One 、 Example XML The contents of the document

The following is the... Used in this article xml The content of the document

<?xml version="1.0" encoding="UTF-8"?>
<root>
    <childNode1 attruKey="attriVal">childNode1 Val</childNode1>
    <childNode2 attruKey="attriVal">
        <cChildNode1 shuxing1="1">cChildNode1 Val</cChildNode1>
        <cChildNode2 shuxing2="2">cChildNode2 Val</cChildNode2>
    </childNode2>
</root>

Two 、XML Writing files

Below is XML File written source code , The code contents are as follows ：

1. QDomDocument Object creation and xml Addition of file header
2. Create a root node
3. Create child nodes that contain attributes and node values
4. Create more complex child nodes （ Contains attributes and third level nodes ）
5. write file

        // establish QDomDocument object 
    QDomDocument xDoc;
    QDomProcessingInstruction inStruction;
    // write in xml The file header (xml Version information and coding information )
    inStruction = xDoc.createProcessingInstruction("xml","version=\"1.0\" encoding=\"UTF-8\"");
    xDoc.appendChild(inStruction);

    // Create a root node and add it to xDoc in 
    QDomElement root = xDoc.createElement("root");
    xDoc.appendChild(root);

    // Create child nodes 1
    QDomElement childNode1 = xDoc.createElement("childNode1");
    // Is a child node childNode1 Set properties and property values 
    childNode1.setAttribute("attruKey", "attriVal");
    //!  Is a child node childNode1 Add node value 
    //!  establish QDomText Object and set its value 
    QDomText nodeVal = xDoc.createTextNode("childNode1 Val");
    // Use QDomElement Object's nodes , To add a node value, you need to add QDomText object , Otherwise, the value may not be displayed 
    childNode1.appendChild(nodeVal);
    // Put the child nodes 1 Add to the root node 
    root.appendChild(childNode1);

    //!  Create a multi-level node childNode2

    // Create multi-level nodes 2
    QDomElement childNode2 = xDoc.createElement("childNode2");
    // It is a multi-level node childNode2 Set properties and property values 
    childNode2.setAttribute("attruKey", "attriVal");
    // Create child nodes of multi-level nodes 1
    QDomElement cChildNode1 = xDoc.createElement("cChildNode1");
    // Set up cChildNode1 Properties and values of 
    cChildNode1.setAttribute("shuxing1", 1);
    // Set up cChildNode1 Node value 
    cChildNode1.appendChild(xDoc.createTextNode("cChildNode1 Val"));
    // take cChildNode1 Add nodes to multi-level nodes 
    childNode2.appendChild(cChildNode1);

    // Create child nodes of multi-level nodes 2
    QDomElement cChildNode2 = xDoc.createElement("cChildNode2");
    // Set up cChildNode2 Properties and values of 
    cChildNode2.setAttribute("shuxing2", 2);
    // Set up cChildNode2 Node value 
    cChildNode2.appendChild(xDoc.createTextNode("cChildNode2 Val"));
    // take cChildNode2 Add nodes to multi-level nodes 
    childNode2.appendChild(cChildNode2);

    // Multi level node childNode2 Add to the root node 
    root.appendChild(childNode2);

    // Appoint xml File path 
    QFile file("./xmlTest.xml");
    // Open as read-only , And will empty the contents of the file 
    if(!file.open(QIODevice::WriteOnly | QIODevice::Truncate))
        return 0;
    // Write to a file using a text stream 
    QTextStream outputStream(&file);
    xDoc.save(outputStream, 4); // Indent four spaces 
    file.close();

3、 ... and 、XML File reading

3.1 File reading source code

Below is XML File reading source code , The code contents are as follows ：

1. establish QDomDocument Object and open the file to add its data source
2. Get root node
3. Read simpler child nodes （ Only one attribute and node value ）
4. Read more complex child nodes （ Contains attributes and different ）

// establish QDomDocument object 
    QDomDocument xDoc;
    // Specifies the number of bytes to read xml File path 
    QFile file("./xmlTest.xml");
    //xml The file is clocked in as read-only 
    if (!file.open(QIODevice::ReadOnly))
        return 0;
    // call setContent Function to set the data source 
    if (!xDoc.setContent(&file)) {
    
        file.close();
        return 0;
    }
    file.close();

    // obtain xDoc Medium QDomElement object 
    QDomElement docElem = xDoc.documentElement();
    // obtain docElem The root node 
    QDomNode node = docElem.firstChild();


    //! Get the first child node , And read its properties and values 
    QDomElement  childNode1 = node.toElement();
    // obtain childNode1 The attribute value 
    QString attri1 = childNode1.attribute("attruKey");
    // obtain childNode1 Node value （ Since setting the node value requires inserting child nodes , Then you should also read its child nodes ）
    QDomNode node1Child = childNode1.firstChild();
    QString node1Val = node1Child.nodeValue();

    // Output attribute value and node value 
    qDebug() << " Attribute value and node value of the first child node ";
    qDebug() << attri1 << node1Val;

    // Move the node to the next node 
    node = node.nextSibling();

    //!  Get the second node , And use the loop to get each value 
    QDomElement  childNode2 = node.toElement();
    qDebug() << " Reading of the second node ";
    // obtain childNode1 The attribute value 
    QString attri2 = childNode2.attribute("attruKey");
    qDebug() << " The attribute value of the second node :" << attri2;

    // Get the first child node in the second node 
    QDomNode cChildNode = childNode2.firstChild();
    while(!node.isNull()) {
    
        // Get the object of the current child node 
        QDomElement e = cChildNode.toElement();
        if(!e.isNull()) {
    
            qDebug() << e.firstChild().nodeValue(); // the node really is an element.
        }
        // Get the next node element 
        cChildNode = cChildNode.nextSibling();
    }

3.2 Example of reading results

Below is XML File read output example

summary

XML Files use QDomDocument When writing and reading objects, you need to pay attention to the following , Add when needed QDomText Object settings ; When reading, you need to read its first child node , And get the value .（ The more complex the file structure , More complex code is needed to read and write ）

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notes ： This paper summarizes the problems encountered by the author in the process of programming , The content is for reference only , If there are any mistakes, please point out .
notes ： If there is any infringement , Please contact the author for deletion