Android: Beginner

1. Android App
CALCULATOR
MUHAMMAD SHAHAB AHMAD R.NO
“142”
ASAD ULLAH R.NO “168”
SECTION „C‟ BS(CS) HONS IBMS
THE UNIVERSITY OF AGRICULTURE,
PESHAWAR,KP.

2. ANDROID
 A Java program (such as an
Android application
program) undergoes several
translation steps between
the time you write the
program and the time a
processor runs the program.
 One of the reasons is
simple: Instructions that are
convenient for processors to
run are not convenient for
people to write.
JAVA SOURCE CODE:
public static void sum()
{
Int a=3,b=4;
System.out.println(“sum of a
and b”);
System.out.println(a+b);
}
Public static void main(String
arg[]){
Sum();
}
}
ANDROID

3.  The processors in
computers, phones, and
other devices don‟t
normally follow
instructions like the
instructions in Source
code.
 i.e processors don‟t
follow Java source code
instructions.
 Instead, processors
follow cryptic (having a
secret or hidden
meaning) instructions like
Java Byte code
0 aload_0
1 getfield #19
<com/allmycode/samples/MyA
ctivity/room
Lcom/allmycode/samples/Roo
m;>
4 getfield #47
<com/allmycode/samples/Roo
m/numGuests I>
7 ifne 22 (+15)
10 aload_0
……
……
……
ANDROID

4. ANDROID
 When we write a Java
program, we write source
code instructions.
 After writing the source
code, we run a program (that
is, we apply a tool) to the
source code. The program is
a COMPILER: It translates
the source code instructions
into Java byte code
instructions.
 In other words, the compiler
translates code that we can
write and understand into
Java Byte code
0 aload_0
1 getfield #19
<com/allmycode/samples/MyA
ctivity/room
Lcom/allmycode/samples/Roo
m;>
4 getfield #47
<com/allmycode/samples/Roo
m/numGuests I>
7 ifne 22 (+15)
10 aload_0
……
……
……

5. ANDROID
 In 2007, Dan Bornstein at
Google created Dalvik
bytecode — another way to
represent instructions for
processors to follow.
 Dalvik bytecode is optimized
(best use) for the limited
resources on a phone or a
tablet device.
Dalvik Byte code
.method public
checkVacancy(Landroid/view/
View;)V
.limit registers 4
; parameter[0] : v3
(Landroid/view/View;)
.line 30
iget-object
v0,v2,com/allmycode/samples/
MyActivity.room
Lcom/allmycode/samples/Roo
m;
; v0 :
……
……
……

6. CREATING AN ANDROID APP
 For Creation of An Android App the requirements
are:
 JDK (Java Development Kit)
 for JAVA
 Android SDK (Software Development Kit)
 for ANDROID
 An IDE (Integrated Development Environment. A
programming environment meshed into a software
program. It provides a text or code editor, a GUI
builder, a compiler, interpreter and debugger)
 Eclipse OR
 Android Studio

7.  When we create an Android app, Eclipse/Android
Studio performs at least two compilations:
 One compilation creates Java bytecode from
our Java source files.
 The source filenames have the .java extension;
the Java bytecode filenames have the .class
extension.
 Another compilation creates Dalvik bytecode
from our Java bytecode files.
 Dalvik bytecode file names have the .dex
extension.
ANDROID

8.  Android app has
 XML files,
 java files, and possibly other elements.
 Before we install an app on a device.
 Eclipse/ Android Studio combines all these elements
into a single file — one with the .apk extension
 To perform the compilation from source code to Java
bytecode, Eclipse uses a program named javac, also
known as the Java compiler.
 To perform the compilation from Java bytecode to
Dalvik code, Eclipse uses a program named dx
(known affectionately as “the dx tool”).
 To combine all your app‟s files into one .apk file,
Eclipse uses a program named apkbuilder.
ANDROID

9. Open an
ANDROID STUDIO

10. To Start a Project;
Click on File Menu and then select NEW PROJECT

11. Name of your
APP

12. This Dialog box will let you choose the ICON of
your app

13. Choose which type of Activity you want to work
on

14. Name your
ACTIVITY
Then Click FINISH

15. XML file
contains;
•Design
View (Drag
and Drop)
And
•Text View
(Coding of
the Widgets)
Design
View

16. XML file
contains;
•Design
View (Drag
and Drop)
And
•Text View
(Coding of
the Widgets)
TEXT
View

17. Java File.
Here is the
actual
coding of the
working of
the app

18. To RUN your
app, start the
AVD
Manager
By Clicking
On The
ICON

19. Click on the
available
AVD,
And then
click START

20. The EMULATOR is Starting

21. The
EMULATOR

22. By Clicking on RUN Button. The APP is running
now!