1. Mobile Computing With Android ACST 4550 XML and the Android GUI

2. What is XML? eXtensible Markup Language
Markup language for documents containing structured information
Based on Standard Generalized Markup Language (SGML)
Version 1.0 introduced by World Wide Web Consortium (W3C) in 1998
Bridge for data exchange on
the Web

3. XML HTML XML to HTML Comparison Extensible set of tags
Content orientated
Standard Data infrastructure
Allows multiple output forms
Fixed set of tags
Presentation oriented
No data validation capabilities
Single presentation

4. Authoring XML Elements
An XML element is made up of a start tag, an end tag, and data in between.
Example:
<director> Matthew Dunn </director>
Example of another element with the same value:
<actor> Matthew Dunn </actor>
XML tags are case-sensitive:
<CITY> <City> <city>
XML can abbreviate empty elements, for example:
<married> </married> can be abbreviated to
<married/>

5. Authoring XML Elements (cont’d)
An attribute is a name-value pair separated by an equal sign (=).
Example:
<City ZIP=“94608”> Emeryville </City>
Attributes are used to attach additional, secondary information to an element.

6. Authoring XML Documents
A basic XML document is an XML element that can, but might not, include nested XML elements.
Example:
<books>
<book isbn=“123”>
<title> Second Chance </title>
<author> Matthew Dunn </author>
</book>
</books>

7. XML Data Model: Example
<BOOKS>
<book id=“123” loc=“library”>
<author>Hull</author>
<title>California</title>
<year> 1995 </year>
</book>
<article id=“555” ref=“123”>
<author>Su</author>
<title> Purdue</title>
</article>
</BOOKS>
Purdue
BOOKS
123
555
California Su
title
author
article
book
year
1995
ref
loc=“library”
Hull

8. Apps – Android Manifest
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="
package="com.example.helloandroid"
android:versionCode="1"
android:versionName="1.0">
<application
<activity android:name=".HelloAndroid"
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>
@2011 Mihail L. Sichitiu

9. Apps – res (Resources) Folder
anim
drawable
hdpi
mdpi
ldpi
layout
values
arrays.xml
colors.xml
strings.xml
xml
raw

10. Apps – R.java
Autogenerated, best if not manually edited
gen/

11. Apps – View Hierarchy All the views in a window are arranged in a tree
You show the tree by calling setContentView(rootNode) in the activity
@2011 Mihail L. Sichitiu

12. Apps – Layout
Defines how elements are positioned relative to each other (next to each other, under each other, in a table, grid, etc.)
Can have a different layouts for each ViewGroup
@2011 Mihail L. Sichitiu

13. Apps – Widgets All are View objects Examples: TextFields EditFields
Buttons
Checkboxes
RadioButtons
etc.
@2011 Mihail L. Sichitiu

14. UI Events
Usually handled by defining a Listener of the form On<something>Listener and register it with the View
For example:
OnClickListener() for handling clicks on Buttons or Lists
OnTouchListener() for handling touches
OnKeyListener() for handling key presses
Alternatively, Override an existing callback if we implemented our own class extending View
@2011 Mihail L. Sichitiu

15. Create the following Android App: SimpleCalculator Name your Activity: CalculatorActivity

16. You will create the following GUI: