In an android app an activity is created and then destroyed, for example when the user open another activity or when the user presses the back button, later the user opens again the same activity that is is recreated using the data saved before the earlier destruction of the activity.
The data are saved in an object Bundle in the onSaveInstanceState method and restored in the onRestoreInstanceState method (see Recreating an Activity).
The Bundle class provides several setter and getter methods to save and restore data such as getInt and setInt for the integers and similar methods for other types of primitives, strings and one dimensional array.
In this post I write some examples to save and restore more complex objects such as the following CustomObject:
Quod erat demonstrandum