animationtest.java

J2ME的动画制作程序, 在很短的时间内, 连续在同一个位置画上好几张图, 最适合的时间是在一秒中内画20到30张图, 这样的效果是让用户看起来会有不间断的感觉.

import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;
import java.util.*;

public class AnimationTest extends MIDlet{

	Display display;
	MyCanvas myCanvas;

	public AnimationTest(){
		display = Display.getDisplay(this);
		myCanvas = new MyCanvas();
	}

	public void startApp(){
		myCanvas.start();
		display.setCurrent(myCanvas);
	}

	public void pauseApp(){
	}

	public void destroyApp(boolean unconditional){
	}

	class MyCanvas extends Canvas implements CommandListener{

		int gameAction;
		Sprite sprite;
		Command exitCmd;
		Image offScreen;
		Image[] spriteImage = new Image[3];
		int interval = 300;

		public MyCanvas(){

			if(!isDoubleBuffered()){
				offScreen = Image.createImage(getWidth(), getHeight());
			}

			try{
				for(int i=0;i<spriteImage.length;i++){
					spriteImage[i] = Image.createImage("/sprite"+i+".png");
				}
			}
			catch(Exception ex){}

			sprite = new Sprite(this, spriteImage);

			exitCmd = new Command("退出", Command.EXIT, 1);
			addCommand(exitCmd);
			setCommandListener(this);
		}

		public void paint(Graphics g){

			Graphics old = g;

			if(offScreen != null){
				g = offScreen.getGraphics();
			}

			g.setColor(0xFFFFFF);
			g.fillRect(0, 0, getWidth(), getHeight());
            sprite.paintSprite(g);

			g.setColor(0);
			g.drawString("间隔："+interval+"ms",
						  10,
						  getHeight() - 20,
						  Graphics.LEFT|Graphics.TOP);

			if(g != old){
				old.drawImage(offScreen, 0, 0, Graphics.LEFT|Graphics.TOP);
			}
		}

		void start(){
        	sprite.start();
		}

		public void keyPressed(int keyCode){
			int gameAction = getGameAction(keyCode);
			switch(gameAction){
			case Canvas.LEFT:
				interval -= 100;
				if(interval <= 200) interval = 200;
                sprite.setInverval(interval);
			break;
			case Canvas.RIGHT:
				interval += 100;
				if(interval >= 2000) interval = 2000;
                sprite.setInverval(interval);
			break;
			}
			repaint();
		}

		public void keyReleased(int keyCode){
		}

		public void keyRepeated(int keyCode){
		}

		public void commandAction(Command c, Displayable d){

			if(c == exitCmd){
				destroyApp(true);
				notifyDestroyed();
			}
		}
	}

	class Sprite extends Thread{

		int gameAction;
		int x, y;
		int width, height;
		Image[] image;
		MyCanvas canvas;
		int index = 0;
		int timeInterval;
		Random random = new Random();
		boolean reverse = false;

		public Sprite(MyCanvas canvas, Image[] image){
			super();
			this.image = image;
			this.canvas = canvas;
			width = image[0].getWidth();
			height = image[0].getHeight();
			x = (canvas.getWidth()-width)/2;
			y = (canvas.getHeight()-height)/2;
			timeInterval = 500;
		}

		public void paintSprite(Graphics g){
			g.drawImage(image[index], x, y, Graphics.LEFT|Graphics.TOP);
			if(index == 2) reverse = true;
			else if(index == 0)reverse = false;

			if(reverse == false) index++;
			else if(reverse == true) index--;

		}

		public void run(){
			while(true){
				canvas.repaint(x, y, width, height);
				try{
					Thread.sleep(timeInterval);
				}
				catch(Exception ex){}
			}
		}

		public void setInverval(int interval){
			timeInterval = interval;
		}
	}

}