android 使用两个surfaceview 在摄像机画面上绘图

使用双surface，将第一个设置为透明背景，在摄像机上绘制图像，纠结搞了一天。

其中参考了http://blog.csdn.net/yanzi1225627/article/details/7934710 的思路和代码，但是，始终会出现 canvas=holder.lockcanvas();返回的canvas为null的情况。加入线程后解决问题。

主Activity：

public class MainActivity extends Activity {

private SVDraw surfaceDraw = null;
private SurfaceView surfaceView = null;
private SurfaceHolder holder1 = null;
private Canvas canvas = null;
private Camera cam = null;
private boolean previewRunning = true;

@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

//绘制surface1
  surfaceView = (SurfaceView) findViewById(R.id.surface1);
holder1 = surfaceView.getHolder();
holder1.addCallback(new MySurfaceViewCallback());
holder1.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
holder1.setFixedSize(500, 350);
holder1.setFormat(PixelFormat.TRANSPARENT);

canvas = holder1.lockCanvas();
if (canvas != null) {
canvas.drawColor(Color.TRANSPARENT);
Paint p = new Paint();
p.setAntiAlias(true);
p.setColor(Color.RED);
p.setStyle(Style.STROKE);
// canvas.drawPoint(100.0f, 100.0f, p);
canvas.drawLine(0, 110, 500, 110, p);
}

// 绘制surface2 其中使用线程
surfaceDraw = (SVDraw) findViewById(R.id.mDraw);
surfaceDraw.setVisibility(View.VISIBLE);
surfaceDraw.drawLine();
}

// =============================create surface 1=================================================
private class MySurfaceViewCallback implements SurfaceHolder.Callback {
@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width,
int height) {
}

@SuppressWarnings("deprecation")
@Override
public void surfaceCreated(SurfaceHolder holder) {
cam = Camera.open(); // 取得第一个摄像头
Parameters param = cam.getParameters();
// param.setPreviewSize(display.getWidth(), display.getHeight()) ;
param.setPreviewFrameRate(5); // 一秒5帧
param.setPictureFormat(PixelFormat.JPEG); // 图片形式
param.set("jpen-quality", 80);
cam.setParameters(param);
cam.setDisplayOrientation(90); // 纠正摄像头自动旋转，纠正角度，如果引用，则摄像角度偏差90度

try {
cam.setPreviewDisplay(holder);
} catch (IOException e) {
}

cam.startPreview(); // 进行预览
previewRunning = true; // 已经开始预览
}

@Override
public void surfaceDestroyed(SurfaceHolder holder) {
if (cam != null) {
if (previewRunning) {
cam.stopPreview(); // 停止预览
previewRunning = false;
}
cam.release();
}
}
}
}

/*只不过一个是继承的view一个是surfaceview，将AttributeSetattrs加上。只要处理好谁是顶层的view谁设成透明，预览视频的surfaceview设成底层，在且要在xml属性文件里设成visible就可以了*/
public class SVDraw extends SurfaceView implements SurfaceHolder.Callback{

protected SurfaceHolder sh;
private int mWidth;
private int mHeight;
private MyThread thread;

public SVDraw(Context context, AttributeSet attrs) {
super(context, attrs);
sh = this.getHolder();
sh.addCallback(this);
sh.setFormat(PixelFormat.TRANSPARENT);
setZOrderOnTop(true);
}

public void surfaceChanged(SurfaceHolder arg0, int arg1, int w, int h) {
mWidth = w;
mHeight = h;
}

public void surfaceCreated(SurfaceHolder arg0) {

}

public void surfaceDestroyed(SurfaceHolder arg0) {

}
void clearDraw()
{
Canvas canvas = sh.lockCanvas();
canvas.drawColor(Color.BLUE);
sh.unlockCanvasAndPost(canvas);
}
public void drawLine()
{
//预览视频的时候绘制图像
/*Canvas canvas = sh.lockCanvas();
canvas.drawColor(Color.TRANSPARENT);
Paint p = new Paint();
p.setAntiAlias(true);
p.setColor(Color.RED);
p.setStyle(Style.STROKE);
//canvas.drawPoint(100.0f, 100.0f, p);
canvas.drawLine(0,110, 500, 110, p);
canvas.drawCircle(110, 110, 10.0f, p);
sh.unlockCanvasAndPost(canvas);*/

thread = new MyThread(sh);
thread.setRun(true);
thread.start();
}
}

// 绘制线程
public class MyThread extends Thread {
private SurfaceHolder holder;
private boolean run;

public MyThread(SurfaceHolder holder) {
this.holder = holder;
run = true;
}

@Override
public void run() {
int counter = 0;
Canvas canvas = null;
while (run) {
// 具体绘制工作
try {
// 获取Canvas对象，并锁定之
canvas = holder.lockCanvas();
// 设定Canvas对象的背景颜色
canvas.drawColor(Color.TRANSPARENT);

// 创建画笔
Paint p = new Paint();
// 设置画笔颜色
p.setColor(Color.RED);
// 设置文字大小
p.setTextSize(30);

// 创建一个Rect对象rect
Rect rect = new Rect(100, 50, 380, 330);
// 在canvas上绘制rect
canvas.drawRect(rect, p);
// 在canvas上显示时间
canvas.drawText("Interval = " + (counter++) + " seconds.", 100, 410, p);
Thread.sleep(1000);
} catch (Exception e) {
e.printStackTrace();
} finally {
if (canvas != null) {
// 解除锁定，并提交修改内容
holder.unlockCanvasAndPost(canvas);
}
}
}
}

public boolean isRun() {
return run;
}

public void setRun(boolean run) {
this.run = run;
}
}

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.test02"
android:versionCode="1"
android:versionName="1.0" >

<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="18" />

<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name="com.example.test02.MainActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />

<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>

<!--z>
&nbsp;<uses-feature android:name="android.hardware.camera" />
<uses-feature android:name="android.hardware.camera.autofocus" />
<uses-permission android:name="android.permission.CAMERA" />
<uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
</manifest>