创建的xml文件为什么是空的

可能是因为你没有向xml文件中写入任何内容。在创建xml文件后，你需要使用相应的编程语言或工具将信息写入xml文件中，才能在文件中看到内容。以下是一些写入xml文件的示例代码：

使用Python语言写入xml文件：

import xml.etree.ElementTree as ET

root = ET.Element("root")
doc = ET.SubElement(root, "doc")

ET.SubElement(doc, "field1", name="blah").text = "some value1"
ET.SubElement(doc, "field2", name="asdfasd").text = "some vlaue2"

tree = ET.ElementTree(root)
tree.write("filename.xml")

使用Java语言写入xml文件：

import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import javax.xml.stream.XMLOutputFactory;
import javax.xml.stream.XMLStreamException;
import javax.xml.stream.XMLStreamWriter;

public class WriteXMLFile {
    public static void main(String[] args) throws IOException, XMLStreamException {
        XMLOutputFactory xmlOutputFactory = XMLOutputFactory.newInstance();
        XMLStreamWriter xmlStreamWriter = xmlOutputFactory.createXMLStreamWriter(new FileWriter(new File("filename.xml")));
        xmlStreamWriter.writeStartDocument();
        xmlStreamWriter.writeStartElement("root");
        xmlStreamWriter.writeStartElement("doc");
        xmlStreamWriter.writeStartElement("field1");
        xmlStreamWriter.writeAttribute("name", "blah");
        xmlStreamWriter.writeCharacters("some value1");
        xmlStreamWriter.writeEndElement();
        xmlStreamWriter.writeStartElement("field2");
        xmlStreamWriter.writeAttribute("name", "asdfasd");
        xmlStreamWriter.writeCharacters("some value2");
        xmlStreamWriter.writeEndElement();
        xmlStreamWriter.writeEndElement();
        xmlStreamWriter.writeEndElement();
        xmlStreamWriter.writeEndDocument();
        xmlStreamWriter.flush();
        xmlStreamWriter.close();
    }
}

使用C#语言写入xml文件：

using System;
using System.Xml;

public class WriteXML {
    public static void Main() {
        XmlWriterSettings settings = new XmlWriterSettings();
        settings.Indent = true;
        XmlWriter writer = XmlWriter.Create("filename.xml", settings);

        writer.WriteStartDocument();
        writer.WriteStartElement("root");
        writer.WriteStartElement("doc");
        writer.WriteStartElement("field1");
        writer.WriteAttributeString("name", "blah");
        writer.WriteString("some value1");
        writer.WriteEndElement();
        writer.WriteStartElement("field2");
        writer.WriteAttributeString("name", "asdfasd");
        writer.WriteString("some value2");
        writer.WriteEndElement();
        writer.WriteEndElement();
        writer.WriteEndElement();
        writer.WriteEndDocument();
        writer.Flush();
        writer.Close();
    }
}

这些是只是一些示例代码，你可以根据自己的需要进行修改。