         JFrame frame = new MouseFrame();
         frame.setTitle("MouseTest");
         frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
         frame.setVisible(true);
      });
   }
}

package mouse;

import javax.swing.*;

/**
 * A frame containing a panel for testing mouse operations
 */
public class MouseFrame extends JFrame
{
   public MouseFrame()
   {
      add(new MouseComponent());
      pack();
   }
}

package mouse;

import java.awt.*;
import java.awt.event.*;
import java.awt.geom.*;
import java.util.*;
import javax.swing.*;

/**
 * A component with mouse operations for adding and removing squares.
 */
public class MouseComponent extends JComponent
{
   private static final int DEFAULT_WIDTH = 300;
   private static final int DEFAULT_HEIGHT = 200;

   private static final int SIDELENGTH = 10;
   private ArrayList<Rectangle2D> squares;
   private Rectangle2D current; // 包含鼠标光标的正方形
   public MouseComponent()
   {
      squares = new ArrayList<>();
      current = null;

      addMouseListener(new MouseHandler());
      addMouseMotionListener(new MouseMotionHandler());
   }

   public Dimension getPreferredSize() { return new Dimension(DEFAULT_WIDTH, DEFAULT_HEIGHT); }   
   
   public void paintComponent(Graphics g)
   {
      Graphics2D g2 = (Graphics2D) g;

      // 绘制所有方块
      for (Rectangle2D r : squares)
         g2.draw(r);
   }

   /**
    * Finds the first square containing a point.
    * @param p a point
    * @return the first square that contains p
    */
   public Rectangle2D find(Point2D p)
   {
      for (Rectangle2D r : squares)
      {
         if (r.contains(p)) return r;
      }
      return null;
   }

   /**
    * Adds a square to the collection.
    * @param p the center of the square
    */
   public void add(Point2D p)
   {
      double x = p.getX();
      double y = p.getY();

      current = new Rectangle2D.Double(x - SIDELENGTH / 2, y - SIDELENGTH / 2, SIDELENGTH,
            SIDELENGTH);
      squares.add(current);
      repaint();
   }

   /**
    * Removes a square from the collection.
    * @param s the square to remove
    */
   public void remove(Rectangle2D s)
   {
      if (s == null) return;
      if (s == current) current = null;
      squares.remove(s);
      repaint();
   }

   private class MouseHandler extends MouseAdapter
   {
      public void mousePressed(MouseEvent event)
      {
         // 如果光标不在正方形内，则添加一个新的正方形
         current = find(event.getPoint());
         if (current == null) add(event.getPoint());
      }

      public void mouseClicked(MouseEvent event)
      {
         // 如果双击，则删除当前正方形
         current = find(event.getPoint());
         if (current != null && event.getClickCount() >= 2) remove(current);
      }
   }

   private class MouseMotionHandler implements MouseMotionListener
   {
      public void mouseMoved(MouseEvent event)
      {
         //如果鼠标光标位于内部，则将其设置为交叉头发
//矩形
         if (find(event.getPoint()) == null) setCursor(Cursor.getDefaultCursor());
         else setCursor(Cursor.getPredefinedCursor(Cursor.CROSSHAIR_CURSOR));
      }

      public void mouseDragged(MouseEvent event)
      {
         if (current != null)
         {
            int x = event.getX();
            int y = event.getY();

            // drag the current rectangle to center it at (x, y)
            current.setFrame(x - SIDELENGTH / 2, y - SIDELENGTH / 2, SIDELENGTH, SIDELENGTH);
            repaint();
         }
      }
   }   
}

l 掌握GUI程序中鼠标事件处理技术。

实验2：结对编程练习

利用班级名单文件、文本框和按钮组件，设计一个有如下界面（图1）的点名器，要求用户点击开始按钮后在文本输入框随机显示2017级网络与信息安全班同学姓名，如图2所示，点击停止按钮后，文本输入框不再变换同学姓名，此同学则是被点到的同学姓名。

 

图1 点名器启动界面

 

图2 点名器点名界面

实验结果如下：

 代码如下：

package 点名器;

import java.awt.EventQueue;

import javax.swing.JFrame;

/**
 * @version 1.34 2015-05-12
 * @author Cay Horstmann
 */
public class Demo
{
   public static void main(String[] args)
   {
      EventQueue.invokeLater(() ->
         {
            JFrame frame = new ButtonFrame();
            frame.setTitle("ButtonTest");
            frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            frame.setVisible(true);
         });
   }
}

package 点名器;

import java.awt.Color;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStreamReader;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Scanner;
import java.util.Timer;
import java.util.TimerTask;

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

/**
 * A frame with a button panel
 */
public class ButtonFrame extends JFrame {
    private JPanel buttonPanel;
    private static final int DEFAULT_WIDTH = 300 * 2;
    private static final int DEFAULT_HEIGHT = 200 * 2;
    private ArrayList<String> arrayList;

    public ButtonFrame() {
        setSize(DEFAULT_WIDTH, DEFAULT_HEIGHT);
        buttonPanel = new JPanel();
        buttonPanel.setLayout(null);
        JLabel jLabel = new JLabel("点名器");
        JButton jButton = new JButton("开始");
        jLabel.setBounds(250, 80, 100, 60);
        jButton.setBounds(250, 150, 100, 60);
        arrayList = new ArrayList<>();
        File file = new File("E:/学生.txt");
        FileInputStream fis;
        try {
            fis = new FileInputStream(file);
            InputStreamReader in = new InputStreamReader(fis);
            BufferedReader buf = new BufferedReader(in);
            String readLine;
            while ((readLine = buf.readLine()) != null) {
                arrayList.add(readLine);

            }
        } catch (FileNotFoundException e1) {
            // TODO Auto-generated catch block
            e1.printStackTrace();
        } catch (IOException e1) {
            // TODO Auto-generated catch block
            e1.printStackTrace();
        }

        jButton.addActionListener(new ActionListener() {
            Timer timer;

            public void actionPerformed(ActionEvent e) {
                if (jButton.getText().equals("开始")) {

                    timer = new Timer();
                    TimerTask timerTask = new TimerTask() {
                        public void run() {
                            jButton.setText("停止");
                            jLabel.setText(arrayList.get((int) (Math.random() * 42)));

                        }
                    };
                    timer.schedule(timerTask, 0, 15);
                }
                if (jButton.getText().equals("停止")) {
                    timer.cancel();
                    jButton.setText("开始");
                }
            }
        });
        jButton.setBackground(Color.orange);
        buttonPanel.add(jLabel);
        buttonPanel.add(jButton);
        add(buttonPanel);
    }

}

实验总结

掌握了事件处理的基本原理和用途；掌握了AWT事件模型的工作机制和事件处理的基本编程模型；了解了GUI界面组件观感设置方法；