scrollimage.java

java applet 非常全的实例。比较利于初学者进行研究。

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

public final class ScrollImage extends Applet
{
	private int width,height;
	
	private Image offI,img;
	private Graphics offG;
        private MediaTracker imageTracker;

	private Point pointInitial = new Point(0, 0);
	
	private int posImageX = 0, posImageY = 0;
	
	int tailleImageX = 540;
	int tailleImageY = 380;

	int positionInitialeX = 0;
	int positionInitialeY = 0;

	Object frame;


	public void init()
	{
		setBackground(new Color(255, 200, 50));
		
		Integer intObj;
		
		String s = new String("");
		s = getParameter("Image");
		System.out.println(s);
		img = getImage(getCodeBase(),s);
	        imageTracker = new MediaTracker(this);
	        imageTracker.addImage(img,0);
	        try
	        {
	          imageTracker.waitForID(0);
	        }
	        catch(InterruptedException e){}
	        
	        tailleImageX = img.getWidth(this);
	        tailleImageY = img.getHeight(this);
	        System.out.println(tailleImageX + "," + tailleImageY);
	        
	        try
        	{
	            intObj = new Integer(getParameter("width"));
        	    width = intObj.intValue();
	        } 
        	catch (Exception e)
	        {
        	    width = 200;
	        }
	
        	try
        	{
            	intObj = new Integer(getParameter("height"));
            	height = intObj.intValue();
	        }
        	catch (Exception e)
        	{
	            height = 200;
        	}

		offI = createImage(tailleImageX, tailleImageY);
		offG = offI.getGraphics();
                
		frame = getParent();
		while(! (frame instanceof Frame))
			frame = ((Component) frame).getParent ();
	        repaint();
	        
	}
	
	public void start()
	{
	        offG.drawImage(img,0,0,this);
                repaint();
                
	}

	public final boolean mouseDown(Event evt, int x, int y)
	{
		pointInitial = new Point(x, y);

		((Frame) frame).setCursor(Frame.HAND_CURSOR);

		positionInitialeX = posImageX;
		positionInitialeY = posImageY;

		return true;
	}
	
	public final boolean mouseDrag(Event evt, int x, int y)
	{
		posImageX = positionInitialeX - (pointInitial.x - x);
		posImageY = positionInitialeY - (pointInitial.y - y);

		repaint();
		
		return true;
	}

	public final boolean mouseUp(Event evt, int x, int y)
	{
		((Frame) frame).setCursor(Frame.DEFAULT_CURSOR);
		
		return true;
	}

	public final void update(Graphics g)
	{
		paint(g);
	}

	public final void paint(Graphics g)
	{
		if (posImageX < width - tailleImageX) posImageX = width - tailleImageX;
		if (posImageY < height - tailleImageY) posImageY = height - tailleImageY;
		if (posImageX > 0) posImageX = 0;
		if (posImageY > 0) posImageY = 0;
		
		g.drawImage(offI,posImageX,posImageY,this);
		
		
	}
}