当我使用CameraX的代码“imageCapture.takePicture”时，没有任何反应。

Question

我正在尝试探索CameraX beta版本。

我的实现卡住了。 imageCapture.takePicture() 报错 imageCapture 为空。

        // Bind the CameraProvider to the LifeCycleOwner
    val cameraSelector = CameraSelector.Builder().requireLensFacing(lensFacing).build()
    val cameraProviderFuture = ProcessCameraProvider.getInstance(this)
    cameraProviderFuture.addListener(Runnable {

    // CameraProvider
    val cameraProvider: ProcessCameraProvider = cameraProviderFuture.get()

    // ImageCapture
    imageCapture = ImageCapture.Builder()
        .setCaptureMode(ImageCapture.CAPTURE_MODE_MINIMIZE_LATENCY)
        .build()


        // Must unbind the use-cases before rebinding them
        cameraProvider.unbindAll()

        try {
            // A variable number of use-cases can be passed here -
            // camera provides access to CameraControl & CameraInfo
            camera = cameraProvider.bindToLifecycle(
                this, cameraSelector, imageCapture)
        } catch(exc: Exception) {
            Log.e("TAG", "Use case binding failed", exc)
        }

    }, ContextCompat.getMainExecutor(this))

    // Create output file to hold the image
    photoFile = createFile(externalMediaDirs.first(), FILENAME, PHOTO_EXTENSION)

    // Setup image capture metadata
    val metadata = Metadata().apply {

        // Mirror image when using the front camera
        isReversedHorizontal = lensFacing == CameraSelector.LENS_FACING_FRONT
    }
    // Create output options object which contains file + metadata
    outputOptions = ImageCapture.OutputFileOptions.Builder(photoFile)
        .setMetadata(metadata)
        .build()

    // Setup image capture listener which is triggered after photo has been taken
    imageCapture?.takePicture(
        outputOptions, cameraExecutor, object : ImageCapture.OnImageSavedCallback {
            override fun onError(exc: ImageCaptureException) {
                Log.e(TAG, "Photo capture failed: ${exc.message}", exc)
            }

            override fun onImageSaved(output: ImageCapture.OutputFileResults) {
                val savedUri = output.savedUri ?: Uri.fromFile(photoFile)
                Log.d(TAG, "Photo capture succeeded: $savedUri")

            }
        })
  }

我不使用onClickListener。

我的函数由一个服务调用。

如果我移除cameraProviderFuture.addListener(Runnable，我会得到"Not bound to a valid Camera"。

我使用的是camerax beta版本。

- Neila Niati

Answer 1

ImageCapture这个用例目前不能单独使用，必须与至少一个Preview或者ImageAnalysis用例结合使用。这可能会在CameraX的未来版本中发生改变。现在，您可以查看支持的用例组合文档。解决问题的简单方法是添加一个ImageAnalysis用例，其Analyzer可以立即关闭接收到的图像。

val imageAnalysis = ImageAnalysis.Builder()
      .build()
      .apply {
            setAnalyzer(executor, ImageAnalysis.Analyzer { image ->
            image.close()
        })
      }

// Then bind both the imageAnalysis and ImageCapture
cameraProvider.bindToLifecycle(this, cameraSelector, imageCapture, imageAnalysis)

- Husayn Hakeem