Code Barn Hello Anim Thread C

posted 9 years ago

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[b]CODE[/b]

[code=java]
// Simple Animation --last in a series of four --- series started with HelloAnimThreadFirst
// A rectangle bounces off the edges of the applet, forever. 
// Uses double-buffering to provide smooth, flicker-free animation

import java.awt.* ;
import java.applet.Applet ;
    
public class HelloAnimThreadC extends Applet implements Runnable 
{
    private int maxWidth , maxHeight ; // animation boundary
    private int currX , currY ; // left,top (x,y) of the animating rectangle
    private int currXVelocity , currYVelocity ; // pixels per move
    private int imageHeight , imageWidth ; // size of animating rectangle
    
    // new stuff for dbl-buffering
    Graphics offscreen ;
    Image imageForOffscreen ;
    
    public void init() 
    {
        setBackground( Color.yellow ) ;
        maxWidth = 200 ;
        maxHeight = 200 ;
        imageHeight = 25 ;
        imageWidth = 40 ;
        currXVelocity = 3 ;
        currYVelocity = 3 ;
    
        // set up random positions to start the images
        currX = (int)( ( Math.random() * 80 ) + 1 );
        currY = (int)( ( Math.random() * 80 ) + 10 );
    
        // new stuff for dbl-buffering
        imageForOffscreen = createImage( maxWidth , maxHeight );
        offscreen = imageForOffscreen.getGraphics();
    
        Thread animator = new Thread( this );
        animator.start();
    } // close init
    
    public void paint( Graphics g ) //<-- dbl-buffered now 
    { 
        // first do what the update would have done -- 
        //erase the background of the offscreen Graphics surface
        offscreen.setColor( getBackground() );
        offscreen.fillRect( 0 ,0 ,maxWidth , maxHeight );
    
        // paint the rectangle onto the offscreen surface
        // If there were more images to be painted, it would
        // all happen here. Paint ALL images at this step
        offscreen.setColor( Color.black );
        offscreen.drawRect( currX , currY , imageWidth , imageHeight );
    
        // then blast that final image to the screen
        g.drawImage( imageForOffscreen , 0 , 0 , this );
    } // close paint
    
    // override update to prevent it from erasing the background
    public void update( Graphics g ) 
    {
        paint( g );
    }
    
    public void run() 
    {
        // update location/velocity of the rectangle 
        while ( true ) 
        {
            try 
            {
                Thread.sleep( 50 );
            } 
            catch ( InterruptedException e ) 
            {
            }

currX = currX + currXVelocity ;
            currY = currY + currYVelocity ;
    
            if ( ( currX + imageWidth ) >= maxWidth )
            {
                currXVelocity = -3 ; 
            }
            else if ( currX <= 0 )
            {
                currXVelocity = 3 ;
            }
    
            if ( ( currY + imageHeight ) >= maxHeight ) 
            {
                currYVelocity = -3 ;
            }
            else if ( currY <= 0 ) 
            {
                currYVelocity = 3 ;
            }
    
            repaint(); 
        } // close while loop 
    } // close run
} // close class

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