由网友(冰肌玉骨)分享简介：我在做一个虚拟现实应用中的相机会自动侦测脸部，找到他们，并表明他们对相机preVIEW位置。I'm making a virtual reality application where the camera should detect faces, locate them and show their locatio...

我在做一个虚拟现实应用中的相机会自动侦测脸部，找到他们，并表明他们对相机preVIEW位置。

I'm making a virtual reality application where the camera should detect faces, locate them and show their location on the camera preview.

我知道3种方式来做到这一点，我想用GLSurfaceView要尽可能快地（根据这个帖子），但目前我想画上的一样的SurfaceView，其中相机使用其preVIEW。我的回调吸取这将是 onFaceDetection 像这样：

I know of 3 ways to do it, I'd like to use GLSurfaceView to be as fast as possible (according to this post), but currently I'm trying to draw on the same SurfaceView where the camera is using for its preview. My callback to draw on it would be onFaceDetection like so:

public class MyActivity extends Activity implements SurfaceHolder.Callback, Camera.FaceDetectionListener {
    Camera camera;
    SurfaceView svPreview;
    SurfaceHolder previewHolder;
    TextView tvInfo;
    Paint red;

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

        svPreview = (SurfaceView) findViewById(R.id.svPreview);
        tvInfo = (TextView) findViewById(R.id.tvInfo);

        red = new Paint();
        red.setStyle(Paint.Style.STROKE);
        red.setStrokeWidth(3);

        previewHolder = svPreview.getHolder();
        previewHolder.addCallback(this);
        previewHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
    }

    public void surfaceCreated(SurfaceHolder arg0) {
        camera = Camera.open();
        try {
            camera.setDisplayOrientation(90);
            camera.setFaceDetectionListener(this);
            camera.setPreviewDisplay(previewHolder);
        }
        catch (IOException e) {
            e.printStackTrace();
        }
    }

    public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
        // . . .
        camera.startPreview();
        camera.autoFocus(null);
        camera.startFaceDetection();
    }

    public void surfaceDestroyed(SurfaceHolder arg0) {
        camera.stopFaceDetection();
        camera.cancelAutoFocus();
        camera.stopPreview();
        camera.release();
        camera = null;
    }

    public void onFaceDetection(Face[] faces, Camera camera) {  
        tvInfo.setText("Faces: " + String.valueOf(faces.length));

        Canvas canvas = previewHolder.lockCanvas();
        for(int i=0; i < faces.length; i++) {
            Point leftEye = faces[i].leftEye;
            Point rightEye = faces[i].rightEye;
            // this is not working
            canvas.drawPoint(leftEye.x, leftEye.y, red);
        }
        previewHolder.unlockCanvasAndPost(canvas);
    }
}

通过这个code我不断收到此错误：

With this code I keep getting this error:

09-03 19:35:42.743: E/SurfaceHolder(19394): Exception locking surface
09-03 19:35:42.743: E/SurfaceHolder(19394): java.lang.IllegalArgumentException
09-03 19:35:42.743: E/SurfaceHolder(19394):     at android.view.Surface.lockCanvasNative(Native Method)
09-03 19:35:42.743: E/SurfaceHolder(19394):     at android.view.Surface.lockCanvas(Surface.java:76)
09-03 19:35:42.743: E/SurfaceHolder(19394):     at android.view.SurfaceView$4.internalLockCanvas(SurfaceView.java:744)
09-03 19:35:42.743: E/SurfaceHolder(19394):     at android.view.SurfaceView$4.lockCanvas(SurfaceView.java:720)
09-03 19:35:42.743: E/SurfaceHolder(19394):     at com.bluetooth.activities.MyActivity.onFaceDetection(MyActivity.java:90)
09-03 19:35:42.743: E/SurfaceHolder(19394):     at android.hardware.Camera$EventHandler.handleMessage(Camera.java:729)
09-03 19:35:42.743: E/SurfaceHolder(19394):     at android.os.Handler.dispatchMessage(Handler.java:99)
09-03 19:35:42.743: E/SurfaceHolder(19394):     at android.os.Looper.loop(Looper.java:137)
09-03 19:35:42.743: E/SurfaceHolder(19394):     at android.app.ActivityThread.main(ActivityThread.java:4424)
09-03 19:35:42.743: E/SurfaceHolder(19394):     at java.lang.reflect.Method.invokeNative(Native Method)
09-03 19:35:42.743: E/SurfaceHolder(19394):     at java.lang.reflect.Method.invoke(Method.java:511)
09-03 19:35:42.743: E/SurfaceHolder(19394):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
09-03 19:35:42.743: E/SurfaceHolder(19394):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
09-03 19:35:42.743: E/SurfaceHolder(19394):     at dalvik.system.NativeStart.main(Native Method)
09-03 19:35:42.743: W/dalvikvm(19394): threadid=1: thread exiting with uncaught exception (group=0x40a561f8)
09-03 19:35:42.766: E/AndroidRuntime(19394): FATAL EXCEPTION: main
09-03 19:35:42.766: E/AndroidRuntime(19394): java.lang.IllegalArgumentException
09-03 19:35:42.766: E/AndroidRuntime(19394):    at android.view.Surface.unlockCanvasAndPost(Native Method)
09-03 19:35:42.766: E/AndroidRuntime(19394):    at android.view.SurfaceView$4.unlockCanvasAndPost(SurfaceView.java:775)
09-03 19:35:42.766: E/AndroidRuntime(19394):    at com.bluetooth.activities.MyActivity.onFaceDetection(MyActivity.java:99)
09-03 19:35:42.766: E/AndroidRuntime(19394):    at android.hardware.Camera$EventHandler.handleMessage(Camera.java:729)
09-03 19:35:42.766: E/AndroidRuntime(19394):    at android.os.Handler.dispatchMessage(Handler.java:99)
09-03 19:35:42.766: E/AndroidRuntime(19394):    at android.os.Looper.loop(Looper.java:137)
09-03 19:35:42.766: E/AndroidRuntime(19394):    at android.app.ActivityThread.main(ActivityThread.java:4424)
09-03 19:35:42.766: E/AndroidRuntime(19394):    at java.lang.reflect.Method.invokeNative(Native Method)
09-03 19:35:42.766: E/AndroidRuntime(19394):    at java.lang.reflect.Method.invoke(Method.java:511)
09-03 19:35:42.766: E/AndroidRuntime(19394):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
09-03 19:35:42.766: E/AndroidRuntime(19394):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
09-03 19:35:42.766: E/AndroidRuntime(19394):    at dalvik.system.NativeStart.main(Native Method)

有没有用相机试图绘制它的preVIEW在同一个SurfaceView的人脸检测回调的一个问题？我怎样才能做到这一点没有层次感SurfaceViews？

Is there a problem with the camera trying to draw its preview on the same SurfaceView the face detection callback? How can I do this without layering SurfaceViews?

推荐答案

您不能锁定，并借鉴了SurfaceView有Type.PUSH_BUFFERS，（你显示帧的）。你必须创建上面你原来在Z方向另一种观点认为，借鉴在查看一个SurfaceView。

You can't locK and draw on a SurfaceView which has Type.PUSH_BUFFERS, (the one you're displaying frames to). You have to create another view above your original one in the Z direction and draw on a SurfaceView in that View.

因此​​，在您main.xml中创建低于原始视图自定义视图中的FrameLayout。

So in your main.xml create a custom view below your original view in a FrameLayout.

创建和处理在活动视图一个SurfaceView。添加这种观点的摄像头preVIEW显示。启动您的自定义视图传递SurfaceHolder。在此视图可以锁定并绘制在画布上。

Create and handle a SurfaceView in your Activity View. Add this view to the Camera preview display. Start your custom view passing the SurfaceHolder. In this view can lock and draw on a canvas.