感觉是一个完美的实现，如果觉得哪地方不好，请指出，共同进步
/**
The Animation class manages a series of images (frames) and
the amount of time to display each frame.
*/
public class Animation {
private ArrayList frames;
private int currFrameIndex;
private long animTime;
private long totalDuration;
/**
Creates a new, empty Animation.
*/
public Animation() {
this(new ArrayList(), 0);
}
private Animation(ArrayList frames, long totalDuration) {
this.frames = frames;
this.totalDuration = totalDuration;
start();
}
/**
Creates a duplicate of this animation. The list of frames
are shared between the two Animations, but each Animation
can be animated independently.
*/
public Object clone() {
return new Animation(frames, totalDuration);
}
/**
Adds an image to the animation with the specified
duration (time to display the image).
*/
public synchronized void addFrame(Image image,
long duration)
{
totalDuration += duration;
frames.add(new AnimFrame(image, totalDuration));
}
/**
Starts this animation over from the beginning.
*/
public synchronized void start() {
animTime = 0;
currFrameIndex = 0;
}
/**
Updates this animation's current image (frame), if
neccesary.
*/
public synchronized void update(long elapsedTime) {
if (frames.size() > 1) {
animTime += elapsedTime;
if (animTime >= totalDuration) {
animTime = animTime % totalDuration;
currFrameIndex = 0;
}
while (animTime > getFrame(currFrameIndex).endTime) {
currFrameIndex++;
}
}
}
/**
Gets this Animation's current image. Returns null if this
animation has no images.
*/
public synchronized Image getImage() {
if (frames.size() == 0) {
return null;
}
else {
return getFrame(currFrameIndex).image;
}
}
private AnimFrame getFrame(int i) {
return (AnimFrame)frames.get(i);
}
private class AnimFrame {
Image image;
long endTime;
public AnimFrame(Image image, long endTime) {
this.image = image;
this.endTime = endTime;
}
}
}