mobile computing · introduction to java language. what is java? java is a computer programming...
TRANSCRIPT
Mobile ComputingLECTURE # 2
The CourseCourse Code: IT-4545
Course Title: Mobile Computing
Instructor: JAWAD AHMAD◦ Email Address: [email protected]
Web Address: http://csandituoslahore.weebly.com/mc.html
Term (Semester): Spring 2018
Duration: 15/16 Weeks
Introduction to Java Language
What is Java?Java is a computer programming Language
just like
◦ C
◦ C++
Developed by Sun Microsystems in around
1990s and now Oracle corporation.
Converts Human understandable instructions
to Machine understandable instructions
Java Program Flow
Java Program ComponentsJava Code (.java)
• Set of instructions
• Written by following
Language rules
• A programmer writes
these instructions
• Also called Source
Code
• Saved in a file with
.java extension
• Can be written in any
text Editor
• Notepad
Java Program ComponentsJava Compiler (javac)
• Reads Java Source Code
• Converts into Computer Readable
Form
• Checks for Errors
• Makes sure all the instructions are
in proper order
• Creates Java Byte Code
Java Source Code
(.java)
Java Compiler
(javac)
Java Byte Code
Java Program ComponentsJava Byte Code (.class)
• Set of instructions compiled by
Java Compiler
• These are instructions readable by
JVM (Java Virtual Machine)
• Normally not editable in normal
Text Editors like Notepad
• Special Editors are used
• Java Byte Code Editor
• Programmer does not need to
understand Java Byte Code
Java Compiler
Java Source Code
Java Byte Code
Java Program ComponentsJava Virtual Machine (JVM)
• It’s a platform independent
execution environment
• It is actually a program that reads
other program
• Normally Java Byte Code
• It provides a runtime environment
for Java Byte Code
• According to Sun Microsystems,
there are almost 5.5 Billion JVM
Enabled devices
Java Virtual
Machine
Java Byte Code
Output of a Program
Object Oriented Programming Language(OOP)
Object Oriented ProgrammingOOP has
◦ Objects
◦ Classes
◦ Methods
◦ Encapsulation
◦ Inheritance
◦ Polymorphism
Object in OOP
Everything is an Object
An Object
◦ Knows something
◦ Does something
Knowing something is Instance
Variables
Doing something is Methods
Vehicle• type
• color
• name
Drive()
En
gin
eSta
rt()
Turn()
En
gin
eSto
p()
Variables Methods
What is a Class?• Classes are used to create an Object
• It tells JVM how to make an Object
How to create a Class?
public class HelloWorld
{
public static void main (String[] args)
{
System.out.println("Hello World!");
}
}
Modifier
Identifier
Return TypeMethod Arguments
Class Name
Method Name
Part of Class not Object Print output to console
String to be displayed
Encapsulation
• Makes the data private
• Uses Getters and Setters
• Others can use only the data you want them to use
Access Modifiers
• Private
• Public
• protected
Some other Objects
Button
• Label
• Color
• getLabel()
• getColor()
• setLabel()
• setColor()
• click()
Song
• Title
• Duration
• getTitle()
• getDuration()
• setTitle()
• setDuration()
• play()
Variable
Method
• Programmers normally have getter and setter methods for variables
• Getters
• getLabel()
• getColor()
• getTitle()
• getDuration()
• Setters
• setLabel()
• setColor()
• setTitle()
• setDuration()
Inheritance
• Subclass inherit from Superclass
• Subclass will inherit
• Variable
• Methods
• Subclasses can override the methods of superclass
• Make their own versions of methods
• Backward inheritance is not possible
• Superclass cannot extend methods, variable from subclass
Inheritance
Super class
Sub class
Polymorphism
Polymorphism
Abstract Classes
Abstract Classes• Some classes should not instantiate
• Abstract classes should always be extended
• We will never create an object of that class
• We can however make reference for that class
• Some general classes have no definition as object instantiation
• Vehicle
• Animal
abstract class Vehicle
{
public void drive()
{
}
}
abstract public class Vehicle
{
public void drive()
{
}
}
Abstract Classes
abstract public class Vehicle
{
public void drive()
{
}
}
public class MakeVehicle
{
public void start()
{
Vehicle vehicle;
vehicle = new car();
}
}
public class MakeVehicle
{
public void start()
{
Vehicle vehicle;
vehicle = new vehicle();
}
}
Abstract Methods• An abstract method has no body
• An abstract method can reside in Abstract class only
• Non-Abstract Classes cannot carry Abstract methods
• Abstract class can carry both Abstract and Non-Abstract methods
abstract public class Vehicle
{
public void drive()
{
}
public abstract void idle();
}Abstract Method
Non- Abstract Method
Multiple Inheritance not allowed in Java
Multiple Inheritance not allowed in Java
Interfaces in Java
Replace class with
interface
Interfaces in Java
A class can implement multiple interfaces
Introduction to Android Development
What is Android?
Its an OS for mobile phones
It is a modified form of Linux
It runs on Linux Kernel 3.18
Bought by Google in 2005
Android is open source
Source Code is available at
http://source.android.com/
Different hardware vendors can build their devices
and run Android on them
Android Versions
Android FeaturesStorage
◦ SQLite
Connectivity
◦ GSM
◦ CDMA
◦ LTE
◦ Wi-Fi
◦ WiMax
Messaging
Multitouch
Multitasking
Android Architecture
Android ArchitectureLinux Kernel
◦ Android runs on Linux Kernel 3.18
◦ A Kernel is collection of programs that helps in interaction of software
and hardware. These programs are called drivers.
◦ Android because of its foundation on Linux Kernel contains all the basic
functionality of Linux e.g. Memory Management.
◦ A device with certain hardware should have a proper driver in the Linux
Kernel to work properly
◦ Bluetooth will not work until the driver is available for that hardware.
Android ArchitectureLibraries
◦ Android contains some core libraries which help build different other
libraries.
◦ Some of the most important libraries are
◦ Media Framework
◦ Contains all the codes for media
◦ WebKit
◦ It is a browser engine that runs HTML content
◦ SQLite
◦ Handles storage of data
Android ArchitectureAndroid Runtime
◦ Dalvik Virtual Machine
◦ It is a virtual machine like JVM.
◦ It does not run .class file, instead it runs .dex files
◦ These files are created from .class files at compilation time.
◦ Multiple instances of DVM can run simultaneously.
◦ Core Libraries
◦ It contains different libraries from Java SE and Java ME
Android ArchitectureApplication Framework
◦ As a developer we directly interact with this layer.
◦ This layer contains libraries which provide basic functionality for android
like call, messaging and resource management etc.
◦ Some of them are
◦ Activity Manager
◦ It takes care of the activity life cycle
◦ Location Manager
◦ It handles the location
Android ArchitectureApplications
◦ Based on all the previously mentioned layers, our
applications will be available at Applications Layer.
◦ Almost all the applications are handled at this layer.
◦ Default apps also fall in this category
◦ Some of the default apps are
◦ Phone
◦ Messaging
Android Smart Phones
Galaxy S II Motorola Atrix 4G, HTC EVO 4G
Android Tablets
Samsung Galaxy Tab 10.1 Asus Eee Pad Transformer TF101
Android EBook Readers
Barnes and Noble’s NOOK Color Amazon’s Kindle Fire
Android Based TV
Scandinavia Android TV
Mashup CompatibilityCombination of two or more service to create an App.
◦ Geolocation + Social networking
◦ Geolocation + Gaming
◦ Camera + Geolocation
◦ Contacts + Maps
Components of Android Programming
Activities
◦ Android Application are composed
of Activities
◦ Each Application will have at least
one Activity
◦ Activities are like container
◦ Code
◦ User Interface
◦ Its like Form for Windows in Vb.net
Hello World !
Activity
Components of Android Programming
Intents
Intent = Action + Data
◦ It can be transition between two activities
◦ It can be launching an app from one app
◦ It’s a message to Android System to tell app
will do something
Components of Android Programming
Cursorless Control
◦ Unlike PCs, no cursor on screen
◦ Fingers are used to perform Screen Actions
◦ Multitouch gestures
◦ Zooming
◦ Dragging
◦ Long Press right click
Components of Android Programming
Views and Widgets
◦ View is a rectangular area on screen for
drawing
◦ Menu
◦ Context Menu
◦ Widgets are advanced UI Controls
◦ Buttons
◦ Checkboxes
◦ DatePickers etc.
Components of Android Programming
Background Service
◦ Service is a program that doesn’t need to have a UI
◦ A background service runs in the background
◦ Antivirus application in windows is a background
service
◦ Alarm app runs in background for mobile phones
Android Hardware Tools
Google APIs
Android can do more than Calls and Messages
It can help in navigating
It can help in showing a friend on map
Android in Cloud
Information can be stored in Cloud
Information can be retrieved from Cloud
Android Development Tools
Requirements
Any PC running◦ Windows
◦ Mac OS X
◦ Linux
Android Studio
JDK