WKWebView at Mobify

A talk on WKWebView, why it's better (and worse) that UIWebView, and how we made it work for us at Mobify.

Transcript

1. WKWebView Oct. 1, 2015
2. What is a UIWebView? • Original web rendering component introduced in iOS 2.0 • This is what was historically used to build out hybrid aps or load any web content inside an iOS app
3. Remember this app?
4. UIWebView !== Safari • Mobile Safari tends to load pages 2-3x quicker than a UIWebView • Changes and fixes applied to Safari usually not ported into UIWebView • Clunky, crashy, leaks memory • Scrolling blocks images loading (though we recently found a hack to fix this) • Different rendering and JavaScript engine than Safari (i. e. not Nitro)
5. Why doesn’t UIWebView have Nitro? • Cynical answer: ◦ Nitro is excluded because Apple wanted to make hybrid apps less performant and force everybody to use their native platform • Real answer: ◦ Excluded due to security reasons ◦ Running a Just-In-Time (JIT) compiler requires marking pages in RAM as executable - iOS does not allow this out of security concerns (except in Safari)
6. Introducing WKWebView • Introduced in iOS 8 to give developers a performant web view (“same” performance as Safari) • Key: WKWebView's rendering is all done in a separate process owned by the WKWebView
7. WKWebView == WebKit Webview
8. What does WKWebView give us?
9. Better HTML5 Support
10. What does WKWebView give us? • Significant performance gains in WebGL applications (though supported in UIWebview) • Less "crashy" behaviour when rendering bugs are triggered from HTML/CSS/JavaScript
11. More benefits! • Faster JavaScript and page rendering (thanks Nitro!) • 60fps scrolling • Better communication between Swift and JS (we haven’t experimented with this yet) • Since we are sharing the JS engine with Safari, WKWebView should be better maintained and more reliable
12. How do I implement it? • Don’t worry, there’s a tonne of great documentation! • What was formerly a single class (UIWebView) and protocol (UIWebViewDelegate) is now 14 classes and 3 protocols (WKNavigationDelegate, WKScriptMessageHandler, WKUIDelegate) • Other than class docs (and stackoverflow), no official “How-To WKWebView” from Apple
13. WebKit Related Classes WKBackForwardList WKBackForwardListItem WKFrameInfo WKNavigation WKNavigationAction WKNavigationResponse WKPreferences WKProcessPool WKScriptMessage WKSecurityOrigin WKUserContentController WKUserScript WKWebViewConfiguration WKWebsiteDataRecord WKWebsiteDataStore WKWindowFeatures WKWebView
14. More code required • Automatically handled by UIWebView ◦ App store links ◦ JS alerts, confirms, inputs ◦ Sharing cookies between web views
15. Bugs, Workarounds, and Current Limitations
16. Cannot load local file URLs • This is sorta critical for Astro… ◦ file: ///Users/jason/Library/Developer/CoreSimulator/Devic es/3AB02B9E-B5F4-4668-B9F3- 633F1D5053AD/data/Containers/Bundle/Application/E368 F75E-DD6B-44C2-B739-F8868BE0EED8/Astro%20Sandbox. app/www/index.html • UIWebView: ◦ webView!.loadRequest(request)
17. Our Solution • High-level: copy the files we need to load into a /tmp directory that we can load files from • Alternative: copy files we need to a local webserver running on the device • Appears to be fixed this in iOS 9
19. Cannot intercept POST requests • Previously did this to stack web views • POST bodies are missing in NSURLRequest sent to delegate methods • Solution: ◦ for now leave it -- in line with Android behavior ◦ future -- potential hack to let the post navigate, extract the result and put that in a new webview • Good news: WebKit forums indicate this is a bug and there seems to be a bit of traction
20. UI state preservation/restoration broken • WKWebView cannot be archived and doesn’ t participate in state/preservation/restoration • Previously used to reduce memory footprint and prevent crashes • Solution: build our own by saving the last known URL
21. WSOD - White Screen of Death • Seeing some webviews display about:blank for no reason upon navigating back • Appears to be a memory issue • Thought: is it fixed in iOS 9?
22. WSOD - Our Solution
23. WKWebView and self-signed certs • Bug in WKWebView where the documented way of doing custom analysis of SSL certificates is broken ◦ webView(_:didReceiveAuthenticationChallenge: completionHandler:) is *never* called • Important for internal use • No workaround
26. No Cordova Support...yet! (will be iOS 9 only)
27. Are others using it? • Firefox for iOS is built using WKWebView and is now in public preview (Sept. 3) • Some other apps have started using it
28. Chrome (as of Jan.) is not
29. So, is it worth it? Can we work around all the issues?
30. WKWebView in Astro today • Currently disabled by default • Turned on in the Catalogue app • Hoping to try it on next release of ThinkGeek and hopefully Ritchie Bros. • Working on tests and seeing what is fixed in iOS 9 -- feeling solid for iOS 9 • Goal is to maintain both for now
31. (Currently working on docs update) How do I enable it in my app?