Camera2拍照kotlin

Camera2 API 是Android 6.0 (API level 23) 引入的一个用于拍照和录像的强大工具，它提供了更灵活、高效和低级别的控制，相比之前的Camera API。在 Kotlin 中使用 Camera2，你可以更好地控制相机的各种设置和流。

以下是使用 Camera2 在 Kotlin 中进行拍照的基本步骤：

1. **初始化CameraManager**:

   val cameraManager = getSystemService(Context.CAMERA_SERVICE) as CameraManager

2. **获取相机列表**:

   val cameraIds = cameraManager.cameraIdList

3. **请求权限**:

   val permissions = arrayOf(Manifest.permission.CAMERA)
   if (!ContextCompat.checkSelfPermission(this, permissions) == PackageManager.PERMISSION_GRANTED) {
       // 请求权限
   }

4. **打开相机并选择后置或前置摄像头**:

   val cameraId = cameraIds.firstOrNull { cameraManager.isCameraPresent(it) } ?: throw RuntimeException("No camera found")
   val camera = cameraManager.openCamera(cameraId, CameraDevice.StateCallback(), null)

5. **创建CaptureSession并配置相机参数**:

   val surfaceHolder: SurfaceHolder = ... // 获取SurfaceView的SurfaceHolder
   val previewRequestBuilder = camera.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW)
   previewRequestBuilder.addTarget(surfaceHolder.surface)
   camera.createCaptureSession(List.of(surfaceHolder), object : CameraCaptureSession.StateCallback() {
       ...
   }, null)

6. **启动预览并准备拍照**:

   cameraManager.createCameraCaptureSession(cameraId, object : CameraCaptureSession.StateCallback() {
       override fun onConfigured(session: CameraCaptureSession) {
           val preview = session.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW)
           session.setRepeatingRequest(preview, null, null)
           // 添加拍照请求
           val photoRequestBuilder = session.createCaptureRequest(CameraDevice.TEMPLATE_STILL_CAPTURE)
           photoRequestBuilder.addTarget(surfaceHolder.surface)
           takePicture(session, photoRequestBuilder)
       }
   }, null)

7. **处理拍照请求**:

   private fun takePicture(session: CameraCaptureSession, photoRequestBuilder: CaptureRequest.Builder) {
       photoRequestBuilder.addTarget(surfaceHolder.surface)
       session.capture(photoRequestBuilder.build(), object : CaptureCallback() {
           @Throws(InterruptedException::class)
           override fun onCaptureCompleted(captureSession: CameraCaptureSession, request: CaptureRequest, result: TotalCaptureResult) {
               // 处理图片，关闭相机等
           }
       }, null)
   }

8. **释放资源**:

   session.close()
   camera.close()