{"id":324,"date":"2010-11-17T22:39:00","date_gmt":"2010-11-17T22:39:00","guid":{"rendered":"http:\/\/www.javacodegeeks.com\/2012\/10\/boost-your-android-xml-parsing-with-xml-pull.html"},"modified":"2012-10-21T19:21:49","modified_gmt":"2012-10-21T19:21:49","slug":"boost-android-xml-parsing-xml-pull","status":"publish","type":"post","link":"https:\/\/www.javacodegeeks.com\/2010\/11\/boost-android-xml-parsing-xml-pull.html","title":{"rendered":"Boost your Android XML parsing with XML Pull"},"content":{"rendered":"

In today’s technology world, XML parsing capabilities are a necessity for a big number of applications whether they are mobile, enterprise or in the cloud. Despite the fact that XML is bloated and very verbose, it still remains king in the field of data exchange (JSON is a nice alternative, check our tutorial for JSON integration with GWT<\/a>).<\/p>\n

There are two main approaches in XML parsing: SAX and DOM. The SAX<\/a> specification defines an event-based approach where the implemented parsers scan through XML data and they use call-back handlers whenever certain parts of the document have been reached. On the other hand, the DOM<\/a> specification defines a tree-based approach to navigating an XML document.<\/p>\n

In a previous tutorial<\/a> we saw how to parse XML documents using SAX. DOM object is relatively resources intensive and perhaps not suitable for use in a mobile environment. A SAX parser is quite more lightweight and uses a smaller memory footprint. SAX is a push parsing API but the approach it uses is somewhat \u201cbroken\u201d in the sense that, rather than being called by the parsing application, the SAXParser uses a message handler with \u201ccall backs\u201d.<\/p>\n

An alternative to that is using a relatively new practice, the \u201cpull parsing\u201d approach. In short, the main difference with this approach is that the user code is in control and can pull more data when it is ready to process it. You can find an excellent article in processing XML with the XML Pull Parser<\/a> as well as some XML pull parsing patterns<\/a>.<\/p>\n

The Android SDK includes support for XML Pull parsing (which surprisingly is there from Level 1 API) via the XML Pull package<\/a>. The main class used is the XmlPullParser<\/a> with the Javadoc page including a simple example of how to use the parser. In this tutorial I am going to show you how to add pull parsing capabilities into your Android application and how to implement a more sophisticated parser than the one provided by the API docs.<\/p>\n

If you are a regular JavaCodeGeeks<\/a> reader, you probably know that I have started a tutorial series where I am building a full application<\/a> from scratch. In its third part (\u201cAndroid Full App, Part 3: Parsing the XML response\u201d<\/a>), I use an XML based external API in order to perform movies search. A sample XML response is the following:
\n
\nMovies search for \u201cTransformers\u201d and (year) \u201c2007\u201d<\/a><\/p>\n

In that tutorial I presented the SAX based approach, but know we are going to boost things up by using Android’s XML pull parser. First, let’s create a new Android project inside Eclipse. I am calling it \u201cAndroidXmlPullParserProject\u201d. Here is a screenshot of the configuration used:<\/p>\n

\"\"<\/a><\/p>\n

The first step in using the XML Pull API is to obtain a new instance of the XmlPullParserFactory class. This class is used to create implementations of XML Pull Parser defined in XMPULL V1 API. We will disable the namespace awareness of the factory since it is not required by the application’s needs. Note that this will also improve the parsing speed.<\/p>\n

Next, we create a new XmlPullParser<\/a> by invoking the newPullParser<\/a> factory method. An input has to be provided to our parser and that is accomplished via the setInput method, which requires an InputStream<\/a> and an encoding as arguments. We provide an input stream obtained by a URL connection (since our XML document is an internet resource), but we do not provide an input encoding (null is just fine).<\/p>\n

XML Pull parsing is event-based and in order to parse the whole document, the trick is to create a loop inside which we serially get all the parsing events until we reach the END_DOCUMENT<\/a> event. As a showcase example, the code will just print log statements when the following events are encountered:<\/p>\n