为基于J2ME的手机开发移动3D游戏

减小字体增大字体作者：网络来源：转载发布时间：2008-7-10 17:22:36

七、刷新视图

为了刷新视图，你可以用TimerTask来调用画布的repaint()方法。另一种方法是直接使用线程，然后创建ExampleCanvas（画布类的名字）来实现Runnable接口。

列表4.　刷新视图

private class RefreshTask extends TimerTask
{
　public void run(){
if(myCanvas != null && myGraphics3D != null && myWorld != null) {
　int startTime = (int)System.currentTimeMillis();
　int validity = myWorld.animate(startTime);
　myCanvas.repaint(viewport_x, viewport_y, viewport_width, viewport_height);
}
　}
}

八、完整的例程代码分析

在列表5中，你会看到应用程序的完整代码。虽然长些，但是比Sun的例子要简单许多。你可以通过给应用程序添加上一些动作和逻辑来练习你的MIDP技能。

列表5. 完整的例程代码

package com.kontio;
import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;
import java.lang.IllegalArgumentException;
import java.io.*;
import java.util.*;
import javax.microedition.m3g.*;
public class Example3D extends MIDlet implements CommandListener{
　//我们在场景中使用的对象的UserID
　static final int POGOROO = 554921620;
　static final int CAMERA = 769302310;
　static final int TRANSFORM = 347178853;
　static final int ROO = 418071423;
　
　private Display myDisplay = null;
　private ExampleCanvas myCanvas = null;
　private Timer myRefreshTimer = new Timer();
　private TimerTask myRefreshTask = null;
　private Command exitCommand = new Command("Exit", Command.ITEM, 1);
　Graphics3D myGraphics3D = Graphics3D.getInstance();
　World myWorld = null;
　private AnimationController animRoo = null;
　private Group tRoo = null;
　private Group tCams = null;
　private Group acRoo = null;
　private int animLength = 0;
　int viewport_x;
　int viewport_y;
　int viewport_width;
　int viewport_height;
　public Example3D(){
super();
myDisplay = Display.getDisplay(this);
myCanvas = new ExampleCanvas(this);
myCanvas.setCommandListener(this);
myCanvas.addCommand(exitCommand);
　}
　public void startApp() throws MIDletStateChangeException{
myDisplay.setCurrent(myCanvas);
try{
　// 从文件中加载World
　myWorld = (World)Loader.load("/pogoroo.m3g")[0];
　getObjects();
　setupAspectRatio();
}
catch(Exception e){
　e.printStackTrace();
}
myRefreshTask = new RefreshTask();
// 调度一个重要执行的计时器以显示出帧速率20fps.
myRefreshTimer.schedule(myRefreshTask, 0, 50);
　}
　void setupAspectRatio(){
viewport_x = 0;
viewport_y = 0;
viewport_width = myCanvas.getWidth();
viewport_height = myCanvas.getHeight();
Camera cam = myWorld.getActiveCamera();
float[] params = new float[4];
int type = cam.getProjection(params);
if(type != Camera.GENERIC){
　//计算窗口的宽高比例
　float waspect=viewport_width/viewport_height;
　if (waspectfloat height = viewport_width/params[1];
viewport_height=(int)height;
viewport_y=(myCanvas.getHeight()-viewport_height)/2;
　}
　else{
float width = viewport_height*params[1];
viewport_width=(int)width;
viewport_x=(myCanvas.getWidth()-viewport_width)/2;
　}
}
　}
　public void getObjects(){
try{
　tRoo = (Group) myWorld.find(POGOROO);
　tCams = (Group) myWorld.find(CAMERA);
　acRoo = (Group) myWorld.find(TRANSFORM);
　animRoo = (AnimationController) myWorld.find(ROO);
　//取得动画的长度
　AnimationTrack track = acRoo.getAnimationTrack(0);
　animLength = 1000; // 缺省的长度，1秒
　if (track != null){
KeyframeSequence ks = track.getKeyframeSequence();
if (ks != null)
　animLength = ks.getDuration();
　}
}
catch(Exception e){
　e.printStackTrace();
}
　}
　public void pauseApp(){}
　public void destroyApp(boolean unconditional) throws
MIDletStateChangeException{
myRefreshTimer.cancel();
myRefreshTimer = null;
myRefreshTask = null;
　}
　public void paint(Graphics g){
if(g.getClipWidth() != viewport_width ||
　g.getClipHeight() != viewport_height ||
　g.getClipX() != viewport_x ||
　g.getClipY() != viewport_y){
g.setColor(0x00);
g.fillRect(0, 0, myCanvas.getWidth(), myCanvas.getHeight());
　}
　if ((myGraphics3D != null) && (myWorld != null)){
myGraphics3D.bindTarget(g);
myGraphics3D.setViewport(viewport_x, viewport_y, 
viewport_width, viewport_height);
myGraphics3D.render(myWorld);
myGraphics3D.releaseTarget();
　}
}
public void commandAction(Command cmd, Displayable disp)
{
　if (cmd == exitCommand){
try{
　destroyApp(false);
　notifyDestroyed();
}
catch(Exception e){
　e.printStackTrace();
}
　}
}
private class RefreshTask extends TimerTask{
　public void run(){
if(myCanvas !=null && myGraphics3D != null && myWorld != null{
　int startTime = (int)System.currentTimeMillis();
　int validity = myWorld.animate(startTime);
　myCanvas.repaint(viewport_x, viewport_y,
viewport_width, viewport_height);
}
　}
}
class ExampleCanvas extends Canvas{
　Example3D myRooMIDlet;
　int i = 0;
　ExampleCanvas(Example3D Testlet) { myRooMIDlet = Testlet; }
　void init() { }
　void destroy() { }
　protected void paint(Graphics g) { myRooMIDlet.paint(g); }
　protected void keyPressed(int i) { }
　protected void keyReleased(int i) { }
　protected void keyRepeated(int i) { }
　protected void pointerDragged(int x, int y) { }
　protected void pointerPressed(int x, int y) { }
　protected void pointerReleased(int x, int y) { }
}
}