Camera2 预览练习

本文是阅读大神的文章https://www.jianshu.com/p/df3c8683bb90做的总结, 要学习Camera2请到原文中阅读

预览的步骤

完整相机预览需要以下几步

• 获取CameraId
• 创建用于显示预览图像的Surface
• openCamera
• 创建Session
• 创建Request

获取所有的CameraId

当然要首先获取到CameraId

private val cameraManager by lazy {
    
    
    getSystemService(CameraManager::class.java) as CameraManager
}

获取到所有的CameraId

val cameraIdList = cameraManager.cameraIdList
logcat("cameraList:${
      
      GsonManager.instance.toJson(cameraIdList)}")
for (id in cameraIdList) {
    
    
    val character = cameraManager.getCameraCharacteristics(id)
    if (character[CameraCharacteristics.LENS_FACING] == CameraCharacteristics.LENS_FACING_FRONT) {
    
    
        logcat("is font:$id")
        mFortCameraId = id
        mFortCharacter = character
    } else if (character[CameraCharacteristics.LENS_FACING] == CameraCharacteristics.LENS_FACING_BACK) {
    
    
        logcat("is back:$id")
        if (id == "0") {
    
    
            mBackCameraId = id
            mBackCharacter = character
        }
    }
}

这里我们强行给了一个id为0的id. 因为我发现摄像头背后一共有4个Camera. 他们的区别我们先不深究

创建Surface

这里我们使用TextureView. 在onCreate中调用

 private fun loadPreview() {
    
    
        binding.cameraPreview.surfaceTextureListener = object : TextureView.SurfaceTextureListener {
    
    
            override fun onSurfaceTextureAvailable(
                surface: SurfaceTexture?,
                width: Int,
                height: Int
            ) {
    
    ```````````
                if (surface == null) return
                logcat("onSurfaceTextureAvailable")
                val previewSize = getOptimalSize(
                    mBackCharacter,
                    resources.displayMetrics.heightPixels,
                    resources.displayMetrics.widthPixels
                ) ?: return
                logcat("cameraPreview:${
      
      previewSize.width} ${
      
      previewSize.height}")
                surface.setDefaultBufferSize(previewSize.width, previewSize.height)
                val lp = binding.cameraPreview.layoutParams
                lp.width = previewSize.height
                lp.height = previewSize.width
                binding.cameraPreview.layoutParams = lp
                mPreviewSurface = Surface(surface)
            }

            override fun onSurfaceTextureSizeChanged(
                surface: SurfaceTexture?,
                width: Int,
                height: Int
            ) {
    
    
                logcat("onSurfaceTextureSizeChanged")
            }

            override fun onSurfaceTextureDestroyed(surface: SurfaceTexture?): Boolean {
    
    
                logcat("onSurfaceTextureDestroyed")
                return true
            }

            override fun onSurfaceTextureUpdated(surface: SurfaceTexture?) {
    
    
//                logcat("onSurfaceTextureUpdated")
            }
        }
    }

openCamera

我们在onResume中进行openCamera的操作

cameraManager.openCamera(mBackCameraId, object : CameraDevice.StateCallback() {
    
    
           override fun onOpened(camera: CameraDevice) {
    
    
               logcat("onOpened")
               mCameraDevice = camera
               //打开Camera成功之后, 我们进行createSession的操作
               mCameraDevice?.createCaptureSession(listOf(mPreviewSurface), mSessionStateCallback, mHandler)
           }

           override fun onDisconnected(camera: CameraDevice) {
    
    
               logcat("onDisconnected")
               camera.close()
           }

           override fun onClosed(camera: CameraDevice) {
    
    
               super.onClosed(camera)
               logcat("onClosed")
               mCameraDevice = null
           }

           override fun onError(camera: CameraDevice, error: Int) {
    
    
               logcat("onError")
               camera.close()
           }
       }, mHandler)

创建Session

如上文, 我们在openCamera成功之后, 进行创建session的操作

mCameraDevice?.createCaptureSession(listOf(mPreviewSurface), mSessionStateCallback, mHandler)

创建Request

session创建成功之后, 我们在回调成功的时候, 发起capture request

private var mSessionStateCallback = object : CameraCaptureSession.StateCallback() {
    
    
    override fun onConfigured(session: CameraCaptureSession) {
    
    
        logcat("onSession coufigured")
    }

    override fun onConfigureFailed(session: CameraCaptureSession) {
    
    
        logcat("onSession failed")
    }

    override fun onClosed(session: CameraCaptureSession) {
    
    
        super.onClosed(session)
        logcat("onSession closed")
    }

    override fun onReady(session: CameraCaptureSession) {
    
    
        super.onReady(session)
        logcat("onReady")
        mSession = session
        val camera = mCameraDevice ?: return

        val requestBuilder = camera.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW)
        requestBuilder.addTarget(mPreviewSurface)
        val request = requestBuilder.build()
        mSession.setRepeatingRequest(
            request, object : CameraCaptureSession.CaptureCallback() {
    
    
                override fun onCaptureStarted(session: CameraCaptureSession, request: CaptureRequest, timestamp: Long, frameNumber: Long) {
    
    
//                        logcat("onCaptureStarted")
                }

                override fun onCaptureProgressed(session: CameraCaptureSession, request: CaptureRequest, partialResult: CaptureResult) {
    
    
//                        logcat("onCaptureProgressed")
                }

                override fun onCaptureCompleted(session: CameraCaptureSession, request: CaptureRequest, result: TotalCaptureResult) {
    
    
//                        logcat("onCapturecompleted")
                }
            }, mHandler
        )
    }
}

至此, 可以完成预览了