如何等到imageCapture初始化后才拍照？

Question

我怎样才能等到imageCapture初始化的那一刻，我尝试使用

while (imageCapture == null) {}

，但它只会使应用程序崩溃，使用延迟也不是一个选项，因为我也想用后置摄像头拍照，而且它会花费太长时间，因为有时可能需要一些时间来初始化

这是我当前的代码

class MainActivity : AppCompatActivity() {

    private var imageCapture: ImageCapture? = null
    private lateinit var viewBinding: ActivityMainBinding
    private lateinit var outputDirectory: File
    private lateinit var cameraExecutor: ExecutorService

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        viewBinding = ActivityMainBinding.inflate(layoutInflater)
        setContentView(viewBinding.root)
        supportActionBar?.hide()
        startCamera()
        takePhoto()
        startCameraBack()
        takePhoto()
        outputDirectory = getOutputDirectory()
        cameraExecutor = Executors.newSingleThreadExecutor()
    }
    private fun startCamera() {
        val cameraProviderFuture = ProcessCameraProvider.getInstance(this)
        cameraProviderFuture.addListener({
            val cameraProvider: ProcessCameraProvider = cameraProviderFuture.get()
            val preview = Preview.Builder().build()
            preview.setSurfaceProvider(findViewById<PreviewView>(R.id.viewFinder).surfaceProvider)
            val cameraSelector = CameraSelector.DEFAULT_FRONT_CAMERA
            imageCapture = ImageCapture.Builder().build()
            cameraProvider.unbindAll()
            cameraProvider.bindToLifecycle(this, cameraSelector, preview, imageCapture)
        }, ContextCompat.getMainExecutor(this))
    }
    private fun takePhoto() {
        val imageCapture = imageCapture ?: return
        val photoFile = File(
            outputDirectory,
            SimpleDateFormat(FILENAME_FORMAT, Locale.US).format(System.currentTimeMillis()) + ".jpg"
        )
        val outputOptions = ImageCapture.OutputFileOptions.Builder(photoFile).build()
        imageCapture.takePicture(
            outputOptions,
            ContextCompat.getMainExecutor(this),
            object : ImageCapture.OnImageSavedCallback {
                override fun onError(exc: ImageCaptureException) {
                }
                override fun onImageSaved(output: ImageCapture.OutputFileResults) {
                    var savedUri: Uri = Uri.fromFile(photoFile)
                    Toast.makeText(this@MainActivity,"Saved to $savedUri", Toast.LENGTH_LONG).show()
                }
            })
    }
    private fun getOutputDirectory(): File {
        val mediaDir = externalMediaDirs.firstOrNull()?.let {
            File(it, resources.getString(R.string.app_name)).apply { mkdirs() }
        }
        return if (mediaDir != null && mediaDir.exists())
            mediaDir else filesDir
    }

    companion object {
        private const val TAG = "CameraXGFG"
        private const val FILENAME_FORMAT = "yyyy-MM-dd-HH-mm-ss-SSS"
    }

    override fun onDestroy() {
        super.onDestroy()
        cameraExecutor.shutdown()
    }

Answer 1

您的问题来自异步的

cameraProviderFuture.addListener()

。调用

imageCapture

后访问

addListener()