Data storage might not, at first glance, seem to be at all related to a user interface, but in the majority of applications, the user interface exists to manipulate long-lived data both on the device and on the network. This means that while it does not directly influence the look of the application, it does influence the user experience. Users expect the application to always reflect the latest data available to them, as we explored in Chapter 5, Binding Data to Widgets. Applications written using a reactive pattern ensure that the user interface is always up to date with the latest data available to the application, and the Android data binding system helps to make writing reactive applications easy. Even without the data binding framework, Android itself has always been built for reactive applications from the very bottom layers upward, but until recently, this behavior required huge amounts of boilerplate code.
When you develop any sort of application...