Android 使用CameraX实现预览/拍照/录制视频/图片分析/对焦/缩放/切换摄像头等操作
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1. CameraX架构
看官方文档 CameraX架构
有如下这一段话
使用CameraX，借助名为"用例"的抽象概念与设备的相机进行交互。
- 预览 : 接受用于显示预览的Surface，例如
PreviewView - 图片分析 : 为分析 (例如机器学习) 提供CPU可访问的缓冲区
- 图片拍摄 : 拍摄并保存图片
- 视频拍摄 : 通过
VideoCapture拍摄视频和音频
不同用例可以组合使用，也可以同时处于活跃状态。
例如，应用中可以加入预览用例，以便让用户查看进入相机视野的画面
加入图片分析用例，以确定照片里的人物是否在微笑
还可以加入图片拍摄用例，以便在人物微笑时拍摄照片
第一次看的时候，一脸懵逼，“用例”，是个什么鬼玩意。
后来，研究了一下，知道"用例"的英文原文叫做Use Case，CameraX中的每一项操作，对应着一种UseCase
- 预览 :
Preview.java - 图片分析 :
ImageAnalysis.java - 图片拍摄 :
ImageCapture.java - 视频拍摄 :
VideoCapture.java
可以看到，这几个类都是继承自UseCase.java类的
public final class Preview extends UseCase
//...
public final class ImageAnalysis extends UseCase
//...
public final class ImageCapture extends UseCase
//...
public final class VideoCapture extends UseCase
//...
接下来让我们来尝试使用一下。
2. 前置操作
首先，我们需要新建一个项目，然后引入依赖
// CameraX core library using the camera2 implementation
def camerax_version = "1.2.0-alpha02" //1.2.0-alpha02
// The following line is optional, as the core library is included indirectly by camera-camera2
implementation "androidx.camera:camera-core:$camerax_version"
implementation "androidx.camera:camera-camera2:$camerax_version"
// If you want to additionally use the CameraX Lifecycle library
implementation "androidx.camera:camera-lifecycle:$camerax_version"
// If you want to additionally use the CameraX VideoCapture library
implementation "androidx.camera:camera-video:$camerax_version"
// If you want to additionally use the CameraX View class
implementation "androidx.camera:camera-view:$camerax_version"
// If you want to additionally add CameraX ML Kit Vision Integration
implementation "androidx.camera:camera-mlkit-vision:$camerax_version"
// If you want to additionally use the CameraX Extensions library
implementation "androidx.camera:camera-extensions:$camerax_version"
在AndroidManifest.xml里添加权限
<!--摄像头权限-->
<uses-permission android:name="android.permission.CAMERA" />
<!--具备摄像头-->
<uses-feature android:name="android.hardware.camera.any" />
<!--存储图像或者视频权限-->
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<!--录制音频权限-->
<uses-permission android:name="android.permission.RECORD_AUDIO" />
别忘了申请权限
ActivityCompat.requestPermissions(
this, arrayOf(
Manifest.permission.CAMERA,
Manifest.permission.WRITE_EXTERNAL_STORAGE,
Manifest.permission.READ_EXTERNAL_STORAGE,
Manifest.permission.RECORD_AUDIO
), 123
)
3. 预览 : Preview.java
首先修改activity_main.xml
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="@+id/camera_container"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@android:color/black">
<androidx.camera.view.PreviewView
android:id="@+id/previewView"
android:layout_width="0dp"
android:layout_height="0dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
修改MainActivity.kt
class MainActivity : AppCompatActivity()
private lateinit var binding: ActivityMainBinding
private lateinit var cameraProvider: ProcessCameraProvider
private var preview: Preview? = null
private var camera: Camera? = null
override fun onCreate(savedInstanceState: Bundle?)
super.onCreate(savedInstanceState)
binding = ActivityMainBinding.inflate(layoutInflater)
setContentView(binding.root)
//TODO 省略了权限申请，具体看文章中 "前置操作" 部分
setUpCamera(binding.previewView)
private fun setUpCamera(previewView: PreviewView)
val cameraProviderFuture: ListenableFuture<ProcessCameraProvider> =
ProcessCameraProvider.getInstance(this)
cameraProviderFuture.addListener(
try
cameraProvider = cameraProviderFuture.get()
bindPreview(cameraProvider, previewView)
catch (e: Exception)
e.printStackTrace()
, ContextCompat.getMainExecutor(this))
private fun bindPreview(
cameraProvider: ProcessCameraProvider,
previewView: PreviewView
)
//解除所有绑定，防止CameraProvider重复绑定到Lifecycle发生异常
cameraProvider.unbindAll()
preview = Preview.Builder().build()
camera = cameraProvider.bindToLifecycle(
this,
CameraSelector.DEFAULT_BACK_CAMERA, preview
)
preview?.setSurfaceProvider(previewView.surfaceProvider)
看下效果
4. 图像分析 : ImageAnalysis.java
图像分析用例ImageAnalysis为应用提供可实时分析的图像数据，我们可以对这些图像执行图像处理、计算机视觉或机器学习推断。
val imageAnalysis = ImageAnalysis.Builder()
// enable the following line if RGBA output is needed.
// .setOutputImageFormat(ImageAnalysis.OUTPUT_IMAGE_FORMAT_RGBA_8888)
.setTargetResolution(Size(1280, 720))
.setBackpressureStrategy(ImageAnalysis.STRATEGY_KEEP_ONLY_LATEST)
.build()
imageAnalysis.setAnalyzer(executor, ImageAnalysis.Analyzer imageProxy ->
val rotationDegrees = imageProxy.imageInfo.rotationDegrees
// insert your code here.
// 在这里处理图片的解析，比如解析成二维码之类的
...
// after done, release the ImageProxy object
imageProxy.close()
)
在调用cameraProvider.bindToLifecycle()时，进行传入
cameraProvider.bindToLifecycle(
this, CameraSelector.DEFAULT_BACK_CAMERA, preview, imageAnalysis
)
5. 拍照 : ImageCapture.java
5.1 仅拍照
这里，我们需要先创建一个imageCapture
imageCapture = ImageCapture.Builder()
.setCaptureMode(ImageCapture.CAPTURE_MODE_MINIMIZE_LATENCY)
//.setTargetAspectRatio(screenAspectRatio)
//.setTargetRotation(binding.previewView.display.rotation)
.build()
然后，在调用cameraProvider.bindToLifecycle()时，进行传入
camera = cameraProvider.bindToLifecycle(
this,CameraSelector.DEFAULT_BACK_CAMERA, preview, imageCapture
)
增加takePicture()方法进行拍照
//进行拍照
private fun takePicture()
imageCapture?.let imageCapture ->
val mainExecutor = ContextCompat.getMainExecutor(this)
imageCapture.takePicture(mainExecutor, object : ImageCapture.OnImageCapturedCallback()
override fun onCaptureSuccess(image: ImageProxy)
super.onCaptureSuccess(image)
override fun onError(exception: ImageCaptureException)
super.onError(exception)
)
// 让画面闪一下，营造拍照的感觉
// We can only change the foreground Drawable using API level 23+ API
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M)
// Display flash animation to indicate that photo was captured
binding.root.postDelayed(
binding.root.foreground = ColorDrawable(Color.WHITE)
binding.root.postDelayed(
binding.root.foreground = null , 50L
)
, 100L)
5.2 拍照并保存到本地存储
我们也可以拍照后，保存到本地存储中
/** Helper function used to create a timestamped file */
private fun createFile(baseFolder: File, format: String, extension: String) =
File(
baseFolder, SimpleDateFormat(format, Locale.US)
.format(System.currentTimeMillis()) + extension
)
/** Use external media if it is available, our app's file directory otherwise */
fun getOutputDirectory(context: Context): File
val appContext = context.applicationContext
val mediaDir = context.externalMediaDirs.firstOrNull()?.let
File(it, appContext.resources.getString(R.string.app_name)).apply mkdirs()
return if (mediaDir != null && mediaDir.exists())
mediaDir else appContext.filesDir
companion object
private const val FILENAME = "yyyy-MM-dd-HH-mm-ss-SSS"
private const val PHOTO_EXTENSION = ".jpg"
//进行拍照并保存到本地
private fun takePictureSaveToDisk()
imageCapture?.let imageCapture ->
// Create output file to hold the image
val photoFile = createFile(getOutputDirectory(this), FILENAME, PHOTO_EXTENSION)
Log.i(TAG, "photoFile:$photoFile")
// Setup image capture metadata
val metadata = ImageCapture.Metadata().apply
// Mirror image when using the front camera
isReversedHorizontal = lensFacing == CameraSelector.LENS_FACING_FRONT
// Create output options object which contains file + metadata
val outputOptions = ImageCapture.OutputFileOptions.Builder(photoFile)
.setMetadata(metadata)
.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 = output.savedUri ?: Uri.fromFile(photoFile)
Log.d(TAG, "Photo capture succeeded: $savedUri")
// Implicit broadcasts will be ignored for devices running API level >= 24
// so if you only target API level 24+ you can remove this statement
if (Build.VERSION.SDK_INT < Build.VERSION_CODES.N)
application.sendBroadcast(
Intent(android.hardware.Camera.ACTION_NEW_PICTURE, savedUri)
)
// If the folder selected is an external media directory, this is
// unnecessary but otherwise other apps will not be able to access our
// images unless we scan them using [MediaScannerConnection]
val mimeType = MimeTypeMap.getSingleton()
.getMimeTypeFromExtension(savedUri.toFile().extension)
MediaScannerConnection.scanFile(
application,
arrayOf(savedUri.toFile().absolutePath),
arrayOf(mimeType)
) _, uri ->
Log.d(TAG, "Image capture scanned into media store: $uri")
)
// 让画面闪一下，营造拍照的感觉
// We can only change the foreground Drawable using API level 23+ API
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M)
// Display flash animation to indicate that photo was captured
binding.root.postDelayed(
binding.root.foreground = ColorDrawable(Color.WHITE)
binding.root.postDelayed(
binding.root.foreground = null , 50L
)
, 100L)
然后，我们可以在相册里找到这张图片了，图片的真实位置位于/storage/emulated/0/Android/media/你的包名/项目名/中。
6. 视频录制 : VideoCapture.java
视频录制用的是VideoCapture
videoCapture = VideoCapture.Builder()
//.setTargetRotation(previewView.getDisplay().getRotation())
.setVideoFrameRate(25)
.setBitRate(3 * 1024 * 1024)
.build()
在调用cameraProvider.bindToLifecycle()时，进行传入。
camera = cameraProvider.bindToLifecycle(
this,CameraSelector.DEFAULT_BACK_CAMERA, preview, videoCapture
)
需要注意的是，videoCapture无法和imageAnalysis、imageCapture一起使用。
如果同一个页面中这几个功能融合在一起，则需要通过标志位来进行判断。
if (isVideo)
mCamera = cameraProvider.bindToLifecycle(this, cameraSelector,
preview, videoCapture);
else
mCamera = cameraProvider.bindToLifecycle(this, cameraSelector,
preview, imageCapture, imageAnalysis);
开始录制
private val RECORDED_FILE_NAME = "recorded_video"
private val RECORDED_FILE_NAME_END = "video/mp4"
@SuppressLint("RestrictedApi")
private fun startRecording()
//TODO 这里省略了RECORD_AUDIO、PERMISSION_GRANTED权限的判断
val contentValues = ContentValues()
contentValues.put(
MediaStore.MediaColumns.DISPLAY_NAME,
RECORDED_FILE_NAME + "_" + System.currentTimeMillis()
)
contentValues.put(MediaStore.MediaColumns.MIME_TYPE, RECORDED_FILE_NAME_END)
val outputFileOptions = VideoCapture.OutputFileOptions.Builder(
getContentResolver(),
MediaStore.Video.Media.EXTERNAL_CONTENT_URI, contentValues
).build()
videoCapture.startRecording(
outputFileOptions,
ContextCompat.getMainExecutor(this),
object : VideoCapture.OnVideoSavedCallback
override fun onVideoSaved(outputFileResults: VideoCapture.OutputFileResults)
Log.i(TAG, "视频保存成功:$outputFileResults.savedUri")
override fun onError(
videoCaptureError: Int,
message: String,
cause: Throwable?
)
Log.i(TAG, "当出现异常 cause:$cause")
)
停止视频录制
videoCapture.stopRecording()
当我们执行停止视频录制之后，就可以在相册里看到多了一个录制的视频了。
介绍了CameraX里一些常用的UseCase，我们接下来来看下CameraX中的其他一些功能。
7. 切换前后摄像头
我们之前使用cameraProvider.bindToLifecycle()的时候，有一个参数是CameraSelector。
CameraX默认给我们提供了前置摄像头和后置摄像头的CameraSelector
public final class CameraSelector
@NonNull
public static final CameraSelector DEFAULT_FRONT_CAMERA =
new CameraSelector.Builder().requireLensFacing(LENS_FACING_FRONT).build();
@NonNull
public static final CameraSelector DEFAULT_BACK_CAMERA =
new CameraSelector.Builder().requireLensFacing(LENS_FACING_BACK).build();
//...
我们去切换摄像头的时候，就是重新调用一下bindPreview方法，传入新的cameraSelector值就好了
private fun bindPreview(
cameraProvider: ProcessCameraProvider,
previewView: PreviewView,
cameraSelector : CameraSelector
)
// 解除所有绑定，防止CameraProvider重复绑定到Lifecycle发生异常
cameraProvider.unbindAll()
preview = Preview.Builder().build()
camera = cameraProvider.bindToLifecycle(
this,
cameraSelector, preview
)
preview?.setSurfaceProvider(previewView.surfaceProvider)
CameraX还为我们提供了判断前置/后置摄像头是否存在的方法
/** Returns true if the device has an available back camera. False otherwise */
private fun hasBackCamera(): Boolean
return cameraProvider?.hasCamera(CameraSelector.DEFAULT_BACK_CAMERAAndroid CameraX使用，预览拍照获取静态图像