Android Application
Development
2013 PClassic
Chris Murphy
cdmurphy@cis.upenn.edu
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First things first: WiFi!
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Overview

What is Android?

Creating an Android app

Basic Android user interfaces: forms

Handling button clicks and user interaction

Dialogs
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What is Android?

An open source Linux-based operating system
intended for mobile computing platforms

Includes a Java API for developing applications

It is not a device or product
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Creating an Android App
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Creating an Android App
1.Set up your development environment
2.Create a new Android project in Eclipse
3.Implement it
4.Run it
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1. Set Up Your Android Environment

http://developer.android.com/sdk

Install Eclipse

Install Android SDK (Android libraries)

Install ADT plugin (Android development tools)

Create AVD (Android virtual device)
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2. Create an Android Project in Eclipse

File → New → Android Application Project

Fill in Project details...

After first screen, just keep choosing “Next” button
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Name that appears
on device
Project
directory
Android
version
Java package
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3. Run the Android Application



Run → Run As… → Android Application
If it says “No AVD Found” or something like that,
create a new one from Window → Android Virtual
Device Manager
The emulator may take a few minutes to start, so
be patient!
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Android Basic UI: Forms
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Layout Files

Android uses XML files to specify the arrangement
of elements in the UI

Activity: Java class that corresponds to a screen

Layout: specifies the position of elements

View: a visible element in the UI
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1.
Navigate
to here
2.
Then
click here
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activity_main.xml
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We want something like this…
TextView
EditText
Button
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3.
Then right
click, select
Edit Text, and
change it
2.
Then drag
this to
the top
1.
Click here
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1.
Drag two
Buttons to
the
bottom
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2.
Then click
here
1.
Right-click,
select Edit
Text, and
change
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2.
Don’t forget
to save it!
1.
Drag this to
the middle
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The Layout should look
like this now
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The XML should
look like this
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Helpful Hints: Running your app



The Graphical Layout tool only helps you edit the
layout; it doesn’t actually run your app
After you've edited activity_main.xml, run the
project as an Android app and you should see it
(re-)appear in the emulator
Don't close the emulator! You don't need to restart
it every time you rebuild your app!!
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Handling Button Clicks
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Handling Button Clicks



The activity_main.xml file also can specify the
method that should be called when the user clicks
a Button
This method should reside in the Java class that
extends Activity
Pay close attention to details when implementing
the button click method!
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2.
Add this line
1.
Click here
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1.
Navigate to
here and
open the file
2.
Then add
this method
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Helpful Hints: Accessing Views


In the class that extends Activity, you can get
access to the Views in its Layout by using the
findViewById method, along with the ID that is
specified in activity_main.xml
You do need to cast the View to the appropriate
subclass, however
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Helpful Hints: Debugging
• Log.v(tag, message);
• Window > Show View > Other > Android > LogCat
• Stack traces go in LogCat, too
• To show a pop-up window:
Toast.makeText(
getApplicationContext(),
message,
Toast.LENGTH_LONG).show();
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Dialogs
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Dialogs



Dialogs are pop-ups that have associated Buttons,
which have associated actions (methods)
Use a DialogBuilder to assemble the Dialog
Note: the way I’m going to show you here is the
“old” way (but it’s a bit easier)
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1.
Modify this
line
2.
Then this
one
3.
Then add
this method
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Helpful Hints: Activities


Keep in mind that the class that extends
Activity is just a regular old Java class
Its methods can communicate via shared
variables (aka “fields”)
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1.
Add this line
2.
Add this line
3.
Add/modify
these three
lines
4.
Add this line
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Just for fun!

Add an “Are you ready?” Dialog that is shown
when the app starts

Hint: you’d need to call showDialog from the
onCreate method

Keep track of the best (lowest) time

Randomly choose a sentence to display
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Android Resources
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Android Resources

developer.android.com

stackoverflow.com

anddev.org
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Installing your app on a device



You can use Eclipse to install your app via a wired
connection with your device
Or... go into the /bin directory of the Eclipse
project, find the .apk file, email it to yourself, and
install it on the device via your email client
You can also upload the .apk file to manymo.com
to see how it would like on various other devices
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Good luck
today!
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