1

我的应用程序有一组托管 FragmentActivity 的选项卡。其中一些选项卡包含 GoogleMaps Api v2 Support MapFragment 和/或 MapView,另一个选项卡是 QR 扫描仪。

我面临的问题是,如果您当前在一个选项卡上查看 SupportMapFragment 或 MapView,然后切换到 Scanner 选项卡,SurfaceView 仍然被之前的 SupportMapFragment / MapView 接管(当然,除非 Fragment/View 被删除在选择扫描仪选项卡之前)。由于使用了 SurfaceView,在尝试将 GoogleMaps Api v2 合并到 v1 之前,这不是问题。

我不确定如何解决这个问题,我在选择“扫描仪”选项卡并启动camerapreview时沿着“清除”表面视图的线路进行思考吗?并以某种方式使用画布实现这一目标?但是我对 SurfaceView 类的知识并不多。

附件是我的“CameraPreview”类,用于处理扫描仪选项卡上的 Android 相机。GoogleMaps api v2 类只是 Google 提供的基本设置,没什么特别的。

感谢您的时间和帮助。

class CameraPreview extends ViewGroup implements SurfaceHolder.Callback {
    private final String TAG = "CameraPreview";

    SurfaceView mSurfaceView;
    SurfaceHolder mHolder;
    Size mPreviewSize;
    List<Size> mSupportedPreviewSizes;
    Camera mCamera;
    PreviewCallback mPreviewCallback;
    AutoFocusCallback mAutoFocusCallback;

    CameraPreview(Context context, PreviewCallback previewCallback, AutoFocusCallback autoFocusCb) {
        super(context);

        mPreviewCallback = previewCallback;
        mAutoFocusCallback = autoFocusCb;        
        mSurfaceView = new SurfaceView(context);
        addView(mSurfaceView);

        // Install a SurfaceHolder.Callback so we get notified when the
        // underlying surface is created and destroyed.
        mHolder = mSurfaceView.getHolder();
        mHolder.addCallback(this);
        mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);

    }

    public void setCamera(Camera camera) {
        mCamera = camera;
        if (mCamera != null) {
            mSupportedPreviewSizes = mCamera.getParameters().getSupportedPreviewSizes();
            requestLayout();
        }
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        // We purposely disregard child measurements because act as a
        // wrapper to a SurfaceView that centers the camera preview instead
        // of stretching it.
        final int width = resolveSize(getSuggestedMinimumWidth(), widthMeasureSpec);
        final int height = resolveSize(getSuggestedMinimumHeight(), heightMeasureSpec);
        setMeasuredDimension(width, height);

        if (mSupportedPreviewSizes != null) {
            mPreviewSize = getOptimalPreviewSize(mSupportedPreviewSizes, width, height);
        }
    }

    @Override
    protected void onLayout(boolean changed, int l, int t, int r, int b) {
        if (changed && getChildCount() > 0) {
            final View child = getChildAt(0);

            final int width = r - l;
            final int height = b - t;

            int previewWidth = width;
            int previewHeight = height;
            if (mPreviewSize != null) {
                previewWidth = mPreviewSize.width;
                previewHeight = mPreviewSize.height;
            }

            // Center the child SurfaceView within the parent.
            if (width * previewHeight > height * previewWidth) {
                final int scaledChildWidth = previewWidth * height / previewHeight;
                child.layout(0, 0, width, height);
            } else {
                final int scaledChildHeight = previewHeight * width / previewWidth;
                child.layout(0, 0, width,height);

            }
        }
    }

    public void surfaceCreated(SurfaceHolder holder) {

        // The Surface has been created, acquire the camera and tell it where
        // to draw.
        try {
            if (mCamera != null) {
                mCamera.setPreviewDisplay(holder);
                mCamera.setDisplayOrientation(90);
            }
        } catch (IOException exception) {
            Log.e(TAG, "IOException caused by setPreviewDisplay()", exception);
        }
    }

    public void surfaceDestroyed(SurfaceHolder holder) {
        // Surface will be destroyed when we return, so stop the preview.
        if (mCamera != null) {
            mCamera.stopPreview();
        }
    }


    private Size getOptimalPreviewSize(List<Size> sizes, int w, int h) {
        final double ASPECT_TOLERANCE = 0.1;
        double targetRatio = (double) w / h;
        if (sizes == null) return null;

        Size optimalSize = null;
        double minDiff = Double.MAX_VALUE;

        int targetHeight = h;

        // Try to find an size match aspect ratio and size
        for (Size size : sizes) {
            double ratio = (double) size.width / size.height;
            if (Math.abs(ratio - targetRatio) > ASPECT_TOLERANCE) continue;
            if (Math.abs(size.height - targetHeight) < minDiff) {
                optimalSize = size;
                minDiff = Math.abs(size.height - targetHeight);
            }
        }

        // Cannot find the one match the aspect ratio, ignore the requirement
        if (optimalSize == null) {
            minDiff = Double.MAX_VALUE;
            for (Size size : sizes) {
                if (Math.abs(size.height - targetHeight) < minDiff) {
                    optimalSize = size;
                    minDiff = Math.abs(size.height - targetHeight);
                }
            }
        }
        return optimalSize;
    }

    public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) {
        if (holder.getSurface() == null){
            // preview surface does not exist
            return;
        }

        // Now that the size is known, set up the camera parameters and begin
        // the preview.
        if(mCamera!=null){
            Camera.Parameters parameters = mCamera.getParameters();

            parameters.setPreviewSize(mPreviewSize.width, mPreviewSize.height);
            requestLayout();

            mCamera.setParameters(parameters);
            mCamera.setPreviewCallback(mPreviewCallback);
            mCamera.startPreview();
            mCamera.autoFocus(mAutoFocusCallback);
        }
    }

}   
4

2 回答 2

1

从文档的声音来看,您一次应该只运行一个表面视图。

我在前面有一个类似的带有 CameraPreview 的 MapFragment,发现我需要 MapFragment 在相机预览片段起作用之前释放其资源。

这意味着将 MapFragment 换成 CamreaPreviewFragment 而不仅仅是将其添加到顶部。

于 2013-03-07T22:56:07.310 回答
0

几天前我遇到了同样的问题,我需要在 GoogleMap v2 上显示一个相机预览视图,以下是我的解决方案,希望对您有所帮助。

    // construct a camera preview layout then show it, or remove it then hide
    popCamera.setOnClickListener(new OnClickListener() {
        @Override
        public void onClick(View v) {
            if(cameraBar.getVisibility() == View.VISIBLE) {
                cameraBar.removeAllViews();
                cameraBar.setVisibility(View.INVISIBLE);
            }else if(cameraBar.getVisibility() == View.INVISIBLE) {
                // new camera surface view then add to preview area
                if (cameraSurfaceView == null) {
                    cameraSurfaceView = new CameraSurfaceView(getApplicationContext());
                    // === the key point ===
                    **cameraSurfaceView.setZOrderOnTop(true);**
                    LinearLayout.LayoutParams param = new LinearLayout.LayoutParams(
                            LinearLayout.LayoutParams.MATCH_PARENT,
                            LinearLayout.LayoutParams.MATCH_PARENT);
                    previewArea.addView(cameraSurfaceView, param);
                }

                cameraBar.removeAllViews();

                cameraBar.addView(previewArea);
                cameraBar.addView(snapArea);
                cameraBar.setVisibility(View.VISIBLE);
            }
        }
    });
于 2013-08-01T14:51:39.367 回答