android usb camera 例子

以下是一个示例代码，用于在Android设备上使用USB摄像头：

public class MainActivity extends AppCompatActivity {
    private final String TAG = "MainActivity";
    private final int VID = 0x1a86;
    private final int PID = 0x7523;
    private final int REQUEST_CAMERA_PERMISSION = 0x01;
    private UsbManager mUsbManager;
    private CameraManager mCameraManager;
    private String[] mCameraIds;
    private CameraDevice mCameraDevice;
    private CameraCaptureSession mCaptureSession;
    private SurfaceTexture mSurfaceTexture;
    private Size mPreviewSize;
    private HandlerThread mBackgroundThread;
    private Handler mBackgroundHandler;

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

        mUsbManager = (UsbManager) getSystemService(Context.USB_SERVICE);
        mCameraManager = (CameraManager) getSystemService(Context.CAMERA_SERVICE);

        if (ActivityCompat.checkSelfPermission(this, Manifest.permission.CAMERA) != PackageManager.PERMISSION_GRANTED) {
            ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.CAMERA}, REQUEST_CAMERA_PERMISSION);
        } else {
            startCamera();
        }
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);

        if (requestCode == REQUEST_CAMERA_PERMISSION) {
            if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                startCamera();
            } else {
                Toast.makeText(this, "请允许访问相机权限！", Toast.LENGTH_SHORT).show();
            }
        }
    }

    private void startCamera() {
        try {
            mCameraIds = mCameraManager.getCameraIdList();

            for (String cameraId : mCameraIds) {
                CameraCharacteristics characteristics = mCameraManager.getCameraCharacteristics(cameraId);
                Integer facing = characteristics.get(CameraCharacteristics.LENS_FACING);

                if (facing != null && facing == CameraCharacteristics.LENS_FACING_EXTERNAL) {
                    StreamConfigurationMap map = characteristics.get(CameraCharacteristics.SCALER_STREAM_CONFIGURATION_MAP);

                    if (map != null) {
                        mPreviewSize = map.getOutputSizes(SurfaceTexture.class)[0];
                        Log.d(TAG, "Preview size: " + mPreviewSize);

                        UsbDevice usbDevice = null;

                        for (UsbDevice device : mUsbManager.getDeviceList().values()) {
                            if (device.getVendorId() == VID && device.getProductId() == PID) {
                                usbDevice = device;
                                break;
                            }
                        }

                        if (usbDevice != null) {
                            mUsbManager.requestPermission(usbDevice, new UsbPermissionReceiver() {
                                @Override
                                public void onPermissionGranted(UsbDevice device) {
                                    try {
                                        mCameraManager.openCamera(cameraId, new CameraDevice.StateCallback() {
                                            @Override
                                            public void onOpened(@NonNull CameraDevice camera) {
                                                mCameraDevice = camera;
                                                startPreview();
                                            }

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

                                            @Override
                                            public void onError(@NonNull CameraDevice camera, int error) {
                                                camera.close();
                                                mCameraDevice = null;
                                            }
                                        }, mBackgroundHandler);
                                    } catch (CameraAccessException e) {
                                        e.printStackTrace();
                                    }
                                }

                                @Override
                                public void onPermissionDenied(UsbDevice device) {
                                    Toast.makeText(MainActivity.this, "USB相机权限被拒绝！", Toast.LENGTH_SHORT).show();
                                }
                            });
                        } else {
                            Toast.makeText(this, "未找到USB相机！", Toast.LENGTH_SHORT).show();
                        }
                    }
                }
            }
        } catch (CameraAccessException e) {
            e.printStackTrace();
        }
    }

    private void startPreview() {
        try {
            mSurfaceTexture = new SurfaceTexture(0);
            mSurfaceTexture.setDefaultBufferSize(mPreviewSize.getWidth(), mPreviewSize.getHeight());
            Surface surface = new Surface(mSurfaceTexture);

            mCameraDevice.createCaptureSession(Arrays.asList(surface), new CameraCaptureSession.StateCallback() {
                @Override
                public void onConfigured(@NonNull CameraCaptureSession session) {
                    try {
                        mCaptureSession = session;

                        CaptureRequest.Builder builder = mCameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);
                        builder.addTarget(surface);

                        CaptureRequest request = builder.build();
                        mCaptureSession.setRepeatingRequest(request, null, mBackgroundHandler);
                    } catch (CameraAccessException e) {
                        e.printStackTrace();
                    }
                }

                @Override
                public void onConfigureFailed(@NonNull CameraCaptureSession session) {
                    Toast.makeText(MainActivity.this, "相机预览配置失败！", Toast.LENGTH_SHORT).show();
                }
            }, mBackgroundHandler);
        } catch (CameraAccessException e) {
            e.printStackTrace();
        }
    }

    @Override
    protected void onResume() {
        super.onResume();

        if (mBackgroundThread == null) {
            mBackgroundThread = new HandlerThread("CameraBackground");
            mBackgroundThread.start();
            mBackgroundHandler = new Handler(mBackgroundThread.getLooper());
        }
    }

    @Override
    protected void onPause() {
        super.onPause();

        if (mCameraDevice != null) {
            mCameraDevice.close();
            mCameraDevice = null;
        }

        if (mCaptureSession != null) {
            mCaptureSession.close();
            mCaptureSession = null;
        }

        if (mSurfaceTexture != null) {
            mSurfaceTexture.release();
            mSurfaceTexture = null;
        }

        if (mBackgroundThread != null) {
            mBackgroundThread.quitSafely();
            try {
                mBackgroundThread.join();
                mBackgroundThread = null;
                mBackgroundHandler = null;
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
}

请注意，此示例代码仅用于演示如何在Android设备上使用USB摄像头。您需要根据自己的需求进行修改和调整。