Add browser chooser

android/src/main/kotlin/com/linusu/flutter_web_auth/FlutterWebAuthPlugin.kt

@@ -28,16 +28,27 @@ class FlutterWebAuthPlugin(private val context: Context): MethodCallHandler {
         "authenticate" -> {
           val url = Uri.parse(call.argument("url"))
           val callbackUrlScheme = call.argument<String>("callbackUrlScheme")!!
+          val showBrowserChooser = call.argument<Boolean>("showBrowserChooser")!!
 
           callbacks[callbackUrlScheme] = resultCallback
 
-          val intent = CustomTabsIntent.Builder().build()
           val keepAliveIntent = Intent(context, KeepAliveService::class.java)
 
-          intent.intent.addFlags(Intent.FLAG_ACTIVITY_SINGLE_TOP or Intent.FLAG_ACTIVITY_NEW_TASK)
-          intent.intent.putExtra("android.support.customtabs.extra.KEEP_ALIVE", keepAliveIntent)
-
-          intent.launchUrl(context, url)
+          if (showBrowserChooser) {
+            val intent = Intent(Intent.ACTION_VIEW)
+            intent.data = url
+            intent.addFlags(Intent.FLAG_ACTIVITY_SINGLE_TOP or Intent.FLAG_ACTIVITY_NEW_TASK)
+            intent.putExtra("android.support.customtabs.extra.KEEP_ALIVE", keepAliveIntent)
+            // Create intent to show the chooser dialog
+            val chooser = Intent.createChooser(intent, "")
+            context.startActivity(chooser)
+          } else {
+            val intent = CustomTabsIntent.Builder().build()
+            intent.intent.addFlags(Intent.FLAG_ACTIVITY_SINGLE_TOP or Intent.FLAG_ACTIVITY_NEW_TASK)
+            intent.intent.putExtra("android.support.customtabs.extra.KEEP_ALIVE", keepAliveIntent)
+            intent.launchUrl(context, url)
+          }
+
         }
         "cleanUpDanglingCalls" -> {
           callbacks.forEach{ (_, danglingResultCallback) ->

lib/flutter_web_auth.dart

@@ -26,15 +26,21 @@ class FlutterWebAuth {
 
   /// Ask the user to authenticate to the specified web service.
   ///
-  /// The page pointed to by [url] will be loaded and displayed to the user. From the page, the user can authenticate herself and grant access to the app. On completion, the service will send a callback URL with an authentication token, and this URL will be result of the returned [Future].
+  /// The page pointed to by [url] will be loaded and displayed to the user. 
+  /// From the page, the user can authenticate herself and grant access to the app. 
+  /// On completion, the service will send a callback URL with an authentication token, 
+  /// and this URL will be result of the returned [Future].
   ///
-  /// [callbackUrlScheme] should be a string specifying the scheme of the url that the page will redirect to upon successful authentication.
-  static Future<String> authenticate({@required String url, @required String callbackUrlScheme}) async {
+  /// [callbackUrlScheme] a string specifying the scheme of the url that the page will redirect to upon successful authentication.
+  /// [showBrowserChooser] a boolean to always show a browser chooser to the user when he has multiple browser installed,
+  /// can be usefull if some browser restriction rules are set by the authentication service).
+  static Future<String> authenticate({@required String url, @required String callbackUrlScheme, bool showBrowserChooser = false}) async {
     WidgetsBinding.instance.removeObserver(_resumedObserver); // safety measure so we never add this observer twice
     WidgetsBinding.instance.addObserver(_resumedObserver);
     return await _channel.invokeMethod('authenticate', <String, dynamic>{
       'url': url,
       'callbackUrlScheme': callbackUrlScheme,
+      'showBrowserChooser': showBrowserChooser,
     }) as String;
   }