Android Things - 创建相机预览会话失败，并且不显示预览

我正在尝试部署 Android TensorFlow-Lite 示例，特别是检测器活动。

我已成功将其部署在平板电脑中。该应用程序运行良好，它能够检测对象，在其周围放置一个边界矩形，并带有标签和置信度。

然后，我设置了 Raspberry Pi 3 B 型板，在其中安装了 Android Things，通过 ADB 连接，然后从 Android Studio 部署了相同的程序。然而，我用于 Rπ 板的屏幕是空白的。

经检查Android Things 相机演示教程 https://github.com/weichen2046/CameraDemoForAndroidThings，我有这个想法，启用硬件加速以支持相机预览。我添加了：

android:hardwareAccelerated="true"

in the application清单的标签。

我还在应用程序标签中添加了以下内容：

<uses-library android:name="com.google.android.things" />

我的活动标签中有一个意图过滤器：

<intent-filter>
    <action android:name="android.intent.action.MAIN" />
    <category android:name="android.intent.category.IOT_LAUNCHER" />
    <category android:name="android.intent.category.DEFAULT" />
</intent-filter>

以便 TensorFlow App 在启动后运行。

我再次部署了该应用程序，但同样的错误仍然存​​在——我无法配置预览屏幕会话。

以下是 TensorFlow 示例中包含的以下代码：

private void createCameraPreviewSession() {
    try {
        final SurfaceTexture texture = textureView.getSurfaceTexture();
        assert texture != null;

        // We configure the size of default buffer to be the size of camera preview we want.
        texture.setDefaultBufferSize(previewSize.getWidth(), previewSize.getHeight());

        // This is the output Surface we need to start preview.
        final Surface surface = new Surface(texture);

        // We set up a CaptureRequest.Builder with the output Surface.
        previewRequestBuilder = cameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);
        previewRequestBuilder.addTarget(surface);

        LOGGER.e("Opening camera preview: " + previewSize.getWidth() + "x" + previewSize.getHeight());

        // Create the reader for the preview frames.
        previewReader =
                ImageReader.newInstance(
                        previewSize.getWidth(), previewSize.getHeight(), ImageFormat.YUV_420_888, 2);

        previewReader.setOnImageAvailableListener(imageListener, backgroundHandler);
        previewRequestBuilder.addTarget(previewReader.getSurface());

        // Here, we create a CameraCaptureSession for camera preview.
        cameraDevice.createCaptureSession(
                Arrays.asList(surface, previewReader.getSurface()),
                new CameraCaptureSession.StateCallback() {

                    @Override
                    public void onConfigured(final CameraCaptureSession cameraCaptureSession) {
                        // The camera is already closed
                        if (null == cameraDevice) {
                            return;
                        }

                        // When the session is ready, we start displaying the preview.
                        captureSession = cameraCaptureSession;
                        try {
                            // Auto focus should be continuous for camera preview.
                            previewRequestBuilder.set(
                                    CaptureRequest.CONTROL_AF_MODE,
                                    CaptureRequest.CONTROL_AF_MODE_CONTINUOUS_PICTURE);
                            // Flash is automatically enabled when necessary.
                            previewRequestBuilder.set(
                                    CaptureRequest.CONTROL_AE_MODE, CaptureRequest.CONTROL_AE_MODE_ON_AUTO_FLASH);

                            // Finally, we start displaying the camera preview.
                            previewRequest = previewRequestBuilder.build();
                            captureSession.setRepeatingRequest(
                                    previewRequest, captureCallback, backgroundHandler);
                        } catch (final CameraAccessException e) {
                            LOGGER.e(e, "Exception!");
                            LOGGER.e("camera access exception!");
                        }
                    }

                    @Override
                    public void onConfigureFailed(final CameraCaptureSession cameraCaptureSession) {
                        showToast("Failed");
                        LOGGER.e("configure failed!!");
                    }
                },
                null);
    } catch (final CameraAccessException e) {
        LOGGER.e("camera access exception!");
        LOGGER.e(e, "Exception!");
    }
}

错误日志位于onConfigureFailedoverride 方法，以及导致该语句的相关错误日志是：

11-12 14:02:40.677 1991-2035/org.tensorflow.demo E/CameraCaptureSession: Session 0: Failed to create capture session; configuration failed
11-12 14:02:40.679 1991-2035/org.tensorflow.demo E/tensorflow: CameraConnectionFragment: configure failed!!

然而，我无法追踪Session 0:堆栈跟踪。

除了开启硬件加速和在Manifest中添加其他几个标签之外，我还没有尝试过任何东西。

我已经完成了研究，也看到了其他示例，但它们只是通过单击按钮来拍照。我需要一个可以正常工作的相机预览。

我也有 CameraDemoForAndroidThings 示例，但恐怕我不了解 Kotlin，无法猜测它是如何工作的。

如果有人设法在 Raspberry Pi Android Things 上运行 Java 版本的 TensorFlow 检测活动，请贡献并告诉我们您是如何做到的。

UPDATE:

显然，相机一次只能支持一种流配置。我还能够推断出我必须修改createCaptureSession()函数仅使用一个表面，我的函数现在如下所示：

cameraDevice.createCaptureSession(
//                    Arrays.asList(surface, previewReader.getSurface()),
        Arrays.asList(surface),
        new CameraCaptureSession.StateCallback() {

            @Override
            public void onConfigured(final CameraCaptureSession cameraCaptureSession) {
                // The camera is already closed
                if (null == cameraDevice) {
                    return;
                }

                // When the session is ready, we start displaying the preview.
                captureSession = cameraCaptureSession;
                try {
                    // Auto focus should be continuous for camera preview.
//                                previewRequestBuilder.set(
//                                        CaptureRequest.CONTROL_AF_MODE,
//                                        CaptureRequest.CONTROL_AF_MODE_CONTINUOUS_PICTURE);
                    // Flash is automatically enabled when necessary.
//                                previewRequestBuilder.set(
//                                        CaptureRequest.CONTROL_AE_MODE, CaptureRequest.CONTROL_AE_MODE_ON_AUTO_FLASH);

                    // Finally, we start displaying the camera preview.
                    previewRequest = previewRequestBuilder.build();
                    captureSession.setRepeatingRequest(
                            previewRequest, captureCallback, backgroundHandler);

                    previewRequestBuilder.addTarget(previewReader.getSurface());

                } catch (final CameraAccessException e) {
                    LOGGER.e("exception hit while configuring camera!");
                    LOGGER.e(e, "Exception!");
                }
            }

            @Override
            public void onConfigureFailed(final CameraCaptureSession cameraCaptureSession) {
                LOGGER.e("Configure failed!");
                showToast("Failed");
            }
        },
        null);

这使我能够获得实时预览。但是，代码不会继续将图像从预览发送到processImage() block.

有人成功实施了涉及 Android Things 实时相机预览的 TensorFlow-Lite 示例吗？