Android -- SurfaceView绘制

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);
}
} } }
} } }

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参考:http://www.cnblogs.com/mengdd/archive/2013/04/09/3009897.html

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