flutter - Web Camera 插件无法在 Flutter 中运行(仅在 iOS 中)
问题描述
我使用“camera.dart”包来访问网络摄像头。它在机器浏览器上运行良好,但一旦涉及移动设备,问题就会出现。即使在安卓上也可以。但在 iOS 上,在请求许可后,相机流未加载。任何帮助都将非常感谢您发现我缺少的部分。我的代码在 Camera 类中如下所示。
String getRandString() {
var random = Random.secure();
var values = List<int>.generate(8, (i) => random.nextInt(255));
return base64UrlEncode(values);
}
类实现
class _WebcamPageState extends State<WebcamPage> {
// VideoElement
late final VideoElement _webcamVideoElement;
final String videoTag = getRandString();
@override
void initState() {
super.initState();
// Create an video element which will be provided with stream source
_webcamVideoElement = VideoElement();
// Register an webcam
ui.platformViewRegistry.registerViewFactory(
videoTag, (int viewId) => _webcamVideoElement);
loadCameraStream();
}
// I suppose the issue is here
void loadCameraStream() {
var constraints = {
"audio": false,
"video": {
'mandatory':
{ 'minAspectRatio': 1.333, 'maxAspectRatio': 1.334 },
'optional':
[{ 'minFrameRate': 60 },
{ 'maxWidth': 400 }]
}
};
window.navigator.mediaDevices?.getUserMedia(constraints).then((MediaStream stream) {
_webcamVideoElement.srcObject = stream;
_webcamVideoElement.play();
});
}
@override
Widget build(BuildContext context) =>
Scaffold(
body: SingleChildScrollView(
child: Container(
height: 500.0,
child: HtmlElementView(key: UniqueKey(),
viewType:videoTag),
)
)//SingleChildScrollView
);//Scaffold
}
我有单独的处置方法
@override
void dispose() {
if (_webcamVideoElement.srcObject != null &&
(_webcamVideoElement.srcObject!.active ?? false)) {
_webcamVideoElement.pause();
var tracks = _webcamVideoElement.srcObject?.getTracks();
_webcamVideoElement.srcObject = null;
tracks?.forEach((track) {
track.stop();
});
}
super.dispose();
}
解决方案
对于那些像我一样被困住的人,这里有一个简单的演示应用程序代码,可以在任何浏览器和任何设备上运行。
import 'package:flutter/material.dart';
import 'dart:html' as html;
import 'dart:ui' as ui;
void main() {
runApp(MyApp());
}
class MyApp extends StatelessWidget {
@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> {
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(widget.title),
),
body: Center(
child: Container(),
),
floatingActionButton: FloatingActionButton(
onPressed: () async {
await showDialog(
context: context,
builder: (BuildContext context) {
return FractionallySizedBox(
heightFactor: 0.5,
widthFactor: 0.5,
child: WebCam(),
);
});
},
// tooltip: 'Increment',
child: Icon(Icons.add),
),
);
}
}
class WebCam extends StatefulWidget {
@override
_WebCamState createState() => _WebCamState();
}
class _WebCamState extends State<WebCam> {
static html.VideoElement _webcamVideoElement = html.VideoElement();
@override
void initState() {
super.initState();
// Register a webcam
// ignore: undefined_prefixed_name
ui.platformViewRegistry.registerViewFactory('webcamVideoElement',
(int viewId) {
getMedia();
return _webcamVideoElement;
});
}
getMedia() {
html.window.navigator.mediaDevices
.getUserMedia({"video": true}).then((streamHandle) {
_webcamVideoElement
..srcObject = streamHandle
..autoplay = true;
}).catchError((onError) {
print(onError);
});
}
switchCameraOff() {
if (_webcamVideoElement.srcObject != null &&
_webcamVideoElement.srcObject.active) {
var tracks = _webcamVideoElement.srcObject.getTracks();
//stopping tracks and setting srcObject to null to switch camera off
_webcamVideoElement.srcObject = null;
tracks.forEach((track) {
track.stop();
});
}
}
@override
void dispose() {
switchCameraOff();
super.dispose();
}
@override
Widget build(BuildContext context) {
return Scaffold(
body: Stack(
children: [
Container(
child: new HtmlElementView(
key: UniqueKey(),
viewType: 'webcamVideoElement',
)),
Container(
child: Column(
children: [
RaisedButton(
child: Text('Play/Pause'),
onPressed: () async {
if (_webcamVideoElement.paused) {
_webcamVideoElement.play();
} else {
_webcamVideoElement.pause();
}
},
),
RaisedButton(
child: Text('Switch off'),
onPressed: () {
switchCameraOff();
},
),
RaisedButton(
child: Text('Switch on'),
onPressed: () {
if (_webcamVideoElement.srcObject == null) getMedia();
},
),
],
),
),
],
),
);
}
}
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