Android-Earthquake(地震显示器)项目详解

Earthquake(地震显示器) 项目 详解

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本文地址: http://blog.csdn.net/caroline_wendy/article/details/21976997

环境: Android Studio 0.5.2, Gradle 1.11, kindle fire

时间: 2014-3-24

Earthquake项目, 主要是读取USGS(United States Geological Survey, 美国地址勘探局)提供的feeds(订阅源), 进行显示数据;

需要读取互联网的数据, 进行格式解析(parse), 数据类型是atom类型, 类似XML.

订阅源地址: http://earthquake.usgs.gov/earthquakes/feed/v1.0/summary/2.5_day.atom

格式:

  2014-03-24T07:56:39Z  U.S. Geological Survey http://earthquake.usgs.gov/   http://earthquake.usgs.gov/earthquakes/feed/v1.0/summary/2.5_day.atom   http://earthquake.usgs.gov/favicon.ico  urn:earthquake-usgs-gov:ci:15479569  2014-03-24T07:48:34.609Z  
 DYFI? - I
Time
2014-03-24 07:38:10 UTC
2014-03-23 23:38:10 -08:00 at epicenter
Location
32.222°N 115.274°W
Depth
14.10 km (8.76 mi)
 ]]> 
 32.2215 -115.274 -14100    ...... ......

Earthquake的具体设计:

新建项目: Earthquake

1. 新建Quake(Quake.java)类, 显示地震数据.

位置: java->package->Quake

package mzx.spike.earthquake.app;  import android.location.Location;  import java.text.SimpleDateFormat; import java.util.Date;  public class Quake {     private Date date;     private String details;     private Location location;     private double magnitude;     private String link;      public Date getDate() { return date; }     public String getDetails() { return details; }     public Location getLocation() { return location; }     public double getMagnitude() { return magnitude; }     public String getLink() { return link; }      public Quake(Date _d, String _det, Location _loc, double _mag, String _link) {         date = _d;         details = _det;         location = _loc;         magnitude = _mag;         link = _link;     }      @Override     public String toString() {         SimpleDateFormat sdf = new SimpleDateFormat("HH.mm");         String dateString = sdf.format(date);         return dateString + ": " + magnitude + " " + details;     }  }

详解:

1. 显示的类型: date, 日期; details, 详细信息, 地点; location, 位置; magnitude, 震级; link, 链接;

2. get()方法, 返回信息; 构造函数, 赋初值; toString(), 默认输出信息;

2. 修改activity_main.xml, 添加fragment.

位置: res->layout->activity_main.xml

添加Fragment, 指定实现(.java)文件位置.

3. 新建EarthquakeListFragment.java

位置: java->package->EarthquakeListFragment.java

package mzx.spike.earthquake.app;  import android.app.ListFragment; import android.location.Location; import android.os.Bundle; import android.os.Handler; import android.util.Log; import android.widget.ArrayAdapter;  import org.w3c.dom.Document; import org.w3c.dom.Element; import org.w3c.dom.NodeList; import org.xml.sax.SAXException;  import java.io.IOException; import java.io.InputStream; import java.net.HttpURLConnection; import java.net.MalformedURLException; import java.net.URL; import java.net.URLConnection; import java.text.ParseException; import java.text.SimpleDateFormat; import java.util.ArrayList; import java.util.Date; import java.util.GregorianCalendar;  import javax.xml.parsers.DocumentBuilder; import javax.xml.parsers.DocumentBuilderFactory; import javax.xml.parsers.ParserConfigurationException;  public class EarthquakeListFragment extends ListFragment {      ArrayAdapter aa;     ArrayList earthquakes = new ArrayList();      @Override     public void onActivityCreated(Bundle savedInstanceState) {         super.onActivityCreated(savedInstanceState);          int layoutID = android.R.layout.simple_list_item_1;         aa = new ArrayAdapter(getActivity(), layoutID , earthquakes);         setListAdapter(aa);          Thread t = new Thread(new Runnable() {             @Override             public void run() {                 refreshEarthquakes();             }         });          t.start();     }      private static final String TAG = "EARTHQUAKE";     private Handler handler = new Handler();        private void refreshEarthquakes() {         // Get the XML         URL url;         try {              String quakeFeed = getString(R.string.quake_feed);             url = new URL(quakeFeed);              URLConnection connection;             connection = url.openConnection();              HttpURLConnection httpConnection = (HttpURLConnection)connection;             int responseCode = httpConnection.getResponseCode();              if (responseCode == HttpURLConnection.HTTP_OK) {                 InputStream in = httpConnection.getInputStream();                  DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();                 DocumentBuilder db = dbf.newDocumentBuilder();                  // Parse the earthquake feed.                 Document dom = db.parse(in);                 Element docEle = dom.getDocumentElement();                  // Clear the old earthquakes                 earthquakes.clear();                  // Get a list of each earthquake entry.                 NodeList nl = docEle.getElementsByTagName("entry");                 if (nl != null && nl.getLength() > 0) {                     for (int i = 0 ; i < nl.getLength(); i++) {                          Element entry = (Element)nl.item(i);                         Element title = (Element)entry.getElementsByTagName("title").item(0);                         Element g = (Element)entry.getElementsByTagName("georss:point").item(0);                         Element when = (Element)entry.getElementsByTagName("updated").item(0);                         Element link = (Element)entry.getElementsByTagName("link").item(0);                          String details = title.getFirstChild().getNodeValue();                         String hostname = "http://earthquake.usgs.gov";                         String linkString = hostname + link.getAttribute("href");                          String point = g.getFirstChild().getNodeValue();                         String dt = when.getFirstChild().getNodeValue();                         SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd'T'hh:mm:ss.SSS'Z'");                         Date qdate = new GregorianCalendar(0,0,0).getTime();                         try {                            qdate = sdf.parse(dt);                         } catch (ParseException e) {                             Log.d(TAG, "Date parsing exception.", e);                         }                          String[] location = point.split(" ");                         Location l = new Location("dummyGPS");                         l.setLatitude(Double.parseDouble(location[0]));                         l.setLongitude(Double.parseDouble(location[1]));                          String magnitudeString = details.split(" ")[1];                         int end =  magnitudeString.length()-1;                         double magnitude = Double.parseDouble(magnitudeString.substring(0, end));                          details = details.split(",")[1].trim();                          final Quake quake = new Quake(qdate, details, l, magnitude, linkString);                          // Process a newly found earthquake                         handler.post(new Runnable() {                             @Override                             public void run() {                                 addNewQuake(quake);                             }                         });                      }                 }             }         } catch (MalformedURLException e) {             Log.d(TAG, "MalformedURLException", e);         } catch (IOException e) {             Log.d(TAG, "IOException", e);         } catch (ParserConfigurationException e) {             Log.d(TAG, "Parser Configuration Exception", e);         } catch (SAXException e) {             Log.d(TAG, "SAX Exception", e);         }         finally {         }     }      private void addNewQuake(Quake _quake) {         // Add the new quake to our list of earthquakes.         earthquakes.add(_quake);          // Notify the array adapter of a change.         aa.notifyDataSetChanged();     }  }

详解:

1. 重写onActivityCreated()方法, 绑定适配器, 在线程(thread)中刷新地震信息(refreshEarthquakes);

2. 刷新地震信息refreshEarthquakes()方法, 根据订阅源(feed), 创建HTTP链接;

3. 解析文档(parse), 清空数据(clear);

4. 解析atom格式的标签, 根据标签属性, 输出相应的信息;

5. 实例化(new)Quake类, 在handler(句柄)中, 运行添加地震信息的方法(addNewQuake);

6. 注意链接需要相应的异常捕获(catch)方式, 否则报错;

7. 网络调用(network call)在主Activity调用, 会报错, 需要在线程,后台(asynctask)运行;

8. Handler会产生歧义, 注意使用Android的相应类, 不是java的, 否则无法实例化(initialized)

9. 日期格式(SimpleDateFormat)解析, 需要匹配相应的字符串, 否则抛出异常, 无法解析(parse);

10 添加新的地震信息(addNewQuake), 通知适配器(notifyDataSetChanged), 进行改变.

4. 修改strings信息

位置: res->values->strings

       Earthquake     Hello world!     Settings     http://earthquake.usgs.gov/earthquakes/feed/v1.0/summary/2.5_day.atom  

添加相应的订阅源(feeds).

5. 修改AndroidManifest.xml

位置: root->AndroidManifest.xml

提供网络访问权限(permission), .

6. 运行程序.

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