使用适配器和内部类来处理事件

刚才我们看到一个 BT 的例子，在实现 MouseListener 接口时必须要撰写处理每一个鼠标事件的方法。这里介绍 Adapter 。轻松点。

import java.applet.Applet;

import java.awt.*;

import java.awt.event.*;

public class MouseEventAdapterDemo extends Applet {

BlankArea blankArea;

TextArea textArea;

static final int maxInt = java.lang.Integer.MAX_VALUE;

String newline;

public void init() {

GridBagLayout gridbag = new GridBagLayout();

GridBagConstraints c = new GridBagConstraints();

setLayout(gridbag);

c.fill = GridBagConstraints.BOTH;

c.gridwidth = GridBagConstraints.REMAINDER;

c.weightx = 1.0;

c.weighty = 1.0;

c.insets = new Insets(1, 1, 1, 1);

blankArea = new BlankArea(new Color(0.98f, 0.97f, 0.85f));

gridbag.setConstraints(blankArea, c);

add(blankArea);

c.insets = new Insets(0, 0, 0, 0);

textArea = new TextArea(5, 20);

textArea.setEditable(false);

gridbag.setConstraints(textArea, c);

add(textArea);

//Register for mouse events on blankArea and applet (panel).

blankArea.addMouseListener(new MyEvent());

addMouseListener(new MyEvent());

newline = System.getProperty("line.separator");

}

class MyEvent extends MouseAdapter {

public void mousePressed(MouseEvent e) {

saySomething("Mouse pressed; # of clicks: " + e.getClickCount(), e);

}

void saySomething(String eventDescription, MouseEvent e) {

textArea.append(

eventDescription

+ " detected on "

+ e.getComponent().getClass().getName()

+ newline);

textArea.setCaretPosition(maxInt); //hack to scroll to bottom

}

}

}

无须多说了。