如何使用Flutter创建自定义弹出菜单

Question

我想在应用栏上单击按钮时创建一个弹出菜单..我希望这样的东西出现：

有办法做到这一点吗？包装还是什么？

Answer 1

我尝试过，但是在以这种方式显示subwidget时遇到了一些问题。因此，这里有两个解决方案：

class TestScreen extends StatefulWidget {
  @override
  State<StatefulWidget> createState() => _TestScreenState();
}

class _TestScreenState extends State<TestScreen> with SingleTickerProviderStateMixin {
  AnimationController animationController;
  bool _menuShown = false;

  @override
  void initState() {
    animationController = AnimationController(vsync: this, duration: Duration(milliseconds: 500));
    super.initState();
  }

  @override
  Widget build(BuildContext context) {    
    Animation opacityAnimation = Tween(begin: 0.0, end: 1.0).animate(animationController);
    if (_menuShown)
      animationController.forward();
    else
      animationController.reverse();
    return Scaffold(
      appBar: AppBar(
        actions: <Widget>[IconButton(icon: Icon(Icons.menu), onPressed: (){
          setState(() {
            _menuShown = !_menuShown;
          });
        })],
      ),
      body: Stack(
        overflow: Overflow.visible,
        children: <Widget>[
          Positioned(
            child: FadeTransition(
              opacity: opacityAnimation,
              child: _ShapedWidget(),
            ),
            right: 4.0,
            top: 16.0,
          ),
        ],
      ),
    );
  }
}

class _ShapedWidget extends StatelessWidget {
  _ShapedWidget();
  final double padding = 4.0;

  @override
  Widget build(BuildContext context) {
    return Center(
      child: Material(
          clipBehavior: Clip.antiAlias,
          shape:
          _ShapedWidgetBorder(borderRadius: BorderRadius.all(Radius.circular(padding)), padding: padding),
          elevation: 4.0,
          child: Container(
            padding: EdgeInsets.all(padding).copyWith(bottom: padding * 2),
            child: SizedBox(width: 150.0, height: 250.0, child: Center(child: Text('ShapedWidget'),),),
          )),
    );
  }
}

class _ShapedWidgetBorder extends RoundedRectangleBorder {
  _ShapedWidgetBorder({
    @required this.padding,
    side = BorderSide.none,
    borderRadius = BorderRadius.zero,
  }) : super(side: side, borderRadius: borderRadius);
  final double padding;

  @override
  Path getOuterPath(Rect rect, {TextDirection textDirection}) {
    return Path()
      ..moveTo(rect.width - 8.0 , rect.top)
      ..lineTo(rect.width - 20.0, rect.top - 16.0)
      ..lineTo(rect.width - 32.0, rect.top)
      ..addRRect(borderRadius
          .resolve(textDirection)
          .toRRect(Rect.fromLTWH(rect.left, rect.top, rect.width, rect.height - padding)));
  }
}

在这种情况下，子控件位于appbar下方

class TestScreen extends StatefulWidget {
  @override
  State<StatefulWidget> createState() => _TestScreenState();
}

class _TestScreenState extends State<TestScreen> with SingleTickerProviderStateMixin {
  AnimationController animationController;
  bool _menuShown = false;

  @override
  void initState() {


    animationController = AnimationController(vsync: this, duration: Duration(milliseconds: 500));
    super.initState();
  }

  @override
  Widget build(BuildContext context) {

    Animation opacityAnimation = Tween(begin: 0.0, end: 1.0).animate(animationController);
    if (_menuShown)
      animationController.forward();
    else
      animationController.reverse();
    return Scaffold(
      appBar: AppBar(
        elevation: 0.0,
        actions: <Widget>[Stack(
          overflow: Overflow.visible,
          children: <Widget>[IconButton(icon: Icon(Icons.menu), onPressed: (){
          setState(() {
            _menuShown = !_menuShown;
          });    
        }),
          Positioned(
            child: FadeTransition(
              opacity: opacityAnimation,
              child: _ShapedWidget(onlyTop: true,),
            ),
            right: 4.0,
            top: 48.0,
          ),    
          ],)],
      ),
      body: Stack(
        overflow: Overflow.visible,
        children: <Widget>[
          Positioned(
            child: FadeTransition(
              opacity: opacityAnimation,
              child: _ShapedWidget(),
            ),
            right: 4.0,
            top: -4.0,
          ),
        ],
      ),
    );
  }
}  

class _ShapedWidget extends StatelessWidget {
  _ShapedWidget({this.onlyTop = false});
  final double padding = 4.0;
  final bool onlyTop;

  @override
  Widget build(BuildContext context) {
    return Center(
      child: Material(
          clipBehavior: Clip.antiAlias,
          shape:
          _ShapedWidgetBorder(borderRadius: BorderRadius.all(Radius.circular(padding)), padding: padding),
          elevation: 4.0,
          child: Container(
            padding: EdgeInsets.all(padding).copyWith(bottom: padding * 2),
            child: onlyTop ? SizedBox(width: 150.0, height: 20.0,) :  SizedBox(width: 150.0, height: 250.0, child: Center(child: Text('ShapedWidget'),),),
          )),
    );
  }
}

class _ShapedWidgetBorder extends RoundedRectangleBorder {
  _ShapedWidgetBorder({
    @required this.padding,
    side = BorderSide.none,
    borderRadius = BorderRadius.zero,
  }) : super(side: side, borderRadius: borderRadius);
  final double padding;

  @override
  Path getOuterPath(Rect rect, {TextDirection textDirection}) {
    return Path()
      ..moveTo(rect.width - 8.0 , rect.top)
      ..lineTo(rect.width - 20.0, rect.top - 16.0)
      ..lineTo(rect.width - 32.0, rect.top)
      ..addRRect(borderRadius
          .resolve(textDirection)
          .toRRect(Rect.fromLTWH(rect.left, rect.top, rect.width, rect.height - padding)));
  }
}

在这种情况下，子控件的顶部位于应用程序栏上，但是应用程序栏必须具有0.0的仰角

实际上，我认为这两种解决方案都不完整，但是可以帮助您找到所需的东西

Answer 2

回答可能为时已晚。但这可以通过使用OverlayEntry小部件简单地实现。我们创建该形状的小部件并将其传递给OverlayEntry小部件，然后用于Overlay.of(context).insert(overlayEntry)显示覆盖层和overlayEntry.remove删除它的方法。

这是创建自定义下拉菜单的中等链接

希望这可以帮助！