A notification is a message that appears outside an application's UI to get user attention, provide reminders, notify about events, etc. A typical notification consists of a small icon, title...

Internal storage is used to save and retrieve the application's private data. Other applications don't have access to this data. Files will be removed when the user uninstalls the application...

Shared preferences are used to save and retrieve key-value data. It only allows to save primitive data types: int, long, float, boolean, and string. The data are stored in an...

OpenCV is an open-source library that can be used for image processing, computer vision, machine learning, etc. OpenCV 4 can be easily integrated into Android via Gradle using com.quickbirdstudios:opencv dependency...

A list view is a scrollable list that displays a list of items. A ListView class is used to create a list view. It is empty and requires an adapter...

An ultrasonic sensor HC-SR04 is an electronic device that allows to measure a distance. This sensor provides the non-contact distance measurement between 2 cm to 400 cm (1 in to...

A popup menu button displays a list of menu items when it was clicked. A popup menu button can be created using PopupMenuButton class. The itemBuilder property is used to...

A ButtonBar allows arranging buttons in a row. If there is not enough horizontal space, then buttons laying out into a column. The alignment property defines how buttons should be...

A dropdown button displays a list of items when it was clicked and lets the user select one of them. A DropdownButton class can be used to create a dropdown...

An outlined button is a rectangle shaped button that decorated with rounded corners. It is a Material Design button. A OutlinedButton class is used for creating an outlined button. By...