Troubleshooting decidePolicyForNavigationAction Not Triggering in WKWebView

Описание: Discover why the `decidePolicyForNavigationAction` method in WKWebView doesn’t trigger after the initial load and learn how to troubleshoot this common issue.
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Understanding the Issue: decidePolicyForNavigationAction Not Triggering

If you're working with WKWebView in Objective-C and have encountered the issue where the decidePolicyForNavigationAction method is not being triggered after the web view loads a new page, you're not alone. Many developers face this problem, especially when dealing with Single Page Applications (SPAs) such as those built with frameworks like Angular.

In this post, we will explore why this issue occurs and provide clear solutions to troubleshoot and resolve it effectively.

The Problem Explained

The decidePolicyForNavigationAction method is designed to determine whether a navigation action is allowed to proceed or not. At first glance, it seems to work perfectly fine during the initial load of the web page. However, once the main screen is loaded, you may notice that this method does not get triggered for subsequent navigations, leading to unexpected app behavior.

Key Symptoms:

The method logs the URL on the initial load but fails to execute on subsequent page transitions.

This affects the ability to detect specific URLs, such as when a user needs to log out or handle special cases like custom URL schemes.

The Underlying Cause

Upon investigation, it often turns out that the webpage in question is functioning as a Single Page Application (SPA). This means that instead of reloading the page for new content, the SPA dynamically updates the content through JavaScript without changing the actual URL or triggering a new navigation event.

For instance, Angular applications manipulate the history state and modify the browser's URL without performing a traditional page navigation, which is essential for the decidePolicyForNavigationAction callback to be triggered.

Solutions to the Problem

1. Verify the Type of Web Page

Before diving deeper into code fixes, confirm whether your web application is an SPA or a traditional multi-page app.

If it's an SPA, be aware that URL changes may not coincide with actual page loads.

Check if the application utilizes proper routing techniques that maintain a clear state of navigation for the user.

2. Use JavaScript for Notification

If your web app is indeed an SPA, you might need to use JavaScript injection to inform your Objective-C code when navigation occurs. You can listen for specific events that indicate a new "page" has loaded within the SPA.

Here’s how you can achieve this:

Inject JavaScript into the WKWebView that detects navigation events and communicates with the native layer. For instance, utilize window.location change events that you can relay back to the Objective-C code.

3. Handling URL Updating Correctly

Ensure that the URLs being visited are being correctly updated. For instance, navigate changes should adequately reflect the updated window.location in JavaScript.

Implementation Example:

[[See Video to Reveal this Text or Code Snippet]]

In this example, you're sending a message back to the native side every time the page finishes loading—the equivalent of firing a navigation event.

4. Check Your WebView Setup

In addition, ensure that your WKWebView is set up and referenced correctly. For example:

Confirm the proper assignment and lifecycle management of self.wkWebMain.

Make sure there are no memory or retention issues that could inadvertently affect the web view's delegate methods.

Conclusion

In summary, if you encounter issues with the decidePolicyForNavigationAction method not triggering after the initial page load in a WKWebView, first verify if the web page is an SPA. If so, implement JavaScript event listeners to effectively communicate with your native Objective-C code. Proper management of your web view's lifecycle i