final options = InAppBrowserClassSettings(
  browserSettings: InAppBrowserSettings(
    hideTitleBar: true,
    allowGoBackWithBackButton: false,
    shouldCloseOnBackButtonPressed: true,
    hideToolbarTop: !displayNavigation,
    hideUrlBar: true,
  ),
  webViewSettings: InAppWebViewSettings(
    useShouldOverrideUrlLoading: true,
    javaScriptEnabled: true,
    isInspectable: true,
    clearCache: true,
    clearSessionCache: true,
  ),
);

final InAppBrowser browser = CustomBrowser(
  onCloseCallback: () {
    // Do something
  },
);
  
browser.openUrlRequest(
urlRequest: URLRequest(url: WebUri(url)),
settings: options,
);

class CustomBrowser extends InAppBrowser {
  CustomBrowser({
    this.onCloseCallback,
    int? windowId,
    UnmodifiableListView<UserScript>? initialUserScripts,
  }) : super(
          windowId: windowId,
          initialUserScripts: initialUserScripts,
        );

  final Function()? onCloseCallback;

  @override
  Future onBrowserCreated() async {
    developer.log("Browser Created!");

    if (webViewController != null) {
      developer.log('Adding JS handler');

      webViewController!.addJavaScriptHandler(
        handlerName: JavaScriptHandlerType.closeInAppBrowser,
        callback: (_) {
          if (onCloseCallback != null) {
            onCloseCallback!();
          }

          close();
        },
      );
    }
  }
}