Uni Links

A Flutter plugin project to help with App/Deep Links (Android) and Universal Links and Custom URL schemes (iOS).

These links are simply web-browser-like-links that activate your app and may contain information that you can use to load specific section of the app or continue certain user activity from a website (or another app).

App Links and Universal Links are regular https links, thus if the app is not installed (or setup correctly) they'll load in the browser, allowing you to present a web-page for further action, eg. install the app.

Installation

To use the plugin, add uni_links as a dependency in your pubspec.yaml file.

Permission

Android and iOS require to declare links' permission in a configuration file.

Feel free to examine tha example app in the example directory for Deep Links (Android) and Custom URL schemes (iOS).

For Android

Uni Links supports two types of Android links: "App Links" and "Deep Links".

  • App Links only work with https scheme and require a specified host, plus a hosted file - assetlinks.json. Check the Guide links below.
  • Deep Links can have any custom scheme and do not require a host, nor a hosted file. The downside is that any app can claim a scheme + host combo, so make sure yours are as unique as possible, eg. HST0000001://host.com.

You need to declare at least one of the two permissions in android/app/src/main/AndroidManifest.xml:

<manifest ...>
  <!-- ... other tags -->
  <application ...>
    <activity ...>
      <!-- ... other tags -->

      <!-- Deep Links -->
      <intent-filter>
        <action android:name="android.intent.action.VIEW" />
        <category android:name="android.intent.category.DEFAULT" />
        <category android:name="android.intent.category.BROWSABLE" />
        <data
          android:scheme="[YOUR_SCHEME]"
          android:host="[YOUR_HOST]" />
      </intent-filter>

      <!-- App Links -->
      <intent-filter android:autoVerify="true">
        <action android:name="android.intent.action.VIEW" />
        <category android:name="android.intent.category.DEFAULT" />
        <category android:name="android.intent.category.BROWSABLE" />
        <data
          android:scheme="https"
          android:host="[YOUR_HOST]" />
      </intent-filter>
    </activity>
  </application>
</manifest>

The android:host attribute is optional for Deep Links.

To further the specificity you can add an android:pathPrefix attribute:

<data
  android:scheme="[YOUR_SCHEME_OR_HTTPS]"
  android:host="[YOUR_HOST]"
  android:pathPrefix="/[NAME][/NAME...]" />

For more info read The Ultimate Guide. Pay close attention to the App Links section in the Guide regarding the required /.well-known/assetlinks.json file.

The Android developer docs are also a great source of information for both Deep Links and App Links.

For iOS

There are two kinds of links in iOS: "Universal Links" and "Custom URL schemes".

  • Universal Links only work with https scheme and require a specified host, entitlements and a hosted file - apple-app-site-association. Check the Guide links below.
  • Custom URL schemes can have... any custom scheme and there is no host specificity, nor entitlements or a hosted file. The downside is that any app can claim any scheme, so make sure yours is as unique as possible, eg. hst0000001 or myIncrediblyAwesomeScheme.

You need to declare at least one of the two.

--

For Universal Links you need to add or create a com.apple.developer.associated-domains entitlement - either through Xcode or by editing (or creating and adding to Xcode) ios/Runner/Runner.entitlements file.

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
  <!-- ... other keys -->
  <key>com.apple.developer.associated-domains</key>
  <array>
    <string>applinks:[YOUR_HOST]</string>
  </array>
  <!-- ... other keys -->
</dict>
</plist>

At the moment Flutter v0.4.4 does not support Universal Links, so a bit of Objective-C code will be required in ios/Runner/AppDelegate.m:

// ... other imports
#import <uni_links/UniLinksPlugin.h>

@implementation AppDelegate

// ... other methods

// NOTE: Necessary, until Flutter supports
//       `application:continueUserActivity:restorationHandler` within the
//       `FlutterPlugin` protocol.
- (BOOL)application:(UIApplication *)application continueUserActivity:(NSUserActivity *)userActivity restorationHandler:(void (^)(NSArray * _Nullable))restorationHandler {
    return [[UniLinksPlugin sharedInstance] application:application continueUserActivity:userActivity restorationHandler:restorationHandler];
}

@end

NOTE: If you get errors, make sure to run flutter run so the pod installation can occur.

For more information, read Apple's guide for Universal Links.

--

For Custom URL schemes you need to declare the scheme in ios/Runner/Info.plist (or through Xcode's Target Info editor, under URL Types):

<?xml ...>
<!-- ... other tags -->
<plist>
<dict>
  <!-- ... other tags -->
  <key>CFBundleURLTypes</key>
  <array>
    <dict>
      <key>CFBundleTypeRole</key>
      <string>Editor</string>
      <key>CFBundleURLName</key>
      <string>[ANY_URL_NAME]</string>
      <key>CFBundleURLSchemes</key>
      <array>
        <string>[YOUR_SCHEME]</string>
      </array>
    </dict>
  </array>
  <!-- ... other tags -->
</dict>
</plist>

For a little more information, read Apple's guide for Inter-App Communication.

Usage

Initial Link (String)

Returns the link that the app was started with, if any.

import 'dart:async';
import 'dart:io';

import 'package:uni_links/uni_links.dart';

// ...

  Future<Null> initUniLinks() async {
    // Platform messages may fail, so we use a try/catch PlatformException.
    try {
      String initialLink = await getInitialLink();
      // Parse the link and warn the user, if it is not correct,
      // but keep in mind it could be `null`.
    } on PlatformException {
      // Handle exception by warning the user their action did not succeed
      // return?
    }
  }

// ...

Initial Link (Uri)

Same as the getInitialLink, but converted to a Uri.

    // Uri parsing may fail, so we use a try/catch FormatException.
    try {
      Uri initialUri = await getInitialUri();
      // Use the uri and warn the user, if it is not correct,
      // but keep in mind it could be `null`.
    } on FormatException {
      // Handle exception by warning the user their action did not succeed
      // return?
    }
    // ... other exception handling like PlatformException

One can achieve the same by using Uri.parse(initialLink), which is what this convenience method does.

On change event (String)

Usually you would check the getInitialLink and also listen for changes.

import 'dart:async';
import 'dart:io';

import 'package:uni_links/uni_links.dart';

// ...

  StreamSubscription _sub;

  Future<Null> initUniLinks() async {
    // ... check initialLink

    // Attach a listener to the stream
    _sub = getLinksStream().listen((String link) {
      // Parse the link and warn the user, if it is not correct
    }, onError: (err) {
      // Handle exception by warning the user their action did not succeed
    });

    // NOTE: Don't forget to call _sub.cancel() in dispose()
  }

// ...

On change event (Uri)

Same as the stream, but transformed to emit Uri objects.

Usually you would check the getInitialUri and also listen for changes.

import 'dart:async';
import 'dart:io';

import 'package:uni_links/uni_links.dart';

// ...

  StreamSubscription _sub;

  Future<Null> initUniLinks() async {
    // ... check initialUri

    // Attach a listener to the stream
    _sub = getUriLinksStream().listen((Uri uri) {
      // Use the uri and warn the user, if it is not correct
    }, onError: (err) {
      // Handle exception by warning the user their action did not succeed
    });

    // NOTE: Don't forget to call _sub.cancel() in dispose()
  }

// ...

Contributing

For help on editing plugin code, view the documentation.

License

BSD 2-clause

Libraries