Android游戏开发：物理游戏之重力系统开发--圆形自由落体Demo

    本节为大家提供有关物理游戏的知识，讲解了一个简单的圆形自由落体Demo的编写。。
Java代码
package com.himi;
import java.util.Random;
import java.util.Vector;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.util.Log;
import android.view.KeyEvent;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.view.SurfaceHolder.Callback;
public class MySurfaceViee extends SurfaceView implements Callback, Runnable {
    private Thread th;
    private SurfaceHolder sfh;
    private Canvas canvas;
    private Paint paint;
    private boolean flag;
    public static int screenW, screenH;
    private Vector<MyArc> vc;//这里定义装我们自定义圆形的容器
    private Random ran;//随即库
    public MySurfaceViee(Context context) {
        super(context);
        this.setKeepScreenOn(true);
        vc = new Vector<MyArc>();
        ran = new Random();//备注1
        sfh = this.getHolder();
        sfh.addCallback(this);
        paint = new Paint();
        paint.setAntiAlias(true);
        setFocusable(true);
    }
    public void surfaceCreated(SurfaceHolder holder) {
        flag = true;//这里都是上一篇刚讲过的。。。
        th = new Thread(this);
        screenW = this.getWidth();
        screenH = this.getHeight();
        th.start();
    }
    public void draw() {
        try {
            canvas = sfh.lockCanvas();
            canvas.drawColor(Color.BLACK);
            if (vc != null) {//当容器不为空，遍历容器中所有圆形画方法
                for (int i = 0; i < vc.size(); i++) {
                    vc.elementAt(i).drawMyArc(canvas, paint);
                }
            }
        } catch (Exception e) {
            // TODO: handle exception
        } finally {
            try {
                if (canvas != null)
                    sfh.unlockCanvasAndPost(canvas);
            } catch (Exception e2) {
            }
        }
    }
    private void logic() {//主逻辑
        if (vc != null) {//当容器不为空，遍历容器中所有圆形逻辑
            for (int i = 0; i < vc.size(); i++) {
                vc.elementAt(i).logic();
            }
        }
    }
    @Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {
        //当按键事件响应，我们往容器中仍个我们的圆形实例
        vc.addElement(new MyArc(ran.nextInt(this.getWidth()), ran.nextInt(100), ran.nextInt(50)));
        return true;
    }
    public void run() {
        // TODO Auto-generated method stub
        while (flag) {
            logic();
            draw();
            try {
                Thread.sleep(100);
            } catch (Exception ex) {
            }
        }
    }
    public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
        Log.v("Himi", "surfaceChanged");
    }
    public void surfaceDestroyed(SurfaceHolder holder) {
        flag = false;
    }
}
       OK，代码都很简单，也很清晰！ 稍微说一句：像MyArc里面也有类似MysurfaceView中一样的方法 logic() 以及draw()，这样能更好的管理我们的代码结构，思路清晰，各尽其责，避免混乱。