Dart / Flutter - Validating a string for URL

I'm trying to create a system in which I can validate a string to check if it's a url or not. (https://www.google.com/)

I found the flutter package [validator][1] but this isn't dart 2 compatible, so won't be compatible with my code.

Similarly named, I also found the [validators][2] package but I can't seem to get it working correctly with my code, as it throws the following error; (hope you like my project name ;)

Because every version of flutter_test from sdk depends on test 1.3.0
and every version of validators depends on test ^1.3.3, flutter_test from sdk is incompatible with validators.
So, because gucci depends on both validators ^1.0.0+1 and flutter_test any from sdk, version solving failed.
Unable to reload your application because "flutter packages get" failed to update package dependencies.
Exception: pub get failed (1)

If you could either find a fix for `validators` so that it doesn't throw this error and thus works correctly with my code, or suggest another method of validating a string to be URL compliant that would be great.

Thanks

**Edit** - My `pubspec.yaml` file

name: gucci
description: A new Flutter project.

dependencies:
flutter:
sdk: flutter

cupertino_icons:
barcode_scan:
gradient_app_bar:
url_launcher:
validate: ^1.7.0

dev_dependencies:
flutter_test:
sdk: flutter

fonts:
- family: PlayfairDisplay
fonts:
- asset: fonts/PlayfairDisplay-BoldItalic.ttf

- family: Kanit
fonts:
- asset: fonts/Kanit-ExtraBoldItalic.ttf

- family: Poppins
fonts:
- asset: fonts/Poppins-BoldItalic.ttf

- family: PoppinsLightItalic
fonts:
- asset: fonts/Poppins-LightItalic.ttf

- family: PoppinsMediumItalic
fonts:
- asset: fonts/Poppins-MediumItalic.ttf



[1]:

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[2]:

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For some reason, the `validators` package is requiring a pretty recent version of flutter's testing library rather than leaving it up to the application. Maybe there's a good reason for that (i.e. they're using a new feature).

The flutter engine internally requires a particular version of the flutter_test library (which is why it's generally a bad idea to specify a version of it). So to fix this you'll have to upgrade your flutter by running `flutter upgrade`. If you're already at the most recent version of the channel you're in, you may have to run `flutter channel dev` or `flutter channel master` to switch to a channel (branch really) that's updated more often.

I run on the `dev` branch/channel for the most part and while it very occasionally has problems, it doesn't happen a lot. I'd advise against using the master branch if possible though.

To check Valid URL string you just have to use `Uri.parse()` like below.

bool _validURL = Uri.parse(_adVertData.webLink).isAbsolute;


Just check value of `_validURL`

For RegExp, if you are going to find URL in a string, you can use this one.

r'^((?:.|\n)*?)((http:\/\/www\.|https:\/\/www\.|http:\/\/|https:\/\/)?[a-z0-9]+([\-\.]{1}[a-z0-9]+)([-A-Z0-9.]+)(/[-A-Z0-9+&@#/%=~_|!:,.;]*)?(\?[A-Z0-9+&@#/%=~_|!:‌​,.;]*)?)'

It can be used when you are highlighting URL in a string. For example in a chat app, you can highlight URL in a sent chat message.
This validates google.com, https://google.com, http://google.com all.

Uri.tryParse(mystring)?.hasAbsolutePath ?? false;

Some example results:

| url | result |
| --- | --- |
| `'https://stackoverflow.com/questions/52975739/dart-flutter-validating-a-string-for-url'` | true |
| `asd` | false |
| `asd:asd` | false |
| `%EMPTY_STRING%` | false |
| `google.nl` | false |
| `https:` | false |
| `https://` | false |
| `https://a` | false |
| `https://a/` | true |

Validation using **RegEx**

String hasValidUrl(String value) {
String pattern = r'(http|https)://[\w-]+(\.[\w-]+)+([\w.,@?^=%&:/~+#-]*[\w@?^=%&/~+#-])?';
RegExp regExp = new RegExp(pattern);
if (value.length == 0) {
return 'Please enter url';
}
else if (!regExp.hasMatch(value)) {
return 'Please enter valid url';
}
return null;
}

Validation using **in-built** package

final Uri uri = Uri.tryParse(value);
if (!uri.hasAbsolutePath) {
return 'Please enter valid url';
}

If you want some special case like you have to validate **deepLink** then RegEx practice is best.

I'm using this way to validate Urls. In your TextFormField's use this validator. here your url should be start from www.

validator: (website) {
String pattern =
r'^((?:.|\n)*?)((http:\/\/www\.|https:\/\/www\.|http:\/\/|https:\/\/)?[a-z0-9]+([\-\.]{1}[a-z0-9]+)([-A-Z0-9.]+)(/[-A-Z0-9+&@#/%=~_|!:,.;]*)?(\?[A-Z0-9+&@#/%=~_|!:‌​,.;]*)?)';
RegExp regExp = RegExp(pattern);
if (website.isEmpty) {
return "Please enter your website";
} else if (!(regExp.hasMatch(website))) {
return "Website Url must be started from www";
} else {
return null;
}
},

TextEditingController urlController = TextEditingController();
String urlData = '';
static final GlobalKey<FormFieldState<String>> _orderFromkey =
GlobalKey<FormFieldState<String>>();



@override
Widget build(BuildContext context) {
return SafeArea(
child: Scaffold(
resizeToAvoidBottomInset: false,

body: Column(
children: [
appBar(label: appName),
Padding(
padding: const EdgeInsets.all(8.0),
child: TextFormField(
key: _orderFromkey,
controller: urlController,
validator: (value) {
String patttern = r"((https?:www\.)|(https?:\/\/)|(www\.))[-a-zA-Z0-9@:%._\+~#=]{1,256}\.[a-zA-Z0-9]{1,6}(\/[-a-zA-Z0-9()@:%_\+.~#?&\/=]*)?";
RegExp regExp = new RegExp(patttern);
if (!regExp.hasMatch(value!)) {
return 'Please enter valid URL';
}
},




decoration: InputDecoration(

fillColor: appColor,
labelText: "url",
labelStyle: new TextStyle(color: appColor),
contentPadding: EdgeInsets.only(left: 10, right: 10),
enabledBorder: UnderlineInputBorder(
borderSide: BorderSide(color: appColor),
),
focusedBorder: UnderlineInputBorder(
borderSide: BorderSide(color: black),
),
hintText: 'Enter Your URL'),
),
),
Padding(
padding: const EdgeInsets.all(8.0),
child: InkWell(
onTap: () {
print('_orderFromkey: ${_orderFromkey}');
final FormFieldState<String>? form =
_orderFromkey.currentState;
if (form!.validate()) {
urlData = urlController.text;
Get.toNamed('/showQr', arguments: urlData);
print('text : ${urlData}');
} else {
// _autoValidation = true;
}
},
child: Container(
width: ScreenSize.size.width * 0.6,
height: ScreenSize.size.height * 0.1,
decoration: BoxDecoration(
borderRadius: BorderRadius.circular(10),
color: appColor,
),
child: const Align(
alignment: Alignment.center,
child: Text(
'Submit',
style: TextStyle(
fontSize: 20,
color: white,
fontWeight: FontWeight.w700),
textAlign: TextAlign.center,
)),
),
),
),
],
)),
);

}

var urlPattern = r"(https?|http)://([-A-Z0-9.]+)(/[-A-Z0-9+&@#/%=~_|!:,.;]*)?(\?[A-Z0-9+&@#/%=~_|!:‌​,.;]*)?";
var match = new RegExp(urlPattern, caseSensitive: false).firstMatch('https://www.google.com');


You can use RegExp too.

I used the following method below. Depending on your rec, all valid URLs need to have a host (ex, google.com). If a URL does not have a host it returns an empty string (not undefined or null).

bool isURLValid = Uri.parse('https://google.com/').host.isNotEmpty;

Using .isAbsolute, as some have already reported, marks URLs such as 'http:' to be valid URLs which not.