I’ve been playing recently with some Android development and recently I needed to load an XML resource (for API 3). I was very surprised to find that Android doesn’t have a super easy way of loading XML resource files.
The XMLPullParser works but it’s very bare metal and does leave quite a bit to be desired. So I decided to go ahead and create a generic XML parser that all android developers can use (and improve).
public class XMLData {
public String mValue;
public XMLData mParent;
public List mChild;
public XMLData(String value, XMLData parent) {
mParent = parent;
mChild = new ArrayList();
mValue = value;
}
}
First we establish a base XML data structure I decided to keep things simple here so I'm not at all doing anything about attributes if you wish to handle attributes you need to add a new ArrayList for attributes.
Now that we have our basic XML data type we can start create a class to read it:
public static XMLData Load(XmlPullParser parser) {
XMLData xmlModel = null;
XMLData currentNode = null;
try
{
int eventType = parser.getEventType();
while (eventType != XmlPullParser.END_DOCUMENT){
String name = null;
switch (eventType) {
case XmlPullParser.START_DOCUMENT:
xmlModel = new XMLData("root", null);
currentNode = xmlModel;
break;
case XmlPullParser.START_TAG:
name = parser.getName();
if (name != null) {
XMLData dataNode = new XMLData(name, currentNode);
currentNode.mChild.add(dataNode);
currentNode = dataNode;
}
break;
case XmlPullParser.TEXT:
name = parser.getText();
if (name != null) {
XMLData fieldNode = new XMLData(name,currentNode);
currentNode.mChild.add(fieldNode);
}
break;
case XmlPullParser.END_TAG:
name = parser.getName();
currentNode = currentNode.mParent;
break;
}
eventType = parser.next();
}
} catch (XmlPullParserException e) {
Log.e("ParseEx", e.getMessage());
} catch (IOException e) {
Log.e("IOEx", e.getMessage());
}
return xmlModel;
}
So let's back up for a second and look at what this does. We start off by first executing:
int eventType = parser.getEventType();
This reads off our first tag for the XMLPullParser.what follows is the main while loop.
There are 4 Major event types we are concerned with:
XmlPullParser.START_DOCUMENT
XmlPullParser.END_DOCUMENT
XmlPullParser.START_TAG
XmlPullParser.END_TAG
XmlPullParser.TEXT
START_DOCUMENT and END_DOCUMENT denote the beginning and end of the document when we get a start we concern ourselves with initializing the XMLData so we can start to build an XML tree.
START_TAG and END_TAG denote when each of the tags expand. On a START_TAG we prepare ourselves to traverse into the ENTRY by creating a new XMLData.
case XmlPullParser.START_TAG:
name = parser.getName();
if (name != null) {
XMLData dataNode = new XMLData(name, currentNode);
currentNode.mChild.add(dataNode);
currentNode = dataNode;
}
break;
dataNode in this case is the newly created node ready for traversal. We then perform
currentNode = dataNode remember that we are now traversing down the node.
On END_TAG we do one and only one thing we go up one level from our tree structure. This is accomplished with the following code:
case XmlPullParser.END_TAG:
name = parser.getName();
currentNode = currentNode.mParent;
break;
Finally we have TEXT in which we read off the actuall data of an element:
case XmlPullParser.TEXT:
name = parser.getText();
if (name != null) {
XMLData fieldNode = new XMLData(name,currentNode);
currentNode.mChild.add(fieldNode);
}
break;
Hopefully this tutorial breaks down an easy way to access your XML data. If you want to use
XMLData right away you can grab it here! I haven't decided what license I'll release it under but I'm thinking it'll be under the same license as Google SDK.
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