使用SAX Parser的Kotlin Android XML解析

XML文档通常用于在Internet上共享数据。 XML格式提供的数据能够经常更新, 并且解析它们是基于网络的应用程序的常见任务。

在Android中, 有三种类型的XML解析器可以解析XML数据并在android应用程序中读取它们, 它们是：

1. DOM解析器
2. SAX解析器
3. XMLPullParser

在Android中, SAX（XML的简单API）被广泛用于XML解析的API。 SAX解析器将逐字符检查XML文档, 并将其转换为一系列事件, 例如startElement(), endElement()和character()。要使用SAX解析器读取和解析XML数据, 我们需要在android应用程序中创建SAXParserFactory, SAXParser和DefaultHandler对象的实例。

使用SAX Parser进行XML解析的示例

在此示例中, 我们将使用SAX解析器解析XML数据并将其显示在ListView中。

activity_main.xml

在activity_main.xml布局中添加ListView。

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="example.srcmini02.com.kotlinxmlparsingusingsaxparser.MainActivity">

   <ListView
        android:id="@+id/listView"
        android:layout_width="match_parent"
        android:layout_height="match_parent">
    </ListView>

</android.support.constraint.ConstraintLayout>

empdetail.xml

在资产目录中创建XML文档empdetail.xml, 以使用SAX解析器解析数据。

<?xml version="1.0" encoding="utf-8"?>
<records>
    <employee>
        <name>Sachin Kumar</name>
        <salary>50000</salary>
        <designation>Developer</designation>
    </employee>
    <employee>
        <name>Rahul Kumar</name>
        <salary>60000</salary>
        <designation>Team Leader</designation>
    </employee>
    <employee>
        <name>John Mike</name>
        <salary>70000</salary>
        <designation>Manager</designation>
    </employee>
    <employee>
        <name>Ajay Kumar</name>
        <salary>45000</salary>
        <designation>Developer</designation>
    </employee>
    <employee>
        <name>Toni Nayer</name>
        <salary>55000</salary>
        <designation>Marketing</designation>
    </employee>
    <employee>
        <name>Mr Bony</name>
        <salary>42000</salary>
        <designation>Sales</designation>
    </employee>
    <employee>
        <name>Raj Kumar</name>
        <salary>30000</salary>
        <designation>Production</designation>
    </employee>
    <employee>
        <name>Rahul Kumar</name>
        <salary>60000</salary>
        <designation>Team Leader</designation>
    </employee>
    <employee>
        <name>John Mike</name>
        <salary>70000</salary>
        <designation>Manager</designation>
    </employee>
    <employee>
        <name>Sachin Kumar</name>
        <salary>50000</salary>
        <designation>Developer</designation>
    </employee>
    <employee>
        <name>Rahul Kumar</name>
        <salary>60000</salary>
        <designation>Team Leader</designation>
    </employee>
    <employee>
        <name>John Mike</name>
        <salary>70000</salary>
        <designation>Manager</designation>
    </employee>
</records>

custom_list.xml

创建一个自定义布局以将数据列表显示到ListView中。

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="horizontal">
        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:orientation="vertical">

            <TextView
                android:id="@+id/name"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:text="name"
                android:textStyle="bold"
                android:layout_marginLeft="15dp"
                android:layout_marginStart="15dp"
                android:textAppearance="@style/Base.TextAppearance.AppCompat.Medium" />

            <TextView
                android:id="@+id/salary"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:text="salary"
                android:layout_marginLeft="15dp"
                android:layout_marginStart="15dp"
                android:layout_marginTop="5dp"
                android:textSize="16sp"/>
            <TextView
                android:id="@+id/designation"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:text="designation"
                android:layout_marginLeft="15dp"
                android:layout_marginStart="15dp"
                android:layout_marginTop="5dp"
                android:textSize="16sp"/>
        </LinearLayout>
</LinearLayout>

MainActivity.kt

添加以下代码, 以使用SAX解析器读取和解析XML数据。创建SAXParserFactory, SAXParser和DefaultHandler对象的实例。

HashMap <String, String>用于从XML文档读取数据并将其添加到ArrayList()中。

package example.srcmini02.com.kotlinxmlparsingusingsaxparser

import android.support.v7.app.AppCompatActivity
import android.os.Bundle
import org.xml.sax.helpers.DefaultHandler
import javax.xml.parsers.SAXParserFactory
import android.widget.ListView
import android.widget.SimpleAdapter
import org.xml.sax.SAXException
import java.io.IOException
import java.util.ArrayList
import java.util.HashMap
import javax.xml.parsers.ParserConfigurationException
import javax.xml.parsers.SAXParser

class MainActivity : AppCompatActivity() {
    internal var empList = ArrayList<HashMap<String, String>>()
    internal var empData = HashMap<String, String>()
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        val lv:ListView = findViewById(R.id.listView)
        try {
                        //instancing the SAXParserFactory class
            val parserFactory:SAXParserFactory = SAXParserFactory.newInstance()
            //instancing the SAXParser class
            val saxParser:SAXParser = parserFactory.newSAXParser()
            val defaultHandler= object : DefaultHandler() {
                var currentValue = ""
                var currentElement = false
                //overriding the startElement() method of DefaultHandler
                override fun startElement(uri: String, localName: String, qName: String, attributes: org.xml.sax.Attributes) {
                    currentElement = true
                    currentValue = ""
                    if (localName == "employee") {
                        empData = HashMap()
                    }
                }
                //overriding the endElement() method of DefaultHandler
                override fun endElement(uri: String, localName: String, qName: String) {
                    currentElement = false
                    if (localName.equals("name", ignoreCase = true))
                        empData["name"] = currentValue
                    else if (localName.equals("salary", ignoreCase = true))
                        empData["salary"] = currentValue
                    else if (localName.equals("designation", ignoreCase = true))
                        empData["designation"] = currentValue
                    else if (localName.equals("employee", ignoreCase = true))
                        empList.add(empData)
                }
                //overriding the characters() method of DefaultHandler
                override fun characters(ch: CharArray, start: Int, length: Int) {
                    if (currentElement) {
                        currentValue = currentValue + String(ch, start, length)
                    }
                }
            }
            val istream = assets.open("empdetail.xml")
            saxParser.parse(istream, defaultHandler)
            //creating Adapter class to access the custom list
            val adapter = SimpleAdapter(this@MainActivity, empList, R.layout.custom_list, arrayOf("name", "salary", "designation"), intArrayOf(R.id.name, R.id.salary, R.id.designation))
            lv.adapter = adapter
        } catch (e: IOException) {
            e.printStackTrace()
        } catch (e: ParserConfigurationException) {
            e.printStackTrace()
        } catch (e: SAXException) {
            e.printStackTrace()
        }

    }
}

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