eventhandlingdemo4.java

JAVA程序设计课程中各章节的程序实例。

/**
*A event handling program as keyboard event.
*it creates a small text edo=itor that displays text on screen
*2004.12.29. xhcprince
*/

import java.applet.*;
import java.awt.*;
import java.awt.event.*;

public class EventHandlingDemo4 extends Applet
{
	private String text;
	
	public void init()
	{
		showStatus("Initializing");
		text = "";
		addKeyListener(new KeyHandler());
		requestFocus();
    /*-------------------------------------------------------------
    	By requesting the focus of the keyboard,the keys pressed
    	will be sent to your application,if not done then you might 
    	not be able to process the keyboard input,so you have to 
    	use requestFocus()!
    -------------------------------------------------------------*/		
	}

	public void paint(Graphics g)
	{
		g.drawString(text,50,150);
	}

	class KeyHandler implements KeyListener	//Inner class!
	{
	/*-------------------------------------------------------------
		A character key has been pressed
	-------------------------------------------------------------*/
		public void keyTyped(KeyEvent k)
		{
			text += k.getKeyChar();
			repaint();
		}
	/*-------------------------------------------------------------
		A keyboard key has been pressed
	-------------------------------------------------------------*/
		public void keyPressed(KeyEvent k)
		{
			showStatus("Key is pressed");
		}
	/*-------------------------------------------------------------
		A keyboard key has been released
	-------------------------------------------------------------*/
		public void keyReleased(KeyEvent k)
		{
			showStatus("Key is released");
		}
	}
}
/*
<applet code = "EventHandlingDemo4.class" width = 300 height = 180>
</applet>
*/