为什么在我的应用程序扫描它使用ML-Kit看到的第一个文本后，相机关闭并且屏幕变黑?

Question

我正在使用CameraX和ML-Kit的Android文本识别API来制作文本识别应用程序。相机工作正常，直到我指向一个单词并识别它。然后屏幕变黑，我看到字写在那里(这是我的想法，但我希望这个字在相机预览仍然打开时就在那里)。我最初认为可能这个单词有一些背景色导致了这个，所以我将背景色设置为透明，但这并没有改变任何东西。我试着搜索堆栈溢出，没有找到任何东西在这里。MLKit和Camera X文档也没有提到这一点。

这是我的activity_main.xml文件，这可能是原因。

<FrameLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">

<androidx.camera.view.PreviewView
android:id="@+id/cameraPreviewView"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_constraintTop_toTopOf="parent">
</androidx.camera.view.PreviewView>
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:fontFamily="sans-serif-black"
android:textColor="@color/white"
android:textSize="20sp"
android:textStyle="bold"
app:layout_constraintBottom_toTopOf="@+id/cameraPreviewView"
app:layout_constraintTop_toTopOf="parent"
android:id="@+id/Result"
android:gravity="bottom"/>

这是我唯一的Kotlin文件。

import android.Manifest
import android.annotation.SuppressLint
import android.content.pm.PackageManager
import android.media.Image
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.util.Log
import android.widget.TextView
import android.widget.Toast
import androidx.camera.core.*
import androidx.camera.lifecycle.ProcessCameraProvider
import androidx.core.app.ActivityCompat
import androidx.core.content.ContextCompat
import com.example.myapplication3.databinding.ActivityMainBinding
import com.google.mlkit.vision.common.InputImage
import com.google.mlkit.vision.text.Text
import com.google.mlkit.vision.text.TextRecognition
import java.io.IOException
import java.util.concurrent.ExecutorService
import java.util.concurrent.Executors
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
val binding = ActivityMainBinding.inflate(layoutInflater)
setContentView(binding.root)
if (allPermissionsGranted()) {
startCamera()
} else {
requestPermissions()
}
}
private val cameraExecutor: ExecutorService by lazy { Executors.newSingleThreadExecutor() }
override fun onDestroy() {
super.onDestroy()
cameraExecutor.shutdown()
}
private companion object {
val TAG: String = MainActivity::class.java.simpleName
const val REQUEST_CODE_PERMISSIONS = 10
val REQUIRED_PERMISSIONS = arrayOf(Manifest.permission.CAMERA)
}
private fun allPermissionsGranted() = REQUIRED_PERMISSIONS.all {
ContextCompat.checkSelfPermission(baseContext, it) == PackageManager.PERMISSION_GRANTED
}
private fun requestPermissions() {
ActivityCompat.requestPermissions(
this,
REQUIRED_PERMISSIONS,
REQUEST_CODE_PERMISSIONS
)
}
override fun onRequestPermissionsResult(
requestCode: Int,
permissions: Array<String>,
grantResults: IntArray
) {
super.onRequestPermissionsResult(requestCode, permissions, grantResults)
if (requestCode == REQUEST_CODE_PERMISSIONS) {
if (allPermissionsGranted()) {
startCamera()
} else {
Toast.makeText(
this,
"Permissions not granted.",
Toast.LENGTH_SHORT
).show()
finish()
}
}
}
class TextReaderAnalyzer(
private val textFoundListener: (String) -> Unit
) : ImageAnalysis.Analyzer {

@SuppressLint("UnsafeOptInUsageError")
override fun analyze(imageProxy: ImageProxy) {
imageProxy.image?.let {process(it, imageProxy) }
}
private fun process(image: Image, imageProxy: ImageProxy) {
try {
readTextFromImage(InputImage.fromMediaImage(image, 90), imageProxy)
} catch (e: IOException) {
Log.d(TAG, "Failed to load the image")
e.printStackTrace()
}
}
@SuppressLint("UnsafeOptInUsageError")
private fun readTextFromImage(image: InputImage, imageProxy: ImageProxy) {
TextRecognition.getClient()
.process(image)
.addOnSuccessListener { visionText ->
processTextFromImage(visionText)
}
.addOnFailureListener { error ->
Log.d(TAG, "Failed to process the image")
error.printStackTrace()
imageProxy.close()
}
}
private fun processTextFromImage(visionText: Text) {
for (block in visionText.textBlocks) {
// You can access whole block of text using block.text
for (line in block.lines) {
// You can access whole line of text using line.text
for (element in line.elements) {
textFoundListener(element.text)
}
}
}
}
}
private val imageAnalyzer by lazy {
ImageAnalysis.Builder()
.setTargetAspectRatio(AspectRatio.RATIO_16_9)
.build()
.also {
it.setAnalyzer(
cameraExecutor,
TextReaderAnalyzer(::onTextFound)
)
}
}
private fun onTextFound(foundText: String)  {
val binding = ActivityMainBinding.inflate(layoutInflater)
setContentView(binding.root)
val textView: TextView = binding.Result
textView.text = foundText
}
private fun startCamera() {
val binding = ActivityMainBinding.inflate(layoutInflater)
setContentView(binding.root)
val cameraProviderFuture = ProcessCameraProvider.getInstance(this)
cameraProviderFuture.addListener(
{
val preview = Preview.Builder()
.build()
.also { it.setSurfaceProvider(binding.cameraPreviewView.surfaceProvider) }
cameraProviderFuture.get().bind(preview, imageAnalyzer)
},
ContextCompat.getMainExecutor(this)
)
}
private fun ProcessCameraProvider.bind(
preview: Preview,
imageAnalyzer: ImageAnalysis
) = try {
unbindAll()
bindToLifecycle(
this@MainActivity,
CameraSelector.DEFAULT_BACK_CAMERA,
preview,
imageAnalyzer
)
} catch (ise: IllegalStateException) {
// Thrown if binding is not done from the main thread
Log.e(TAG, "Binding failed", ise)
}
}

Answer 1

你应该稍微改变一下你的.addOnSuccessListener块。

TextRecognition.getClient()
.process(image)
.addOnSuccessListener { visionText ->
processTextFromImage(visionText)
//Add below line here
imageProxy.close() 
}
.addOnFailureListener { error ->
Log.d(TAG, "Failed to process the image")
error.printStackTrace()
imageProxy.close()
}