试手一下CameraX（APP）

原创已于 2024-06-17 01:27:04 修改 · 488 阅读

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于 2024-03-03 22:22:28 首次发布

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本文介绍了如何在Android项目中集成Camerax库，包括添加依赖、配置环境、设置权限，以及使用CameraX进行图像预览、拍照和录像的基本步骤。作者强调了Camerax对应用层面的影响以及权限管理的重要性。

书接上回。

首先还是看谷歌的官方文档：

https://developer.android.com/media/camera/camerax?hl=zh-cn

https://developer.android.com/codelabs/camerax-getting-started?hl=zh-cn#1

注：这里大部分内容也来自谷歌文档。

官方文档用的是Kotlin，和Java也大差不差。看看流程就好。

API 级别设置为 21。

我觉得其实从App这个层面，用camera1，camera2还是camerax其实都并不重要，很多重大的改变对app层应该都是不可见的。为什么还要折腾上层呢？这个就要问谷歌的设计师了。。。

1 环境配置

在Gardle中增加依赖，我理解就是增加底层库，这几个应该就是camerax所使用的Framework的so，下面应该是AIDL调用的HAL。这个部分和底层驱动关系就很大了，后面还会单独写一篇。

dependencies {
  def camerax_version = "1.1.0-beta01"
  implementation "androidx.camera:camera-core:${camerax_version}"
  implementation "androidx.camera:camera-camera2:${camerax_version}"
  implementation "androidx.camera:camera-lifecycle:${camerax_version}"
  implementation "androidx.camera:camera-video:${camerax_version}"

  implementation "androidx.camera:camera-view:${camerax_version}"
  implementation "androidx.camera:camera-extensions:${camerax_version}"
}

同时要增加Java8和viewBinding的支持。

    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }

    buildFeatures {
        viewBinding true
    }

在Layout的activity_main.xml中使用PreviewView。这个应该是camerax的控件。

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

增加两个按键，分别是takephoto和capturevideo，并增加按键事件。

       // Set up the listeners for take photo and video capture buttons
       viewBinding.imageCaptureButton.setOnClickListener { takePhoto() }
       viewBinding.videoCaptureButton.setOnClickListener { captureVideo() }

在AndroidManifest.xml中增加权限。

<uses-feature android:name="android.hardware.camera.any" />
<uses-permission android:name="android.permission.CAMERA" />
<uses-permission android:name="android.permission.RECORD_AUDIO" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"
   android:maxSdkVersion="28" />

在运行时会让你授权。

刚开始运行时，要检查权限。

override fun onRequestPermissionsResult(
   requestCode: Int, permissions: Array<String>, grantResults:
   IntArray) {
   if (requestCode == REQUEST_CODE_PERMISSIONS) {
       if (allPermissionsGranted()) {
           startCamera()
       } else {
           Toast.makeText(this,
               "Permissions not granted by the user.",
               Toast.LENGTH_SHORT).show()
           finish()
       }
   }
}

2 CameraX调用代码

主要用到的的几个包：

import androidx.camera.core.ImageCapture
import androidx.camera.video.Recorder
import androidx.camera.video.Recording
import androidx.camera.video.VideoCapture

2.1 提供图像预览：

大体的流程就是首先取得surface，然后使用cameraProvider.bindToLifecycle，将surface作为参数传进去。

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

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

       // Preview
       val preview = Preview.Builder()
          .build()
          .also {
              it.setSurfaceProvider(viewBinding.viewFinder.surfaceProvider)
          }

       // Select back camera as a default
       val cameraSelector = CameraSelector.DEFAULT_BACK_CAMERA

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

           // Bind use cases to camera
           cameraProvider.bindToLifecycle(
               this, cameraSelector, preview)

       } catch(exc: Exception) {
           Log.e(TAG, "Use case binding failed", exc)
       }

   }, ContextCompat.getMainExecutor(this))
}

2.2 拍照：

可以看到，基本上就是围绕着imageCapture.takePicture这个方法。name，contentValues，outputOptions都是作为参数传进去。

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

   // Create time stamped name and MediaStore entry.
   val name = SimpleDateFormat(FILENAME_FORMAT, Locale.US)
              .format(System.currentTimeMillis())
   val contentValues = ContentValues().apply {
       put(MediaStore.MediaColumns.DISPLAY_NAME, name)
       put(MediaStore.MediaColumns.MIME_TYPE, "image/jpeg")
       if(Build.VERSION.SDK_INT > Build.VERSION_CODES.P) {
           put(MediaStore.Images.Media.RELATIVE_PATH, "Pictures/CameraX-Image")
       }
   }

   // Create output options object which contains file + metadata
   val outputOptions = ImageCapture.OutputFileOptions
           .Builder(contentResolver,
                    MediaStore.Images.Media.EXTERNAL_CONTENT_URI,
                    contentValues)
           .build()

   // Set up 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 msg = "Photo capture succeeded: ${output.savedUri}"
               Toast.makeText(baseContext, msg, Toast.LENGTH_SHORT).show()
               Log.d(TAG, msg)
           }
       }
   )
}

2.3 拍视频：

基本就是围绕着videoCapture.output。name，contentValues，mediaStoreOutputOptions都是作为参数使用。在output中，好像是使用了lambda函数，弄了一些内置行为。

// Implements VideoCapture use case, including start and stop capturing.
private fun captureVideo() {
   val videoCapture = this.videoCapture ?: return

   viewBinding.videoCaptureButton.isEnabled = false

   val curRecording = recording
   if (curRecording != null) {
       // Stop the current recording session.
       curRecording.stop()
       recording = null
       return
   }

   // create and start a new recording session
   val name = SimpleDateFormat(FILENAME_FORMAT, Locale.US)
              .format(System.currentTimeMillis())
   val contentValues = ContentValues().apply {
       put(MediaStore.MediaColumns.DISPLAY_NAME, name)
       put(MediaStore.MediaColumns.MIME_TYPE, "video/mp4")
       if (Build.VERSION.SDK_INT > Build.VERSION_CODES.P) {
           put(MediaStore.Video.Media.RELATIVE_PATH, "Movies/CameraX-Video")
       }
   }

   val mediaStoreOutputOptions = MediaStoreOutputOptions
       .Builder(contentResolver, MediaStore.Video.Media.EXTERNAL_CONTENT_URI)
       .setContentValues(contentValues)
       .build()
   recording = videoCapture.output
       .prepareRecording(this, mediaStoreOutputOptions)
       .apply {
           if (PermissionChecker.checkSelfPermission(this@MainActivity,
                   Manifest.permission.RECORD_AUDIO) ==
               PermissionChecker.PERMISSION_GRANTED)
           {
               withAudioEnabled()
           }
       }
       .start(ContextCompat.getMainExecutor(this)) { recordEvent ->
           when(recordEvent) {
               is VideoRecordEvent.Start -> {
                   viewBinding.videoCaptureButton.apply {
                       text = getString(R.string.stop_capture)
                       isEnabled = true
                   }
               }
               is VideoRecordEvent.Finalize -> {
                   if (!recordEvent.hasError()) {
                       val msg = "Video capture succeeded: " +
                           "${recordEvent.outputResults.outputUri}"
                       Toast.makeText(baseContext, msg, Toast.LENGTH_SHORT)
                            .show()
                       Log.d(TAG, msg)
                   } else {
                       recording?.close()
                       recording = null
                       Log.e(TAG, "Video capture ends with error: " +
                           "${recordEvent.error}")
                   }
                   viewBinding.videoCaptureButton.apply {
                       text = getString(R.string.start_capture)
                       isEnabled = true
                   }
               }
           }
       }
}

好了，就到这了。先概要看看就行了。