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Lecture Series on Android Programming
Chapter.2 First Android
Application
Lecturer: Prof.Luqun Li ([email protected])
Teaching Assistants: Fengyou Sun, Haijun Yang, Ting Sun
Contents
2
1
Set up the environment
2
Learing the Fundamental Components
3
Hello world
4
Exploring the Structure of an Android Applica
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Introducing Andorid computing
platform
3
5
Analyzing the Stucture of an Andorid Applicat
6
Analyzing the Notepad Application
7
Examining the Applicationg Lifecycle
8
Debugging the App
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Setting Up Your Environment
To build Android applications, we need to establish
a development environment. In Prepare the softwar
e bundles
Java JDK & Java Doc (optional)
IDE Environment can be setup by:
Approach.1 Use:Android SDK + ADT+Eclipes
Approach.2 Use:Android SDK+MotoDEV studio
See videos for: android related software's download & IDE setup
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Aproach.1 Eclipse+Android SDK+ADT
step1
Downloading JDK 7 and Eclipse 4.2
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step2
Downloading the Android SDK
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step3
Installing Android Development Tools (ADT)
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Learning the Fundamental Components
Every application framework has some key components
that developers need to understand before they can begin to
write applications based on the framework
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The Fundamental Components
View
Activity
Intent
Content Provider
Service
AndroidManifest.xm
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A Hello World Demo
Hello World!
Now we ready to build our first Andr
oid application. We’ll start by buildin
g a simple
“Hello World!” program. Create the sk
eleton of the application by followin
g these steps:
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step 1
Launch Eclipse and select File ➤ New ➤ Project.
In the “New Project” dialog box, select “Android”
and then click “Next.” You will then see the
“New Android Project” dialog box
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step 2
enter HelloAndroid as the project name, pro.
android asthe package name, HelloActivity as the
activity name, and HelloAndroidApp as the
application name
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step 3
Click the “Finish” button, which tells ADT
to generate the project skeleton for you.For now,
open the HelloActivity.java file under he src folder
and modify the onCreate() method as follows
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/** Called when the activity is first created. *
/
@Override
public void onCreate(Bundle savedInstanceStat
e) {
super.onCreate(savedInstanceState);
/** create a TextView and write Hello World!
*/ TextView tv = new TextView(this); tv.setText
("Hello World!");
/** set the content view to the TextView */
setContentView(tv);
}
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create an Eclipse launch configuration
Click the “Browse…” button and select
the HelloAndroid project
Under “Launch Action,” select “Launch” and select
“pro.android.HelloActivity” from the drop-down list
Click “Apply” and then “Run.” You should see the
emulator launched with the Hello Android projec.
Next page
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create an Eclipse launch configuration
Select Run ➤ Run Configurations
In the “Run Configurations” dialog box, double-click
“Android Application" in the left pane. The wizard will insert
a new configuration named “New Configuration.”
Rename the configuration RunHelloWorld.
Create the Eclipse launch configuration
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Exploring the Structure of an Androi
d Application
Although the size and complexity of Android appli
cations can vary greatly, their structures will be
similar
An Android application is primarily ma
de up of three pieces
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an Android application
the application
descriptor
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a collection of vari the application’
ous resources
s source code.
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Analyzing the Notepad Application
analyzing its components will give you some realistic insight
into Android development.
Follow these steps to load the Notepad sa
mple into the Eclipse IDE:
 1. Start Eclipse.
 2. Go to File ➤ New ➤ Project.
 3. In the “New Project” dialog, select An
droid ➤ Android Project.
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 4.In the “New Android Project” dialog, se
lect “Create project from existing source”
and set the “Location” field to the path of
the Notepad application. Note that the N
otepad application is located in c:\Androi
dSDK\samples\, which you downloaded e
arlier. After you set the path, the dialog
reads the AndroidManifest.xml file and p
repopulates the remaining fields in the
“New Android Project” dialog box.
 5. Click the “Finish” button.
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Next, we see the activity execute a mana
ged query and get a cursor for the result.
A managed query means that Android wil
l manage the returned cursor. In other w
ords, if the application has to be unloade
d or reloaded, neither the application nor
the activity has to worry about positionin
g the cursor, loading it, or unloading it. T
he parameters to managedQuery(), show
n in Table , are interesting
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Parameters to
Activity.managedQuery
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Parameter
Data Type
Description
URI
Uri
projection
String[]
URI of the conten
t provider
The column to ret
urn (column name
s)
selection
String
Optional where cl
ause
selectionArgs
String[]
The arguments t
o the selection, i
f the query contai
ns
sortOrder
String
SortShanghai
order Normal
to be University
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Examining the Application Lifecycle
The lifecycle of Android applications differs great
ly from the lifecycle of web-based J2EE applicat
ions. J2EE apps are loosely managed by the con
tainer they run in. For example, a J2EE contain
er can remove an application from memory if it
sits idle for a predetermined time period. But th
e container generally won’t move applications i
n and out of memory based on load and/or avai
lable resources. In other words, it’s up to the ap
plication owners to ensure that resources are av
ailable.
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The concept of application lifecycle is logical, bu
t a fundamental aspect of Android applications c
omplicates matters. Specifically, the Android ap
plication architecture is compo- nent- and integ
ration-oriented. This allows a rich user experien
ce, seamless reuse, and easy application integr
ation, but creates a complex task for the applica
tion-lifecycle manager.
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The following graph shows the list of lifecycle met
hods that Android calls during the life of an acti
v- ity. It’s important to understand when each
of the methods is called by the system to ensur
e that you implement a stable application. Note
that you do not need to react to all of these met
hods. If you do, however, be sure to call the sup
erclass versions as well.
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onRestart
Activity Start
onCreate
onStop
onStar
r
onResume
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onDestroy
Activity Stop
onPause
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Debugging Your App
After we write a few lines of code for our first application, w
e’ll start wondering if it’s pos- sible to have a debug sessi
on while you interact with your application in the emulator.
Shortly after that, you’ll instinctively run to System.out.p
rintln(), which will fail because the code is running on the
emulator and the sys-out statement is not fed back to th
e IDE. But don’t worry; the Android SDK includes a host
of applications that we can use for debugging purposes.
The SDK also includes a file-explorer tool that you can us
e to view files on the device. These tools
are integrated with the Eclipse IDE
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You can view the tools b
y selecting the Debug per
spective in Eclipse. You c
an also launch each tool
by going to Window ➤ Sh
ow View ➤ Other ➤ Andr
oid.
One of the tools that you’l
l use throughout your And
roid development is LogC
at. This tool displays the l
og messages that you em
it using android.util.Log,
exceptions, and so on. W
e
will introduce the other tools
throughout the book.t.
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Summary
This chapter showed:
1.
2.
3.
4.
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how to set up IDE
discussed & introduced views, activities, i
ntents, content providers, and services.
Talk about the Android application lifecycle.
Finally, mentioned the Android SDK’s debug
ging tools
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