【读书笔记《Android游戏编程之从零开始》】18.游戏开发基础（碰撞检测）

import android.content.Context;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Rect;
import android.graphics.Region;
import android.view.KeyEvent;
import android.view.MotionEvent;
import android.view.SurfaceHolder;
import android.view.SurfaceHolder.Callback;
import android.view.SurfaceView;

/**
 * 
 * @author David
 * 
 */
public class MySurfaceView extends SurfaceView implements Callback, Runnable {
    // 用于控制SurfaceView 的大小、格式等，并且主要用于监听SurfaceView 的状态
    private SurfaceHolder sfh;
    // 声明一个画笔
    private Paint paint;
    // 声明一个画布
    private Canvas canvas;
    // 声明一个线程
    private Thread th;
    // 线程消亡的标识符
    private boolean flag;
    // 声明屏幕的宽高
    private int screenW, screenH;

    // 定义碰撞矩形
    private Rect rect = new Rect(0, 0, 50, 50);
    // 定义Region类实例
    private Region r = new Region(rect);
    // 表示是否发生碰撞的标识位
    private boolean isInclude;

    /**
     * SurfaceView 初始化函数
     * 
     * @param context
     */
    public MySurfaceView(Context context) {
        super(context);
        // 实例SurfaceView
        sfh = this.getHolder();
        // 为SurfaceView添加状态监听
        sfh.addCallback(this);
        // 实例一个画笔
        paint = new Paint();
        // 设置字体大小
        paint.setTextSize(20);
        // 设置画笔的颜色
        paint.setColor(Color.WHITE);
        // 设置画布无锯齿
        paint.setAntiAlias(true);
        // 设置焦点
        setFocusable(true);
    }

    /**
     * SurfaceView 视图状态发生改变时，响应此函数
     */
    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int width,
            int height) {

    }

    /**
     * SurfaceView 视图创建，响应此函数
     */
    @Override
    public void surfaceCreated(SurfaceHolder holder) {
        screenW = this.getWidth();// 屏幕的宽
        screenH = this.getHeight();// 屏幕的高
        flag = true;
        // 实例线程
        th = new Thread(this);
        // 启动线程
        th.start();
    }

    /**
     * SurfaceView 视图消亡时，响应此函数
     */
    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {
        flag = false;
    }

    /**
     * 游戏绘图
     */
    private void myDraw() {
        try {
            // 获取SurfaceView 的Canvas 对象，
            canvas = sfh.lockCanvas();
            if (canvas != null) {
                // 刷新画布，背景为黑色
                canvas.drawColor(Color.BLACK);
                // 标识位为真时，绘制icon图
                if (isInclude) {
                    canvas.drawBitmap(BitmapFactory.decodeResource(
                            this.getResources(), R.drawable.ic_launcher), 100,
                            50, paint);
                }
                // 绘制矩形区域（便于观察）
                canvas.drawRect(rect, paint);
            }
        } catch (Exception e) {

        } finally {
            if (canvas != null) {
                // 解锁画布和提交
                sfh.unlockCanvasAndPost(canvas);
            }
        }
    }

    /**
     * 触屏事件监听
     */
    @Override
    public boolean onTouchEvent(MotionEvent event) {
        // 判定用户触屏的坐标点是否在碰撞矩形内
        if (r.contains((int) event.getX(), (int) event.getY())) {
            isInclude = true;
        } else {
            isInclude = false;
        }
        return true;
    }

    @Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {
        return super.onKeyDown(keyCode, event);
    }

    /**
     * 游戏逻辑
     */
    private void logic() {
    }

    @Override
    public void run() {
        while (flag) {
            long start = System.currentTimeMillis();
            myDraw();
            logic();
            long end = System.currentTimeMillis();
            try {
                if (end - start < 50) {
                    Thread.sleep(50 - (end - start));
                }
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }
}