Johan Nilsson

Why Ads In STHLM Traveling?

2011-09-03T00:00:00-07:00

Google App Engine is a cloud service that deals with a lot of usually hard things to cope with like automatic scaling during high load, easy deploy and a lot of other things I’ve come to like. I’ve used App Engine as a backend for STHLM Traveling since 2009, always knowing that it has been in beta and things can and most likely will change. The App Engine team have also announced that their price model will change when they leave beta.

App Engine left beta a few days ago, but no one had guesed that the price will increase by this much. For STHLM Traveling this means that the monthly cost will increase from $0.5 to approximate $150. I develop STHLM Traveling in my spare time and previous cost has been covered by my self and with donations, thank you all that have been donating!

To try to cover some of the new costs I’ve added ads on a few spots in the app. Hopefully they will not hide any functionality and be in the way for any use case. They might even show some interesting things to read while commuting, who knows?

The plan is to have the ads for a period to see how much of the hosting costs can be covered and then evaluate what the next step will be. I’ve also started the work to migrate away from App Engine to reduce the cost. During this period some of the functionality in the app may have to be disabled depending on how long it takes to migrate to a new platform.

Please don’t hesitate to ask if you have any question on this or other things on the app. I have many new things planned for the app and the app is still open source but the next thing on the agenda is the migration away from App Engine.

Thank you for your patience and I hope you will understand why I needed to do this change.

Update

I realized that just adding ads without an alternative was not a good way to do this. The latest version on Android Market has the ads disabled, the way forward is to focus on rebuilding and migrating the server.

During this time I hope that the cost will be covered by donations. I accept donations using Pledgie or Flattr. If you or anyone you know want to sponsor the costs please don’t hesitate to contact me. If you donate and I still decide to introduce a paid version I promise that you will get that app for free.

Authenticated API requests on Google App Engine

2011-04-13T00:00:00-07:00

Ever wanted to do authenticated API requests on Google App Engine using the provided User Service?

When we first released droidgiro we needed to do this, we later on migrated to another solution but that’s another story. It’s was really easy to add login functionality on a regular web using the User Service, but it turned out to be a bit harder to do it through the API. Last year I held an presentation about Android C2DM and using examples from that presentation I got it to work in a similar fashion with App Engine.

Here’s an example handler that demonstrates how to identify a logged in user.

class ExampleHandler(webapp.RequestHandler):
    def post(self):
        user = users.get_current_user()
        if user:
            self.response.out.write("Welcome, %s." % user.nickname())
        else:
            self.error(401)
            self.response.out.write(":(")

In the examples below I’m using cURL since I believe that’s the easiest way to see what’s actually is going on.

Development Environment

To obtain the necessary cookie for a user we first need to authenticate against the dev server. This script demonstrates how to authenticate the user test@example.com.

curl http://localhost:8080/_ah/login \
  -d "email=test@example.com&action=Log+In" \
  -c -

This will return something like.

localhost	FALSE	/	FALSE	0	dev_appserver_login	"test@example.com:False:18580..."

Take the last value test@example.com:False:18580... and construct a new request to our API.

curl -X POST http://localhost:8080/example \
  -b "dev_appserver_login="test@example.com:False:18580..."; Path=/;"

This will print the welcome message for the authenticated user.

Welcome, test@example.com.

Production Environment

To do the same on a deployed app we first we need to authenticate against the Google ClientLogin service. This is similar for what we do when using C2DM (and other Google services). The important part here is that we specify the service name ah for App Engine. I believe source is optional but it’s recommended to specify your app name together with the current version there. Apart from that we need to specify the Email and Password we want to login with. Google has also put together an article of how to use cURL to interact with Google data services that brings some more light to this topic.

The following script obtains the auth token from the Google ClientLogin service.

curl https://www.google.com/accounts/ClientLogin \
  -d "Email=YOUR EMAIL HERE" \
  -d "Passwd=YOUR PASSWORD HERE" \
  -d "accountType=HOSTED_OR_GOOGLE" \
  -d "source=YOUR APP NAME HERE" \
  -d "service=ah"

This will return something like.

SID=DQAAA...
LSID=DQAAA...
Auth=DQAAA...

Take the value of Auth, DQAAA... and use in the next request.

curl http://example.appspot.com/_ah/login?auth=DQAAA...&continue=http%3A%2F%2Fexample.appspot.com \
  -c -

This will return the ACSID cookie.

#HttpOnly_example.appspot.com	FALSE	/	FALSE	129...	ACSID	AJKiY...

Now we can post to our API similar to what we did on the dev server.

curl http://example.appspot.com/example \
  -b "ACSID=AJKiY..."

This will print the welcome message for the authenticated user.

Welcome, test.

There’s no need to authenticate the user for each request we do. When we’ve obtained the ACSID we can reuse that until the token expires. When sending messages using C2DM the header Update-Client-Auth is included when the token has expired. The new token should be used the next time a request is done to the API. I’m not sure if that header is returned here though.

That’s it, happy hacking!

Help to create a list of apps using the Android Action Bar and the Pull to Refresh widget

2011-03-27T00:00:00-07:00

I want to put together a list of applications using the Android Action Bar or the Android Pull to Refresh widget to see what designs others have come up with. It would also be fun for me to know if someone is actually using them :)

It’s definitly optional but if you want to be featured please edit the Apps wiki page of Android Action Bar or the Apps wiki page of Android Pull to Refresh. You can also send me the App name, Market link (if available) and a screenshot (optional) by email.

I’m also very interesting to know what’s sucks and what’s not with these widgets.

Appening

2011-03-20T00:00:00-07:00

A month ago I tweeted about Appening (a 24 hour hackathon on public data in Sundsvall) and that I wanted to participate. A couple of hours later me Johan Mjönes, Joakim Bodin, Jonas Beckman and Patrik Åkerfeldt decided to participate.

Data

Försäkringskassan (Social Insurance), Bolagsverket (Swedish Companies Registration Office) and Riksantikvarieämbetet (The Swedish National Heritage Board) participated and held presentations on their available APIs.

Försäkringskassan mostly handle very sensitive data and could because of this not open up their data. Even though I believe I should have the possibility to export whatever data they have on me in their system. For the event they did their best and brought a server with mocked data about a fictive family for us to query and build new services upon.

Bolagsverket didn’t have any available APIs available for us instead we had to screen scrape their web to be able to build anything useful. However they provided us with login credentials for their service that they normally charge quite a lot of money for.

Riksantikvarieämbetet presented a quite impressive and and well documented API.

Other data sources was also available but not presented in detailed, instead they where listed on the Appening website. There was lot of data available from Sundsvall municipality, if the data would have been presented in a better way or by someone I’m sure we would have seen this data used in some apps.

Avtryck

We created the Android app Avtryck (roughly translated to mark). Our idea was to build a service where users could create routes by marking out points of cultural heritage with their own descriptions. By creating routes like this we allowed users to put the data into a context which we believe is more appealing. During the event we focused on the Android app and built a mocked API for fetching routes.

Our presentation is available on Bambuser, around 3.40, slides is uploaded to GitHub (PDF). More information about the project is available at our organization on GitHub. During the event we also registered the domain tidensavtryck.se and we hope to continue the work on both the app the service so users can actually start to create routes. We also want to combine other data sources to create richer routes. A route I would like to see for the summer is the best flea markets around Stockholm combined with recommended cafés along the route.

Avtryck won prize for best idea, sponsored by Sundsvall42 and a prize from Riksantikvarieämbetet. Thank you!

Summary

I was very impressed by what all teams presented during the event, all teams and their presentations will soon be available at the Appening website. Four out of seven teams used the data available from Riksantikvarieämbetet. I believe most of the teams decided to use this data because it was not only the most interesting data it was also the most structured and well documented data set available. I believe/hope that the other authorities that participated got inspired and will start working on open up their data soon.

Thank you Mittuniversitetet, E-delegationen, Sundsvall42 and Dragon Open Source Foundation for organizing this event.

I hope Appening will be an annual event and that we will have more data sources available and authorities participating next year.

Yet Another Blog

2011-03-16T00:00:00-07:00

Last Sunday I created a blog, and here it is.

It’s amazing to see how easy the tools has become to use. In just a couple of hours I created this blog using Jekyll, HTML5 Boilerplate, Disqus comments, Robert Nymans javascript for Twitter reactions and hosting using GitHub pages.

I’ve previously blogged in different forms, first using static html files. Couple of years later using Textpattern that I also created a few plugins for. A move from one server to antoher caused me to lose the data but some pages is still available at the Internet Archive though. Then I decided to try Tumblr but didn’t have anything interesting to post. My next jump was to Blogger, same story there two post so far which I imported here. So no promises that there will be any posts, but it’s worth a try and it’s back to static html files.

Android Pull To Refresh Update

2011-03-13T00:00:00-08:00

Today I pushed a few changes to the Android Pull To Refresh project that actually makes it possible to use it in a project.

There’s still work to do and I wouldn’t call it stable, but please test it and let me know how it runs. There’s an example project distributed with the source and examples in the README that should get one up and running fairly quick.

I’m very greatful for the high quality contributions I’ve got so far, thank you Eddie Ringle, Jason Knight, mattg1981 and MantaMay.

Force Close and STHLM Traveling

2010-01-28T00:00:00-08:00

I’m really sorry that the latest release of STHLM Traveling has caused a force close when starting the application on some devices.

This is actually a bug in Android that I and many others got to learn about the hard way. This is the short background of why some user is getting a force close. When uploading a application to Android Market you have the choice to enable copy protection for the application. I once activated this and recently removed it. What I did not know was that when the application has a database or writes files to disk something goes wrong and causes a force close on start up when switching the copy protection setting. The only solution to this problem is to first uninstall and then install the application again. Another downside off this is that you loose all saved data. From what I have understand the force close issue only affects devices that runs Android 1.5.

While fiddling around with this copy protection setting I also noticed that some phone models and carriers did not list copy protected application in Android Market, this is also discussed in the Android developer group.

Once again I’m really sorry about all this. I hope it will not happen again.

But now to something slightly more fun, the latest release of STHLM Traveling. I added a Swedish translation with great help by Jean Diarbakerli that did all the hard work with the translation. The application will automatically choose Swedish if you have selected this in the Android settings. Unfortunately Android does not have a official Swedish translation but some roms support this for example HTC Sense. For the rest off us we need to go to the settings menu in the STHLM Traveling and set the preferred language there. I also added history and shortcuts for departures.

I would also like to thank all of you that has sent me crash reports, it has helped me a lot when trying to make this application as stable as possible.

Get the latest version of STHLM Traveling from Android Market.

Crime Sweeper

2009-05-12T00:00:00-07:00

Last weekend I participated in the first GTUG Stockholm Android Hackathon in Sweden hosted by Bwin Games. A part from all the hacking there was also two great presentations by Dirk Groten, CTO from Layar and Johan Burell all organized by Peter Svensson, Peter also did a great write up of the event at his blog.

Before the hackathon me and my other team mates Albert Ramstedt, Joakim Kolsjö and Joakim Bodin had an idea to build something on top of the data from brottsplatsstockholm.se, the site it self scrapes the Swedish police departments website for crimes committed in Stockholm. I contacted Pär Thernström to ask if it was possible for him to provide us with a simple API. Pär was really nice and created the API just a couple of days after I first contacted him.

Once we had the API, we had a short meeting to discuss what to build during the hackathon. First we thought of building a application that just listed recently committed crimes and show them on a map. But we thought that was kinda boring instead we come up with the idea to create a game.

The game we decided to build is sort of a geocaching game. We plotted all the crime sites on a map and showed the players position on it. The player can then start the game at any time by pressing a start button. To get points the player need to visit as many crime sites as possible during a fixed time. For each visited site the player earned 10 points and the possibility to see which type of crime that was committed at that place. Players that dare to visit areas with a high crime rate will probably get more points.

Here is a short screen cast demonstrating CrimeSweeper. Crime sites are listed as stars on the map.

So will CrimeSweeper be released on Android Market? Not sure, first of we probably need to rewrite it to use a service for the game logic. This to be able to track movements and hits even if the player is doing something else with the phone. It would also be fun to extend it to not only use crime sites, perhaps a map with tourist points would be nice as well? And of course a high score list. Anyway the source is at GitHub if anyone feel to hack around with it.

I really love hackathons it is truly amazing to see what people manage to build during just a couple of hours. This was the second hackathon I participated in. Last time was in Amsterdam at Hyves HQ. Me, Joakim Bodin and Johan Mjönes then built a Android app called Mystery Hangout. If you are interested you can find the source and a video demonstrating it at GitHub.