Flutter 旋转 CupertinoPicker

Question

有什么方法可以将 Flutter 中的 CupertinoPicker 旋转 90 度？这样您就可以水平选择而不是垂直选择。 Transform.rotate 不是一个选项，因为 Picker 的宽度被限制为父窗口小部件的高度。或者有什么好方法可以强制 Cupertino 选择器大于其父小部件？

Answer 1

RotatedBox 小部件怎么样？

RotatedBox(
  quarterTurns: 1,
  child: CupertinoPicker(...),
)

与在绘制之前应用变换的 Transform 不同，此对象在布局之前应用其旋转，这意味着整个旋转的框仅占用旋转子对象所需的空间。

Answer 2

所以我找到了 2 个解决方案。首先，您可以使用 RotatedBox。感谢 josxha 的这个想法。 2.解决方案：制作一个完整的自定义选择器。所以如果有人有同样的问题，你可以使用我的自定义选择器。代码一团糟，请不要评判lmao。

class CustomPicker extends StatefulWidget {
  CustomPicker(
      {@required double this.width,
      @required double this.height,
      @required double this.containerWidth,
      @required double this.containerHeight,
      @required double this.gapScaleFactor,
      @required List<Widget> this.childrenW,
      Function(int) this.onSnap});

  double width;
  double height;
  double containerWidth;
  double containerHeight;
  double gapScaleFactor;
  List<Widget> childrenW;
  Function(int) onSnap;

  _CustomPicker createState() => _CustomPicker(width, height, containerWidth,
      containerHeight, gapScaleFactor, childrenW, onSnap);
}

class _CustomPicker extends State<CustomPicker>
    with SingleTickerProviderStateMixin {
  AnimationController controller;
  double width;
  double height;
  double containerWidth;
  double containerHeight;
  double gapScaleFactor;
  double currentScrollX = 0;
  double oldAnimScrollX = 0;
  double animDistance = 0;
  int currentSnap = 0;
  List<Widget> childrenW;
  List<Positioned> scrollableContainer = [];
  final Function(int) onSnap;

  int currentPos;
  _CustomPicker(
      double this.width,
      double this.height,
      double this.containerWidth,
      double this.containerHeight,
      double this.gapScaleFactor,
      List<Widget> this.childrenW,
      Function(int) this.onSnap) {
    initController();
    init();
  }

  void initController() {
    controller = AnimationController(
      vsync: this,
      duration: Duration(milliseconds: 200),
      lowerBound: 0,
      upperBound: 1,
    )..addListener(() {
        setState(() {
          currentScrollX = oldAnimScrollX + controller.value * animDistance;
          init();
        });
      });
  }

  void init() {
    scrollableContainer.clear();
    if (currentScrollX < 0) {
      currentScrollX = 0;
    }
    double scrollableLength =
        (containerWidth + containerWidth * gapScaleFactor) *
                (childrenW.length) -
            containerWidth * gapScaleFactor;

    if (currentScrollX > scrollableLength - containerWidth) {
      currentScrollX = scrollableLength - containerWidth;
    }
    for (int i = 0; i < childrenW.length; i++) {
      double leftPos = width / 2 -
          containerWidth / 2 -
          currentScrollX +
          containerWidth * i +
          containerWidth * gapScaleFactor * i;
      double mid = width / 2 - containerWidth / 2;
      double topPos = containerHeight *
          0.9 *
          ((leftPos - mid).abs() / scrollableLength) /
          2;
      scrollableContainer.add(Positioned(
          //calculate X position
          left: leftPos,
          top: topPos,
          child: Container(
            height: containerHeight -
                containerHeight *
                    0.9 *
                    ((leftPos - mid).abs() / scrollableLength),
            width: containerWidth -
                containerWidth *
                    0.9 *
                    ((leftPos - mid).abs() / scrollableLength),
            child: childrenW[i],
          )));
    }
  }

  void lookForSnappoint() {
    double distance = 1000000;
    double animVal = 0;
    int index = -2032;
    for (int i = 0; i < scrollableContainer.length; i++) {
      double snappoint = width / 2 - containerWidth / 2;
      double currentLeftPos = width / 2 -
          containerWidth / 2 -
          currentScrollX +
          containerWidth * i +
          containerWidth * gapScaleFactor * i;
      if ((currentLeftPos - snappoint).abs() < distance) {
        distance = (currentLeftPos - snappoint).abs();
        animVal = currentLeftPos - snappoint;
        index = i;
      }
    }
    animDistance = animVal;
    oldAnimScrollX = currentScrollX;
    controller.reset();
    controller.forward();
    this.onSnap(index);
  }

  @override
  Widget build(BuildContext context) {
    return Container(
      width: widget.width,
      height: widget.height,
      child: GestureDetector(
        onPanUpdate: (DragUpdateDetails dragUpdateDetails) {
          setState(() {
            this.currentScrollX -= dragUpdateDetails.delta.dx;
            init();
          });
        },
        onPanEnd: (DragEndDetails dragEndDetails) {
          lookForSnappoint();
        },
        behavior: HitTestBehavior.translucent,
        child: LayoutBuilder(builder: (context, constraint) {
          return Container(
            child: Stack(
              children: <Widget>[
                Stack(children: scrollableContainer),
              ],
            ),
          );
        }),
      ),
    );
  }
}