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Android Programming with Kotlin for Beginners

You're reading from  Android Programming with Kotlin for Beginners

Product type Book
Published in Apr 2019
Publisher Packt
ISBN-13 9781789615401
Pages 698 pages
Edition 1st Edition
Languages
Author (1):
John Horton John Horton
Profile icon John Horton

Table of Contents (33) Chapters

Android Programming with Kotlin for Beginners
Contributors
Preface
1. Getting Started with Android and Kotlin 2. Kotlin, XML, and the UI Designer 3. Exploring Android Studio and the Project Structure 4. Getting Started with Layouts and Material Design 5. Beautiful Layouts with CardView and ScrollView 6. The Android Lifecycle 7. Kotlin Variables, Operators, and Expressions 8. Kotlin Decisions and Loops 9. Kotlin Functions 10. Object-Oriented Programming 11. Inheritance in Kotlin 12. Connecting Our Kotlin to the UI and Nullability 13. Bringing Android Widgets to Life 14. Android Dialog Windows 15. Handling Data and Generating Random Numbers 16. Adapters and Recyclers 17. Data Persistence and Sharing 18. Localization 19. Animations and Interpolations 20. Drawing Graphics 21. Threads and Starting the Live Drawing App 22. Particle Systems and Handling Screen Touches 23. Android Sound Effects and the Spinner Widget 24. Design Patterns, Multiple Layouts, and Fragments 25. Advanced UI with Paging and Swiping 26. Advanced UI with Navigation Drawer and Fragment 27. Android Databases 28. A Quick Chat Before You Go Other Book You May Enjoy Index

Declaring and initializing the objects from the layout


We know that when we call setContentView in the onCreate function, Android inflates all the widgets and layouts, and turns them into real instances on the Heap.

We know that to use a widget from the Heap, we must have an object of the correct type by using its unique id property. Sometimes, we must specifically obtain a widget from a layout. For example, to get a reference to a TextView class with an id property of txtTitle and assign it to a new object called myTextView, we can do the following:

// Grab a reference to an object on the Heap
val myTextView = findViewById<TextView>(R.id.txtTitle)

The left-hand side of the declaration of the myTextView instance should look familiar to all the instances of other classes that we declared throughout the previous three chapters. What is new here is that we are relying on the return value of a function to supply the instance. The findViewById function does indeed return an instance that...

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