Flutter 使用 BorderRadiusTween 分离 ClipRRect 边界半径

Question

在这段代码中我们可以轻松地为所有角设置边框半径，例如topLeft, topRight, bottomLeft, bottomRight 以一行代码为例:

borderRadius: borderRadius.evaluate(CurvedAnimation(parent: _controller, curve: Curves.ease)),

现在我如何将它用于分离的角？例如:

borderRadius: BorderRadius.only(
  topLeft: borderRadius.evaluate(CurvedAnimation(parent: _controller, curve: Curves.ease)),
  topRight: borderRadius.evaluate(CurvedAnimation(parent: _controller, curve: Curves.ease)),
),

完整源代码:

import 'package:flutter/material.dart';

void main() => runApp(MaterialApp(
      home: HomePage(),
    ));

class HomePage extends StatefulWidget {
  @override
  _HomePageState createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> with SingleTickerProviderStateMixin {
  AnimationController _controller;
  BorderRadiusTween borderRadius;
  Duration _duration = Duration(milliseconds: 500);
  Tween<Offset> _tween = Tween(begin: Offset(0, 1), end: Offset(0, 0));
  double _height, min = 0.1, initial = 0.3, max = 1;
  GlobalKey<ScaffoldState> _scaffoldKey = GlobalKey<ScaffoldState>();

  @override
  void initState() {
    super.initState();
    _controller = AnimationController(vsync: this, duration: _duration);
    borderRadius = BorderRadiusTween(
      begin: BorderRadius.circular(75.0),
      end: BorderRadius.circular(0.0),
    );
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      key: _scaffoldKey,
      appBar: AppBar(
        title: Text('DraggableScrollableSheet'),
      ),
      floatingActionButton: GestureDetector(
        child: FloatingActionButton(
          child: AnimatedIcon(icon: AnimatedIcons.menu_close, progress: _controller),
          elevation: 5,
          backgroundColor: Colors.deepOrange,
          foregroundColor: Colors.white,
          onPressed: () async {
            if (_controller.isDismissed)
              _controller.forward();
            else if (_controller.isCompleted) _controller.reverse();
          },
        ),
      ),
      body: SizedBox.expand(
        child: Stack(
          children: <Widget>[
            FlutterLogo(size: 500),
            SizedBox.expand(
              child: SlideTransition(
                position: _tween.animate(_controller),
                child: DraggableScrollableSheet(
                  minChildSize: min, // 0.1 times of available height, sheet can't go below this on dragging
                  maxChildSize: max, // 0.7 times of available height, sheet can't go above this on dragging
                  initialChildSize: initial, // 0.1 times of available height, sheet start at this size when opened for first time
                  builder: (BuildContext context, ScrollController controller) {
                    if (controller.hasClients) {
                      var dimension = controller.position.viewportDimension;
                      _height ??= dimension / initial;
                      if (dimension >= _height * max * 0.9)
                        _onWidgetDidBuild(() {
                          _scaffoldKey.currentState.showSnackBar(SnackBar(
                            content: Text('ON TOP'),
                            duration: Duration(seconds: 3),
                          ));
                        });
                      else if (dimension <= _height * min * 1.1)
                        _onWidgetDidBuild(() {
                          _scaffoldKey.currentState.showSnackBar(SnackBar(
                            content: Text('ON BOTTOM'),
                            duration: Duration(seconds: 3),
                          ));
                        });
                    }
                    return AnimatedBuilder(
                      animation: controller,
                      builder: (context, child) {
                        return ClipRRect(
                          borderRadius: borderRadius.evaluate(CurvedAnimation(parent: _controller, curve: Curves.ease)),
                          child: Container(
                            color: Colors.blue[800],
                            child: ListView.builder(
                              controller: controller,
                              itemCount: 5,
                              itemBuilder: (BuildContext context, int index) {
                                return ListTile(title: Text('Item $index'));
                              },
                            ),
                          ),
                        );
                      },
                    );
                  },
                ),
              ),
            ),
          ],
        ),
      ),
    );
  }
  _onWidgetDidBuild(Function callback) {
    WidgetsBinding.instance.addPostFrameCallback((_) {
      callback();
    });
  }
}

Answer 1

您不需要为它使用Tween 或任何类型的动画。

查看此示例。

class HomePage extends StatefulWidget {
  @override
  _HomePageState createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> with SingleTickerProviderStateMixin {
  AnimationController _controller;
  Duration _duration = Duration(milliseconds: 500);
  Tween<Offset> _tween = Tween(begin: Offset(0, 1), end: Offset(0, 0));
  static double _origRadius = 80;
  double _height, min = 0.1, initial = 0.5, max = 1, _radius = _origRadius;
  GlobalKey<ScaffoldState> _key = GlobalKey();

  @override
  void initState() {
    super.initState();
    _controller = AnimationController(vsync: this, duration: _duration, value: 1);
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      key: _key,
      floatingActionButton: GestureDetector(
        child: FloatingActionButton(
          child: AnimatedIcon(icon: AnimatedIcons.menu_close, progress: _controller),
          elevation: 5,
          backgroundColor: Colors.deepOrange,
          foregroundColor: Colors.white,
          onPressed: () async {
            if (_controller.isDismissed)
              _controller.forward();
            else if (_controller.isCompleted) _controller.reverse();
          },
        ),
      ),
      body: SizedBox.expand(
        child: Stack(
          children: <Widget>[
            FlutterLogo(size: 500),
            SizedBox.expand(
              child: SlideTransition(
                position: _tween.animate(_controller),
                child: DraggableScrollableSheet(
                  minChildSize: min, // 0.1 times of available height, sheet can't go below this on dragging
                  maxChildSize: max, // 0.7 times of available height, sheet can't go above this on dragging
                  initialChildSize: initial, // 0.1 times of available height, sheet start at this size when opened for first time
                  builder: (BuildContext context, ScrollController controller) {
                    if (controller.hasClients) {
                      var dimension = controller.position.viewportDimension;
                      _height ??= dimension / initial;

                      // this is used for border radius
                      double initialTop = (_height * max) - _origRadius;
                      if (dimension > initialTop) {
                        if (_radius >= 0) {
                          _radius = _origRadius - (dimension - initialTop);
                        }
                      }
                    }

                    return ClipRRect(
                      borderRadius: BorderRadius.only(topLeft: Radius.circular(_radius), topRight: Radius.circular(_radius)),
                      child: Container(
                        height: 500.0,
                        color: Colors.blue[800],
                        child: ListView.builder(
                          controller: controller,
                          itemCount: 15,
                          itemBuilder: (BuildContext context, int index) {
                            return ListTile(title: Text('Item $index'));
                          },
                        ),
                      ),
                    );
                  },
                ),
              ),
            ),
          ],
        ),
      ),
    );
  }
}