Lab project update 1

Today I work on the project for my summer intern in the lab. Previously, I build it so that it could record and store user's location in the local db periodically in the background, also make it work with google places API and 4sq API. Since we are aiming at "guess" user's semantic location (like in a shop, in a campus, etc) based on their coordinates (either from GPS or cellular or wifi), although we haven't come up with a cool algorithm to guess, it would be better to draw our initial guess on the map so we could have a feel about it.

Instead of integrating a google map with the current android app, I choose to build a web app and let the android app send data to the web app so that it would draw the map. The major reason is we won't need a map, live or not, in the app; it would be overkill. The map is more for analyzing and improving our guess algorithm, not a part of implementation. Besides, I am more confident on my python skill in writing algorithms than Java.

Therefore, my second heroku app born with duty. I still use django. This app is expected to be able to receive data from http request ( generated from the android app), store into its own db, then draw markers using such data on google map. That's it. Might improve later but first let's get it going.

For the http communication part, I look into receiving http request first. It's easy in web framework because they are made to receive http request. For data transmission, coordinates, specifically, I choose to add them into the request url on the sender side. Then when the web app receives the url it will parse it and find correct data:

	def query(request):
	latitude_pass = request.GET.get('lat', None)
	longitude_pass = request.GET.get('long', None)
	if latitude_pass and longitude_pass:
	Track(
	time=datetime.now().isoformat(' '),
	longitude = longitude_pass,
	latitude = latitude_pass
	).save()
	else:
	return redirect('/')

view raw query.py hosted with ❤ by GitHub

This method is used as the function described above. Track is the model I create to store coordinates data. After parsing, it will redirect to the home page, if necessary, because the request is only for transmitting data, not displaying web page. Yes you could yell at me because I use GET instead of POST to transmit data. But again, first I want to get it going. GET is fast to implement that is why. I promise I will fix it and return you a long long post about how good and safe to use POST instead of GET.

After this on the android app side, there are a lot of tutorials to tell you how to setup a http request in android/Java using bundled apache libs. Anyway, I insert the request function in my service, so that every time it updates the coordinates it will also send them to my web app.

So that's the first part. How to draw them on the map? after some googling I realize the fact that there is simply no easy and once-for-all effort to create a google map in python. Then I just use js API in my django app. Luckily google has a detailed dev guide. Another good news is, as long as you keep your js script within the html file, you could use django template language to call variables of your app in the js script; it will not work in an independent js file. The rest of story is easy, just do a for loop to extract each pair of coordinate out from the db and create new marker.

I am gonna test it maybe this weekend, after I make some improvements.