Pro Android with Kotlin

2
CHAPTER 1: System
Above the low-level libraries and the Android Runtime sits the 
application framework
, which 
defines the outer structure of any app you build for Android. It deals with activities, GUI 
widgets, notifications, resources, and so on. While understanding the low-level libraries 
certainly helps you to write good programs, knowing the application framework is essential 
to writing any Android app at all.
On top of all that you will find the apps your users launch for tasks they have to accomplish. 
See Figure 
1-1
.
Figure 1-1.
The Android OS

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3
CHAPTER 1: System
You as a developer will create Android apps using Kotlin, Java, or C++ as a programming 
language, or a combination of them. And you will be using the application framework and 
the libraries to talk to the Android OS and the hardware. Using C++ as a programming 
language on a lower level, addressing target architecture peculiarities, leads to incorporating 
the 
Native Development Kit
(NDK), which is an optional part of the Android SDK. While for 
special purposes it might be necessary to use the NDK, in most cases the extra effort to 
deal with yet another language and the special challenges it bears does not pay off. So in 
this book, we will be mainly talking about Kotlin, and sometimes Java where appropriate.
The Development System
The operating system running on handhelds is one part of the story; you as a developer also 
need a system for creating Android apps. The latter happens on a PC or laptop, and the 
software suite you use for it is 
Android Studio
.
Android Studio is the IDE you use for development, but while you install and operate it, the 
software development kit (see the section “The SDK”) gets installed as well, and we will be 
talking about both in the following sections. We will also cover virtual devices, which provide 
an invaluable aid for testing your app on various target devices.
Android Studio
The Android Studio IDE is the dedicated development environment for creating and running 
Android apps. Figure 
1-2
 shows its main window together with an emulator view.
Android Studio provides the following:
 
Managing program sources for Kotlin, Java, and C++ (NDK)
 
Managing program resources
 
The ability to test-run apps inside emulators or connected real devices
 
More testing tools
 
A debugging facility
 
Performance and memory profilers
 
Code inspection
 
Tools for building local or publishable apps

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