Learning Processing: A Beginner's Guide to Programming Images ...

350 Learning Processing
Other useful functions that can call XMLElement objects are:
• getChildCount( ) —returns the total number of children of an XMLElement.
• getChildren( ) —returns all of the children as an array of XMLElements.
In Example 18-3 , we used a series of comma separated values in a text fi le to store information related to
Bubble objects. An XML document can also be used in the same manner. Here is a possible solution to
Exercise 18-11, an XML tree of Bubble objects. (Note that this solution uses element attributes for red
and green colors; this was not the format provided in Exercise 18-11 since we had not yet learned about
attributes.)
� ?xml version = " 1.0 " ? �
� bubbles �
� bubble �
� diameter � 40 � /diameter �
� color red = " 75 " green = " 255 " / �
� /bubble �
� bubble �
� diameter � 20 � /diameter �
� color red = " 255 " green = " 75" / �
� /bubble �
� bubble �
� diameter � 80 � /diameter �
� color red = " 100 " green = " 150 " / �
� /bubble �
� /bubbles �
We can use getChildren( ) to receive the array of “ Bubble ” elements and make a Bubble object from each
one. Here is the example (which uses the identical Bubble class from earlier). Th e new elements are in bold.
Example 18-9: Using Processing’s XML library
import processing.xml.*;
// An array of Bubble objects
Bubble[] bubbles;
void setup() {
size(200,200);
smooth();
// Load an XML document
XMLElement xml = new XMLElement(this, " bubbles.xml " );
// Get the total number of bubbles
int totalBubbles = xml.getChildCount();
// Make an array the same size
bubbles = new Bubble[totalBubbles];
// Get all the child elements
XMLElement[] children = xml.getChildren();
for (int i = 0; i < children.length; i + + ) {
// The diameter is child 0
The root element is “bubbles”, which has
three children.
Each child “bubble” has two children,
“diameter” and “color.” The “color” element
has two attributes, “red” and “green”.
Getting the total number of Bubble objects
with getChildCount().