calc app
DESCRIPTION
Android: BeginnerTRANSCRIPT
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.
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
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 the ones.
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
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 code that a computer can
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
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 :
……
……
……
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
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
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
Open an
ANDROID STUDIO
To Start a Project;
Click on File Menu and then select NEW PROJECT
Name of your
APP
This Dialog box will let you choose the ICON of
your app
Choose which type of Activity you want to work
on
Name your
ACTIVITY
Then Click FINISH
XML file
contains;
•Design
View (Drag
and Drop)
And
•Text View
(Coding of
the Widgets)
Design
View
XML file
contains;
•Design
View (Drag
and Drop)
And
•Text View
(Coding of
the Widgets)
TEXT
View
Java File.
Here is the
actual
coding of the
working of
the app
To RUN your
app, start the
AVD
Manager
By Clicking
On The
ICON
Click on the
available
AVD,
And then
click START
The EMULATOR is Starting
The
EMULATOR
By Clicking on RUN Button. The APP is running
now!