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Android Programming Fundamentals
Android Apps are written in Java programing language.
Java classes are compiled.
Every App run its own process.
Each App is assigned a unique ID.
Android Application Components
Activity
An activity is usually a single screen that the user sees on the device at one time.
It is the most visible part of the android application.
It use Views and Fragments to create user interfaces and to interact with the user.
Service
A service is an application component that can perform long-running operations in the background and does not provide any user interface.
Broadcast Receiver
It receive and react to broadcast announcements.
Example:
Announcement like the time zone has changed.
Intent
It holds the content of a message.
Example:
Convey a request for an activity to present an image to the user or let the user edit some text.
Android Application Framework
Content Provider
These are the standard interfaces that connect data in one process with code running in another process.
Resource Manager
Provides access to non-code resources.
Manages the storing of strings and layout files and bitmaps.
Notification Manager
Enables all applications to display alerts in the status bar.
Activity Manager
Manages the lifecycle of applications.
Dalvik Virtual Machine
A specialized virtual machine designed specifically for Android app.
Provides environment on which every Android application runs.
Each Android application runs in its own process, with its own instance of the Dalvik VM.
Dalvik code has been written so that a device can run multiple VMs efficiently.
Executing the Dalvik Executable (.dex) format.
Android Software Development Kit (SDK)
Android SDK includes a comprehensive set of development tools such as:
Debugger
Libraries
Documentation
Sample code
These tools are accessed through an Eclipse plugin called ADT (Android Development Tools) or from command line.
Developing with Eclipse IDE is mostly preferred.
Essential Android command line tools
When developing in IDEs or editors other than Eclipse, be familiar with all of the tools below.
Android
Android is an important development tool.
It helps create, delete, and view Android Virtual Devices (AVDs)
Android Emulator
It runs Android applications on an emulated Android platform.
Android Debug Bridge (ADB)
Interface with emulator or connected device.
In addition to the above tools that are included with the SDK, we need following open source and third-party tools:
Ant
To compile and build Android project into an installable .apk file.
Key tool
To generate the key store and a private key which are used to sign in the .apk file.
Key tool is part of the JDK.
Jarsigner (or similar signing tool)
To sign .apk file with a private key generated by key tool.
Jarsigner is part of the JDK.
Android Security
Android relies on Linux version 2.6 for core system services such as:
Security
Memory management
Process management
Network stack
Driver model
Most security between applications and the system is enforced at the process level through standard Linux facilities, such as user and group IDs that are assigned to applications.
Android APK Format
The APK file is consist of all programming code like the AndroidManifest.xml file, application code (.dex files), resource files, and other files etc.
A project is compiled into a single. apk file.
