var camera: Camera? = null
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        //为surfaceholder添加监听
        surface.holder.addCallback(object : SurfaceHolder.Callback{
            override fun surfaceChanged(p0: SurfaceHolder?, p1: Int, p2: Int, p3: Int) {
            }
            override fun surfaceDestroyed(p0: SurfaceHolder?) {
            }
            override fun surfaceCreated(p0: SurfaceHolder?) {
                //当surface创建完成初始化相机
                initCamera1()
            }
        })
        take.setOnClickListener {
            //拍照
            takePicture1()
        }
    }
    fun initCamera1(){
        //打开相机，开启预览
        camera = Camera.open()
        camera?.setPreviewDisplay(surface.holder)
        camera?.startPreview()
    }
    fun takePicture1(){
        //拍照，通过回调获取图片数据
        camera?.takePicture({},
                {bytes, camera ->
                    if(bytes == null){
                        return@takePicture
                    }
                    var b = BitmapFactory.decodeByteArray(bytes, 0, bytes.size)
                    imageView.setImageBitmap(b)
                },
                {bytes, camera ->
                    if(bytes == null){
                        return@takePicture
                    }
                    var b = BitmapFactory.decodeByteArray(bytes, 0, bytes.size)
                    imageView2.setImageBitmap(b)
                })
    }
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var mCameraDevice : CameraDevice? = null
    var mCameraCaptureSession : CameraCaptureSession? = null
    var childHandler : Handler? = null
    @SuppressLint("NewApi")
    var imageReader : ImageReader? = null
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        //为surfaceholder添加监听
        surface.holder.addCallback(object : SurfaceHolder.Callback{
            override fun surfaceChanged(p0: SurfaceHolder?, p1: Int, p2: Int, p3: Int) {
            }
            override fun surfaceDestroyed(p0: SurfaceHolder?) {
            }
            override fun surfaceCreated(p0: SurfaceHolder?) {
                //当surface创建完成初始化相机
                initCamera2()
            }
        })
        take.setOnClickListener {
            //拍照
            takePicture2()
        }
    }
    fun initCamera2(){
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
            //因为处理图片比较耗时，所以这里新建一个线程的handler来处理
            var handlerThread = HandlerThread("camera")
            handlerThread.start()
            childHandler = Handler(handlerThread.looper)
            //创建一个ImageReader，后面会通过这个获取拍照的图片
            imageReader = ImageReader.newInstance(500, 500, ImageFormat.JPEG,2)
            //为ImageReader添加回调，这里使用我们新建的线程的handler处理图片
            imageReader?.setOnImageAvailableListener(object : ImageReader.OnImageAvailableListener{
                override fun onImageAvailable(imageReader: ImageReader) {
                    //得到图片后，关闭相机，从ImageReader中获取图片数据
                    mCameraDevice?.close()
                    var image = imageReader.acquireNextImage()
                    var buffer = image.planes[0].buffer
                    var bytes = ByteArray(buffer.remaining())
                    buffer.get(bytes)
                    var bitmap = BitmapFactory.decodeByteArray(bytes, 0, bytes.size)
                    //由于这部分是在子线程中处理的，所以对ui操作要放到主线程中
                    runOnUiThread {
                        imageView.setImageBitmap(bitmap)
                    }
                }
            }, childHandler)
            //通过CameraManager打开相机，注意这里的handler是主线程的。
            var cameraManager = getSystemService(Context.CAMERA_SERVICE) as CameraManager
            cameraManager.openCamera(CameraCharacteristics.LENS_FACING_FRONT.toString(), object : CameraDevice.StateCallback() {
                override fun onOpened(cameraDevice: CameraDevice) {
                    //相机打开后，得到CameraDevice并开启预览
                    mCameraDevice = cameraDevice
                    camera2Preview()
                }
                override fun onDisconnected(p0: CameraDevice) {
                }
                override fun onError(p0: CameraDevice, p1: Int) {
                }
            }, Handler(Looper.getMainLooper()))
        }
    }
    fun camera2Preview(){
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
            mCameraDevice?.let {
                //新建一个PRIVIEW的CaptureRequest，将surface添加进去
                var builder = it.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW)
                builder.addTarget(surface.holder.surface)
                //通过CameraDevice新建一个CaptureSession事务，在回调中开启预览
                it.createCaptureSession(Arrays.asList(surface.holder.surface, imageReader?.surface), object : CameraCaptureSession.StateCallback() {
                    override fun onConfigureFailed(p0: CameraCaptureSession) {
                    }
                    override fun onConfigured(cameraCaptureSession: CameraCaptureSession) {
                        //获得对应的CaptureSession事务，并设置预览的request开始预览
                        mCameraCaptureSession = cameraCaptureSession
                        var previewRequest = builder.build()
                        mCameraCaptureSession?.setRepeatingRequest(previewRequest, null ,childHandler)
                    }
                }, childHandler)
            }
        }
    }
    //拍照
    fun takePicture2(){
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
            mCameraDevice?.let {
                //新建一个拍照请求，并添加之前创建的ImageReader的surface
                var builder = it.createCaptureRequest(CameraDevice.TEMPLATE_STILL_CAPTURE)
                builder.addTarget(imageReader!!.surface)
                var previewRequest = builder.build()
                //通过预览是获取的CaptureSession事务，执行拍照请求，结果会通过之前设置的ImageReader的回调返回
                mCameraCaptureSession?.setRepeatingRequest(previewRequest, null ,childHandler)
            }
        }
    }
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