用J2ME在移动设备上实现动画的实例讲解

import java.util.*; 
import javax.microedition.lcdui.*; 
// 定义了一个动画，该动画其实只是一系列相同大小的图片 
// 轮流显示，然后模拟出的动画 
public class AnimatedImage extends TimerTask {; 
private Canvas canvas; 
private Image[] images; 
private int[][] clipList; 
private int current; 
private int x; 
private int y; 
private int w; 
private int h; 

// Construct an animation with no canvas. 

public AnimatedImage( Image[] images ){; 
this( null, images, null ); 
}; 

// Construct an animation with a null clip list. 

public AnimatedImage( Canvas canvas, Image[] 
images ){; this( canvas, images, null ); 
}; 

// Construct an animation. The canvas can be null, 
// but if not null then a repaint will be triggered 
// on it each time the image changes due to a timer 
// event. If a clip list is specified, the image is 
// drawn multiple times, each time with a different 
// clip rectangle, to simulate transparent parts. 

public AnimatedImage( Canvas canvas, Image[] images, 
int[][] clipList ){; 
this.canvas = canvas; 
this.images = images; 
this.clipList = clipList; 

if( images != null && clipList != null ){; 
if( clipList.length < images.length ){; 
throw new IllegalArgumentException(); 
}; 
}; 

if( images != null && images.length > 0 ){; 
w = images[0].getWidth(); 
h = images[0].getHeight(); 
}; 
}; 

// Move to the next frame, wrapping if necessary. 

public void advance( boolean repaint ){; 
if( ++current >= images.length ){; 
current = 0; 
}; 

if( repaint && canvas != null && canvas.isShown() 
){; 
canvas.repaint( x, y, w, h ); 
canvas.serviceRepaints(); 
}; 
}; 

// Draw the current image in the animation. If 
// no clip list, just a simple copy, otherwise 
// set the clipping rectangle accordingly and 
// draw the image multiple times. 

public void draw( Graphics g ){; 
if( w == 0 || h == 0 ) return; 

int which = current; 

if( clipList == null || clipList[which] == null 
){; 
g.drawImage( images[which], x, y, 
g.TOP | g.LEFT ); 
}; else {; 
int cx = g.getClipX(); 
int cy = g.getClipY(); 
int cw = g.getClipWidth(); 
int ch = g.getClipHeight(); 

int[] list = clipList[which]; 

for( int i = 0; i + 3 <= list.length; i += 
4 ){; 
g.setClip( x + list[0], y + list[1], 
list[2], list[3] ); 
g.drawImage( images[which], x, y, 
g.TOP | g.LEFT ); 
}; 

g.setClip( cx, cy, cw, ch ); 
}; 
}; 

// Moves the animation's top left corner. 

public void move( int x, int y ){; 
this.x = x; 
this.y = y; 
}; 

// Invoked by the timer. Advances to the next frame 
// and causes a repaint if a canvas is specified. 

public void run(){; 
if( w == 0 || h == 0 ) return; 

advance( true ); 
}; 
};

private Image[] loadFrames( String name, int frames ) 
throws IOException {; 
Image[] images = new Image[frames]; 
for( int i = 0; i < frames; ++i ){; 
images = Image.createImage( name + i + 
".png" ); 
}; 

return images; 
};