SurfaceView
SurfaceView是View的一个特殊子类，它的目的是另外提供一个线程进行绘制操作。
- 步骤
1.用SurfaceView进行绘制，首先要创建一个类，继承 SurfaceView，同时这个类应该实现SurfaceHolder.Callback接口。
这个接口中的三个回调函数（surfaceChanged(SurfaceHolder holder, int format, int width, int height)，surfaceCreated(SurfaceHolder holder)，surfaceDestroyed(SurfaceHolder holder)）分别对应Surface何时更改、创建和销毁。
2.对Surface对象的操作是通过SurfaceHolder来进行的。所以，在你的SurfaceView类初始化的时候，你需要调用 getHolder()来获得SurfaceHolder对象，然后用addCallback()加上回调接口（因为你的类实现了相应的接口，所以此处传入this即可）。
3.在你的SurfaceView类中应该建立一个线程类，处理绘制操作。为此，要向这个线程类传递上面获得的SurfaceHolder对象。
4.绘制：在线程类的run()方法中进行绘制操作，通过lockCanvas()方法获得Canvas对象，然后就可以用这个对象进行绘制，绘制完成后调用unlockCanvasAndPost()，传入Canvas对象，这时Surface将会按Canvas进行绘制。
注意：每次利用SurfaceHolder获得画布时，前一次的内容将会保留。
Code
public class MySurfaceView extends SurfaceView implements SurfaceHolder.Callback { private DrawThread mThread = null; public MySurfaceView(Context context, AttributeSet attrs, int defStyle) { super(context, attrs, defStyle); init(); } public MySurfaceView(Context context, AttributeSet attrs) { super(context, attrs); init(); } public MySurfaceView(Context context) { super(context); init(); } private void init() { Log.d(AppConstants.LOG_TAG, "init"); SurfaceHolder holder = getHolder(); holder.addCallback(this); mThread = new DrawThread(holder); } @Override protected void onSizeChanged(int w, int h, int oldw, int oldh) { Log.d(AppConstants.LOG_TAG, "onSizeChanged"); super.onSizeChanged(w, h, oldw, oldh); } @Override public void surfaceCreated(SurfaceHolder holder) { Log.d(AppConstants.LOG_TAG, "surfaceCreated"); mThread.setRun(true); mThread.start(); } @Override public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) { Log.d(AppConstants.LOG_TAG, "surfaceChanged"); } @Override public void surfaceDestroyed(SurfaceHolder holder) { Log.d(AppConstants.LOG_TAG, "surfaceDestroyed"); mThread.setRun(false); } /** * 绘制线程类 * */ public class DrawThread extends Thread { private SurfaceHolder mHolder = null; private boolean isRun = false; public DrawThread(SurfaceHolder holder) { Log.d(AppConstants.LOG_TAG, "DrawThread Constructor"); mHolder = holder; } public void setRun(boolean isRun) { Log.d(AppConstants.LOG_TAG, "DrawThread setRun: " + isRun); this.isRun = isRun; } @Override public void run() { Log.d(AppConstants.LOG_TAG, "DrawThread run"); int count = 0; while (isRun) { Canvas canvas = null; synchronized (mHolder) { try { Log.d(AppConstants.LOG_TAG, "Drawing-------------"); canvas = mHolder.lockCanvas(); canvas.drawColor(Color.WHITE); Paint p = new Paint(); p.setColor(Color.BLACK); Rect r = new Rect(100, 50, 300, 250); canvas.drawRect(r, p); canvas.drawText("这是第" + (count++) + "秒", 100, 310, p); Thread.sleep(1000);// 睡眠时间为1秒 } catch (Exception e) { Log.d(AppConstants.LOG_TAG, "throw Exception in run"); e.printStackTrace(); } finally { if (null != canvas) { mHolder.unlockCanvasAndPost(canvas); } } } } } } }
