Monday, October 24, 2011

AT&T Mobile Hackathon SF

I have not been doing Android development for a while, and decided to get my feet wet again by signing up for my very first hackathon. Most hackathons last until the wee hours of the night, so I was rather excited to find one that was scheduled for 10am to 8:30pm, when I am normally awake. It was the AT&T Mobile Hackathon in San Francisco on October 22, 2011.


Since it was a mobile hackathon, I knew I was going to be coding either in Android or html5. Last time I did any Android development was more than a year ago though, so I downloaded the latest SDK and updated my Eclipse setup. I then read through the email from the organizers to see if there were any rules. I didn't see any, because the email mostly consisted of the list of hot sponsored prizes:

  • Tons and tons of Apple Gift Certificates for the top 3 teams, provided by AT&T and Apigee
  • Top hackathon team (yes, the entire team) will receive AT&T Mobile Hotspot Elevate devices (wifi pucks) with 1 month of free service courtesy of Sierra Wireless
  • $200 Gift Certificate for Best App Built with Apigee OAuth API
  • Amazon certificates for Best App Built with the YP API
  • The top two apps built with the HTC OpenSense SDK's Pen API will get two exclusive new AT&T Jetstream tablets
  • Top two apps which leverage the Galaxy S2's GPU the best (can be GPU tweeks for exisiting games) - Two (2) Galaxy S2 - Sponsored by ARM
  • Top app built with ARM NEON instruction API - ODROID - Sponsored by ARM

The sponsored prizes really reminded me of Iron Chef. The secret ingredient was the API, and the dish was the app. Of course you can also just write any mobile app without using the sponsor APIs, but I thought it was much more fun to compete with a common ingredient. Though I wasn't sure how anyone was going to build an app with the ARM NEON instruction API just like that...

Tables and Talks

I took the Caltrain up, and arrived quite a bit earlier than 10am. They were still setting up the breakfast area and the sponsor tables when I got there. Since I ate already, I went to check out the different sponsors. The HTC table really caught my eyes with their gadget - the new JetStream tablet. Michael from HTC carefully unwrapped one from his towel (!) and showed me the cool apps using the pen. I was hooked, and decided then and there that I my secret ingredient would be the pen api.

As more participants showed up, we were ushered into a big conference room, where the organizers explained the schedule for the day. Each sponsor then gave a quick overview of their api, before we broke for lunch.

Environment setup

With a plate of Mediterranean food in my hand, I looked around for a nice table to set up shop, and stumbled upon a conference room with a few other developers who were already looking at the HTC pen api. Perfect.

My home for the day. Picture by @htcdev

First order of business: get an emulator running with the pen api enabled. The HTC dev site has instructions with screenshots, but unfortunately the Ice Cream Sandwich UI was rather different, so it took me a while to figure out how to give it my downloaded zip files. Even more unfortunate, I could not create an AVD even after importing the HTC add-ons! I asked David from HTC for help, and he had the exact same problem. Perry, a fellow hackathon participant, got an AVD created before he upgraded to Ice Cream Sandwich, so David and I decided to blame Ice Cream Sandwich.

Assigning blame made me feel better, but did not actually address the problem. I was going to beg David to let me develop directly on the device, but then I got this brilliant idea - I could just copy the AVD from Perry! Armed with a USB thumb drive, I obtained the precious AVD files, and voila! Emulator up and running.

Next task: try out the demo projects that came with the pen api add-on. This was when hacking with others really helped, since someone in the room already tried running the demo projects, and found out that only the compatibility demo worked. That saved me the trouble of running into dead ends.

The idea

Finally I was ready to hack out my app. With the pen api as my secret ingredient, I thought it would be natural to use it to write. Not just write anything, but write Chinese, since I still don't type Chinese very fast. But then I realized that not everyone knows Chinese, so hey, I could build an app to teach people to write Chinese! The idea was simple enough for a day's work - load a Chinese character in the background, use the pen to trace it, and when you are done, hide the character so you could see what you actually wrote.

Technical hurdles

The compatibility demo has code for converting onTouchEvent into lines on a SurfaceView, so my little app was already capturing the pen strokes and drawing them on the screen. I thought I would just wrap the SurfaceView with FrameLayout and stick in a view underneath to display the Chinese character. Alas, not so simple, since you cannot put anything beneath a SurfaceView. I brought my problem to Leigh from HTC, and she casually commented, "couldn't you just draw the background directly on the SurfaceView?" And I said, "you're right!", and rushed back to code some more.

At this point the inevitable happened: the wifi stopped working. With so many contests accessing the net at the same time, I was not surprised. My app did not actually need the internet, but to code it, I need access to Android documentation. I wished I downloaded the documentation when I was at home! Oh well. Stephan, who was sitting to my right, just calmly pulled out his tether device and moved on. Now that's what I call prepared! Fortunately we were sitting in a conference room, and I noticed ethernet cables coming out of the phones in the middle of the table. I grabbed one, plugged it in, and phew, it was connected. Back to business again.

The rest of the app was relatively straight-forward. Initially I used drawText for the background Chinese character, but the default font was really ugly. I didn't have time to figure out how to include a prettier font, so I took a shortcut and just displayed an image of a beautiful Chinese character.


By now it was 6pm, and I had a working demo. But it didn't really use the pen api. Yes, you could use the pen to trace the character, but you could also use your finger. We need to submit our app by 7pm, so I didn't have a lot of time. I decided to use the pressure from the pen to vary the stroke width, and started pouring over the HTC documentation. Not sure if I was stressed or what, but for the life of me I just couldn't find the function to get the pressure. I asked David from HTC for help. He couldn't find the function in the documentation either, but had some unpublished sample code, so once again I whipped out my USB thumb drive and got some precious files. The function turned out to be dead simple: it was just event.getPressure() from the MotionEvent. I added that to my app, and spent the rest of the time tweaking the numbers to make the strokes look alright.

Show time

At 7:30pm we all went back to the big conference room for demos. I was the second in line to present, and gave a pretty short demo. But people seemed to like it!

There were a lot of interesting apps, and I was rather impressed by the work everyone managed to do in a day. It took an hour for everyone to demo, and then the judges got together to vote. Afterwards, it was the announcements. They first announced the overall winners. I was very pleasantly surprised when they called out "Calligraphy" for first prize! They tagged on to say that I was also one of the two winners for the pen api category. Double happiness!

Winners of the pen api contest. Bruce from HTC brought giant zucchinis as prizes!

During the day someone from Microsoft developer relations was going around asking people to fill out a survey. They would raffle out two people to win an XBox 360 with Kinect, and they announced the results at the end. As luck would have it, I was one of the winners! Beginner's luck, I suppose?

The organizers and sponsors were quite generous, and gave out a lot of prizes. More at the AT&T Developer Program Blog.

Parting thoughts

I had so much fun at my first hackathon. Working side by side other developers was really nice, and have direct help from the API publishers made the process much smoother. If are were sitting on the fence, I definitely recommend going to one.

Here are a few things I learned:

  1. Assume that the internet will stop working at some point, and download the SDK/documentation beforehand.
  2. Sit with people working on similar projects. The cross pollination is amazing.
  3. Don't be shy to ask for help. People are super friendly, and you don't really have a lot of time to repeat mistakes anyway.

A big hand for the organizers and sponsors! Thank you for this very fun event. I especially enjoyed working with the HTC team.

Last but not least, some pictures of my loot :-)

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