打算寫一個稍微複雜的小程式，練習的項目：
- 使用 Regular Expression
- 使用 Network Connection
- 使用 Thread
以三個項目為出發點，把以前的老題目拿出來：定期抓台灣 Yahoo 首頁的兩則焦點新聞，顯示在 Android 模擬上。因此，先想一下排版問題，大概就三個 TextView，分別為 更新時間 和 兩則新聞。
建立 project
[Eclipse]->[File]->[New]->[Android Project]
Project name: MyWeb
Build Target: Android 2.2
Application name: MyWeb
Package name: com.test.Web
Create Activity: MyWeb
Min SDK Version: 8
設定使用網路權限
點選 AndroidManifest.xml 檔案，在 <manifest> 裡增加 <uses-permission android:name="android.permission.INTERNET" />
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.test.web"
android:versionCode="1"
android:versionName="1.0">
<application android:icon="@drawable/icon" android:label="@string/app_name">
<activity android:name=".MyWeb"
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>
<uses-sdk android:minSdkVersion="8" />
<uses-permission android:name="android.permission.INTERNET" />
</manifest>
設定排版
點選 main.xml 檔案，增加 3 個 TextView，分別為"更新時間"、"新聞1"和"新聞2"。
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
>
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="@string/hello"
/>
<TextView android:id="@+id/UpdateDate" android:layout_width="fill_parent" android:layout_height="wrap_parent"></TextView>
<TextView android:id="@+id/News1" android:layout_width="fill_parent" android:layout_height="wrap_content"></TextView>
<TextView android:id="@+id/News2" android:layout_width="fill_parent" android:layout_height="wrap_content"></TextView>
</LinearLayout>
MyWeb.java
package com.test.web;
import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.widget.TextView;
import java.util.ArrayList;
import java.util.Date;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import com.test.web.GetYahooNews;
public class MyWeb extends Activity {
Handler jobs;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
jobs = new Handler();
new Thread( new GetYahooNews( this )).start();
}
public void updateNews( final ArrayList<String> news )
{
jobs.post( new Runnable(){
public void run()
{
TextView showTextView;
if( news != null && news.size() >= 2 )
{
if( ( showTextView = (TextView) findViewById(R.id.News1) ) != null )
showTextView.setText("[News] "+(String)news.get(0));
if( news.size() == 4 && ( showTextView = (TextView) findViewById(R.id.News2) ) != null )
showTextView.setText("[News] "+(String)news.get(2));
}
if( ( showTextView = (TextView) findViewById(R.id.UpdateDate) ) != null )
{
DateFormat dateFormat = new SimpleDateFormat("yyyy/MM/dd HH:mm:ss");
showTextView.setText( "[Update @ " + dateFormat.format(new Date() ) + "]" );
}
}
});
}
}
GetYahooNews.java
package com.test.web;
import java.io.*;
import java.util.ArrayList;
import java.util.regex.*;
import java.net.HttpURLConnection;
import java.net.URL;
import android.util.Log;
import com.test.web.MyWeb;
public class GetYahooNews implements Runnable {
MyWeb activity;
GetYahooNews( MyWeb n)
{
this.activity = n;
}
public static void report( String message )
{
//System.out.println( "[Report] " + message );
Log.d( "Report" , message );
}
public static ArrayList<String> getHotNews()
{
ArrayList<String> news = new ArrayList<String>();
HttpURLConnection con = null;
try
{
//*
URL url = new URL("http://tw.yahoo.com");
con = (HttpURLConnection) url.openConnection();
con.setReadTimeout(10000);
con.setConnectTimeout(15000);
con.setRequestMethod("GET" );
con.addRequestProperty("User-Agent","Mozilla/5.0 (Windows; U; Windows NT 5.2; en-GB; rv:1.9.2.9) Gecko/20100824 Firefox/3.6.9");
con.setDoInput(true);
con.connect();
BufferedReader reader = new BufferedReader(new InputStreamReader(con.getInputStream(), "UTF-8" ));
// */
// BufferedReader reader = new BufferedReader(new InputStreamReader( new FileInputStream("fetch.html"), "UTF-8" ));
String n, result="";
// while( ( n = reader.readLine() ) != null )
// result += n;
StringBuilder htmlContent = new StringBuilder();
while ((n = reader.readLine()) != null)
htmlContent.append(n);
result = htmlContent.toString();
// BufferedWriter out = new BufferedWriter( new FileWriter("fetch.html") );out.write(result);out.close();
String pattern;
int at;
pattern = "<label class=\"img-border clearfix\">";
if( ( at = result.indexOf(pattern) ) < 0 )
{
news.add( "format error 1" );
report( "format error 1" );
return news;
}
result = result.substring( at );
pattern = "<ol class=\"newsad clearfix\">";
if( ( at = result.indexOf(pattern) ) < 0 )
{
news.add( "format error 2" );
report( "format error 2" );
return news;
}
result = result.substring( 0 , at );
pattern = "<h3[^>]*>[^<]*<a href=\"(.*?)\"[^>]*>(.*?)</a></h3>";
Pattern p = Pattern.compile( pattern , Pattern.CASE_INSENSITIVE | Pattern.DOTALL );
Matcher m = p.matcher( result );
while( m.find() )
{
// report( "\n==== Get === \n" + m.group() + "\n" );
// report( "URL: " + m.group(1) );
// report( "Title: " + m.group(2) );
String newsTitle = ""+ m.group(2);
String newsUrl = "" + m.group(1);
if( ( at = newsUrl.indexOf( "http:" ) ) > 0 )
newsUrl = newsUrl.substring( at );
news.add( newsTitle );
news.add( newsUrl );
}
}catch(Exception e)
{
news.add( "Exception:"+e );
}
finally
{
if ( con != null )
con.disconnect();
}
return news;
}
public void run()
{
try
{
while( true )
{
try
{
// ArrayList<String> demo = new ArrayList<String>();demo.add("Yo1");demo.add("Yo2");demo.add("Yo3");demo.add("Yo4");activity.updateNews( demo );
activity.updateNews( getHotNews() );
Thread.sleep( 1000 * 60 * 60 * 2 ); // 2 hrs
}
catch(Exception e)
{
report( "run while Exception:"+e );
break;
}
}
}
catch( Exception e )
{
report( "run Exception:"+e );
}
}
}
在 MyWeb 裡有一樣東西比較特別，叫做 Handler，可以把他當作管理 Thread 的用法，在官網的描述裡，比較重要的敘述：
There are two main uses for a Handler: (1) to schedule messages and runnables to be executed as some point in the future; and (2) to enqueue an action to be performed on a different thread than your own.
在這邊使用 Handler，是讓更新 UI 的部份能夠透過 Runnable 來處理事件，如果不使用的話，會有無法更新 UI 的現象，暫時還沒了解底層的問題。
接著是 MyWeb 裡的 updateNews 函數，其參數是使用 final 的描述，加上這個描述後，可以讓接下來的 new Runnalbe 裡，可以直接用傳進來的參數，如果不用 final 也有解法啦，就是自己在定義一個實做 Runnable 的物件，然後把參數都傳遞好，稍微麻煩一點：
public void updateNewsPrev( ArrayList<String> news )
{
class UIUpdate implements Runnable
{
ArrayList<String> news;
UIUpdate( ArrayList<String> in )
{
news = in;
}
public void run()
{
TextView showTextView;
if( news != null && news.size() >= 2 )
{
if( ( showTextView = (TextView) findViewById(R.id.News1) ) != null )
showTextView.setText("[News] "+(String)news.get(0));
if( news.size() == 4 && ( showTextView = (TextView) findViewById(R.id.News2) ) != null )
showTextView.setText("[News] "+(String)news.get(2));
}
if( ( showTextView = (TextView) findViewById(R.id.UpdateDate) ) != null )
{
DateFormat dateFormat = new SimpleDateFormat("yyyy/MM/dd HH:mm:ss");
showTextView.setText( "[Update @ " + dateFormat.format(new Date() ) + "]" );
}
}
}
jobs.post( new UIUpdate( news ) );
}
接下來是 GetYahooNews 的部份，其中 getHotNews 函數是擷取台灣 Yahoo 首頁的兩則新聞出來，以此當作資料，接著就只是單純的當個 Runnalbe 在跑，並且設定 2 小時跑一次，跑完一次會呼叫 MyWeb 的 updateNews 去更新 UI 部份。至於怎樣從 GetYahooNews 呼叫 MyWeb 呢？那就是一開始在使用 GetYahooNews 時，就把 MyWeb 傳進去給他記住，在此使用 activity 變數紀錄。
