《Android 应用之路》简易贪吃蛇

最简单的贪吃蛇

最近想着忙里偷闲写点简单的Android应用，增加一些生活乐趣，由于平时工作主要精力并不是集中在书写apk上，更多的是解决代码问题和维护模块稳定，但是写代码本身是一件比较有趣的事情，因为这个过程是从无到有的。

名称：贪吃蛇
开发环境：IntelliJ IDEA 14.0.3
思路：

定时刷新界面，因为蛇是不会停止的
随机产生食物
蛇体的更新
蛇体如何出现移动的效果

缺陷：没有结束，没有碰壁，没有追尾，除非推出（现在知道为什么是最简单的了吧）

代码分析：

MyActivity，主要作用就是定时刷新界面，让蛇不停的前进

private SnakeView mSnakeView;  //填充窗口的View,刷新的对象
private static final int REFRESH = 1; //定义消息 防止硬编码
private static final int REFRESHINTERVAL = 300; //刷新的时间间隔
private boolean isPaused = false; //线程的停止标志位
private Handler mHandler = new Handler() { //thread handler 消息处理
    @Override
    public void handleMessage(Message msg) {
        // TODO Auto-generated method stub
        super.handleMessage(msg);
        if(msg.arg1 == REFRESH) {
            if(mSnakeView != null) {
                mSnakeView.invalidate();
            }
        }
    }

};
private Thread mRefreshThread; //用于发送刷新消息的线程

//Activity的onCreate方法
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    mSnakeView = new SnakeView(this);  
    setContentView(mSnakeView);
    isPaused = false;

    mRefreshThread = new Thread("TimerThread"){

        @Override
        public void run() {
            // TODO Auto-generated method stub
            super.run();
            while(!isPaused) {
                Message msg = mHandler.obtainMessage();
                msg.arg1 = REFRESH;
                mHandler.sendMessage(msg);
                try {
                    Thread.sleep(REFRESHINTERVAL); //休眠一段时间后再发送消息刷新界面
                } catch (InterruptedException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }
        }

    };
    mRefreshThread.start(); //启动线程
}

SnakeView ，主游戏界面，蛇体，背景和食物的显示界面

//自定义View
public class SnakeView extends View{
    public static final String  TAG = "SnakeView";

    private int mWidth;  //view的宽
    private int mHeight; //View的高

    private static final int sXOffset = 0 ; 
    private static final int sYOffset = 0 ; // X坐标和Y坐标的偏移量，可以修改来缩小游戏范围

    private final int BOXWIDTH = 30; //食物的边长，蛇体的宽度
    private Random mRandom = new Random(); //用于产生随机数
    private Point mFoodPosition; //食物的位置
    private boolean mIsFoodDone = true; //食物是否已经被吃掉

    private ArrayList<Point> mSnakeList;  //蛇体可以看做是很多食物组成的
    private Paint mSnakePaint;  //用于画蛇的画笔
    private int mSnakeDirection = 0; //蛇体运动的方向
    private final int UP = 1; 
    private final int DOWN = 2;
    private final int LEFT = 3;
    private final int RIGHT =4;

    private Paint mBgPaint;//游戏背景画笔
    private Paint mFoodPaint;//食物画笔


    public SnakeView(Context context) {
        super(context);
        // TODO Auto-generated constructor stub
        mSnakeList = new ArrayList<Point>();
        mSnakePaint = new Paint();
        mSnakePaint.setColor(Color.RED);
        mSnakePaint.setStyle(Paint.Style.FILL_AND_STROKE);
        mSnakeList.add(new Point(500,500));
        mSnakeList.add(new Point(500,530)); //初始化一条丑陋的蛇

        mSnakeDirection = RIGHT;
        mIsFoodDone = true;
        mFoodPosition= new Point();

        mFoodPaint = new Paint();
        mFoodPaint.setColor(Color.CYAN);
        mFoodPaint.setStyle(Paint.Style.FILL);

        mBgPaint = new Paint();
        Paint paint = new Paint();
        paint.setColor(Color.WHITE);   //初始化各种画笔

    }

    @Override
    public boolean onTouchEvent(MotionEvent event) { //通过手势来改变蛇体运动方向
        // TODO Auto-generated method stub

        int x = (int)(event.getX());
        int y = (int)(event.getY());
        Log.e(TAG, "x =" + x + " y = " + y + " mSnakeDirection = " + mSnakeDirection);
        if(mSnakeDirection == UP || mSnakeDirection == DOWN) {
            if(x < head.x) mSnakeDirection = LEFT;
            if(x > head.x) mSnakeDirection = RIGHT;
        } else if(mSnakeDirection == LEFT || mSnakeDirection == RIGHT) {
            if(y < head.y) mSnakeDirection = UP;
            if(y > head.y) mSnakeDirection= DOWN;
        }
        //Log.e(TAG, "after adjust mSnakeDirection = " + mSnakeDirection);
        return super.onTouchEvent(event);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        // TODO Auto-generated method stub
        //Log.e(TAG ,"onDraw");
        super.onDraw(canvas);

        drawBg(canvas, mBgPaint);  //画背景
        drawFood(canvas, mFoodPaint);//画食物
        drawSnake(canvas, mSnakePaint); //画蛇

    }

    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        // TODO Auto-generated method stub
        super.onSizeChanged(w, h, oldw, oldh);
        mWidth = w;
        mHeight = h;
    }

    //画背景 这里通过sXOffset, sYOffset可以实现对蛇活动区域的限制
    private void drawBg(Canvas canvas, Paint paint) {
        canvas.drawColor(Color.WHITE);
        //Rect rect = new Rect(sXOffset, sYOffset, mWidth - sXOffset, mHeight - sYOffset);
        //canvas.drawRect(rect, paint);
    }

    //画蛇体
    private void drawSnake(Canvas canvas, Paint paint) {
        for(int i = 0 ; i < mSnakeList.size() ; i++ ) {
            Point point = mSnakeList.get(i);
            Rect rect = new Rect(point.x , point.y , point.x + BOXWIDTH , point.y + BOXWIDTH);
            canvas.drawRect(rect, paint);
        }
        //蛇移动，更新list为下一次刷新做准备
        snakeMove(mSnakeList, mSnakeDirection);
        if(isFoodEaten()) {  //如果吃了食物，长度加1
            mIsFoodDone = true;
        } else {    //如果没有吃食物，由于前进时加了一个 这里删除尾巴，出现移动的效果
            mSnakeList.remove(mSnakeList.size() - 1);
        }
    }

    //画食物
    private void drawFood(Canvas canvas, Paint paint) {
        if(mIsFoodDone) {  //只在前一个食物被吃掉的情况下才产生食物
            mFoodPosition.x = mRandom.nextInt(mWidth - 2*sXOffset - BOXWIDTH) + sXOffset ;
            mFoodPosition.y = mRandom.nextInt(mWidth - 2*sYOffset - BOXWIDTH) + sYOffset ;
            mIsFoodDone = false;
        }
        Rect food = new Rect(mFoodPosition.x , mFoodPosition.y , mFoodPosition.x + BOXWIDTH , mFoodPosition.y + BOXWIDTH);
        canvas.drawRect(food, paint);

    }

    public void snakeMove(ArrayList<Point> list , int direction) {
        //Log.e(TAG," snakeMove ArrayList = " + list.toString());
        Point orighead = list.get(0);
        Point newhead = new Point();
        //蛇前进，实现原理就是头加尾减，若吃到食物，头加尾不减
        switch(direction) {
            case UP:
                newhead.x = orighead.x;
                newhead.y = orighead.y  - BOXWIDTH ;
                break;
            case DOWN:
                newhead.x = orighead.x;
                newhead.y = orighead.y  + BOXWIDTH ;
                break;
            case LEFT:
                newhead.x = orighead.x  - BOXWIDTH;
                newhead.y = orighead.y;
                break;
            case RIGHT:
                newhead.x = orighead.x + BOXWIDTH ;
                newhead.y = orighead.y;
                break;
            default:
                break;
        }
        adjustHead(newhead);
        list.add(0, newhead);
    }

    //边界判断
    private boolean isOutBound(Point point) {
        if(point.x < sXOffset || point.x > mWidth - sXOffset) return true;
        if(point.y < sYOffset || point.y > mHeight - sYOffset) return true;
        return false;
    }

    //出了边界，重新回来
    private void adjustHead(Point point) {
        //Log.e(TAG, "checkBound = " + isOutBound(point));
        if(isOutBound(point)){
            if(mSnakeDirection == UP) point.y = mHeight - sYOffset - BOXWIDTH;
            if(mSnakeDirection == DOWN) point.y = sYOffset;
            if(mSnakeDirection == LEFT) point.x = mWidth - sYOffset - BOXWIDTH;
            if(mSnakeDirection == RIGHT) point.x = sXOffset;
        }
    }

    //判断食物是否可以被吃
    private boolean isFoodEaten() {
        if(!mIsFoodDone) {
            Rect foodrect = new Rect(mFoodPosition.x, mFoodPosition.y, mFoodPosition.x + BOXWIDTH, mFoodPosition.y + BOXWIDTH);
            Point head = mSnakeList.get(0);
            Rect headrect = new Rect(head.x, head.y, head.x + BOXWIDTH , head.y + BOXWIDTH);
            return foodrect.intersect(headrect);
        }
        return false;
    }

}