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java中的AWT事件处理问题

作者:SongYuLong的博客

这篇文章主要介绍了java中的AWT事件处理问题,具有很好的参考价值,希望对大家有所帮助。如有错误或未考虑完全的地方,望不吝赐教

事件处理的过程中,主要涉及3类对象

实现AWT事件处理机制的步骤如下

1.实现事件监听器类,该监听器类是一个特殊的java类,必须实现一个XxxListener接口。

2.创建普通组件(事件源),创建事件监听器对象。

3.调用addXxxListener()方法将事件监听器对象注册给普通组件(事件源)。当事件源上发生指定事件时,AWT会触发事件监听器,由事件监听器调用相应的方法(事件处理器)来处理事件,事件源上所发生的事件会作为参数传入事件处理器。

AWT的事件类都是AWTEvent类的子类,AWTEvent是EventObject的子类。

AWT事件分为两在类:低级事件和高组事件

1.低级事件

低级事件是指基于特定动作的事件.比如进入,点击,拖入等动作的鼠标事件,当组件得到焦点失去焦点时触发的事件.

2.高级事件(语义事件)

高级事件是基于语义的事件,它可以不和特定的动作相关联,而依赖于触发此事件的类。

比如,在TextField中按Enter键会触发ActionEvent事件,在滑动条上称动滑块会触发AdjustmentEvent事件,选中项目列表的某一项就会触发ItemEvent事件。

一件级件被多个监听器监听:

package javaAWT;

import java.awt.BorderLayout;
import java.awt.Button;
import java.awt.Frame;
import java.awt.Panel;
import java.awt.TextArea;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

public class MultiListener {

    private Frame frame = new Frame("MultiListener");
    private TextArea textArea = new TextArea(10, 35);
    private Button btn1 = new Button("one");
    private Button btn2 = new Button("two");

    public void init() {
        FirstListener f1 = new FirstListener();
        btn1.addActionListener(f1);
        btn1.addActionListener(new SecondListener());
        btn2.addActionListener(f1);
        frame.add(textArea);
        Panel panel = new Panel();
        panel.add(btn1);
        panel.add(btn2);
        frame.add(panel, BorderLayout.SOUTH);
        frame.pack();
        frame.setVisible(true);
    }

    class FirstListener implements ActionListener{
        @Override
        public void actionPerformed(ActionEvent e) {
            // TODO Auto-generated method stub
            textArea.append("FirstListener, EventSource :" + e.getActionCommand() + "\n");
        }
    }

    class SecondListener implements ActionListener {
        @Override
        public void actionPerformed(ActionEvent e) {
            // TODO Auto-generated method stub
            textArea.append("Clicked:" + e.getActionCommand() + " Button\n");
        }
    }

    public static void main(String[] args) {
        new MultiListener().init();
    }
}

窗口监听 (WindowListener ):

package javaAWT;

import java.awt.Frame;
import java.awt.TextArea;
import java.awt.event.WindowEvent;
import java.awt.event.WindowListener;

public class WindowListenerTest {

    private Frame frame = new Frame("WindowListener");
    private TextArea tArea = new TextArea(6, 40);

    public void init() {
        frame.addWindowListener(new MyListener());
        frame.add(tArea);
        frame.pack();
        frame.setVisible(true);
    }

    class MyListener implements WindowListener {

        @Override
        public void windowOpened(WindowEvent e) {
            // TODO Auto-generated method stub
            tArea.append("窗口初次打开\n");
        }

        @Override
        public void windowClosing(WindowEvent e) {
            // TODO Auto-generated method stub
            tArea.append("关闭窗口\n");
            System.exit(0);
        }

        @Override
        public void windowClosed(WindowEvent e) {
            // TODO Auto-generated method stub
            System.out.println("窗口被关闭");
        }

        @Override
        public void windowIconified(WindowEvent e) {
            // TODO Auto-generated method stub
            tArea.append("窗口最小化\n");
        }

        @Override
        public void windowDeiconified(WindowEvent e) {
            // TODO Auto-generated method stub
            tArea.append("窗口恢复\n");
        }

        @Override
        public void windowActivated(WindowEvent e) {
            // TODO Auto-generated method stub
            tArea.append("窗口被激活\n");
        }

        @Override
        public void windowDeactivated(WindowEvent e) {
            // TODO Auto-generated method stub
            tArea.append("窗口失去焦点\n");
        }

    }

    public static void main(String[] args) {
        new WindowListenerTest().init();
    }
}

事件适配器

事件适配器是监听器接口的空实现–事件适配器实现了监听器接口,并为该接口里的每个方法都提供了实现,这种实现是一种空实现。

监听器接口和事件适配器对应表

监听器接口事件适配器
ContainerListenerContainerAdapter
FocusListenerFocusAdapter
ComponentListenerComponentAdapter
KeyListenerKeyAdapter
MouseListenerMouseAdapter
MousMotionListenerMouseMotionAdapter
WindowListenerWindowAdapter

实现事件监听器有如下几种形式

1.内部类形式:将事件监听器类定义成当前类的内部类。

2.外部类形式:将事件监听器类定义成一个外部类。

3.类本身作为事件监听器类:让当前类本身实现监听器接口或继承事件适配器。

4.匿名内部类形式:使用匿名内部类创建事件监听器对象。

内部类形式

package javaAWT;

import java.awt.BorderLayout;
import java.awt.Frame;
import java.awt.Image;
import java.awt.TextArea;
import java.awt.Toolkit;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;

import javax.swing.ImageIcon;

public class WindowAdapterTest {

    private Frame frame = new Frame("WindowAdapterTest");
    private TextArea textArea = new TextArea(6, 40);
    private ImageIcon imageIcon = new ImageIcon();


    public void init() {
        frame.addWindowListener(new MyAdapterListener());
        frame.add(textArea);
        Image image = Toolkit.getDefaultToolkit().getImage("./123.jpg");
        frame.setIconImage(image);
        frame.pack();
        frame.setVisible(true);
    }

    class MyAdapterListener extends WindowAdapter {
        @Override
        public void windowClosed(WindowEvent e) {
            // TODO Auto-generated method stub
            //super.windowClosed(e);
            System.out.println("Closed window");
            System.exit(0);
        }
    }

    public static void main(String[] args) {
        new WindowAdapterTest().init();
    }
}

外部类形式

外部类监听器

package javaAWT;

import java.awt.TextField;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

public class MailerListener implements ActionListener {
    private TextField mailAddress;

    public MailerListener(TextField mailAddress) {
        // TODO Auto-generated constructor stub
        this.mailAddress = mailAddress;
    }

    public void setMailAddress(TextField mailAddress) {
        this.mailAddress = mailAddress;
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        // TODO Auto-generated method stub
        System.out.println("goto "+mailAddress.getText() + " send eMail");
    }

}

使用外部监听器

package javaAWT;

import java.awt.BorderLayout;
import java.awt.Button;
import java.awt.Frame;
import java.awt.TextField;

import org.omg.CORBA.PRIVATE_MEMBER;

public class SendMailer {

    private Frame frame = new Frame("SendMailer");
    private TextField tField = new TextField(40);
    private Button send = new Button("Send");

    public void init() {
        send.addActionListener(new MailerListener(tField));
        frame.add(tField);
        frame.add(send, BorderLayout.SOUTH);
        frame.pack();
        frame.setVisible(true);

    }


    public static void main(String[] args) {
        new SendMailer().init();
    }
}

类本身作为事件监听器类

GUI类通过继承事件适配器方式(extends XxxAdapter),可以只实现需要的监听器事件处理方法。

package javaAWT;

import java.awt.Frame;
import java.awt.TextArea;
import java.awt.TextField;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;

import org.omg.CosNaming.NamingContextExtPackage.AddressHelper;

public class SimpleEventHandler extends WindowAdapter {

    private Frame frame = new Frame("WindowAdapter");
    private TextArea tArea = new TextArea(6, 40);
    public void init() {
        //将该类的默认对象作为事件监听对象
        frame.addWindowListener(this);
        frame.add(tArea);
        frame.pack();
        frame.setVisible(true);
    }

    // GUI 界面类直接包含事件处理器方法
    @Override
    public void windowClosing(WindowEvent e) {
        // TODO Auto-generated method stub
        super.windowClosing(e);
        System.out.println("Window closed");
        System.exit(0);
    }

    public static void main(String[] args) {

    }
}

GUI类通过实现事件监听器方式( implements XxxListener),需要实现监听器的所有事件处理方法。

package javaAWT;

import java.awt.Frame;
import java.awt.TextArea;
import java.awt.event.WindowEvent;
import java.awt.event.WindowListener;

import javax.swing.text.TabableView;

public class SimpleEventHandlerB implements WindowListener {

    private Frame f = new Frame("WindowListener");
    private TextArea ta = new TextArea(10, 50);

    public void init() {
        f.addWindowListener(this);
        f.add(ta);
        f.pack();
        f.setVisible(true);
    }

    @Override
    public void windowOpened(WindowEvent e) {
        // TODO Auto-generated method stub
        ta.append("windowOpened"+"\n");
    }

    @Override
    public void windowClosing(WindowEvent e) {
        // TODO Auto-generated method stub
        ta.append("windowClosing"+"\n");
        System.exit(0);
    }

    @Override
    public void windowClosed(WindowEvent e) {
        // TODO Auto-generated method stub
        ta.append("windowClosed"+"\n");

    }

    @Override
    public void windowIconified(WindowEvent e) {
        // TODO Auto-generated method stub
        ta.append("windowIconified"+"\n");
    }

    @Override
    public void windowDeiconified(WindowEvent e) {
        // TODO Auto-generated method stub
        ta.append("windowDeiconified"+"\n");
    }

    @Override
    public void windowActivated(WindowEvent e) {
        // TODO Auto-generated method stub
        ta.append("windowActivated"+"\n");
    }

    @Override
    public void windowDeactivated(WindowEvent e) {
        // TODO Auto-generated method stub
        ta.append("windowDeactivated"+"\n");
    }


    public static void main(String[] args) {
        new SimpleEventHandlerB().init();
    }

}

匿名内部类形式

匿名实现XxxxAdapter对象

package javaAWT;

import java.awt.Frame;
import java.awt.TextArea;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;

public class AnonymousEventHandler {

    private Frame frame = new Frame("AnonymousEventHandler");
    private TextArea textArea = new TextArea(5, 20);
    public void init() {

        frame.addWindowListener(new WindowAdapter() {
            @Override
            public void windowClosing(WindowEvent e) {
                // TODO Auto-generated method stub
                super.windowClosing(e);
                System.exit(0);
            }
        });

        frame.add(textArea);
        frame.pack();
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        new AnonymousEventHandler().init();
    }
}

匿名实现XxxListener对象

package javaAWT;

import java.awt.Frame;
import java.awt.TextArea;
import java.awt.event.WindowEvent;
import java.awt.event.WindowListener;

public class AnonymousEventHandlerB {

    private Frame frame = new Frame("AnonymousEventHandlerB");
    private TextArea textArea = new TextArea(5, 50);

    public void init() {
        frame.addWindowListener(new WindowListener() {

            @Override
            public void windowOpened(WindowEvent e) {
                // TODO Auto-generated method stub

            }

            @Override
            public void windowIconified(WindowEvent e) {
                // TODO Auto-generated method stub

            }

            @Override
            public void windowDeiconified(WindowEvent e) {
                // TODO Auto-generated method stub

            }

            @Override
            public void windowDeactivated(WindowEvent e) {
                // TODO Auto-generated method stub

            }

            @Override
            public void windowClosing(WindowEvent e) {
                // TODO Auto-generated method stub
                System.exit(0);
            }

            @Override
            public void windowClosed(WindowEvent e) {
                // TODO Auto-generated method stub

            }

            @Override
            public void windowActivated(WindowEvent e) {
                // TODO Auto-generated method stub

            }
        });

        frame.add(textArea);
        frame.pack();
        frame.setVisible(true);

    }

    public static void main(String[] args) {
        new AnonymousEventHandlerB().init();
    }
}

以上为个人经验,希望能给大家一个参考,也希望大家多多支持脚本之家。

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