Full screen video background in Flutter on Login

A solution which handles overflow using a FittedBox widget:

Stack(
  children: <Widget>[
    SizedBox.expand(
      child: FittedBox(
        fit: BoxFit.cover,
        child: SizedBox(
          width: _controller.value.size?.width ?? 0,
          height: _controller.value.size?.height ?? 0,
          child: VideoPlayer(_controller),
        ),
      ),
    ),
    LoginWidget()
  ],
)

A full example would be:

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

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

class BackgroundVideo extends StatefulWidget {
  @override
  _BackgroundVideoState createState() => _BackgroundVideoState();
}

class _BackgroundVideoState extends State<BackgroundVideo> {
  VideoPlayerController _controller;

  @override
  void initState() {
    super.initState();
    _controller = VideoPlayerController.network(
        'http://www.sample-videos.com/video123/mp4/720/big_buck_bunny_720p_20mb.mp4')
      ..initialize().then((_) {
        _controller.play();
        _controller.setLooping(true);
        // Ensure the first frame is shown after the video is initialized
        setState(() {});
      });
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        body: Stack(
          children: <Widget>[
            SizedBox.expand(
              child: FittedBox(
                fit: BoxFit.cover,
                child: SizedBox(
                  width: _controller.value.size?.width ?? 0,
                  height: _controller.value.size?.height ?? 0,
                  child: VideoPlayer(_controller),
                ),
              ),
            ),
            LoginWidget()
          ],
        ),
      ),
    );
  }

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

class LoginWidget extends StatelessWidget {
  const LoginWidget({
    Key key,
  }) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Column(
      mainAxisAlignment: MainAxisAlignment.spaceAround,
      children: <Widget>[
        Container(),
        Container(
          padding: EdgeInsets.all(16),
          width: 300,
          height: 200,
          color: Colors.grey.withAlpha(200),
          child: Column(
            mainAxisAlignment: MainAxisAlignment.spaceAround,
            children: <Widget>[
              TextField(
                decoration: InputDecoration(
                  hintText: 'Username',
                ),
              ),
              TextField(
                decoration: InputDecoration(
                  hintText: 'Password',
                ),
              ),
              RaisedButton(
                child: Text('Login'),
                onPressed: () {},
              ),
            ],
          ),
        ),
      ],
    );
  }
}

May be stack widget is one of the solution.

Stack class is useful if you want to overlap several children in a simple way, for example having some text and an image, overlaid with a gradient and a button attached to the bottom.

     Stack(
        //alignment:new Alignment(x, y)
        children: <Widget>[
          new Container(
            //play video here
          ),
          new Container(
            //have your Ui here
          ),
        ],
      ),

The only way I have gotten remotely near to the solution is something like this.

Assuming this is a 1920 x 1080 video and you're using video_player.

Container(
  width: *screen width*,
  height: *screen height*,
  child: Stack(
    children: <Widget>[
      Center(
        child: Transform.scale(
          scale: 3.9, //change this number as needed
          AspectRatio(
            aspectRatio: _controller.value.aspectRatio,
            child: VideoPlayer(_controller),
          ),
        ),
      ),
      *widgets will go on top of screen*
    ],
  ),
)

The finding the right scale double is the toughest part, you might need to find a small equation that can tailor to all devices. If you find any typos or want to add onto it, feel free. Hope this helps!

try the below code.

import 'dart:async';

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

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

class VideoPlayerApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Video Player Demo',
      home: VideoPlayerScreen(),
    );
  }
}

class VideoPlayerScreen extends StatefulWidget {
  @override
  _VideoPlayerScreenState createState() => _VideoPlayerScreenState();
}

class _VideoPlayerScreenState extends State<VideoPlayerScreen> {
  VideoPlayerController _controller;
  Future<void> _initializeVideoPlayerFuture;

  @override
  void initState() {
    // Create and store the VideoPlayerController. The VideoPlayerController
    // offers several different constructors to play videos from assets, files,
    // or the internet.
    _controller = VideoPlayerController.network(
      'https://flutter.github.io/assets-for-api-docs/assets/videos/butterfly.mp4',
    );

    // Initialize the controller and store the Future for later use.
    _initializeVideoPlayerFuture = _controller.initialize();

    // Use the controller to loop the video.
    _controller.setLooping(true);

    super.initState();
  }

  @override
  void dispose() {
    // Ensure disposing of the VideoPlayerController to free up resources.
    _controller.dispose();

    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      // Use a FutureBuilder to display a loading spinner while waiting for the
      // VideoPlayerController to finish initializing.
      body: FutureBuilder(
        future: _initializeVideoPlayerFuture,
        builder: (context, snapshot) {
          if (snapshot.connectionState == ConnectionState.done) {
            // If the VideoPlayerController has finished initialization, use
            // the data it provides to limit the aspect ratio of the video.
            return Stack(
              fit: StackFit.expand,
              children: <Widget>[
                Container(
                  child: AspectRatio(
                    aspectRatio: _controller.value.aspectRatio,
                    // Use the VideoPlayer widget to display the video.
                    child: VideoPlayer(_controller),
                  ),
                ),
              ],
            );
          } else {
            // If the VideoPlayerController is still initializing, show a
            // loading spinner.
            return Center(child: CircularProgressIndicator());
          }
        },
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: () {
          // Wrap the play or pause in a call to `setState`. This ensures the
          // correct icon is shown.
          setState(() {
            // If the video is playing, pause it.
            if (_controller.value.isPlaying) {
              _controller.pause();
            } else {
              // If the video is paused, play it.
              _controller.play();
            }
          });
        },
        // Display the correct icon depending on the state of the player.
        child: Icon(
          _controller.value.isPlaying ? Icons.pause : Icons.play_arrow,
        ),
      ), // This trailing comma makes auto-formatting nicer for build methods.
    );
  }
}

the main code which makes the video fit the whole screen perfectly is the fit: StackFit.expand,

I was doing the same stuff and the following code worked for me.

Stack(
      fit: StackFit.expand,
      children: [
        Container(
        child: _controller.value.initialized
            ? AspectRatio(
                aspectRatio: _controller.value.aspectRatio,
                child: VideoPlayer(_controller),
              )
            : Container(),
      ), ] )