This article aims to deeply explore the technical details of the Huawei HarmonyOS Next system (up to API 12 as of now), and is summarized based on actual development practices.
It mainly serves as a vehicle for technical sharing and communication. Mistakes and omissions are inevitable. Colleagues are welcome to put forward valuable opinions and questions so that we can make progress together.
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Introduction

XML is a widely used markup language for describing data structures. In HarmonyOS application development, XML data is commonly used in scenarios such as configuration files, network requests, and data exchange. ArkTS provides XML parsing and generation functions, which can help developers handle XML data with ease. This article will introduce how to use the XML parsing and generation functions of ArkTS and demonstrate their applications through practical cases.

XML Overview

XML (Extensible Markup Language) is a markup language used to describe data, aiming to provide a universal way to transmit and store data. An XML document consists of elements, attributes, and content. An element can contain text, attributes, or other elements. Attributes provide additional information about the element. The content is the data or child elements contained within the element. XML also supports features such as namespaces, entity references, comments, and processing instructions, making it flexible enough to adapt to various data requirements.

XML Parsing

ArkTS provides the XmlPullParser class for parsing XML files. Developers can use the XmlPullParser class to parse XML files and obtain information such as elements, attributes, and content. The following is an example code:

// Parse an XML file
let xmlString = `<?xml version="1.0" encoding="utf-8"?>
<note importance="high" logged="true">
    <title>Play</title>
    <lens>Work</lens>
</note>`;
let parser = new xml.XmlPullParser(xmlString, 'UTF-8');
let eventType = parser.next();
while (eventType!= xml.EventType.END_DOCUMENT) {
    if (eventType == xml.EventType.START_TAG) {
        let tagName = parser.getName();
        let attributes = parser.getAttributes();
        // Process the element
    } else if (eventType == xml.EventType.TEXT) {
        let text = parser.getText();
        // Process the text
    }
    eventType = parser.next();
}

In the above code, we first define an XML string and then create an XmlPullParser object for parsing. During the parsing process, we can obtain information such as the element name, attributes, and text content, and perform corresponding processing.

XML Generation

ArkTS provides the XmlSerializer class for dynamically generating XML data. Developers can use the XmlSerializer class to create XML files and set information such as elements, attributes, and content. The following is an example code:

// Generate an XML file
let serializer = new xml.XmlSerializer(new ArrayBuffer(2048));
serializer.setDeclaration();
serializer.startElement('bookstore');
serializer.startElement('book');
serializer.setAttributes('category', 'COOKING');
serializer.startElement('title');
serializer.setAttributes('lang', 'en');
serializer.setText('Everyday');
serializer.endElement();
serializer.startElement('author');
serializer.setText('Giana');
serializer.endElement();
serializer.endElement();
serializer.endElement();
let buffer = serializer.getBuffer();
let xmlString = new TextDecoder('UTF-8').decode(buffer);
console.info(xmlString);

In the above code, we first create an XmlSerializer object, then set information such as the XML declaration, elements, attributes, and text content, and finally generate an XML string.

Advanced Applications

In addition to the basic XML parsing and generation functions, ArkTS also supports some advanced applications, such as:

• Handling complex XML structures: You can use the getDepth() method of XmlPullParser to obtain the depth of an element, thus better understanding the XML structure.
• Handling attributes: You can use the getAttributes() method of XmlPullParser to obtain the attributes of an element and perform corresponding processing.
• Handling events: You can use the eventType property of XmlPullParser to obtain the type of the current event and perform corresponding processing.

Code Example

The following is a complete example showing how to use ArkTS to parse and generate XML data:

// Parse an XML file
let xmlString = `<?xml version="1.0" encoding="utf-8"?>
<note importance="high" logged="true">
    <title>Play</title>
    <lens>Work</lens>
</note>`;
let parser = new xml.XmlPullParser(xmlString, 'UTF-8');
let eventType = parser.next();
// Parse the elements
while (eventType!= xml.EventType.END_DOCUMENT) {
    if (eventType == xml.EventType.START_TAG) {
        let tagName = parser.getName();
        let attributes = parser.getAttributes();
        // Process the element
    } else if (eventType == xml.EventType.TEXT) {
        let text = parser.getText();
        // Process the text
    }
    eventType = parser.next();
}
// Generate an XML file
let serializer = new xml.XmlSerializer(new ArrayBuffer(2048));
serializer.setDeclaration();
serializer.startElement('bookstore');
serializer.startElement('book');
serializer.setAttributes('category', 'COOKING');
serializer.startElement('title');
serializer.setAttributes('lang', 'en');
serializer.setText('Everyday');
serializer.endElement();
serializer.startElement('author');
serializer.setText('Giana');
serializer.endElement();
serializer.endElement();
serializer.endElement();
let buffer = serializer.getBuffer();
let xmlString = new TextDecoder('UTF-8').decode(buffer);
console.info(xmlString);

Summary

ArkTS provides rich XML parsing and generation functions, which can help developers handle XML data with ease. By learning the principles of XML parsing and generation and combining them with practical cases, we can improve the development efficiency and quality of HarmonyOS applications.