iosWebViewFix/example/integration_test/headless_in_app_webview/take_screenshot.dart

import 'dart:async';
import 'dart:typed_data';

import 'package:flutter/foundation.dart';
import 'package:flutter/widgets.dart';
import 'package:flutter_inappwebview/flutter_inappwebview.dart';
import 'package:flutter_test/flutter_test.dart';

import '../constants.dart';

void takeScreenshot() {
  final shouldSkip = kIsWeb ||
      ![
        TargetPlatform.android,
        TargetPlatform.iOS,
        TargetPlatform.macOS,
      ].contains(defaultTargetPlatform);

  test('take screenshot', () async {
    final Completer<InAppWebViewController> controllerCompleter =
        Completer<InAppWebViewController>();
    final Completer<void> pageLoaded = Completer<void>();

    var headlessWebView = new HeadlessInAppWebView(
        initialUrlRequest: URLRequest(url: TEST_URL_1),
        onWebViewCreated: (controller) {
          controllerCompleter.complete(controller);
        },
        onLoadStop: (controller, url) async {
          if (!pageLoaded.isCompleted) {
            pageLoaded.complete();
          }
        });

    await headlessWebView.run();
    expect(headlessWebView.isRunning(), true);

    final InAppWebViewController controller = await controllerCompleter.future;
    await pageLoaded.future;

    final String? url = (await controller.getUrl())?.toString();
    expect(url, TEST_URL_1.toString());

    final Size? size = await headlessWebView.getSize();
    expect(size, isNotNull);

    final Uint8List? screenshot = await controller.takeScreenshot();
    expect(screenshot, isNotNull);

    await headlessWebView.dispose();

    expect(headlessWebView.isRunning(), false);
  }, skip: shouldSkip);
}