3. XML
eXtensible Markup Language
Simple text (Unicode) underneath
Tags (like in HTML) are used to provide
information about the data
Similar to HTML, but:
HTML is used to describe how to display the data
XML is used to describe what is the data
Often used to store and transfer data
4. HTML Example
<html>
<head><title>Here goes the
title</title></head.
<body>
<h1>This is a header</h1>
Here goes the text of the page
</body>
</html>
• Tags mean
something specific
to the browser
• They are used for
display
6. XML Rules
Tags are enclosed in angle brackets.
Tags come in pairs with start-tags and end-tags.
Tags must be properly nested.
<name><email>…</name></email> is not allowed.
<name><email>…</email><name> is.
Tags that do not have end-tags must be terminated by a ‘/’.
Document has a single root element
10. Attaching Layouts to Java Code
Assume res/layout/main.xml has been created. This layout could be called
by an application using the statement
setContentView(R.layout.main);
Individual widgets, such as my Button could be accessed by the
application using the statement findViewByID(...) as in
Button btn= (Button) findViewById(R.id.myButton);
Where R is a class automatically generated to keep track of resources
available to the application. In particular R.id... is the collection of widgets
defined in the XML layout.
11. Attaching Layouts to Java Code
Assume res/layout/main.xml has been created. This layout could be called
by an application using the statement
setContentView(R.layout.main);
Individual widgets, such as my Button could be accessed by the
application using the statement findViewByID(...) as in
Button btn= (Button) findViewById(R.id.myButton);
Where R is a class automatically generated to keep track of resources
available to the application. In particular R.id... is the collection of widgets
defined in the XML layout.
12. Attaching Layouts to Java Code
Attaching Listeners to the Widgets
The button of our example could now be used, for instance a listener for
the click event could be written as: