我使用CameraX codelab示例构建了一个应用程序，运行良好，但是一旦我的手机进入睡眠状态并关闭屏幕，将手机恢复正常状态后CameraX传输没有恢复，并且CameraX屏幕保持白色？
更新
抱歉，这不是相机本身，相机是不可见的，我有一个图像视图，图像分析器正在显示相机中看到的内容。
val bitmap = view_finder.bitmap ?: return@Analyzer一旦手机进入睡眠状态，它看起来在我下面的代码中返回 null。
private lateinit var viewFinder: TextureView
private fun startCamera() {
val previewConfig = PreviewConfig.Builder().apply {
setTargetAspectRatio(Rational(1, 1))
setTargetResolution(Size(640, 640))
}.build()
val preview = Preview(previewConfig)
preview.setOnPreviewOutputUpdateListener {
val parent = viewFinder.parent as ViewGroup
parent.removeView(viewFinder)
parent.addView(viewFinder, 0)
viewFinder.surfaceTexture = it.surfaceTexture
updateTransform()
}
val imageCaptureConfig = Builder()
.apply {
setTargetAspectRatio(Rational(1, 1))
setCaptureMode(ImageCapture.CaptureMode.MIN_LATENCY)
}.build()
val imageCapture = ImageCapture(imageCaptureConfig)
findViewById<ImageButton>(R.id.capture_button).setOnClickListener {
val file = File(externalMediaDirs.first(),
"${System.currentTimeMillis()}.jpg")
imageCapture.takePicture(file,
object : ImageCapture.OnImageSavedListener {
override fun onError(error: ImageCapture.UseCaseError,
message: String, exc: Throwable?) {
val msg = "Photo capture failed: $message"
Toast.makeText(baseContext, msg, Toast.LENGTH_SHORT).show()
Log.e("CameraXApp", msg)
exc?.printStackTrace()
}
override fun onImageSaved(file: File) {
val msg = "Photo capture succeeded: ${file.absolutePath}"
Toast.makeText(baseContext, msg, Toast.LENGTH_SHORT).show()
Log.d("CameraXApp", msg)
}
})
}
// Setup image analysis pipeline that computes average pixel luminance
val analyzerConfig = ImageAnalysisConfig.Builder().apply {
val analyzerThread = HandlerThread(
"LuminosityAnalysis").apply { start() }
setCallbackHandler(Handler(analyzerThread.looper))
setImageReaderMode(
ImageAnalysis.ImageReaderMode.ACQUIRE_LATEST_IMAGE)
}.build()
val analyzerUseCase = ImageAnalysis(analyzerConfig).apply {
////// This is my own code that I added to the analyzer ///////
analyzer = ImageAnalysis.Analyzer { image, rotationDegrees ->
val bitmap = view_finder.bitmap ?: return@Analyzer
scope.launch(Dispatchers.Unconfined) {
val mat = Mat()
Utils.bitmapToMat(bitmap!!, mat)
val detectedFaces = FaceDetection.detectFaces(bitmap!!)
println("Detected Faces = $detectedFaces")
Toast.makeText(
this@MainActivity, "Detected Faces = ${detectedFaces.toArray().size}",
Toast.LENGTH_SHORT
).show()
if (detectedFaces.toArray().isNotEmpty()) {
val paint = Paint().apply {
isAntiAlias = true
style = Paint.Style.STROKE
color = Color.RED
strokeWidth = 10f
}
for (rect in detectedFaces.toArray()) {
bitmap?.let { Canvas(it) }?.apply {
drawRect(
rect.x.toFloat(), // faceRectangle.left,
rect.y.toFloat(), //faceRectangle.top,
rect.x.toFloat() + rect.width,
rect.y.toFloat() + rect.height,
paint
)
}
}
}
}
runOnUiThread { imageView.setImageBitmap(bitmap) }
}
}
CameraX.bindToLifecycle(
this, preview, imageCapture, analyzerUseCase)
}