android canvas 使用

Canvas 又称为画布，在游戏开发过程中是一个经常使用的类。下面举一个实例在完成画布的基本功能

代码如下：

public class MySurfaceView extends SurfaceView implements Callback, Runnable {
	//用于控制SurfaceView
	private SurfaceHolder sfh;
	//声明一个画笔
	private Paint paint;
	//声明一条线程
	private Thread th;
	//线程消亡的标识位
	private boolean flag;
	//声明一个画布
	private Canvas canvas;
	//声明屏幕的宽高
	private int screenW, screenH;
	//设置画布绘图无锯齿
	private PaintFlagsDrawFilter pfd = new PaintFlagsDrawFilter(0, Paint.ANTI_ALIAS_FLAG | Paint.FILTER_BITMAP_FLAG);
	/**
	 * SurfaceView初始化函数
	 */
	public MySurfaceView(Context context) {
		super(context);
		//实例SurfaceHolder
		sfh = this.getHolder();
		//为SurfaceView添加状态监听
		sfh.addCallback(this);
		//实例一个画笔
		paint = new Paint();
		//设置画笔颜色为白色
		paint.setColor(Color.WHITE);
		//设置焦点
		setFocusable(true);
	}

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

	/**
	 * 游戏绘图
	 */
public void myDraw() {
	try {
		canvas = sfh.lockCanvas();
		if (canvas != null) {
			//----设置画布绘图无锯齿
			canvas.setDrawFilter(pfd);
			//----利用填充画布，刷屏
			canvas.drawColor(Color.BLACK);
			//----绘制文本
			canvas.drawText("drawText", 10, 10, paint);
			//----绘制像素点
			canvas.drawPoint(10, 20, paint);
			//----绘制多个像素点
			canvas.drawPoints(new float[] { 10, 30, 30, 30 }, paint);
			//----绘制直线
			canvas.drawLine(10, 40, 50, 40, paint);
			//----绘制多条直线
			canvas.drawLines(new float[] { 10, 50, 50, 50, 70, 50, 110, 50 }, paint);
			//----绘制矩形
			canvas.drawRect(10, 60, 40, 100, paint);
			//----绘制矩形2
			Rect rect = new Rect(10, 110, 60, 130);
			canvas.drawRect(rect, paint);
			canvas.drawRect(rect, paint);
			//----绘制圆角矩形
			RectF rectF = new RectF(10, 140, 60, 170);
			canvas.drawRoundRect(rectF, 20, 20, paint);
			//----绘制圆形
			canvas.drawCircle(20, 200, 20, paint);
			//----绘制弧形
			canvas.drawArc(new RectF(150, 20, 200, 70), 0, 230, true, paint);
			//----绘制椭圆
			canvas.drawOval(new RectF(150, 80, 180, 100), paint);
			//----绘制指定路径图形
			Path path = new Path();
			//设置路径起点
			path.moveTo(160, 150);
			//路线1
			path.lineTo(200, 150);
			//路线2
			path.lineTo(180, 200);
			//路径结束
			path.close();
			canvas.drawPath(path, paint);
			//----绘制指定路径图形
			Path pathCircle = new Path();
			//添加一个圆形的路径
			pathCircle.addCircle(130, 260, 20, Path.Direction.CCW);
			//----绘制带圆形的路径文本
			canvas.drawTextOnPath("PathText", pathCircle, 10, 20, paint);
		}
	} catch (Exception e) {
		// TODO: handle exception
	} finally {
		if (canvas != null)
			sfh.unlockCanvasAndPost(canvas);
	}
}

	/**
	 * 触屏事件监听
	 */
	@Override
	public boolean onTouchEvent(MotionEvent event) {
		return true;
	}

	/**
	 * 按键事件监听
	 */
	@Override
	public boolean onKeyDown(int keyCode, KeyEvent event) {
		return super.onKeyDown(keyCode, event);
	}


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

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

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