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Android - Earthquake(地震顯示器) 項目 詳解

Earthquake(地震顯示器) 項目 詳解

本文位址: http://blog.csdn.net/caroline_wendy/article/details/21976997

本文的合集已經編著成書，《進階Android開發強化實戰》，歡迎各位讀友的建議和指導。

在京東即可購買：https://item.jd.com/12385680.html

Android - Earthquake(地震顯示器) 項目 詳解

環境: Android Studio 0.5.2, Gradle 1.11, kindle fire

時間: 2014-3-24

修正位置資訊異常: http://blog.csdn.net/caroline_wendy/article/details/24465487

Earthquake項目, 主要是讀取USGS(United States Geological Survey, 美國位址勘探局)提供的feeds(訂閱源), 進行顯示資料;

需要讀取網際網路的資料, 進行格式解析(parse), 資料類型是atom類型, 類似XML.

訂閱源位址: http://earthquake.usgs.gov/earthquakes/feed/v1.0/summary/2.5_day.atom

格式:

<feed xmlns="http://www.w3.org/2005/Atom" xmlns:georss="http://www.georss.org/georss">
<title>USGS Magnitude 2.5+ Earthquakes, Past Day</title>
<updated>2014-03-24T07:56:39Z</updated>
<author>
<name>U.S. Geological Survey</name>
<uri>http://earthquake.usgs.gov/</uri>
</author>
<id>
http://earthquake.usgs.gov/earthquakes/feed/v1.0/summary/2.5_day.atom
</id>
<link rel="self" href="http://earthquake.usgs.gov/earthquakes/feed/v1.0/summary/2.5_day.atom" target="_blank" rel="external nofollow" />
<icon>http://earthquake.usgs.gov/favicon.ico</icon>
<entry>
<id>urn:earthquake-usgs-gov:ci:15479569</id>
<title>M 2.9 - 9km W of Alberto Oviedo Mota, Mexico</title>
<updated>2014-03-24T07:48:34.609Z</updated>
<link rel="alternate" type="text/html" href="http://earthquake.usgs.gov/earthquakes/eventpage/ci15479569" target="_blank" rel="external nofollow" />
<summary type="html">
<![CDATA[
<p class="quicksummary"><a href="http://earthquake.usgs.gov/earthquakes/eventpage/ci15479569#dyfi" target="_blank" rel="external nofollow"  class="mmi-I" title="Did You Feel It? maximum reported intensity (0 reports)">DYFI? - <strong class="roman">I</strong></a></p><dl><dt>Time</dt><dd>2014-03-24 07:38:10 UTC</dd><dd>2014-03-23 23:38:10 -08:00 at epicenter</dd><dt>Location</dt><dd>32.222°N 115.274°W</dd><dt>Depth</dt><dd>14.10 km (8.76 mi)</dd></dl>
]]>
</summary>
<georss:point>32.2215 -115.274</georss:point>
<georss:elev>-14100</georss:elev>
<category label="Age" term="Past Hour"/>
<category label="Magnitude" term="Magnitude 2"/>
</entry>
......
......

Earthquake的具體設計:

建立項目: Earthquake

1. 建立Quake(Quake.java)類, 顯示地震資料.

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;
    }

}

詳解:

1. 顯示的類型: date, 日期; details, 詳細資訊, 地點; location, 位置; magnitude, 震級; link, 連結;

2. get()方法, 傳回資訊; 構造函數, 賦初值; toString(), 預設輸出資訊;

2. 修改activity_main.xml, 添加fragment.

位置: res->layout->activity_main.xml

<RelativeLayout 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"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:paddingBottom="@dimen/activity_vertical_margin"
    tools:context="mzx.spike.earthquake.app.MainActivity">

    <fragment android:name="mzx.spike.earthquake.app.EarthquakeListFragment"
        android:id="@+id/EarthquakeListFragment"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
    />
</RelativeLayout>

添加Fragment, 指定實作(.java)檔案位置.

3. 建立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<Quake> aa;
    ArrayList<Quake> earthquakes = new ArrayList<Quake>();

    @Override
    public void onActivityCreated(Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);

        int layoutID = android.R.layout.simple_list_item_1;
        aa = new ArrayAdapter<Quake>(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(); //修改
                        //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();
    }

}

詳解:

1. 重寫onActivityCreated()方法, 綁定擴充卡, 線上程(thread)中重新整理地震資訊(refreshEarthquakes);

2. 重新整理地震資訊refreshEarthquakes()方法, 根據訂閱源(feed), 建立HTTP連結;

3. 解析文檔(parse), 清空資料(clear);

4. 解析atom格式的标簽, 根據标簽屬性, 輸出相應的資訊;

5. 執行個體化(new)Quake類, 在handler(句柄)中, 運作添加地震資訊的方法(addNewQuake);

6. 注意連結需要相應的異常捕獲(catch)方式, 否則報錯;

7. 網絡調用(network call)在主Activity調用, 會報錯, 需要線上程,背景(asynctask)運作;

8. Handler會産生歧義, 注意使用Android的相應類, 不是java的, 否則無法執行個體化(initialized)

9. 日期格式(SimpleDateFormat)解析, 需要比對相應的字元串, 否則抛出異常, 無法解析(parse);

10 添加新的地震資訊(addNewQuake), 通知擴充卡(notifyDataSetChanged), 進行改變.

4. 修改strings資訊

位置: res->values->strings

<?xml version="1.0" encoding="utf-8"?>
<resources>

    <string name="app_name">Earthquake</string>
    <string name="hello_world">Hello world!</string>
    <string name="action_settings">Settings</string>
    <string name="quake_feed">http://earthquake.usgs.gov/earthquakes/feed/v1.0/summary/2.5_day.atom</string>
</resources>

添加相應的訂閱源(feeds).

5. 修改AndroidManifest.xml

位置: root->AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="mzx.spike.earthquake.app" >

    <uses-permission android:name="android.permission.INTERNET"/>

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="mzx.spike.earthquake.app.MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

提供網絡通路權限(permission), <uses-permission android:name="android.permission.INTERNET"/>.

6. 運作程式.

下載下傳位址: http://download.csdn.net/detail/u012515223/7091879

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