An Android app is a state machine in which each state is called an activity. An activity has a lifecycle. For example, it can be created, paused, resumed, and finished. During a transition between activities, the paused or finished activity can send data to the created or resumed activity. An app can define many activities and transition to them in any order. It can even transition to activities defined by the Android SDK or by other apps.
Note
For more information about Android activities and their lifecycle, refer to the official documentation at http://developer.android.com/guide/components/activities.html.
For more information about OpenCV's Android and Java APIs (used throughout our activity class), refer to the official Javadocs at http://docs.opencv.org/java/. Unfortunately, at the time of writing this book, many of the comments in OpenCV's Javadocs are too closely based on the comments for C++. The class and method signatures in the...