CameraX 使用

优点

• 简单易用：比Camera和Camera2 更简洁
• 生命周期管理：CameraX 和 Lifecycle 结合在一起，方便管理。比camera2 少大量样板代码。
• 兼容性：CameraX 基于Camera2 API 实现，兼容至 Android L (API 21)
• 扩展性：可以使用和原生摄像头应用同样的功能（如：人像、夜间模式、HDR、滤镜、美颜）
• 自动化测试：对摄像头功能进行深度测试

使用

• 添加Gradle依赖

def camerax_version = "1.0.1"
// CameraX core library using camera2 implementation
implementation "androidx.camera:camera-camera2:$camerax_version"
// CameraX Lifecycle Library
implementation "androidx.camera:camera-lifecycle:$camerax_version"
// CameraX View class
implementation "androidx.camera:camera-view:1.0.0-alpha27"

• Java 8

compileOptions {
    sourceCompatibility JavaVersion.VERSION_1_8
    targetCompatibility JavaVersion.VERSION_1_8
}

• 布局

<?xml version="1.0" encoding="utf-8"?>
<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">

   <Button
       android:id="@+id/camera_capture_button"
       android:layout_width="100dp"
       android:layout_height="100dp"
       android:layout_marginBottom="50dp"
       android:scaleType="fitCenter"
       android:text="Take Photo"
       app:layout_constraintLeft_toLeftOf="parent"
       app:layout_constraintRight_toRightOf="parent"
       app:layout_constraintBottom_toBottomOf="parent"
       android:elevation="2dp" />

   <androidx.camera.view.PreviewView
       android:id="@+id/viewFinder"
       android:layout_width="match_parent"
       android:layout_height="match_parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

• 权限

<uses-feature android:name="android.hardware.camera.any" />
<uses-permission android:name="android.permission.CAMERA" />

请求完权限之后

• startCamera

private fun startCamera() {
   val cameraProviderFuture = ProcessCameraProvider.getInstance(this)

   cameraProviderFuture.addListener(Runnable {
       // Used to bind the lifecycle of cameras to the lifecycle owner
       val cameraProvider: ProcessCameraProvider = cameraProviderFuture.get()

       // Preview
       preview = Preview.Builder()
           .build()

       // Select back camera
       val cameraSelector = CameraSelector.Builder().requireLensFacing(CameraSelector.LENS_FACING_BACK).build()

       try {
           // Unbind use cases before rebinding
           cameraProvider.unbindAll()

           // Bind use cases to camera
           camera = cameraProvider.bindToLifecycle(
               this, cameraSelector, preview)
           preview?.setSurfaceProvider(viewFinder.createSurfaceProvider(camera?.cameraInfo))
       } catch(exc: Exception) {
           Log.e(TAG, "Use case binding failed", exc)
       }

   }, ContextCompat.getMainExecutor(this))
}

1、创建的实例ProcessCameraProvider
2、侦听器添加到中cameraProviderFuture
3、添加ProcessCameraProvider，用于将相机的生命周期绑定到应用程序进程中的LifecycleOwner
4、初始化Preview

preview = Preview.Builder().build()

5、CameraSelector 配置前后置镜头

val cameraSelector = CameraSelector.Builder().requireLensFacing(CameraSelector.LENS_FACING_BACK).build()

6、try、catch将cameraSelector和预览对象绑定到cameraProvider。将viewFinder的Surface提供程序附加到preview

• takePhoto 拍照

private fun takePhoto() {
   // Get a stable reference of the modifiable image capture use case
   val imageCapture = imageCapture ?: return

   // Create timestamped output file to hold the image
   val photoFile = File(
       outputDirectory,
       SimpleDateFormat(FILENAME_FORMAT, Locale.US
       ).format(System.currentTimeMillis()) + ".jpg")

   // Create output options object which contains file + metadata
   val outputOptions = ImageCapture.OutputFileOptions.Builder(photoFile).build()

   // Setup image capture listener which is triggered after photo has
   // been taken
   imageCapture.takePicture(
       outputOptions, ContextCompat.getMainExecutor(this), 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 = Uri.fromFile(photoFile)
               val msg = "Photo capture succeeded: $savedUri"
               Toast.makeText(baseContext, msg, Toast.LENGTH_SHORT).show()
               Log.d(TAG, msg)
           }
       })
}

1、获得ImageCapture
2、创建一个文件来保存图像
3、takePicture