Android camera2 MF实现

Android Camera2 API提供了完整的手动对焦控制，可以使用手动对焦实现MF（Manual Focus）。下面是一些实现步骤：

1.获取CameraManager实例

CameraManager cameraManager = (CameraManager) getSystemService(Context.CAMERA_SERVICE);

2.获取相机设备ID

String cameraId = cameraManager.getCameraIdList()[0];

3.获取相机特性

CameraCharacteristics cameraCharacteristics = cameraManager.getCameraCharacteristics(cameraId);

4.检查设备是否支持手动对焦

int[] afAvailableModes = cameraCharacteristics.get(CameraCharacteristics.CONTROL_AF_AVAILABLE_MODES);
if (afAvailableModes == null || afAvailableModes.length == 0 || (afAvailableModes.length == 1 && afAvailableModes[0] == CameraMetadata.CONTROL_AF_MODE_OFF)) {
    // 设备不支持自动对焦
}

5.创建相机捕获会话

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

    @Override
    public void onDisconnected(@NonNull CameraDevice camera) {
        cameraDevice.close();
    }

    @Override
    public void onError(@NonNull CameraDevice camera, int error) {
        cameraDevice.close();
    }
}, null);

6.创建CaptureRequest.Builder对象

CaptureRequest.Builder captureRequestBuilder = cameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);

7.设置手动对焦模式

captureRequestBuilder.set(CaptureRequest.CONTROL_AF_MODE, CameraMetadata.CONTROL_AF_MODE_OFF);

8.设置焦距

float focusDistance = cameraCharacteristics.get(CameraCharacteristics.LENS_INFO_MINIMUM_FOCUS_DISTANCE);
captureRequestBuilder.set(CaptureRequest.LENS_FOCUS_DISTANCE, focusDistance);

9.提交CaptureRequest

CameraCaptureSession cameraCaptureSession;
cameraDevice.createCaptureSession(Arrays.asList(surface), new CameraCaptureSession.StateCallback() {
    @Override
    public void onConfigured(@NonNull CameraCaptureSession session) {
        cameraCaptureSession = session;
        try {
            cameraCaptureSession.setRepeatingRequest(captureRequestBuilder.build(), null, null);
        } catch (CameraAccessException e) {
            e.printStackTrace();
        }
    }

    @Override
    public void onConfigureFailed(@NonNull CameraCaptureSession session) {
    }
}, null);

这样就可以实现手动对焦了。当需要改变焦距时，只需要修改CaptureRequest中LENS_FOCUS_DISTANCE参数的值，然后调用CameraCaptureSession.setRepeatingRequest()方法即可。