android - 无法找到支持的表面信息 - CameraId:null (CameraX) on android things

Question

我有一个运行 android 的树莓派 3。我已经连接了相机，我还可以在 Peripherals -> Camera 中看到输出。我还想预览相机并对每一帧进行图像处理。使用 CameraX api，我使用了此处找到的代码。

这是代码：

MainActivity.kt：

package com.example.sos_project

import android.graphics.Matrix
import android.os.Bundle
import android.util.Size
import android.view.Surface
import android.view.TextureView
import android.view.ViewGroup
import androidx.appcompat.app.AppCompatActivity
import androidx.camera.core.CameraX
import androidx.camera.core.Preview
import androidx.camera.core.PreviewConfig

/**
 * Skeleton of an Android Things activity.
 *
 * Android Things peripheral APIs are accessible through the class
 * PeripheralManagerService. For example, the snippet below will open a GPIO pin and
 * set it to HIGH:
 *
 * <pre>{@code
 * val service = PeripheralManagerService()
 * val mLedGpio = service.openGpio("BCM6")
 * mLedGpio.setDirection(Gpio.DIRECTION_OUT_INITIALLY_LOW)
 * mLedGpio.value = true
 * }</pre>
 * <p>
 * For more complex peripherals, look for an existing user-space driver, or implement one if none
 * is available.
 *
 * @see <a href="https://github.com/androidthings/contrib-drivers#readme">https://github.com/androidthings/contrib-drivers#readme</a>
 *
 */
class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        viewFinder = findViewById(R.id.view_finder)
        viewFinder.post { startCamera() }

        viewFinder.addOnLayoutChangeListener { _, _, _, _, _, _, _, _, _ ->
            updateTransform()
        }
    }

    private lateinit var viewFinder: TextureView

    private fun startCamera() {

        // Create configuration object for the viewfinder use case
        val previewConfig = PreviewConfig.Builder().apply {
            setTargetResolution(Size(640,480))
            setLensFacing(CameraX.LensFacing.FRONT)
        }.build()


        // Build the viewfinder use case
        val preview = Preview(previewConfig)

        // Every time the viewfinder is updated, recompute layout
        preview.setOnPreviewOutputUpdateListener {

            // To update the SurfaceTexture, we have to remove it and re-add it
            val parent = viewFinder.parent as ViewGroup
            parent.removeView(viewFinder)
            parent.addView(viewFinder, 0)

            viewFinder.surfaceTexture = it.surfaceTexture
            updateTransform()
        }

        // Bind use cases to lifecycle
        // If Android Studio complains about "this" being not a LifecycleOwner
        // try rebuilding the project or updating the appcompat dependency to
        // version 1.1.0 or higher.
        CameraX.bindToLifecycle(this, preview)
    }

    private fun updateTransform() {
        val matrix = Matrix()

        // Compute the center of the view finder
        val centerX = viewFinder.width / 2f
        val centerY = viewFinder.height / 2f

        // Correct preview output to account for display rotation
        val rotationDegrees = when(viewFinder.display.rotation) {
            Surface.ROTATION_0 -> 0
            Surface.ROTATION_90 -> 90
            Surface.ROTATION_180 -> 180
            Surface.ROTATION_270 -> 270
            else -> return
        }
        matrix.postRotate(-rotationDegrees.toFloat(), centerX, centerY)

        // Finally, apply transformations to our TextureView
        viewFinder.setTransform(matrix)
    }
}

完全错误：

2019-11-21 11:03:33.555 3823-3823/com.example.___ E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.___, PID: 3823
    java.lang.IllegalArgumentException: Fail to find supported surface info - CameraId:null
        at androidx.camera.camera2.impl.Camera2DeviceSurfaceManager.requiresCorrectedAspectRatio(Camera2DeviceSurfaceManager.java:274)
        at androidx.camera.core.Preview.updateUseCaseConfig(Preview.java:476)
        at androidx.camera.core.UseCase.<init>(UseCase.java:96)
        at androidx.camera.core.Preview.<init>(Preview.java:115)
        at com.example.___.MainActivity.startCamera(MainActivity.kt:60)
        at com.example.___.MainActivity.access$startCamera(MainActivity.kt:35)
        at com.example.___.MainActivity$onCreate$1.run(MainActivity.kt:41)
        at android.os.Handler.handleCallback(Handler.java:790)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:164)
        at android.app.ActivityThread.main(ActivityThread.java:6494)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)

编辑：我试图用java实现同样的事情，我得到了同样的错误

java.lang.IllegalArgumentException: Unable to get camera ID for use case androidx.camera.core.Preview

我的代码有什么问题？

提前致谢

标签： androidkotlinraspberry-pi3android-thingsandroid-camerax