initCameras method

void initCameras([ CameraDescription? cameraDescription ])

Initialize cameras instances. 初始化相机实例

Implementation

void initCameras([CameraDescription? cameraDescription]) {
  // Save the current controller to a local variable.
  final CameraController? _c = _controller;
  // Then unbind the controller from widgets, which requires a build frame.
  safeSetState(() {
    _maxAvailableZoom = 1;
    _minAvailableZoom = 1;
    _currentZoom = 1;
    _baseZoom = 1;
    _controller = null;
    // Meanwhile, cancel the existed exposure point and mode display.
    _exposureModeDisplayTimer?.cancel();
    _exposurePointDisplayTimer?.cancel();
    _lastExposurePoint.value = null;
    if (_currentExposureOffset.value != 0) {
      _currentExposureOffset.value = 0;
    }
  });
  // **IMPORTANT**: Push methods into a post frame callback, which ensures the
  // controller has already unbind from widgets.
  SchedulerBinding.instance?.addPostFrameCallback((_) async {
    // Dispose at last to avoid disposed usage with assertions.
    await _c?.dispose();

    // When the [cameraDescription] is null, which means this is the first
    // time initializing cameras, so available cameras should be fetched.
    if (cameraDescription == null) {
      cameras = await availableCameras();
    }

    // After cameras fetched, judge again with the list is empty or not to
    // ensure there is at least an available camera for use.
    if (cameraDescription == null && (cameras.isEmpty)) {
      handleErrorWithHandler(
        CameraException(
          'No CameraDescription found.',
          'No cameras are available in the controller.',
        ),
        widget.onError,
      );
    }

    final int preferredIndex = cameras.indexWhere(
      (CameraDescription e) =>
          e.lensDirection == widget.preferredLensDirection,
    );
    final int index;
    if (preferredIndex != -1 && _c == null) {
      index = preferredIndex;
      currentCameraIndex = preferredIndex;
    } else {
      index = currentCameraIndex;
    }
    // Initialize the controller with the given resolution preset.
    _controller = CameraController(
      cameraDescription ?? cameras[index],
      widget.resolutionPreset,
      enableAudio: enableAudio,
      imageFormatGroup: widget.imageFormatGroup,
    )..addListener(() {
        if (controller.value.hasError) {
          handleErrorWithHandler(
            CameraException(
              'CameraController exception',
              controller.value.errorDescription,
            ),
            widget.onError,
          );
        }
      });

    try {
      await controller.initialize();
      if (shouldPrepareForVideoRecording) {
        await controller.prepareForVideoRecording();
      }
      Future.wait(<Future<void>>[
        (() async => _maxAvailableExposureOffset =
            await controller.getMaxExposureOffset())(),
        (() async => _minAvailableExposureOffset =
            await controller.getMinExposureOffset())(),
        (() async =>
            _maxAvailableZoom = await controller.getMaxZoomLevel())(),
        (() async =>
            _minAvailableZoom = await controller.getMinZoomLevel())(),
      ]);
    } catch (e) {
      handleErrorWithHandler(e, widget.onError);
    } finally {
      safeSetState(() {});
    }
  });
}