Book excerpt: The First Line of Code is a must-have for developers who want to learn Android and Kotlin, and the best-seller in China. Knowledge between Android and Kotlin is interspersed in a way that readers are easy to understand and get start: · Android part covers all the important aspects of the Android platform, such as activity, service, content provider, broadcast receiver, fragment, basic UI, data storage, network, Jetpack and other application-level knowledge. · Kotlin part covers various aspects of Kotlin, such as standard grammar, common skills, higher-order functions, generics, coroutines, DSL and other language-level knowledge. In addition, The First Line of Code is a very practicing book, illustrating concepts with a complete weather forecast program. You can use and practice all the knowledge comprehensively after learning and see the actual result for what you have learned through the book. All contents of the book are quite easy to understand. It might be a good choice for both beginners and experienced developers. Also suitable for college students, college teachers, etc.