Flutter-WebRTC

<key>NSCameraUsageDescription</key>
<string>$(PRODUCT_NAME) Camera Usage!</string>
<key>NSMicrophoneUsageDescription</key>
<string>$(PRODUCT_NAME) Microphone Usage!</string>

<uses-feature android:name="android.hardware.camera" />
<uses-feature android:name="android.hardware.camera.autofocus" />
<uses-permission android:name="android.permission.CAMERA" />
<uses-permission android:name="android.permission.RECORD_AUDIO" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<uses-permission android:name="android.permission.CHANGE_NETWORK_STATE" />
<uses-permission android:name="android.permission.MODIFY_AUDIO_SETTINGS" />

android {
    //...
    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }
}

import 'package:flutter/material.dart';
import 'package:flutter_webrtc/webrtc.dart';
import 'dart:core';

/**
 * getUserMedia sample
 */
class GetUserMediaSample extends StatefulWidget {
  static String tag = 'get_usermedia_sample';

  @override
  _GetUserMediaSampleState createState() => new _GetUserMediaSampleState();
}

class _GetUserMediaSampleState extends State<GetUserMediaSample> {
  MediaStream _localStream;
  final _localRenderer = new RTCVideoRenderer();
  bool _inCalling = false;

  @override
  initState() {
    super.initState();
    initRenderers();
  }

  @override
  deactivate() {
    super.deactivate();
    if (_inCalling) {
      _hangUp();
    }
  }

  initRenderers() async {
    await _localRenderer.initialize();
  }

  // Platform messages are asynchronous, so we initialize in an async method.
  _makeCall() async {
    final Map<String, dynamic> mediaConstraints = {
      "audio": true,
      "video": {
        "mandatory": {
          "minWidth":'640', // Provide your own width, height and frame rate here
          "minHeight": '480',
          "minFrameRate": '30',
        },
        "facingMode": "user",
        "optional": [],
      }
    };

    try {
      var stream = await navigator.getUserMedia(mediaConstraints);
      _localStream = stream;
      _localRenderer.srcObject = _localStream;
    } catch (e) {
      print(e.toString());
    }
    if (!mounted) return;

    setState(() {
      _inCalling = true;
    });
  }

  _hangUp() async {
    try {
      await _localStream.dispose();
      _localRenderer.srcObject = null;
    } catch (e) {
      print(e.toString());
    }
    setState(() {
      _inCalling = false;
    });
  }

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: new AppBar(
        title: new Text('GetUserMedia API Test'),
      ),
      body: new OrientationBuilder(
        builder: (context, orientation) {
          return new Center(
            child: new Container(
              margin: new EdgeInsets.fromLTRB(0.0, 0.0, 0.0, 0.0),
              width: MediaQuery.of(context).size.width,
              height: MediaQuery.of(context).size.height,
              child: RTCVideoView(_localRenderer),
              decoration: new BoxDecoration(color: Colors.black54),
            ),
          );
        },
      ),
      floatingActionButton: new FloatingActionButton(
        onPressed: _inCalling ? _hangUp : _makeCall,
        tooltip: _inCalling ? 'Hangup' : 'Call',
        child: new Icon(_inCalling ? Icons.call_end : Icons.phone),
      ),
    );
  }
}