我创建了一个用于检查相机使用情况的应用程序。应用程序的后置摄像头的工作方式类似于我手机的默认摄像头，但是当我使用前置摄像头时，它的外观比手机的默认摄像头暗得多。我google了很多，
尝试增加捕获图像之前的延迟时间，第二次尝试增加目标分辨率
但没有一个解决方案对我有用。他们在谷歌上对这个问题没有太多的支持。
MainActivity.kt
package com.asad.camerax
// Your IDE likely can auto-import these classes, but there are several
// different implementations so we list them here to disambiguate.
import android.Manifest
import android.content.pm.PackageManager
import android.graphics.Camera
import android.graphics.Matrix
import android.os.Bundle
import android.os.Handler
import android.util.Log
import android.util.Size
import android.view.Surface
import android.view.TextureView
import android.view.ViewGroup
import android.widget.ImageButton
import android.widget.Toast
import androidx.appcompat.app.AppCompatActivity
import androidx.camera.core.*
import androidx.core.app.ActivityCompat
import androidx.core.content.ContextCompat
import androidx.lifecycle.LifecycleOwner
import java.io.File
import java.util.concurrent.Executors
// This is an arbitrary number we are using to keep track of the permission
// request. Where an app has multiple context for requesting permission,
// this can help differentiate the different contexts.
private const val REQUEST_CODE_PERMISSIONS = 10
// This is an array of all the permission specified in the manifest.
private val REQUIRED_PERMISSIONS = arrayOf(Manifest.permission.CAMERA)
class MainActivity : AppCompatActivity(), LifecycleOwner {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
viewFinder = findViewById(R.id.view_finder)
// Request camera permissions
if (allPermissionsGranted()) {
viewFinder.post { startCamera() }
} else {
ActivityCompat.requestPermissions(
this, REQUIRED_PERMISSIONS, REQUEST_CODE_PERMISSIONS)
}
// Every time the provided texture view changes, recompute layout
viewFinder.addOnLayoutChangeListener { _, _, _, _, _, _, _, _, _ ->
updateTransform()
}
}
private val executor = Executors.newSingleThreadExecutor()
private lateinit var viewFinder: TextureView
private fun startCamera() {
// Create configuration object for the viewfinder use case
val previewConfig = PreviewConfig.Builder().apply {
setLensFacing(CameraX.LensFacing.FRONT)
setTargetResolution(Size(640, 480))
}.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.
// Create configuration object for the image capture use case
val imageCaptureConfig = ImageCaptureConfig.Builder()
.apply {
// We don't set a resolution for image capture; instead, we
// select a capture mode which will infer the appropriate
// resolution based on aspect ration and requested mode
setTargetResolution(Size(640, 480))
setCaptureMode(ImageCapture.CaptureMode.MAX_QUALITY)
setLensFacing(CameraX.LensFacing.FRONT)
}.build()
// Build the image capture use case and attach button click listener
val imageCapture = ImageCapture(imageCaptureConfig)
findViewById<ImageButton>(R.id.capture_button).setOnClickListener {
val file = File(externalMediaDirs.first(),
"${System.currentTimeMillis()}.jpg")
Handler().postDelayed(Runnable {
imageCapture.takePicture(file, executor,
object : ImageCapture.OnImageSavedListener {
override fun onError(
imageCaptureError: ImageCapture.ImageCaptureError,
message: String,
exc: Throwable?
) {
val msg = "Photo capture failed: $message"
Log.e("CameraXApp", msg, exc)
viewFinder.post {
Toast.makeText(baseContext, msg, Toast.LENGTH_SHORT).show()
}
}
override fun onImageSaved(file: File) {
val msg = "Photo capture succeeded: ${file.absolutePath}"
Log.d("CameraXApp", msg)
viewFinder.post {
Toast.makeText(baseContext, msg, Toast.LENGTH_SHORT).show()
}
}
})}, 1000)
}
// 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)
CameraX.bindToLifecycle(this, preview, imageCapture)
}
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)
}
/**
* Process result from permission request dialog box, has the request
* been granted? If yes, start Camera. Otherwise display a toast
*/
override fun onRequestPermissionsResult(
requestCode: Int, permissions: Array<String>, grantResults: IntArray) {
if (requestCode == REQUEST_CODE_PERMISSIONS) {
if (allPermissionsGranted()) {
viewFinder.post { startCamera() }
} else {
Toast.makeText(this,
"Permissions not granted by the user.",
Toast.LENGTH_SHORT).show()
finish()
}
}
}
/**
* Check if all permission specified in the manifest have been granted
*/
private fun allPermissionsGranted() = REQUIRED_PERMISSIONS.all {
ContextCompat.checkSelfPermission(
baseContext, it) == PackageManager.PERMISSION_GRANTED
}
}
这是activity_main.xml
<androidx.constraintlayout.widget.ConstraintLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<TextureView
android:id="@+id/view_finder"
android:layout_width="640px"
android:layout_height="640px"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintEnd_toEndOf="parent" />
<ImageButton
android:id="@+id/capture_button"
android:layout_width="72dp"
android:layout_height="72dp"
android:layout_margin="24dp"
app:srcCompat="@drawable/ic_camera"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"/>
</androidx.constraintlayout.widget.ConstraintLayout>