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_CAMERA) ?: false
}
/** Returns true if the device has an available front camera. False otherwise */
private fun hasFrontCamera(): Boolean {
return cameraProvider?.hasCamera(CameraSelector.DEFAULT_FRONT_CAMERA) ?: false
}
看下效果
8. 对焦
当点击androidx.camera.view.PreviewView的时候，去调用CameraX的对焦方法startFocusAndMetering()就好了。
在onCreate()中添加如下代码
binding.previewView.setOnTouchListener {
view, event ->
val action = FocusMeteringAction.Builder(
binding.previewView.getMeteringPointFactory()
.createPoint(event.getX(), event.getY())
).build();
showTapView(event.x.toInt(), event.y.toInt())
camera?.getCameraControl()?.startFocusAndMetering(action)
true
}
增加showTapView()
private fun showTapView(x: Int, y: Int) {
val popupWindow = PopupWindow(
ViewGroup.LayoutParams.WRAP_CONTENT,
ViewGroup.LayoutParams.WRAP_CONTENT
)
val imageView = ImageView(this)
imageView.setImageResource(R.drawable.ic_focus_view)
popupWindow.contentView = imageView
popupWindow.showAsDropDown(binding.previewView, x, y)
binding.previewView.postDelayed({
popupWindow.dismiss() }, 600)
binding.previewView.playSoundEffect(SoundEffectConstants.CLICK)
}
看下效果
9. 缩放
通过GestureDetector监听缩放事件，然后在回调的时候进行执行如下代码，就可以使用双指放大缩小图像
override fun zoom(delta: Float) {
val zoomState = camera?.cameraInfo?.zoomState
zoomState?.value?.let {
val currentZoomRatio = it.zoomRatio
camera?.cameraControl?.setZoomRatio(currentZoomRatio * delta)
}
}
缩放操作具体详见这篇文章 Android使用CameraX实现相机快速实现放大缩小
10. 本文Demo下载
本文的源码Demo详见 : Android CameraX Demo : 实现预览/拍照/录制视频/图片分析/对焦/切换摄像头等操作
推荐阅读 我的另一篇关于Camera的文章 : Android 从零开发一个简易的相机App