Non-Native Scroller Performance within Android Webviews

Question

Anyone out there done reserch or have real good experience with 3rd party scroller's for apps running in a webview? Especially with more than one divide that scrolls?? i.e. A webview with a navigation panel and a details panel.

When there is only one divide requiring a scroller, it works smoothly but in the situation above, its very choppy. I'm sure a lot of developers have encountered this issue.

I have tried iScroll (and is best so far) along with other plugins but the quality of the scroll is less than desirable. I can't use iFrames because I need to tweak the style of some HTML docs that are pulled from our server. I've searched online for a way to invoke the native scroller in HTML divides and haven't found a way to. Is there a way and how could I do this?

I've been playing around using API's 9 thru 15 on various devices and I'm not seeing any difference when it comes to the performance of a non-native scroller. I'm currently developing the app on 15 if this is a help to your answer. Also, I have hardware acceleration off and this works best.

I've played with jqm, Sencha, and alike and they seen to have satisfactory scroller's. Does anyone know what they use? The issue why I'm not primarily using any of these platforms is the bulk and other performance issues.

Currently I'm building an app using raw javascript and this is proving to have a significant improvement in performance over all in animations within the webview layouts - Significantly better over any of the big name cross platform solutions. Unfortunately I am not experienced enough to build my own scroller so I need to find an out of the box solution.

Any ideas, leads or solutions so others that are better at writing apps with javascript can have a fighting chance building quality apps would be very appreciated.

With you experiences and experties, please include what API level you were using.

Thnx

Answer 1

I did many tests about this. I won't recommend a third party scrolling based only on HTML because on my experience the problem is not the javascript, but the webview itself:

1) Iframes performance on WebView is weak weak weak. I got a nearly 40% decrease on performance for any (complicated) app just for placing it inside an iframe. Besides, they cause much more problems if you use hardware acceleration.

2) Scrolling of DIVS is acceptable if stuff in divs is simple and SHORT, but the performance decreases as you add more elaborate stuff to scroll. For example, in my case it made a difference to enclose everything in ul/li's (slower) or not (noticeabily faster). However, the feeling is not perfect, ie., if you are used to native scroll, you realise this is not native scroll.

3) Raw scrolling of the body is very good. Besides, you get native-like feedback, such as the glowing effect on overscroll, etc. But mind that this scroll is NOT using javascript, it's just a page bigger than the webview that you let the user to scroll and WebView takes care of it. In my case, this was the only acceptable scroll experience I wanted for my users.

So I came with a mixed solution: I did a JavaScript-callable Java function that would open another webview with requested size like if it was an iframe, so I could open it from HTML and fill with stuff, it was not very difficult to do, and the improvement was awesome.

More things:

4) Scrolling a WebView from Java (scrollTo) was very useful in my case, where I had a huge HTML page loaded (kind of a magazine) to be swipped. Performance if I asked the webview to scroll from Java was much, much, much better than relying on JavaScript to do the scroll.

5) Hardware-Acceleration improves the scroll speed a 100% -setLayerType(HARDWARE)- but to be able to use it you have to keep you html very very simple. stuff like Display:none/block, etc completely break the application (see WebView fails to render until touched Android 4.2.2 for more info)

6) HTML5 animations on big images completely kill the scrolling experience.

7) All this is not valid in a couple months, goole is replacing the rendering engine to "Blink", so who knows what's gonna happen. I am restless.