Reading xml in android

Работа с XML в Android

Очень часто приходится хранить информацию форм и для этого можно использовать xml файлы. В данном уроке мы это и рассмотрим, как можно работать с файлами XML.

Библиотеки Android имеют набор классов для работы с XML-документами с произвольной структурой и содержанием.

Шаг 1.

Для того чтобы упаковать статический XML файл вместе с вашим приложением, вам нужно поместить его в папку: res/xml/

В каталоге res/ создайте подкаталог xml/ в котором будет располагаться наш ХМL-файл.

После чего вы получите возможность обращаться в коде программы к этому документу.

Шаг 2.

Рассмотрим загрузку XML-документа произвольной структуры из ресурсов в код программы.

Создадим приложения, которое будет уметь способность читать список имен, фамилий и телефонов, определенных в XML-файле.

Теперь создадим XML файл который будет хранить Имена, Фамилии и номера телефонов сотрудников фирмы и сохраним его в res/xml/ под именем contacts.xml.

Вот как будут выглядеть XML файл contacts.xml

Шаг 3.

Создадим View состоять она будет с LinearLayout и ListView и назовем main.xml:

Шаг 4.

Загружаем файл contacts.xml, созданный ранее:

Метод getXml() возвращает XmlPullParser, используя который можно прочитать загруженный XML-документ в цикле while:

В конечном итоге ваше приложение должно выглядеть так:

Весь код MyActivity:

Обратите внимание что наследуется MyActivity не от Activity а от ListActivity.

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Processing and Parsing XML in Android

Sharing data over the internet is very popular. We share our information with the other users over the internet. Let’s take a very common example, since we all are developers and to be more precise, we all are Android Developers and we all must have visited the StackOverflow website whenever we are stuck into some problem in our projects and in every 99 out of 100 cases, we find the solution to our problem. The answer that we get from the StackOverflow website consists of various parts that we are less bothered about. In general, the answers or the questions present on the website contains the id of the question, type of the question, author name of the article or question, publishing data, URL and many other things are there on the website. But we want only meaningful data i.e. we want answers and the authors and nothing else.

The problem arises when you want to access the data of a particular website in your Android Application. This is because the data present on the websites are in JSON format or in XML format. So, in order to use that data or to extract the meaningful information from that data, you have to parse that XML file or a JSON file.

So, in this blog, we will learn how to process and parse the XML data in Android. So, let’s get started.

What is XML?

XML stands for Extensible Markup Language. It is a set of rules that are used to encode data or documents in a Machine-readable language. There are many websites that use an XML format to share data on the internet. For example, many blogging websites use an XML format to share data between users. So, XML parsing and processing become an important task to use that data in our Android Application.

XML elements

In general, an XML file consists of a number of elements that together make an XML file. They are the basic building blocks of XML document. These elements are used to store some text elements, attributes, media, etc. Below is the syntax of XML element:

Here, element-name is the name of the element and attributes are used to define the property of XML element. Following is an example of an XML document that is used to describe the data of the student:

We can broadly divide the XML elements in four parts:

1. Prolog: It is the first line that contains the information about the XML file i.e. it is the first line of the XML file.
2. Events: An XML file contains a number of events like document start, document end, Tag start, Tag end, etc.
3. Text: In between the tags(opening and closing), there can be some text. For example, in the above example, “John” is the text.
4. Attributes: These are the properties of XML elements.

XML Parsing

So, we have seen the introduction of XML and our next task is, How to parse the XML in Android? So, let’s find out.In Android, there are various parsers that can be used to parse the XML file in Android. Some of these are:

1. XMLPullParser
2. DOM Parser
3. SAX Parser

Among these three parsers, XMLPullParser is the most commonly and most widely used parsers in Android. This is because XMLPullParser is very efficient and easy to use. Also, unlike the DOM Parser which loads the whole file in the memory and then parses it, the XMLPullParser consumes less memory.

Steps involved in XML parsing

Following are the steps that are involved in XML parsing:

• Analyze the feed: There are many cases when you will be provided with a number of data but you need only few of them. SO, before parsing the XML, your first step should be to find the desired element in the XML data. For example, here is example of XML file of StackOverflow:

Here, if you want to extract the data present in the entry tag and the data of its sub tags then you should keep note of these things.

• Create XMLPullParser object: Our next step is to create the object of XMLPullParser and specify the file name for the XMLPullParser that contains XML. You can use a file or a stream. Following is the code to create an object of the XMLPullParser and then passing the file name for the XMLPullParser:

• Read the desired data: Our last step is to parse the data of the XML file. The following readFeed() function is used to parse the XML file and extract only the values of entries and store it into a list:

Here, XMLPullParser.END_TAG is used to find if the parser has reached to the last tag of the file or not. If it has reached then return and it has not reached then we will check for the entry tag and if found then will add the value to the entries list. If the values are not found be to of entries type then we can skip the parser. At last, we return entries.

Following are the methods that can be used while parsing an XML file:

1. getEventType(): This method is used to get the event type. For example, Document start, Document End, Tag start, Tag end, etc.
2. getName(): This is used to get the tag name in a file. For example, in the above code, the tag name is entry.
3. getAttributeValue(): This method is used to get the attribute value of a particular tag.
4. getAttributeCount(): It returns the total number of attributes of the current tag.
5. getAttributeName(int index): It returns the attribute name at a particular index.
6. getColumnNumber(): It returns the current column number using a 0 based indexing.
7. getName(): It returns the name of the tag.
8. getText(): It returns the text present in a particular element.

XML parsing example

Now, let’s do one example to understand the concept of XML parsing ina very easy and clear manner.

Open Android Studio and create a project with Empty Activity template.

The very first step is to create the XML file. Either you create your own XML file or you can use mine. To create an XML file, go to java folder and then right click on it. Then click on New > Folder > Assets folder and then OK. One assets folder will be created for you. Now right click on that folder and create a file and name it as example.xml. Following is the XML content of example.xml file:

This is a simple example of student data containing the name, surname, mobile and section of the student. In this example, we will extract the name, surname and section of the student. We will ignore the mobile number.

Now, let’s code for the UI part of our application. Here we will display the desired data on a TextView. So, open the activity_main.xml file and add the below code:

So, we are done with the UI part. Now, let’s write the code for the XML parsing. Below is the code for the MainActivity.kt file:

Now, run the application on your mobile phone and try to add more data to your XML file i.e. the example.xml file.

Conclusion

In this blog, we learned about XML parsing in Android. We learned how to parse the data present in the XML format in Android Application. We saw how to use XMLPullParser to do XML parsing. At last, we did one example of XML parsing. You can get more contents about XML parsing at the Android Developer Website.

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Learning to Parse XML Data in Your Android App

Introduction

We are in an age where, typically, an application cannot work in total isolation and does not have all the data it needs to do its work. It generally has to communicate to some other application–maybe over the internet–and read or send some data to it.

However, the applications with which your app communicates might not be developed using the same technology as yours. For smooth data exchanges between your app and some other application you might be exchanging data in an open format like Extensible Markup language or XML.

An XML document is a human readable text document that contains some starting and ending tags with attributes and data in those tags. Most of the languages and platforms have support for parsing and creating XML documents in them. Android also provides us APIs so that we can work and process XML documents in our app with ease and flexibility. In this article, we are going to see how you can work effectively with XML documents in your Android app.

The classes for XML parsing in Android

There are various XML parsers we can use on the Android platform. For XML, Android recommends the use of the XMLPullParser . Android gives a multiple implementation of the XMLPullParser and you can use any of them in your program. Depending on the way you create your XMLPullParser , the implementation of the parser will be chosen.

Instantiating your parser

As stated above, there are multiple ways in Android you can create an XMLPullParser . The first way to do it is using the Xml class as shown below:

You have to just call newPullParser which will return you a reference to the XMLPull parser. Or you can get a reference from the XmlPullParserFactory as shown below.

Parsing the XML

Once we have the parser reference it’s now time to use it to parse an XML. We are going to use the following XML as the XML to parse. So now create a file called temp.xml in your assets folder with the content:

The code of the activity to read and parse is as follows:

In the above code we have created a small class called Product which has three members: name, quantity and color.

In the activity we first get the XMLPullParser instance then we open the temp.xml as an inputstream . Once that is done we set the inputstream as input to the parser. Then we parse the xml in our function parseXML .

In the function parseXML we create an ArrayList in which we will store all the products which we will parse from the XML. Once that is done we create a loop which will work till the end of the document is reached.

At the start of the document we created the ArrayList of products. If a tag starts and if the tag is product we know that now it’s a new product so we create a new product instance. Then if the other tags are read we will just read and add the values in our Product instance.

Once the Product tag is ended we add the product to the ArrayList . Once all the products are added we call the function printProducts in which we iterate over the ArrayList and then print the values on the screen.

If we run the activity now we will see the output as follows:

Other Parsers used for XML

There are other parsers also that can be used to parse XML in Android. The DOM parser can be used which creates a complete memory model of the XML and can be used to either create or parse XML. DOM parsers generally consume a lot of memory.

You can get the instance of a DOMBuilder as shown below

SAX Parsers

The SAXParsers can also be used to parse XML and consume much lesser memory then DOM parsers. The SAXParsers can be used only to parse XMLs not to create them. You can get the reference of a SAXParser as shown below:

Conclusion

XML documents are becoming a standard way to exchange data between applications over the internet. With our Android apps becoming smarter and smarter it might be necessary for your Android app to communicate and exchange data between different applications over the internet. Android provides a rich set of APIs to work with XML documents in your Android app.

With the help of these APIs you can easily incorporate XML into your Android app. The XML parsers do the tedious work of parsing the XML and we have to just write the code to fetch the appropriate information from it and store it for further processing.

So, have fun processing XML in your next Android app.

And if you enjoyed reading this post, you’ll love Learnable; the place to learn fresh skills and techniques from the masters. Members get instant access to all of SitePoint’s ebooks and interactive online courses, like Beginning Android Development.

Comments on this article are closed. Have a question about developing Apps? Why not ask it on our forums?

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Processing and Parsing XML in Android

Sharing data over the internet is very popular. We share our information with the other users over the internet. Let’s take a very common example, since we all are developers and to be more precise, we all are Android Developers and we all must have visited the StackOverflow website whenever we are stuck into some problem in our projects and in every 99 out of 100 cases, we find the solution to our problem. The answer that we get from the StackOverflow website consists of various parts that we are less bothered about. In general, the answers or the questions present on the website contains the id of the question, type of the question, author name of the article or question, publishing data, URL and many other things are there on the website. But we want only meaningful data i.e. we want answers and the authors and nothing else.

The problem arises when you want to access the data of a particular website in your Android Application. This is because the data present on the websites are in JSON format or in XML format. So, in order to use that data or to extract the meaningful information from that data, you have to parse that XML file or a JSON file.

So, in this blog, we will learn how to process and parse the XML data in Android. So, let’s get started.

What is XML?

XML stands for Extensible Markup Language. It is a set of rules that are used to encode data or documents in a Machine-readable language. There are many websites that use an XML format to share data on the internet. For example, many blogging websites use an XML format to share data between users. So, XML parsing and processing become an important task to use that data in our Android Application.

XML elements

In general, an XML file consists of a number of elements that together make an XML file. They are the basic building blocks of XML document. These elements are used to store some text elements, attributes, media, etc. Below is the syntax of XML element:

Here, element-name is the name of the element and attributes are used to define the property of XML element. Following is an example of an XML document that is used to describe the data of the student:

We can broadly divide the XML elements in four parts:

1. Prolog: It is the first line that contains the information about the XML file i.e. it is the first line of the XML file.
2. Events: An XML file contains a number of events like document start, document end, Tag start, Tag end, etc.
3. Text: In between the tags(opening and closing), there can be some text. For example, in the above example, “John” is the text.
4. Attributes: These are the properties of XML elements.

XML Parsing

So, we have seen the introduction of XML and our next task is, How to parse the XML in Android? So, let’s find out.In Android, there are various parsers that can be used to parse the XML file in Android. Some of these are:

1. XMLPullParser
2. DOM Parser
3. SAX Parser

Among these three parsers, XMLPullParser is the most commonly and most widely used parsers in Android. This is because XMLPullParser is very efficient and easy to use. Also, unlike the DOM Parser which loads the whole file in the memory and then parses it, the XMLPullParser consumes less memory.

Steps involved in XML parsing

Following are the steps that are involved in XML parsing:

• Analyze the feed: There are many cases when you will be provided with a number of data but you need only few of them. SO, before parsing the XML, your first step should be to find the desired element in the XML data. For example, here is example of XML file of StackOverflow:

Here, if you want to extract the data present in the entry tag and the data of its sub tags then you should keep note of these things.

• Create XMLPullParser object: Our next step is to create the object of XMLPullParser and specify the file name for the XMLPullParser that contains XML. You can use a file or a stream. Following is the code to create an object of the XMLPullParser and then passing the file name for the XMLPullParser:

• Read the desired data: Our last step is to parse the data of the XML file. The following readFeed() function is used to parse the XML file and extract only the values of entries and store it into a list:

Here, XMLPullParser.END_TAG is used to find if the parser has reached to the last tag of the file or not. If it has reached then return and it has not reached then we will check for the entry tag and if found then will add the value to the entries list. If the values are not found be to of entries type then we can skip the parser. At last, we return entries.

Following are the methods that can be used while parsing an XML file:

1. getEventType(): This method is used to get the event type. For example, Document start, Document End, Tag start, Tag end, etc.
2. getName(): This is used to get the tag name in a file. For example, in the above code, the tag name is entry.
3. getAttributeValue(): This method is used to get the attribute value of a particular tag.
4. getAttributeCount(): It returns the total number of attributes of the current tag.
5. getAttributeName(int index): It returns the attribute name at a particular index.
6. getColumnNumber(): It returns the current column number using a 0 based indexing.
7. getName(): It returns the name of the tag.
8. getText(): It returns the text present in a particular element.

XML parsing example

Now, let’s do one example to understand the concept of XML parsing ina very easy and clear manner.

Open Android Studio and create a project with Empty Activity template.

The very first step is to create the XML file. Either you create your own XML file or you can use mine. To create an XML file, go to java folder and then right click on it. Then click on New > Folder > Assets folder and then OK. One assets folder will be created for you. Now right click on that folder and create a file and name it as example.xml. Following is the XML content of example.xml file:

This is a simple example of student data containing the name, surname, mobile and section of the student. In this example, we will extract the name, surname and section of the student. We will ignore the mobile number.

Now, let’s code for the UI part of our application. Here we will display the desired data on a TextView. So, open the activity_main.xml file and add the below code:

So, we are done with the UI part. Now, let’s write the code for the XML parsing. Below is the code for the MainActivity.kt file:

Now, run the application on your mobile phone and try to add more data to your XML file i.e. the example.xml file.

Conclusion

In this blog, we learned about XML parsing in Android. We learned how to parse the data present in the XML format in Android Application. We saw how to use XMLPullParser to do XML parsing. At last, we did one example of XML parsing. You can get more contents about XML parsing at the Android Developer Website.

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