Camera2使用

Camera2使用

添加布局

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/cameraFragment"
    tools:context=".CameraFragment">

    <SurfaceView
        android:id="@+id/surfaceView"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>

    <ImageButton
        android:id="@+id/capture"
        android:layout_gravity="bottom|center"
        android:layout_width="80dp"
        android:layout_height="80dp"
        android:scaleType="fitCenter"
        android:background="@drawable/ic_shutter"/>
FrameLayout>

声明权限

<uses-permission android:name="android.permission.CAMERA" />
<uses-permission android:name="android.permission.RECORD_AUDIO" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

整体流程

// 打开摄像头
cameraDevice = openCamera()

// 创建session
captureSession = createCaptureSession()

// 下发预览
captureSession.setRepeatingRequest(previewRequest, null, cameraHandler)

// 点击下发录像
fragmentCameraBinding.capture.setOnTouchListener {
    view, event -> run {
    when (event.action) {
        MotionEvent.ACTION_DOWN -> lifecycleScope.launch(Dispatchers.IO) {
          	// 下发录像
            captureSession.setRepeatingRequest(recordRequest, null, cameraHandler)

            // 启动MediaRecorder
            recorder.apply {
                prepare()
                start()
            }

            recordingStartMillis = System.currentTimeMillis()
            Log.d(TAG, "Recording started")
        }

        MotionEvent.ACTION_UP -> lifecycleScope.launch(Dispatchers.IO) {
            Log.d(TAG, "Recording stopped. Output file: $outputFile")
            recorder.stop()
        }
        else -> {}
    }
}

Camera2拍照录像的整体流程，一般分为3个步骤：

• 打开摄像头：根据硬件能力，选择对应的cameraId，并获得CameraDevice对象作为Camera管理实例
• 创建CaptureSession：手机与摄像头的数据交互需要通过CameraDevice实例创建一个会话（session），通过会话中的管道（pipe）来进行传输
• 下发指令：通过CaptureSession实例下发的CaptureRequest的类型和参数，可以进行预览、拍照和录像等操作

由于Camera2各个步骤都是通过回调来完成，为了流程更直观清晰，这里使用Kotlin的协程（Coroutine）来执行各个步骤的调用

打开摄像头

• 初始化相机处理的线程

  private val cameraThread = HandlerThread("CameraThread").apply { start() }
  
  private val cameraHandler = Handler(cameraThread.looper)
  

• 获取CameraManager并获取cameraId

  // camera管理实例
  private val cameraManager: CameraManager by lazy {
      var context = requireContext().applicationContext
      context.getSystemService(Context.CAMERA_SERVICE) as CameraManager
  }
  
  // 默认获取后置摄像头
  private val cameraId: String by lazy {
      cameraManager.cameraIdList[0]
  }
  

• 打开摄像头

  @SuppressLint("MissingPermission")
  private suspend fun openCamera(): CameraDevice =
      suspendCancellableCoroutine { cont ->
          cameraManager.openCamera(cameraId, object: CameraDevice.StateCallback() {
              override fun onOpened(camera: CameraDevice) {
                  cont.resume(camera)
              }
  
              override fun onDisconnected(camera: CameraDevice) {
                  Log.w(TAG, "Camera disconnected.")
              }
  
              override fun onError(camera: CameraDevice, error: Int) {
                  val msg = when(error) {
                      ERROR_CAMERA_DEVICE -> "Fatal (device)"
                      ERROR_CAMERA_DISABLED -> "Device policy"
                      ERROR_CAMERA_IN_USE -> "Camera in use"
                      ERROR_CAMERA_SERVICE -> "Fatal (service)"
                      ERROR_MAX_CAMERAS_IN_USE -> "Maximum cameras in use"
                      else -> "Unknown"
                  }
  
                  val exception = RuntimeException("Camera error: $error $msg")
                  Log.e(TAG, exception.message, exception)
                  if (cont.isActive) cont.resumeWithException(exception)
              }
  
          }, cameraHandler)
      }
  

  打开Camera会通过几个回调来返回Camera的状态：

  • onOpend()：表示Camera已正常打开，可以执行后面的流程
  • onDisconnected：表示Camera已断开，一般发生在不同应用间的Camera资源抢占
  • onError：表示打开Camera过程中出现异常，可以根据不同的异常类型做相应处理

创建Session

private suspend fun createCaptureSession(): CameraCaptureSession =
    suspendCoroutine { cont ->
        val targets = listOf(fragmentCameraBinding.surfaceView.holder.surface,
            recorderSurface) as MutableList<Surface>
        cameraDevice.createCaptureSession(targets, object:
            CameraCaptureSession.StateCallback() {
            override fun onConfigured(session: CameraCaptureSession) {
                cont.resume(session)
            }

            override fun onConfigureFailed(session: CameraCaptureSession) {
                val exception = RuntimeException("Camera ${cameraDevice.id} session configuration failed")
                Log.e(TAG, exception.message, exception)
                cont.resumeWithException(exception)
            }

        }, cameraHandler)
    }

通过openCamera获得的CameraDevice实例执行创建Session流程，这里需要添加整个流程中需要使用到的全部Surface，同样也是通过回调来返回执行结果：

• onConfigured: 表示创建Session成功，可以继续执行后续操作
• onConfigureFailed： 表示创建Session失败

下发指令

• 初始化CaptureRequest

  private val previewRequest: CaptureRequest by lazy {
      // Capture request holds references to target surfaces
      captureSession.device.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW).apply {
          // Add the preview surface target
          addTarget(fragmentCameraBinding.surfaceView.holder.surface)
      }.build()
  }
  
  private val recordRequest: CaptureRequest by lazy {
      // Capture request holds references to target surfaces
      captureSession.device.createCaptureRequest(CameraDevice.TEMPLATE_RECORD).apply {
          addTarget(fragmentCameraBinding.surfaceView.holder.surface)
          addTarget(recorderSurface)
      }.build()
  }
  

  根据不同模板和target分别创建出预览的previewRequest和录像的recordRequest，target也就是单个流程中需要用于承载Camera数据的Surface，模板类型有预览的CameraDevice.TEMPLATE_PREVIEW, 拍照的CameraDevice.TEMPLATE_STILL_CAPTURE和录像的CameraDevice.TEMPLATE_RECORD等

• 下发指令

  // 下发预览
  captureSession.setRepeatingRequest(previewRequest, null, cameraHandler)
  
  // 下发录像
  captureSession.setRepeatingRequest(recordRequest, null, cameraHandler)