Android camera2相机MF实现

在 Android 中，使用 Camera2 API 实现相机 MF（Manual Focus）功能需要经过以下步骤：

1. 获取 CameraManager 对象

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

2. 获取可用相机列表

String[] cameraIds = cameraManager.getCameraIdList();

3. 打开相机

CameraCharacteristics cameraCharacteristics = cameraManager.getCameraCharacteristics(cameraId);
StreamConfigurationMap streamConfigurationMap = cameraCharacteristics.get(CameraCharacteristics.SCALER_STREAM_CONFIGURATION_MAP);
cameraManager.openCamera(cameraId, new CameraDevice.StateCallback() {
    @Override
    public void onOpened(@NonNull CameraDevice camera) {
        // 相机打开后的回调
    }

    @Override
    public void onDisconnected(@NonNull CameraDevice camera) {
        // 相机断开连接后的回调
    }

    @Override
    public void onError(@NonNull CameraDevice camera, int error) {
        // 相机出错后的回调
    }
}, null);

4. 创建 CaptureRequest.Builder 对象

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

5. 设置对焦模式为 MF

builder.set(CaptureRequest.CONTROL_AF_MODE, CaptureRequest.CONTROL_AF_MODE_OFF);

6. 设置对焦区域

Rect focusArea = new Rect(-100, -100, 100, 100); // 对焦区域
MeteringRectangle[] focusAreas = new MeteringRectangle[]{new MeteringRectangle(focusArea, 1000)}; // 对焦区域列表
builder.set(CaptureRequest.CONTROL_AF_REGIONS, focusAreas);

7. 设置对焦距离

builder.set(CaptureRequest.LENS_FOCUS_DISTANCE, 0f); // 设置焦距为 0，即最短焦距

8. 构建 CaptureRequest 对象

CaptureRequest request = builder.build();

9. 创建相机预览会话

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

    @Override
    public void onConfigureFailed(@NonNull CameraCaptureSession session) {
        // 预览会话创建失败的回调
    }
}, null);

需要注意的是，MF 对焦模式需要在相机支持列表中，否则会抛出异常。另外，对焦区域和对焦距离要根据实际情况进行设置。