最近在开发个Android应用，本来是想通过CameraX实现同时预览多个摄像头，通过官网文档介绍，在CameraX 1.3 后通过ConcurrentCamera运行多个摄像头，但实际在小米10（Android 13）运行,报错当前设备不支持ConcurrentCamera,代码CameraProvider.availableConcurrentCameraInfos查询也是返回数量0，表示设备不支持。

请教ChatGPT回答，来进行编写，回答可以通过代码创建多个preview和requireLensFacing,但是实际运行时不可行的。程序会报下面代码问题，选择摄像头设备异常。

val cameraSelector =builder
    .requireLensFacing(CameraSelector.LENS_FACING_BACK)
    .requireLensFacing(CameraSelector.LENS_FACING_FRONT)
    .build()

因此个人下定义是在cameraX 1.3.0-alpha07前应该是不支持预览多摄像头的。如果有小伙伴验证OK，希望可以告知，多谢。

故采用Camera2来实现多摄像头同时预览。

Camera2 同时预览摄像头
记得先申请权限,以及动态申请！！

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

记得先申请权限,以及动态申请！！
1、判断设备是否支持摄像头

fun isSupportCamera(): Boolean {
    // 堆代码 duidaima.com
    initCameraManager()
    return cameraManager!!.cameraIdList.isNotEmpty()
}

initCameraManager主要是初始化CameraManager对象cameraManager。我们通过cameraIdList列表是否空来判断是否有摄像头。

private fun initCameraManager() {
    if (cameraManager == null) {
        cameraManager = getApplication<Application>().getSystemService(AppCompatActivity.CAMERA_SERVICE) as CameraManager
    }
}

2、获取摄像头列表
我们遍历第1步获取到的摄像头ID列表，然后通过getCameraCharacteristics查询该摄像头相关的数据，封装到NCameraInfo对象中。这里我们只查询几个简单的信息。

fun getCameraListInfo() {
    
    initCameraManager()
    
    if (cameraManager.cameraIdList.isNotEmpty()) {
        for (cameraId in cameraManager.cameraIdList) {
            val cameInfo = NCameraInfo()
            val characteristics = cameraManager.getCameraCharacteristics(cameraId)
            val facing = characteristics.get(CameraCharacteristics.LENS_FACING)

            cameInfo.id = cameraId
            cameInfo.face ="${ getFaceStr(facing)},CameraId:${cameraId}"
            cameraMap[cameraId] = cameInfo
        }
        cameraInfo.value = cameraMap.values.toList()
    }
}

3、打开摄像头
打开摄像头非常简单，只需要调用openCamera函数即可，主要是stateCallback函数的实现。其中handler，是用来切换到主线程var handler = Handler(Looper.getMainLooper())。

fun openCamera(cameraId: String) {
    initCameraManager()
    cameraManager?.openCamera(cameraId, stateCallback, handler)
}

我们一起看看stateCallback函数的实现。也就是当我们打开摄像头，摄像头相关状态会通过下面三个函数进行回调，因为这里采用ViewModel方式，所以会多一份回调到Activity。不用着急，最后有完整代码。

 private val stateCallback=object : StateCallback() {
        // 堆代码 duidaima.com
        override fun onOpened(camera: CameraDevice) {
            cameraMap[camera.id]?.apply {
                cameraDevice = camera
                state = 1
                cameraCallback?.onCameraOpen(this)
            }

        }

        override fun onDisconnected(camera: CameraDevice) {
            cameraMap[camera.id]?.apply {
                cameraDevice = camera
                state = 0
                cameraCallback?.onCameraClose(this)
            }
        }

        override fun onError(camera: CameraDevice, error: Int) {
            Log.e(TAG, "camera ${camera.id} error code:${error}")
            cameraMap[camera.id]?.apply {
                cameraDevice = camera
                state = 3
                cameraCallback?.onCameraError(this,error)
            }
        }
    }

我们查看Activity中的实现。onCameraOpen函数主要动态创建TextureView对象，添加到界面中，用于预览摄像头内容。

  override fun onCameraOpen(camera: NCameraInfo) {
        adapter.notifyItemChanged(adapter.items.indexOf(camera))
        
        //创建TextureView
        val textureView = TextureView(this)
        textureView.id = View.generateViewId()
        camera.previewId=textureView.id
        val layoutParams = LinearLayout.LayoutParams(previewWidth, LayoutParams.MATCH_PARENT)
        viewBinding.llCameraPreview.addView(textureView, layoutParams)

//textureview 与摄像头绑定
        textureView.surfaceTextureListener=object:SurfaceTextureListener{
            override fun onSurfaceTextureAvailable(surface: SurfaceTexture, width: Int, height: Int) {
               //创建Surface并用于摄像头渲染
               val surface = Surface(textureView.surfaceTexture)
               val builder = camera.cameraDevice?.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW)!!
               builder.addTarget(surface)
                
                camera.cameraDevice?.createCaptureSession(listOf(surface), object : StateCallback() {
                    override fun onConfigured(session: CameraCaptureSession) {
                        session.setRepeatingRequest(builder.build(),null,model.handler)
                    }

                    override fun onConfigureFailed(session: CameraCaptureSession) {

                    }
                }, model.handler)
            }

            override fun onSurfaceTextureSizeChanged(surface: SurfaceTexture, width: Int, height: Int) {
                Log.d(TAG,"onSurfaceTextureSizeChanged")
            }

            override fun onSurfaceTextureDestroyed(surface: SurfaceTexture): Boolean {
                Log.d(TAG,"onSurfaceTextureDestroyed")
                return true
            }

            override fun onSurfaceTextureUpdated(surface: SurfaceTexture) {
                //Log.d(TAG,"onSurfaceTextureUpdated")
            }
        }


    }

    override fun onCameraClose(camera: NCameraInfo) {
        Log.d(TAG,"onCameraClose:${camera}")
        adapter.notifyItemChanged(adapter.items.indexOf(camera))
        camera.cameraDevice?.close()
        val view=viewBinding.llCameraPreview.findViewById<TextureView>(camera.previewId)
        viewBinding.llCameraPreview.removeView(view)
    }

    override fun onCameraError(camera: NCameraInfo, error: Int) {
        Log.e(TAG,"onCameraError:${camera}，${error}")
        adapter.notifyItemChanged(adapter.items.indexOf(camera))
        camera.cameraDevice?.close()
    }

4、效果

5、小坑
.实测在小米10手机，先开启后摄，再开启前摄，前摄无法打开=》异常。先开前摄，再开后摄正常。
.小米11、诺基亚x7实测正常。