问题

By this simple code I can show dialog on bottom of screen like with this screenshot:

But I have three simple issue:

set margin on bottom of dialog such as 20.0 on showing dialog
using controller.reverse() on dismiss dialog
dismiss dialog on click on outside of dialog

Full source code:

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

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

class _MyHomePageState extends State<MyHomePage> {
  void showPopup() {
    showDialog(
      context: context,
      builder: (_) => PopUp(),
    );
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text(
              'You have pushed the button this many times:',
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: showPopup,
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ), // This trailing comma makes auto-formatting nicer for build methods.
    );
  }
}

class PopUp extends StatefulWidget {
  @override
  State<StatefulWidget> createState() => PopUpState();
}

class PopUpState extends State<PopUp> with SingleTickerProviderStateMixin {
  AnimationController controller;
  Animation<double> opacityAnimation;
  Tween<double> opacityTween = Tween<double>(begin: 0.0, end: 1.0);
  Tween<double> marginTopTween = Tween<double>(begin: 300, end: 280);
  Animation<double> marginTopAnimation;

  @override
  void initState() {
    super.initState();

    controller = AnimationController(duration: const Duration(milliseconds: 300), vsync: this);
    marginTopAnimation = marginTopTween.animate(controller)
      ..addListener(() {
        setState(() {});
      });
    controller.forward();
  }

  @override
  Widget build(BuildContext context) {
    return FadeTransition(
      opacity: opacityTween.animate(controller),
      child: Material(
        color: Colors.transparent,
        child: Container(
          margin: EdgeInsets.only(
            top: marginTopAnimation.value,
            left:20.0,
            right:20.0,
          ),
          color: Colors.red,
          child: Text("Container"),
        ),
      ),
    );
  }

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

回答1:

Screenshot:

Code:

floatingActionButton: FloatingActionButton(
  onPressed: () {
    showGeneralDialog(
      barrierLabel: "Label",
      barrierDismissible: true,
      barrierColor: Colors.black.withOpacity(0.5),
      transitionDuration: Duration(milliseconds: 700),
      context: context,
      pageBuilder: (context, anim1, anim2) {
        return Align(
          alignment: Alignment.bottomCenter,
          child: Container(
            height: 300,
            child: SizedBox.expand(child: FlutterLogo()),
            margin: EdgeInsets.only(bottom: 50, left: 12, right: 12),
            decoration: BoxDecoration(
              color: Colors.white,
              borderRadius: BorderRadius.circular(40),
            ),
          ),
        );
      },
      transitionBuilder: (context, anim1, anim2, child) {
        return SlideTransition(
          position: Tween(begin: Offset(0, 1), end: Offset(0, 0)).animate(anim1),
          child: child,
        );
      },
    );
  },
)

回答2:

Output:

Not sure if I got your question clearly, if this is what you are looking for, replace your PopUp class with mine.

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(primarySwatch: Colors.blue),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

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

class _MyHomePageState extends State<MyHomePage> {
  void showPopup() {
    showDialog(
      context: context,
      builder: (_) => PopUp(),
    );
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text(
              'You have pushed the button this many times:',
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: showPopup,
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ), // This trailing comma makes auto-formatting nicer for build methods.
    );
  }
}

class PopUp extends StatefulWidget {
  @override
  State<StatefulWidget> createState() => PopUpState();
}

class PopUpState extends State<PopUp> with TickerProviderStateMixin {
  AnimationController controller;
  double _bottom = 0, _fromTop = 300, _screenHeight, _containerHeight = 300;

  @override
  void initState() {
    super.initState();
    controller = AnimationController(duration: const Duration(milliseconds: 300), vsync: this)
      ..addListener(() {
        Timer.periodic(Duration(milliseconds: 15), (timer) {
          if (_bottom < _screenHeight - _fromTop - _containerHeight) {
            _bottom += 1;
            setState(() {});
          }
        });
      });
    controller.forward();
  }

  @override
  Widget build(BuildContext context) {
    _screenHeight = MediaQuery.of(context).size.height;
    return SizedBox(
      width: double.infinity,
      height: double.infinity,
      child: Stack(
        children: <Widget>[
          Positioned(
            bottom: _bottom,
            left: 0,
            right: 0,
            child: Container(height: _containerHeight, color: Colors.green),
          ),
        ],
      ),
    );
  }

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

回答3:

From top to bottom you can use

bool _fromTop = true;

@override
Widget build(BuildContext context) {
  return Scaffold(
    floatingActionButton: FloatingActionButton(
      onPressed: () {
        showGeneralDialog(
          barrierLabel: "Label",
          barrierDismissible: true,
          barrierColor: Colors.black.withOpacity(0.5),
          transitionDuration: Duration(milliseconds: 700),
          context: context,
          pageBuilder: (context, anim1, anim2) {
            return Align(
              alignment: _fromTop ? Alignment.topCenter : Alignment.bottomCenter,
              child: Container(
                height: 300,
                child: SizedBox.expand(child: FlutterLogo()),
                margin: EdgeInsets.only(top: 50, left: 12, right: 12, bottom: 50),
                decoration: BoxDecoration(
                  color: Colors.white,
                  borderRadius: BorderRadius.circular(40),
                ),
              ),
            );
          },
          transitionBuilder: (context, anim1, anim2, child) {
            return SlideTransition(
              position: Tween(begin: Offset(0, _fromTop ? -1 : 1), end: Offset(0, 0)).animate(anim1),
              child: child,
            );
          },
        );
      },
    ),
  );
}

来源：https://stackoverflow.com/questions/57131978/how-to-animate-alert-dialog-position-in-flutter

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Flutter