Friday 27 November 2009

How To: Android Scrollable Divs

Lately I've been working on a webapp for the Motorola Droid and a QNX CAR device. The application interface is a split screen with one half being a list of items of variable length. Neither of these browsers on these devices support iframes or scrollable divs, so the approach used in a traditional browser was not an option.

The application was using jQuery, so using the jQuery UI Draggable plugin was a natural choice. It was quick and easy to implement and worked well on the QNX device, but didn't work at all on the Android browser.

To get the prototype version of the application finished on time for the deadline, I resorted to adding up/down buttons to the interface that scrolled the div content by manipulating the margin-top via javascript. This satisfied the client, but as a solution it was less than optimal, and in my opinion it made the UI feel clunky.

At the time that I write this, there's not a lot of information about how to deal with this issue in the Android browser. It took me a while to discover that this issue is also a problem for the iPhone/iPod Touch browser and since Android's browser also uses WebKit, there is already a working solution called iScroll developed by Matteo Spinelli on

This code utilises WebKit's "touch" events, which are akin to click events, but are only fired by touch screens. You can find a great introduction to Javascript Touch Events on Michael's "Back To The Code" blog. If you're new to developing mobile webapps, you should probably also take a look at iPhone Webapps 101.

Hopefully posting these bits and pieces together here will help save somebody a lot of time searching on Google.

Friday 20 November 2009

Skype vs XAMPP

I like Skype. I use it everyday. Most of the people I need to communicate with are Skype users. Skype handles chat, voice and file transfers to individuals and groups, and one-to-one video-chat, and allows you to cheaply connect to real-world telephony and SMS too. I'd have to say I am a bit of a fan.

The only annoyance I have found is that when I reboot my PC (which is not that often), Skype starts up and grabs port 80 before my XAMPP install starts. This means that my local XAMPP Apache install fails to start. In the past I've been forced to quit Skype, start Apache and then restart Skype. No big deal, but a little annoying.

Yesterday I had a closer look at Skype's Advanced Settings and found this problem can be resolved by simply unchecking the "Use port 80 and 443 as alternatives for incoming connections" option and restarting Skype. Simple stuff, but I though it was worth posting.

Monday 9 November 2009

Parsing and visualising JSON

Over the last few days I've been working on a project that uses some fairly complex JSON objects. Because JSON (JavaScript Object Notation) is a lightweight data interchange format, it can be a great way to grab complex data structures via Ajax. It's been said that JSON is "the fat-free alternative to XML".

In theory JSON is easy to parse, but if your data structure starts to contain numerous nested objects and arrays, it can be come hard to keep track of and starts looking like a long jumble of punctuation.

I found Brenton Fletcher's JSON 2 HTML to be a quick and easy way to check your JSON syntax and visualize the data. You can either copy+paste a JSON string or sumbit a URL and the will page load the JSON string from the URL. It's definitely worth checking out if you're working with JSON.