Java高级教程:事件处理

黄舟
黄舟 原创
2016-12-27 11:37:06 1402浏览

  Applet类从Container类继承了许多事件处理方法。Container类定义了几个方法,例如:processKeyEvent()和processMouseEvent(),用来处理特别类型的事件,还有一个捕获所有事件的方法叫做processEvent。

  为了响应一个事件,applet必须重写合适的事件处理方法。

import java.awt.event.MouseListener;
import java.awt.event.MouseEvent;
import java.applet.Applet;
import java.awt.Graphics;
  
public class ExampleEventHandling extends Applet
                             implements MouseListener {
  
    StringBuffer strBuffer;
  
    public void init() {
         addMouseListener(this);
         strBuffer = new StringBuffer();
        addItem("initializing the apple ");
    }
  
    public void start() {
        addItem("starting the applet ");
    }
  
    public void stop() {
        addItem("stopping the applet ");
    }
  
    public void destroy() {
        addItem("unloading the applet");
    }
  
    void addItem(String word) {
        System.out.println(word);
        strBuffer.append(word);
        repaint();
    }
  
    public void paint(Graphics g) {
         //Draw a Rectangle around the applet's display area.
        g.drawRect(0, 0,
                      getWidth() - 1,
                      getHeight() - 1);
  
         //display the string inside the rectangle.
        g.drawString(strBuffer.toString(), 10, 20);
    }
  
   
    public void mouseEntered(MouseEvent event) {
    }
    public void mouseExited(MouseEvent event) {
    }
    public void mousePressed(MouseEvent event) {
    }
    public void mouseReleased(MouseEvent event) {
    }
  
    public void mouseClicked(MouseEvent event) {
         addItem("mouse clicked! ");
    }
}

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