如何在Flutter中的Alignmentx，y类中获取x属性的值？

如何解决如何在Flutter中的Alignmentx，y类中获取x属性的值？

我是Flutter和Dart的新手。我使用Flutter Docs上的example project构建了我的应用。

这是代码：

import 'package:flutter/material.dart';
import 'package:flutter/physics.dart';

main() {
  runApp(MaterialApp(home: PhysicsCardDragDemo()));
}

class PhysicsCardDragDemo extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(),body: DraggableCard(
        child: FlutterLogo(
          size: 128,),);
  }
}

/// A draggable card that moves back to [Alignment.center] when it's
/// released.
class DraggableCard extends StatefulWidget {
  final Widget child;
  DraggableCard({this.child});

  @override
  _DraggableCardState createState() => _DraggableCardState();
}

class _DraggableCardState extends State<DraggableCard>
    with SingleTickerProviderStateMixin {
  AnimationController _controller;

  /// The alignment of the card as it is dragged or being animated.
  ///
  /// While the card is being dragged,this value is set to the values computed
  /// in the GestureDetector onPanUpdate callback. If the animation is running,/// this value is set to the value of the [_animation].
  Alignment _dragAlignment = Alignment.center;

  Animation<Alignment> _animation;

  /// Calculates and runs a [SpringSimulation].
  void _runAnimation(Offset pixelsPerSecond,Size size) {
    _animation = _controller.drive(
      AlignmentTween(
        begin: _dragAlignment,end: Alignment.center,);
    // Calculate the velocity relative to the unit interval,[0,1],// used by the animation controller.
    final unitsPerSecondX = pixelsPerSecond.dx / size.width;
    final unitsPerSecondY = pixelsPerSecond.dy / size.height;
    final unitsPerSecond = Offset(unitsPerSecondX,unitsPerSecondY);
    final unitVelocity = unitsPerSecond.distance;

    const spring = SpringDescription(
      mass: 30,stiffness: 1,damping: 1,);

    final simulation = SpringSimulation(spring,1,-unitVelocity);

    _controller.animateWith(simulation);
  }

  @override
  void initState() {
    super.initState();
    _controller = AnimationController(vsync: this);

    _controller.addListener(() {
      setState(() {
        _dragAlignment = _animation.value;
      });
    });
  }

  @override
  void dispose() {
    _controller.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    final size = MediaQuery.of(context).size;
    return GestureDetector(
      onPanDown: (details) {
        _controller.stop();
      },onPanUpdate: (details) {
        setState(() {
          _dragAlignment += Alignment(
            details.delta.dx / (size.width / 2),details.delta.dy / (size.height / 2),);
        });
      },onPanEnd: (details) {
        _runAnimation(details.velocity.pixelsPerSecond,size);
      },child: Align(
        alignment: _dragAlignment,child: Card(
          child: widget.child,);
  }
}

我正在尝试设置DraggableCard（）除位置以外的其他属性的动画；具体来说，我想基于水平拖动来动态更改其旋转度和不透明度。

为此，我尝试获取_dragAlignment的值，以便可以将其提供给Transform.rotate（），但该值对应于一个坐标，我只需要读取x的值坐标。

换句话说，我需要从与_dragAlignment对应的Alignment（x，y）类中提取X值。我尝试了很多事情，但没有任何效果。

我在这里和其他地方搜索了解决方案，但找不到任何帮助，也许我不是在问正确的问题。

很抱歉，这是一个愚蠢的问题，还是以前曾有人问过。

解决方法

我认为您可以做类似的事情，

<ReportCard>
 <ReportIcon src={report.marker_icon} />
 <ReportH2>{report.id}</ReportH2>
 <ReportP>Officer will perform a Quick search of Valid Driver's License and any signs of Intoxication. </ReportP>
</ReportCard>

希望有效！

,

感谢Shri Hari的帮助：）

我通过清除解决了我的问题

var xCoord = 0.0;

还清除了_dragAlignment并比使用

child: Transform.rotate(

                angle: -_dragAlignment.x/200

直接在GestureDetector（）中。

我还不得不在onPanUpdate中编辑值，因为看起来它不再拖动了，但是您只需要增加details.delta.dx ...

赞！

return GestureDetector(

  onPanDown: (details) {
    _controller.stop();
  },onPanUpdate: (details) {

    //print(_dragAlignment);
    setState(() {

      _dragAlignment += Alignment(

        details.delta.dx / (size.width / 300),// X drag sensitivity
        details.delta.dy / (size.height / 9),//Y drag sensitivity

      );
    });
  },onPanEnd: (details) {
    _runAnimation(details.velocity.pixelsPerSecond,size);
  },child: Align(
    alignment: _dragAlignment,child: Transform.rotate(

            angle: -_dragAlignment.x/200,child: Card(
                child: widget.child,),)
  ),);