Using Google places API in Android

Google places API is a service provides information about places. Basically, it will take coordinates and other additional parameters (like city, limits, etc) as input, return information related to the input such as name, address, types of nearby places. Think about Google map and their street-view car; the accuracy of this API should not be bad. I take this as an alternative to the Foursquare API to obtain places information. Actually, I expect it outperforms 4sq because most of places in 4sq are created by users, which leads to inevitable noise.

Anyway, I look into the java library of places API since I need them in my android app. Turns out the bad news is they don't have any specific java lib; moreover, 3rd party java libs I find on github are poorly supported. The good news is, Google provides a general "Google API console" and also its java lib, google-api-java-client. Although this lib does not support places api specifically, build a wrapper using this and places api is sufficient for me. The more good news is, I find this awesome blog and its corresponding sample on github. However the blog is written one year ago thus some methods it uses are deprecated in today's new version. I modified the sample to make it compatible with the latest java client, find it on my github.

Since the blog actually tells us everything we need to know about Places API, I will just skip the basics and write down how the process works in case I forget. Generally, to build your own application using this API, you need to always look into three web pages: the blog, the java doc of Google API and the official doc of places API. 

Basically there are two steps: to request places information using Places API and selective parameters, then parse the output into strings we need. First step, use HttpFactory as parameter to generate a Http request; the HttpFactory object contains a json parser and an arbitrary header. Then we use request.getUrl() to put every option we want to customize our request and send it using request.execute(). Now the second step will automatically be executed when the server returns the result. The result is in json, the json parser in httpFactory would parse it into a java model. Then the blog propose a very clever method (at least to me, a java newbie): create some classes to catch some specific strings from models. With the decorator "@Key" we could define what part of that result we want, e.g. name, types, etc. This is really efficient. Then you do whatever you want with the result.

Places API provides three search URL (I only look into search part), general search (return a list of nearby places), search detail (return the detailed information of a place), search autocomplete (predict and return places based on input). I only need the first two, but the third one is really cool: adding appropriate processing blocks, it could become a real-time prediction search just like google instant search.

Finally, there is one thing holds me back several times. The AndroidManifest.xml file. NOW REMEMBER: you have to explicitly indicate them if you add following components to your project:

1. permissions, internet, gps, etc;
2. service, including intent services;
3. content providers

Every time I use these components I forget to add them and then stuck with it for a while. Now it is done here and I will never make the same mistake again. Also, any networking thing (http GET/POST, for example) is not allowed to be done in the main thread; you have to use a service or similar technique.