使用 okHttp 的 GET 方式讀取 XML 資料

一般在解析 XML 資料大致上有分成 DOM、SAX、JDOM、DOM4J 四種解析方式，我比較有接觸過的 DOM、SAX 這兩種，所以只就介紹介紹 DOM、SAX 的差異。接著本範例會使用 OKHttp 來讀取政府提供的XML格式資料(顯著有感地震報告資料)，並由 DOM 來解析 XML 格式資料，在由App顯示出相關訊息。

呈現效果:

1.build.gradle(picasso和okhttp 衝突到，需要加okhttp-urlconnection )

2.layout.xml

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="gae.melvin.com.app_okhttp_xml.MainActivity">

    <ImageView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:id="@+id/imageView"
        android:layout_gravity="left|top"
        android:src="@mipmap/ic_launcher" />

    <LinearLayout
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="vertical">

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textSize="20sp"
            android:text="Large Text"
            android:layout_marginTop="30dp"
            android:id="@+id/textView"
            android:textColor="#e12222" />

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="30dp"
            android:textSize="26sp"
            android:text="Large Text"
            android:textColor="#5500aa"
            android:id="@+id/textView2" />
    </LinearLayout>
</FrameLayout>

3.MainActivity.java

package gae.melvin.com.app_okhttp_xml;

import android.content.Context;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.widget.ImageView;
import android.widget.TextView;
import com.squareup.okhttp.OkHttpClient;
import com.squareup.okhttp.Request;
import com.squareup.okhttp.Response;
import com.squareup.picasso.Picasso;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NodeList;
import org.xml.sax.SAXException;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.nio.charset.StandardCharsets;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;

public class MainActivity extends AppCompatActivity {

    private TextView textView,textView2;
    private Context context;
    private ImageView imageView;

    @Override

    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        context= this;

        findViews();
        new RunWork().start();
    }


    private void findViews(){
        textView = (TextView)findViewById(R.id.textView);
        textView2 = (TextView)findViewById(R.id.textView2);
        imageView = (ImageView)findViewById(R.id.imageView);
    }

    /*上網抓資料，需要另外開執行緒做處理(Android機制)*/
    private class RunWork extends Thread
    {
        //宣告變數
        String result_xml = "";
       String path = "http://opendata.cwb.gov.tw/govdownload?dataid=E-A0015-001R&authorizationkey=rdec-key-123-45678-011121314";

       Runnable task = new Runnable(){
            @Override
            public void run() {
                parseXml(result_xml);
            }
        };

        //OkHttpClient官網範例使用
        OkHttpClient client = new OkHttpClient();
       String run(String url) throws IOException {
            Request request = new Request.Builder()
                    .url(url)
                    .build();

            Response response = client.newCall(request).execute();
            return response.body().string();
        }

        @Override
        public void run()
        {
            try{
                //1.抓資料
                 result_xml = run(path);
                //2.改變畫面內容只能用主執行緒(Android機制)
              runOnUiThread(task);
            } catch(IOException e) {
                e.printStackTrace();
            }
        }

    }

    //DOM來解析XML格式資料
    private void parseXml(Stringresult_xml){
        try {
            //取得XML根節點
           InputStream is = new ByteArrayInputStream(result_xml.getBytes(StandardCharsets.UTF_8));

            DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();

            DocumentBuilder builder = factory.newDocumentBuilder();

            Document document = builder.parse(is);
            Element root = document.getDocumentElement();

            //取得 TagName 裡的內容
           String reportContent = root.getElementsByTagName("reportContent").item(0).getTextContent();

            String magnitudeValue = root.getElementsByTagName("magnitudeValue").item(0).getTextContent();

            String shakemapImageURI = root.getElementsByTagName("shakemapImageURI").item(0).getTextContent();
            StringBuilder sb = new StringBuilder();
            //取得 Node List
           NodeList shakingAreas = root.getElementsByTagName("shakingArea");

            //取得 Node
            for(int i=0;i<shakingAreas.getLength();i++){
                Element element = (Element) shakingAreas.item(i);
                String areaName = element.getElementsByTagName("areaName").item(0).getTextContent();
                String areaIntensity = element.getElementsByTagName("areaIntensity").item(0).getTextContent();
                //取得 Node內參數值
              String unit = element.getElementsByTagName("areaIntensity").item(0).getAttributes().getNamedItem("unit").getTextContent();
                sb.append(areaName).append("  ").append(areaIntensity).append(unit).append("\n");

            }

            //設定顯示畫面資料
             /*Picasso第三方套件:用來抓 url 圖片*/
           Picasso.with(context).load(shakemapImageURI).into(imageView);
            textView.setText(reportContent +"\n" + magnitudeValue);
            textView2.setText(sb);
        } catch(ParserConfigurationException e) {

          e.printStackTrace();
        } catch(SAXException e) {
            e.printStackTrace();
        } catch(IOException e) {
            e.printStackTrace();
        }

    }


}

參考資料:

Java中四種操作xml方式的比較

Java 處理 XML 的三種主流技術及介紹

1: 文件物件模型（Document Object Model, DOM）

Android 中HttpURLConnection 使用詳解- 壹讀