How to detect DOM load event on UIWebView?

Question

I have an image-heavy web page I'm loading through a UIWebView. I display a spinner on webviewdidstartLoad and dismiss on webviewdidfinishLoad.

It's working OK, but the thing is, webviewdidfinishLoad doesn't get called until all the images on the page have been loaded.

Is there a way to detect DOM ready event so I can dismiss the spinner right after all the DOM elements have been loaded? Waiting for all the images takes too much time..

Answer 1

Straightforward to do. However - and I know this doesn't answer the question specifically - the first thing is to use WKWebView rather than UIWebView .

Then, set up a KVO on one of the properties, estimatedProgress :

override func observeValueForKeyPath(keyPath: String, ofObject object: AnyObject, change: [NSObject: AnyObject], context: UnsafeMutablePointer<Void>) {
    if keyPath == "estimatedProgress"
    {
        if let webView = object as? WKWebView
        {
            webView.evaluateJavaScript("document.readyState == \"interactive\"", completionHandler:{ (isLoaded:AnyObject!, error:NSError!) -> () in
                if let l = isLoaded as? Bool where l
                {
                    println("Loaded!")
                }
        }
    }
}

Take a look at these answers regarding readyState :

How to detect if DOMContentLoaded was fired

Javascript - How to detect if document has loaded (IE 7/Firefox 3)

Because we're working with Safari, or rather WebKit - the same engine as Safari - the above Swift code runs a JavaScript evaluation of:

document.readyState == "interactive"

This line;

if let l = isLoaded as? Bool where l

optionally casts the resulting optional to a Bool and checks that it is true before printing out "Loaded!" to the console.

Answer 2

Check out WKWebKit to replace UIWebView if you only need to support iOS 8 and above. You can inject a javascript that runs on DOM ready and then the script can communicate with your app. See the NSHipster page on the topic for more info: http://nshipster.com/wkwebkit/