35. An Overview of Android Jetpack Data Binding

In the chapter entitled “Modern Android App Architecture with Jetpack”, we introduced the concept of Android Data Binding and briefly explained how it is used to directly connect the views in a user interface layout to the methods and data located in other objects within an app without the need to write code. This chapter will provide more details on data binding with an emphasis on explaining how data binding is implemented within an Android Studio project. The tutorial in the next chapter (“An Android Jetpack Data Binding Tutorial”) will provide a practical example of data binding in action.

35.1 An Overview of Data Binding

Data binding support is provided by the Android Jetpack Data Binding Library, the primary purpose of which is to provide a simple way to connect the views in a user interface layout to the data that is stored within the code of the app (typically within ViewModel instances). Data binding also provides a convenient way to map user interface controls such as Button widgets to event and listener methods within other objects such as UI controllers and ViewModel instances.

Data binding becomes particularly powerful when used in conjunction with the LiveData component. Consider, for example, an EditText view bound to a LiveData variable within a ViewModel using data binding. When connected in this way, any changes to the data value in the ViewModel will automatically appear within the EditText view and, when using two-way binding, any data typed into the EditText will automatically be used to update the LiveData value. Perhaps most impressive is the fact...

35.2 The Key Components of Data Binding

By default, an Android Studio project is not configured for data binding support. In fact, a number of different elements need to be combined before an app can begin making use of data binding. These involve the project build configuration, the layout XML file, data binding classes and use of the data binding expression language. While this may appear to be a little overwhelming at first, when taken separately these are actually quite simple steps which, once completed, are more than worthwhile in terms of saved coding effort. In the remainder of this chapter, each of these elements will be covered in detail. Once these basics have been covered, the next chapter will work through a detailed tutorial demonstrating these steps in practical terms.

35.2.1 The Project Build Configuration

Before a project can make use of data binding it must first be configured to make use of the Android Data Binding Library and to enable support for data binding...

35.3 Summary

Android data bindings provide a system for creating connections between the views in a user interface layout and the data and methods of other objects within the app architecture without having to write code. Once some initial configuration steps have been performed, data binding simply involves the use of binding expressions within the view elements of the layout file. These binding expressions can be either one-way or two-way and may also be used to bind methods to be called in response to events such as button clicks within the user interface.