java调用手机摄像头代码

在Java中，要访问手机摄像头并获取实时视频流，你需要借助Android平台的Camera API或者更现代的CameraX库。以下是使用`CameraX`库的一个简单示例：

// 首先添加CameraX依赖到build.gradle文件中
dependencies {
    implementation 'androidx.camera:camera-camera-lifecycle:1.0.0'
    implementation 'androidx.camera:camera-camera-view:1.0.0-alpha17'
}

// 获取相机实例
private void openCamera() {
    try (Processor<VideoFrame> processor = new ImageAnalysis.Builder()
            .setTargetAspectRatio(new Rational(480, 640)) // 设置目标帧大小
            .setTargetRotation(CameraX.ActivityPreviewConfig.Rotation.auto)
            .build().getProcessor()) {

        ImageCapture imageCapture = new ImageCapture.Builder()
                .setFlashMode(ImageCaptureFLASH_MODE.ON) // 设置闪光灯模式
                .build();

        CameraManager cameraManager = (CameraManager) getSystemService(Context.CAMERA_SERVICE);
        String cameraId = cameraManager.getCameraIdList()[0]; // 获取可用的第一个相机ID

        CameraX.unbindAll();
        CameraX.bindToLifecycle((Activity) context, imageCapture, processor);

        imageCapture.setListener(new ImageCapture.OnImageCapturedListener() {
            @Override
            public void onCaptureSuccess(@NonNull ImageCapture.OutputFileResults outputFileResults,
                                         @NonNull ImageProxy image) {
                // 这里处理捕获到的照片或视频数据
            }

            @Override
            public void onError(@NonNull ImageCapture.UseCaseError useCaseError, @Nullable String message) {
                Log.e(TAG, "Use case error: " + useCaseError.toString());
            }
        });

        cameraManager.openCamera(cameraId, new CameraDevice.StateCallback() {
            @Override
            public void onOpened(@NonNull CameraDevice cameraDevice) {
                createSession(cameraDevice);
            }

            // 更多回调...
        }, null);
    } catch (CameraAccessException e) {
        Log.e(TAG, "Accessing camera failed", e);
    }
}

private void createSession(@NonNull CameraDevice cameraDevice) {
    try {
        StreamConfigurationMap streamConfigurations = cameraDevice.getCameraInfo().getStreamConfigurationMap();
        SurfaceTexture texture = new SurfaceTexture.Builder()
                .createSurfaceTexturesurfaceView.getHolder().getSurface())
                .build();

        Surface surface = new CameraX.SurfaceBuilder(texture).build();

        ImageCaptureConfig config = ImageCaptureConfig.builder()
                .setTargetAspectRatio(streamConfigurations.get(outputFormat, ImageCapture.INFO_OUTPUT_FORMAT_WIDTH, ImageCapture.INFO_OUTPUT_FORMAT_HEIGHT))
                .setTargetRotation(cameraDevice.getCameraInfo().getRotationDegrees())
                .build();

        ImageCapture imageCapture = ImageCapture.create(cameraDevice, config);
        imageCapture.setCaptureRequestListener(new ImageCapture.OnCaptureRequestListener() {
            // 这里处理请求预览、拍照等操作
        });
    } catch (CameraAccessException e) {
        Log.e(TAG, "Setting up capture session failed", e);
    }
}

注意，这只是一个基本的框架，实际应用中你还需要处理生命周期管理、权限请求以及UI显示等问题。另外，CameraX API在API 29及以上版本才开始支持。