Twelve Steps

Music theory is a daunting subject, built out of centuries of mathematical analysis and aristocratic pride. Sometimes I think I’d be better off reinventing it than trying to learn it at this late stage of its maturity. Here’s how I might get started. One day I’d be absently fooling around with a bit of wire, […]

SENG 440: Lecture 12 – Media Player and Ringtones

Dear students, Most of the big ideas of mobile computing are behind us. We’ve discussed the event-driven model of computing, offloading tasks from the main thread onto background threads, persisting data, connecting to web services, and the service-oriented architecture of mobile devices. For the rest of the semester, we just have fun. Today we have […]

SENG 440: Lecture 11 – Resources

Dear students, Today we wrap up our Lately app by presenting its master+detail UI on tablets as a single screen, showing both the list of headlines and the selected article. We’ll also add some labels to the UI to explain the widgets. Both of these tasks will accomplished with the help of Android’s resource system. […]

SENG 440: Lecture 10 – Master + Detail via Fragments

Dear students, Today we extend our Lately app by applying a master+detail UI to it. It will show both a list of headlines and a selected article. One phones, these two views will appear as separate screens, but on a tablet, they will both appear on the same screen. We will use Android’s Fragment class […]

SENG 440: Lecture 9 – RecyclerView

Dear students, On Friday afternoon, I left my office to go pick up my children from school. They went into lockdown right as I arrived. We weren’t sure what to do, so most of us milled about awkwardly for three hours. It didn’t seem like a good idea to congregrate outside the school gates, but […]

SENG 440: Lecture 8 – AsyncTask

Dear students, Today we explore how to fetch JSON data from a web service, which we will eventually show in a list. Our app, which we’ll call Lately, will grab headlines from News API. In this lecture, we’ll be grabbing headlines from the BBC. Helping us today is Android’s AsyncTask. We’ll continue this example in […]

SENG 440: Lecture 7 – Persisting with Files and JSON

Dear students, We’ve now written four little apps together. We’ve used buttons, text labels, text boxes, and lists to form their user interfaces. We’ve used ConstraintLayout to arrange the widgets. We’ve seen how to handle events with lambdas and schedule events with Handler. We’ve seen how to jump from screen to screen or from one […]

Parametric Puzzle

Check out these these parametric equations: $$\begin{array}{rll}x &=& \cos v \cdot \cos u \\y &=& \sin v \\z &=& \cos v \cdot \sin u\end{array}$$ Do you know what they do? They are most assuredly not magic. Here, let’s rename the variables, and you can try again: $$\begin{array}{rll}x &=& \cos \textit{latitude} \cdot \cos \textit{longitude} \\y &=& […]

SENG 440: Lecture 6 – Explicit Intents

Dear students, Last time we got our apps to invoke other apps indirectly through an Intent. Our requests were implicit; we only described the service we needed performed. The OS then offered us a list of all the apps that could do the job. Today, we look at invoking specific Activitys through explicit Intents. We […]

SENG 440: Lecture 5 – List Activity and Implicit Intents

Dear students, A major theme of mobile development (and the web) is services. Our apps tend not to be monolithic beasts that do everything themselves. Rather, they offload some of their work to other apps that have intentionally exposed as service providers. Today we’ll see Android’s Intent model for invoking services from other apps. We’ll […]