怎么用代码调windows平板闪光灯并改闪光灯的颜色

要控制 Windows 平板电脑的闪光灯，可以使用 UWP 应用程序编写代码。下面是一个示例代码片段，可以通过该代码控制闪光灯并更改其颜色：

using Windows.Media.Capture;

// 获取 MediaCapture 对象
MediaCapture mediaCapture = new MediaCapture();
await mediaCapture.InitializeAsync();

// 获取闪光灯控制器
var torchControl = mediaCapture.VideoDeviceController.TorchControl;

// 开启闪光灯
torchControl.Enabled = true;

// 更改闪光灯颜色
torchControl.PowerPercent = 80; // 设置亮度为 80%
torchControl.Color = Windows.Media.Devices.Color.FromArgb(255, 255, 0, 0); // 设置颜色为红色

需要注意的是，这段代码需要在 UWP 应用程序中运行，并且需要获取相机的访问权限。此外，不是所有的 Windows 平板电脑都支持闪光灯和更改其颜色，具体取决于硬件支持情况。

相关问题

Android使用camera2扫码并打开闪光灯代码

下面是一个使用 camera2 API 实现扫码并打开闪光灯的示例代码：

public class ScanActivity extends AppCompatActivity implements SurfaceHolder.Callback {

    private static final String TAG = "ScanActivity";
    private static final int REQUEST_CAMERA_PERMISSION = 1;

    private CameraManager mCameraManager;
    private CameraDevice mCameraDevice;
    private SurfaceView mSurfaceView;
    private ImageReader mImageReader;
    private CaptureRequest.Builder mPreviewRequestBuilder;
    private CaptureRequest mPreviewRequest;
    private HandlerThread mBackgroundThread;
    private Handler mBackgroundHandler;
    private boolean mFlashSupported;
    private boolean mFlashEnabled;
    private Semaphore mCameraOpenCloseLock = new Semaphore(1);

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_scan);

        mSurfaceView = findViewById(R.id.surface_view);
        mSurfaceView.getHolder().addCallback(this);
    }

    @Override
    protected void onResume() {
        super.onResume();
        startBackgroundThread();
        if (mSurfaceView.isAvailable()) {
            openCamera(mSurfaceView.getWidth(), mSurfaceView.getHeight());
        } else {
            mSurfaceView.getHolder().addCallback(this);
        }
    }

    @Override
    protected void onPause() {
        closeCamera();
        stopBackgroundThread();
        super.onPause();
    }

    private void startBackgroundThread() {
        mBackgroundThread = new HandlerThread(TAG);
        mBackgroundThread.start();
        mBackgroundHandler = new Handler(mBackgroundThread.getLooper());
    }

    private void stopBackgroundThread() {
        mBackgroundThread.quitSafely();
        try {
            mBackgroundThread.join();
            mBackgroundThread = null;
            mBackgroundHandler = null;
        } catch (InterruptedException e) {
            Log.e(TAG, "stopBackgroundThread: ", e);
        }
    }

    @Override
    public void surfaceCreated(SurfaceHolder holder) {

    }

    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {

    }

    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {

    }

    private void openCamera(int width, int height) {
        if (ActivityCompat.checkSelfPermission(this, Manifest.permission.CAMERA) != PackageManager.PERMISSION_GRANTED) {
            ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.CAMERA}, REQUEST_CAMERA_PERMISSION);
            return;
        }
        mCameraManager = (CameraManager) getSystemService(Context.CAMERA_SERVICE);
        try {
            if (!mCameraOpenCloseLock.tryAcquire(2500, TimeUnit.MILLISECONDS)) {
                throw new RuntimeException("Time out waiting to lock camera opening.");
            }
            String cameraId = mCameraManager.getCameraIdList()[0];
            CameraCharacteristics characteristics = mCameraManager.getCameraCharacteristics(cameraId);
            StreamConfigurationMap map = characteristics.get(CameraCharacteristics.SCALER_STREAM_CONFIGURATION_MAP);
            mImageReader = ImageReader.newInstance(width, height, ImageFormat.YUV_420_888, 2);
            mImageReader.setOnImageAvailableListener(mOnImageAvailableListener, mBackgroundHandler);
            if (map == null) {
                throw new RuntimeException("Cannot get available preview/video sizes");
            }
            Size largest = Collections.max(Arrays.asList(map.getOutputSizes(ImageFormat.YUV_420_888)), new CompareSizesByArea());
            configureTransform(width, height);
            mCameraManager.openCamera(cameraId, mStateCallback, mBackgroundHandler);
        } catch (CameraAccessException e) {
            Log.e(TAG, "openCamera: ", e);
        } catch (InterruptedException e) {
            throw new RuntimeException("Interrupted while trying to lock camera opening.", e);
        }
    }

    private void closeCamera() {
        try {
            mCameraOpenCloseLock.acquire();
            if (null != mCameraDevice) {
                mCameraDevice.close();
                mCameraDevice = null;
            }
            if (null != mImageReader) {
                mImageReader.close();
                mImageReader = null;
            }
        } catch (InterruptedException e) {
            throw new RuntimeException("Interrupted while trying to lock camera closing.", e);
        } finally {
            mCameraOpenCloseLock.release();
        }
    }

    private void configureTransform(int viewWidth, int viewHeight) {
        if (null == mSurfaceView || null == mPreviewRequestBuilder) {
            return;
        }
        int rotation = getWindowManager().getDefaultDisplay().getRotation();
        Matrix matrix = new Matrix();
        RectF viewRect = new RectF(0, 0, viewWidth, viewHeight);
        RectF bufferRect = new RectF(0, 0, mImageReader.getHeight(), mImageReader.getWidth());
        float centerX = viewRect.centerX();
        float centerY = viewRect.centerY();
        if (Surface.ROTATION_90 == rotation || Surface.ROTATION_270 == rotation) {
            bufferRect.offset(centerX - bufferRect.centerX(), centerY - bufferRect.centerY());
            matrix.setRectToRect(viewRect, bufferRect, Matrix.ScaleToFit.FILL);
            float scale = Math.max((float) viewHeight / mImageReader.getHeight(), (float) viewWidth / mImageReader.getWidth());
            matrix.postScale(scale, scale, centerX, centerY);
            matrix.postRotate(90 * (rotation - 2), centerX, centerY);
        } else if (Surface.ROTATION_180 == rotation) {
            matrix.postRotate(180, centerX, centerY);
        }
        mSurfaceView.setTransform(matrix);
    }

    private void createCameraPreviewSession() {
        try {
            Surface surface = mSurfaceView.getHolder().getSurface();
            mPreviewRequestBuilder = mCameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);
            mPreviewRequestBuilder.addTarget(surface);
            mPreviewRequestBuilder.addTarget(mImageReader.getSurface());
            mCameraDevice.createCaptureSession(Arrays.asList(surface, mImageReader.getSurface()), new CameraCaptureSession.StateCallback() {

                @Override
                public void onConfigured(@NonNull CameraCaptureSession cameraCaptureSession) {
                    if (null == mCameraDevice) {
                        return;
                    }
                    try {
                        mPreviewRequest = mPreviewRequestBuilder.build();
                        cameraCaptureSession.setRepeatingRequest(mPreviewRequest, null, mBackgroundHandler);
                    } catch (CameraAccessException e) {
                        Log.e(TAG, "onConfigured: ", e);
                    }
                }

                @Override
                public void onConfigureFailed(@NonNull CameraCaptureSession cameraCaptureSession) {
                    Log.e(TAG, "onConfigureFailed: ");
                }
            }, null);
        } catch (CameraAccessException e) {
            Log.e(TAG, "createCameraPreviewSession: ", e);
        }
    }

    private final CameraDevice.StateCallback mStateCallback = new CameraDevice.StateCallback() {

        @Override
        public void onOpened(@NonNull CameraDevice cameraDevice) {
            mCameraOpenCloseLock.release();
            mCameraDevice = cameraDevice;
            createCameraPreviewSession();
        }

        @Override
        public void onDisconnected(@NonNull CameraDevice cameraDevice) {
            mCameraOpenCloseLock.release();
            cameraDevice.close();
            mCameraDevice = null;
        }

        @Override
        public void onError(@NonNull CameraDevice cameraDevice, int error) {
            mCameraOpenCloseLock.release();
            cameraDevice.close();
            mCameraDevice = null;
            finish();
        }
    };

    private final ImageReader.OnImageAvailableListener mOnImageAvailableListener = new ImageReader.OnImageAvailableListener() {

        @Override
        public void onImageAvailable(ImageReader reader) {
            Image image = reader.acquireLatestImage();
            if (image == null) {
                return;
            }
            ByteBuffer buffer = image.getPlanes()[0].getBuffer();
            byte[] data = new byte[buffer.remaining()];
            buffer.get(data);
            int width = image.getWidth();
            int height = image.getHeight();
            int format = image.getFormat();
            int stride = image.getPlanes()[0].getRowStride();
            boolean success = false;
            if (format == ImageFormat.YUV_420_888) {
                PlanarYUVLuminanceSource source = new PlanarYUVLuminanceSource(data, width, height, stride, 0, 0, width, height, false);
                BinaryBitmap bitmap = new BinaryBitmap(new HybridBinarizer(source));
                MultiFormatReader reader = new MultiFormatReader();
                try {
                    Result result = reader.decode(bitmap);
                    String text = result.getText();
                    success = true;
                    Log.d(TAG, "onImageAvailable: text = " + text);
                } catch (NotFoundException e) {
                    Log.e(TAG, "onImageAvailable: ", e);
                }
            }
            image.close();
            if (success) {
                runOnUiThread(new Runnable() {
                    @Override
                    public void run() {
                        Toast.makeText(ScanActivity.this, "扫描成功", Toast.LENGTH_SHORT).show();
                    }
                });
            }
        }
    };

    private static class CompareSizesByArea implements Comparator<Size> {

        @Override
        public int compare(Size lhs, Size rhs) {
            return Long.signum((long) lhs.getWidth() * lhs.getHeight() - (long) rhs.getWidth() * rhs.getHeight());
        }
    }

    private void toggleFlash() {
        if (mCameraDevice == null || !mFlashSupported) {
            return;
        }
        try {
            mFlashEnabled = !mFlashEnabled;
            mPreviewRequestBuilder.set(CaptureRequest.FLASH_MODE, mFlashEnabled ? CaptureRequest.FLASH_MODE_TORCH : CaptureRequest.FLASH_MODE_OFF);
            mCameraDevice.createCaptureSession(Arrays.asList(mSurfaceView.getHolder().getSurface(), mImageReader.getSurface()), new CameraCaptureSession.StateCallback() {

                @Override
                public void onConfigured(@NonNull CameraCaptureSession cameraCaptureSession) {
                    try {
                        cameraCaptureSession.setRepeatingRequest(mPreviewRequestBuilder.build(), null, mBackgroundHandler);
                    } catch (CameraAccessException e) {
                        Log.e(TAG, "onConfigured: ", e);
                    }
                }

                @Override
                public void onConfigureFailed(@NonNull CameraCaptureSession cameraCaptureSession) {
                    Log.e(TAG, "onConfigureFailed: ");
                }
            }, null);
        } catch (CameraAccessException e) {
            Log.e(TAG, "toggleFlash: ", e);
        }
    }

    @Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {
        if (keyCode == KeyEvent.KEYCODE_VOLUME_DOWN || keyCode == KeyEvent.KEYCODE_VOLUME_UP) {
            toggleFlash();
            return true;
        }
        return super.onKeyDown(keyCode, event);
    }
}

在该示例中，我们使用 ImageReader 获取相机预览数据，并使用 ZXing 库进行识别。同时，我们还实现了打开闪光灯的功能，可以使用音量键触发。需要注意的是，在使用打开闪光灯的功能时，需要先检查相机设备是否支持闪光灯。

android单独打开闪光灯代码

以下是在 Android 上单独打开闪光灯的代码：

首先，在 AndroidManifest.xml 文件中添加相机权限：

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

然后在需要打开闪光灯的 Activity 中添加以下代码：

private Camera camera;
private boolean isFlashOn = false;

...

// 在 onCreate 方法中获取 Camera 对象
camera = Camera.open();

...

// 打开闪光灯
private void turnOnFlash() {
    if (!isFlashOn) {
        Camera.Parameters params = camera.getParameters();
        params.setFlashMode(Camera.Parameters.FLASH_MODE_TORCH);
        camera.setParameters(params);
        camera.startPreview();
        isFlashOn = true;
    }
}

// 关闭闪光灯
private void turnOffFlash() {
    if (isFlashOn) {
        Camera.Parameters params = camera.getParameters();
        params.setFlashMode(Camera.Parameters.FLASH_MODE_OFF);
        camera.setParameters(params);
        camera.stopPreview();
        isFlashOn = false;
    }
}

...

// 在需要打开或关闭闪光灯的地方调用 turnOnFlash() 或 turnOffFlash() 方法即可

要记得在 Activity 销毁时释放 Camera 对象：

@Override
protected void onDestroy() {
    super.onDestroy();
    if (camera != null) {
        camera.release();
        camera = null;
    }
}