Question

I placed multiple UIWebViews side by side into a UIScrollView. Every UIWebView includes a “web browser” view that displays a local HTML file. Unfortunately I have no idea how to load the webviews in the background and at the same time to prevent or stop the JavaScript functions from executing that are included into the HTML files. I mean by “in the background” as I watch the first few panels and in the meantime the remainder panels just lazy load silently. I saw different applications (like pugpig) do this – it lazy loads the HTML pages and stops the JavaScript animations – it can somehow stop the JavaScript to animate the whole fade effect that I use frequently in my HTML pages between tab switches and at the moment I load the panel it continues the fade animation.

So, the question is:

How can I pause a JavaScript animation and prevent memory issues using Objective-C code and how can I continue the fade animation once I display the panel?

Answer 1

Have you tried injecting JavaScript (i.e. – (NSString*) stringByEvaluatingJavaScriptFromString: (NSString *)script) that observes onblur and onfocus of the window, or pageshow and pagehide? This post proposes a couple of solutions for that.

So, you could try something like

$(window).blur(function(){
  // when the web view loses focus
});
$(window).focus(function(){
  // when the web view gains focus
});

If that fails, you could try pagehide and pageshow events:

function pageShown(evt)
{
    if (evt.persisted)
        // The page was just restored from the Page Cache
    else
        // The initial load. This is the same as the page load event
}

function pageHidden(evt)
{
    if (evt.persisted)
        // The page was suspended and placed into the Page Cache
    else
        // This is the same as the page unload event
}

window.addEventListener("pageshow", pageShown, false);
window.addEventListener("pagehide", pageHidden, false);