Solving the Flutter_inappwebview Conundrum: InterceptAjaxRequest Can’t Add Header

Are you tired of banging your head against the wall trying to figure out why your Flutter app can’t add headers to an AJAX request using the flutter_inappwebview package? You’re not alone! In this article, we’ll dive deep into the world of Flutter, InAppWebView, and AJAX requests to help you overcome this frustrating issue.

Understanding the Problem

Before we dive into the solution, let’s take a step back and understand what’s happening. When you use the flutter_inappwebview package to display a web page in your Flutter app, it’s essential to know that it doesn’t provide direct access to the underlying webview. Instead, it relies on the Android or iOS webview to render the webpage. This is where the problem lies.

The InterceptAjaxRequest method, which is part of the flutter_inappwebview package, allows you to intercept and modify AJAX requests made by the web page. However, when you try to add headers to the request, you might encounter an issue where the headers aren’t being added.

The Reason Behind the Problem

The reason for this issue is that the flutter_inappwebview package doesn’t provide a direct way to access the underlying webview’s AJAX request objects. This means that when you try to add headers using the InterceptAjaxRequest method, it doesn’t have the necessary context to do so.

Solving the Problem

Fear not, dear developer! We’ve got a solution that’ll get you back on track in no time. To add headers to an AJAX request using the flutter_inappwebview package, you’ll need to use a combination of JavaScript and the evaluateJavascript method. Here’s a step-by-step guide to help you do just that:

Step 1: Create a JavaScript Function

Create a JavaScript function that will be used to add headers to the AJAX request. This function will be injected into the web page using the evaluateJavascript method.

<script>
  function addHeadersToAjaxRequest(xhr) {
    xhr.setRequestHeader('Custom-Header', 'Custom-Value');
  }
</script>

In the above code, we’ve created a JavaScript function called addHeadersToAjaxRequest that takes an xhr object as an argument. This function sets a custom header called Custom-Header with a value of Custom-Value.

Step 2: Inject the JavaScript Function

Use the evaluateJavascript method to inject the JavaScript function into the web page. This will make the function available to the web page, allowing it to be used to add headers to the AJAX request.

_inAppWebViewController.evaluateJavascript(source: """
  addHeadersToAjaxRequest(xhr) {
    xhr.setRequestHeader('Custom-Header', 'Custom-Value');
  }
"""),

In the above code, we’ve used the evaluateJavascript method to inject the addHeadersToAjaxRequest function into the web page.

Step 3: Intercept the AJAX Request

Use the InterceptAjaxRequest method to intercept the AJAX request and add the custom headers. This is where the magic happens!

_inAppWebViewController.interceptAjaxRequest((InAppWebViewController controller, AjaxRequestAjaxRequest request) async {
  await controller.evaluateJavascript(source: """
    addHeadersToAjaxRequest(arguments[0]);
  """, args: [request.xhr]);
  return AjaxRequestResponse();
}),

In the above code, we’ve used the InterceptAjaxRequest method to intercept the AJAX request. We then use the evaluateJavascript method to call the addHeadersToAjaxRequest function, passing the xhr object as an argument. This adds the custom headers to the AJAX request.

Putting it All Together

Here’s the complete code snippet that demonstrates how to add headers to an AJAX request using the flutter_inappwebview package:

import 'package:flutter/material.dart';
import 'package:flutter_inappwebview/flutter_inappwebview.dart';

class AjaxRequestExample extends StatefulWidget {
  @override
  _AjaxRequestExampleState createState() => _AjaxRequestExampleState();
}

class _AjaxRequestExampleState extends State<AjaxRequestExample> {
  InAppWebViewController _inAppWebViewController;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('AJAX Request Example'),
      ),
      body: InAppWebView(
        initialUrl: 'https://example.com',
        onWebViewCreated: (InAppWebViewController controller) {
          _inAppWebViewController = controller;
        },
        onLoadStop: (InAppWebViewController controller, String url) async {
          await _inAppWebViewController.evaluateJavascript(source: """
            addHeadersToAjaxRequest(xhr) {
              xhr.setRequestHeader('Custom-Header', 'Custom-Value');
            }
          """);

          _inAppWebViewController.interceptAjaxRequest((InAppWebViewController controller, AjaxRequest request) async {
            await controller.evaluateJavascript(source: """
              addHeadersToAjaxRequest(arguments[0]);
            """, args: [request.xhr]);
            return AjaxRequestResponse();
          });
        },
      ),
    );
  }
}

In this example, we’ve created a Flutter app that displays a web page using the InAppWebView widget. We’ve also added the necessary code to inject the JavaScript function, intercept the AJAX request, and add custom headers to the request.

Conclusion

In this article, we’ve explored the issue of adding headers to an AJAX request using the flutter_inappwebview package. We’ve also learned how to solve this problem by using a combination of JavaScript and the evaluateJavascript method. By following these steps, you should be able to add custom headers to your AJAX requests and overcome this frustrating issue.

Remember, when working with the flutter_inappwebview package, it’s essential to understand the underlying webview and how it interacts with your Flutter app. By doing so, you’ll be able to overcome complex issues like this and create amazing apps that provide a seamless user experience.

Method	Description
evaluateJavascript	Used to inject JavaScript code into the web page.
interceptAjaxRequest	Used to intercept and modify AJAX requests made by the web page.
addHeadersToAjaxRequest	A custom JavaScript function used to add headers to the AJAX request.

• Make sure to inject the JavaScript function before intercepting the AJAX request.
• Use the evaluateJavascript method to call the addHeadersToAjaxRequest function and pass the xhr object as an argument.
• Test your code thoroughly to ensure that the custom headers are being added correctly.

By following these steps and tips, you’ll be able to overcome the issue of adding headers to an AJAX request using the flutter_inappwebview package. Happy coding!

1. flutter_inappwebview package on pub.dev
2. Flutter issue #28167: InAppWebView doesn’t allow modifying Ajax request headers
3. Stack Overflow question: Flutter InAppWebView – How to add HTTP header to AJAX request

Frequently Asked Question

Get ready to dive into the world of Flutter and InAppWebView, where we’ll tackle the most pressing questions about InterceptAjaxRequest and adding headers!