Question

我正在使用增强现实应用程序，我想绘制一条连接相机顶部两个可移动物体的线。但是我得到了这个例外

Process: test.job.reality.augument.job.com.augumentrealitytest, PID: 15056
    java.lang.IllegalArgumentException
    at android.view.Surface.nativeLockCanvas(Native Method)
    at android.view.Surface.lockCanvas(Surface.java:266)
    at custom.MyCameraView$MyThread.run(MyCameraView.java:447)

这是我的代码，你可以看到我在surfaceCreted方法中启动我的线程。我想我不能锁定帆船，因为它是一个;准备好被相机锁定，我是对的吗？但是我画线是可能的（我正在使用beyondAR增强现实库）

public class MyCameraView extends SurfaceView implements SurfaceHolder.Callback, Camera.PictureCallback {
private MyThread thread;

public MyCameraView(Context context, AttributeSet attrs) {
    super(context, attrs);
    init(context);
}

@SuppressWarnings("deprecation")
private void init(Context context) {
    mIsPreviewing = false;
    mHolder = getHolder();
    mHolder.addCallback(this);

    configureCamera();

    if (Build.VERSION.SDK_INT <= 10) {// Android 2.3.x or lower
        mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
    }

    thread=new MyThread(getHolder(),this);
    getHolder().addCallback(this);
    setFocusable(true);
}

 @Override
protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);


}

public void surfaceCreated(SurfaceHolder holder) {
    // The Surface has been created, acquire the camera and tell it where
    // to draw.

    thread.startrun(true);
    thread.start();
    try {

        if (mCamera == null) {
            init(getContext());
            if (mCamera == null) {
                return;
            }
        }

        mCamera.setPreviewDisplay(holder);
    } catch (IOException exception) {
        if (mCamera != null) {
            mCamera.release();
        }
        mCamera = null;
        Logger.e(TAG, "CameraView -- ERROR en SurfaceCreated", exception);
    }
}

public void surfaceDestroyed(SurfaceHolder holder) {
    releaseCamera();

    thread.startrun(false);
    thread.stop();
}

public class MyThread extends Thread{

    private SurfaceHolder msurfaceHolder;
    private MyCameraView mSurfaceView;
    private boolean mrun =false;

    public MyThread(SurfaceHolder holder, MyCameraView mSurfaceView) {

        this.msurfaceHolder = holder;
        this.mSurfaceView=mSurfaceView;
    }

    public void startrun(boolean run) {

        mrun=run;
    }

    @SuppressLint("WrongCall")
    @Override
    public void run() {

        super.run();
        Canvas canvas;
        while (mrun) {
            canvas=null;
            try {
                canvas = msurfaceHolder.lockCanvas();
                synchronized (msurfaceHolder) {
                    mSurfaceView.onDraw(canvas);
                }
            } finally {
                if (canvas != null) {
                    msurfaceHolder.unlockCanvasAndPost(canvas);
                }
            }
        }
    }
}

Answer 1

当使用曲面显示相机预览时，您无法再使用它。原则上，您可以在预览曲面的顶部打开一个单独的透明画布，然后在该画布上绘制。切换到OpenGL预览可能要容易得多（使用SurfaceTexture）;那么你可以为你的绘图使用相同的OpenGL上下文（但它们也必须用OpenGL表示）。您可以找到一个简单的演示项目at GitHub。

但即使在这种情况下，您的任务还有另一个问题：即使您的简历速度非常快，您的增强功能与直接从传感器到屏幕的摄像机框架之间也不会同步。在OpenGL的情况下，一些简单的事情可以在0时间内完成（例如，对接收到的纹理进行简单卷积）。但更有趣的是需要不同的东西。

我们通常隐藏用户的实时预览，获取onPreviewFrame()回调中的帧，处理它们并手动绘制帧和任何其他行或对象。这会引入一些延迟，但如果您的算法非常有效，则此延迟可以忽略不计。

同样，OpenGL在这里通常会有很大的帮助。

Answer 2

不要lockCanvas并停止线程调用＆amp;只需在Draw方法中输入以下代码即可。我希望它能奏效。

protected void onDraw(Canvas canvas) {
    // TODO Auto-generated method stub
    super.onDraw(canvas);

    Paint paint = new Paint();

    DisplayMetrics metrics = Resources.getSystem().getDisplayMetrics();

    int screenWidth = metrics.widthPixels;
    int screenHeight = metrics.heightPixels;

    screenHeight = (int) (metrics.heightPixels * 0.6290);
    paint.setAntiAlias(true);
    paint.setStrokeWidth(1);
    paint.setStyle(Paint.Style.STROKE);

    paint.setColor(Color.argb(255, 255, 255, 255));

    canvas.drawLine((screenWidth / 4), 0,
            (screenWidth / 4), screenHeight + 500, paint);


    if(screenWidth == 1280 && screenHeight == 473)  // this condition for 10" tab only
    canvas.drawLine((screenWidth / 2f), 0,
                (screenWidth / 2f), screenHeight + 500, paint);

    else
    canvas.drawLine((screenWidth / 2.20f), 0,
            (screenWidth / 2.20f), screenHeight + 500, paint);

    canvas.drawLine(0, (screenHeight / 2.15f) * 2, screenWidth,
            (screenHeight / 2.15f) * 2, paint);

    canvas.drawLine(0, (screenHeight / 2.15f) , screenWidth,
            (screenHeight / 2.15f), paint);
}

Android画布在相机上画线

2 个答案: