How to animate Alert dialog position in Flutter?

Issue

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

enter image description here

But I have three simple issue:

  1. set margin on bottom of dialog such as 20.0 on showing dialog
  2. using controller.reverse() on dismiss dialog
  3. 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();
  }
}

Solution

Screenshot:

enter image description here


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,
        );
      },
    );
  },
)

Answered By – CopsOnRoad

Answer Checked By – Timothy Miller (FlutterFixes Admin)

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