Flutter - 原生交互 - 相机Camera - 曝光,缩放,录制视频

曝光

Flutter上CupertinoSlider组件的样式是iOS上的Slider,使用该组件控制曝光量，
Camera插件提供的API是CameraController的

Future<double> setExposureOffset(double offset) async {
   
...
}

最后调用iOS端的系统方法控制曝光值

- (void)setExposureTargetBias:(float)bias completionHandler:(nullable void (^)(CMTime syncTime))handler API_AVAILABLE(ios(8.0), macCatalyst(14.0), tvos(17.0)) API_UNAVAILABLE(macos, visionos);

class TakePictureScreenState extends State<TakePictureScreen> {
   
    /// 设置默认值
    double currentExposure = 0.0;
    /// 是否显示曝光Slider组件
    bool _showedExposure = false;
    ...
    /// 使用CupertinoSlider
    
    Widget showExposure() {
   
        if (_showedExposure) {
   
            return SizedBox(
                height: 44,
                width: MediaQuery.of(context).size.width,
                child: CupertinoSlider(
                    /// 滑动Slider时触发的事件
                    onChanged: (value) {
   
                        setState(() {
   
                            /// 调整相机的曝光值
                            _controller.setExposureOffset(value);
                            currentExposure = value;
                        });
                    },
                    min: -3, /// 设置作用范围
                    max: 3,
                    value: currentExposure, /// 当前Slider显示的值
                ),
            );
        }
    return SizedBox.shrink();
  }
}

两指手势缩放

系统的相机可以双指进行缩放操作,在Flutter中可以在GestureDetector来实现

/// 最小缩放比例
double _minAvailableZoom = 1.0;
/// 最大缩放比例
double _maxAvailableZoom = 1.0;
/// 记录当前的缩放比例
double _currentScale = 1.0;
/// 当前的基础值
double _baseScale = 1.0;

Listener(
    onPointerDown: (_) => _pointers++,
    onPointerUp: (_) => _pointers--, // 用来判断是否双指
    child: CameraPreview(
            _controller,
            // Creates a widget that defers its building until layout.
            // 布局完成再创建
            child: LayoutBuilder(
                builder: (BuildContext context, BoxConstraints constraints) {
   
                  return GestureDetector(
                            // Opaque targets can be hit by hit tests, causing them to both receive events within their bounds and prevent targets visually behind them from also receiving events.
                            // 相机Widget能收到手势
                            behavior: HitTestBehavior.opaque, 
                            // 设置开始缩放事件
                            onScaleStart: _handleScaleStart,
                            // 设置缩放值变化事件