[android] 建立service範例

記錄一下以免以後忘記
Service是沒有UI的，它永遠是在背景工作
練習題目:當執行APP上的播放按鈕後，會開始播放音樂，按下停止就不會繼續播放

Step 1.在eclipse建立一個android project
File -> New -> Other -> Android Project
Step 2.專案建立完成後，建立UI
res -> layout -> main.xml
加入兩個button[紅色字體]

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

    <Button
        android:id="@+id/btnStartService" //service ID & name參見R.java
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="Start Service" //模擬器上button秀出來的名稱
        />

    <Button
        android:id="@+id/btnStopService" //service ID & name參見R.java
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="Stop Service" //模擬器上button秀出來的名稱
        />
</LinearLayout>

Step 3.新增一個class for 繕寫service
在eclipse右邊的package explorer專案中的src，點一下箭頭處，展開src，下面的xxx.xxx，點一下箭頭處，展開xxx.xxx，按滑鼠右鍵New -> Class
Name: Servicetest[第一個字要大寫]
Superclass: android.app.Service
如果Superclass用key的沒反應請在右邊的browse點進去再choose a type處key in
完成後按下finish就可以看到多一個Servicetest.java

Step 4.開啟src -> xxx.xxx -> Service.java加入以下程式碼

package com.nash.service;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;

public class Service_without_UI extends Activity {
    private Button btnStartService;
    private Button btnStopService;

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        
        btnStartService = (Button) findViewById(R.id.btnStartService);
        btnStopService = (Button) findViewById(R.id.btnStopService);
        
        btnStartService.setOnClickListener(new View.OnClickListener() {
   
     @Override
     public void onClick(View v) {
  // TODO Auto-generated method stub
  Intent i = new Intent(Service_without_UI.this,Servicetest.class);
  startService(i);
     }
 });
        
        btnStopService.setOnClickListener(new View.OnClickListener() {
   
     @Override
     public void onClick(View v) {
         // TODO Auto-generated method stub
         Intent i = new Intent(Service_without_UI.this, Servicetest.class);
         stopService(i);
     }
 });
  
    }
}

Step 5.開啟新增的Servicetest.java加入以下程式碼

/**
 * 
 */
package com.nash.service;

import android.app.Service;
import android.content.Intent;
import android.media.MediaPlayer;
import android.os.IBinder;
//import android.util.Log;
import android.widget.Toast;

/**
 * @author nash
 *
 */
public class Servicetest extends Service {

 MediaPlayer m;
 /* (non-Javadoc)
  * @see android.app.Service#onBind(android.content.Intent)
  */
 @Override
 public IBinder onBind(Intent arg0) {
  // TODO Auto-generated method stub
  return null;
 }

 @Override
 public void onCreate() {
  // TODO Auto-generated method stub
  super.onCreate();
 }

 @Override
 public void onStart(Intent intent, int startId) {
  Toast.makeText(this, "Service start", Toast.LENGTH_SHORT).show();

  if (m!=null) m.stop();
  
  m = MediaPlayer.create(this, R.raw.deal); //raw是放mp3的資料夾,deal是mp3的檔名
  m.start();
 }
 
 @Override
 public void onDestroy() {
  Toast.makeText(this, "Service stop", Toast.LENGTH_SHORT).show();
  m.stop();
  m.release();
 }
}

Step 6.開啟AndroidManifest.xml加入以下程式碼

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.nash.service"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk android:minSdkVersion="15" />

    <application
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name" >
        <activity
            android:name=".Service_without_UI"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <service android:name=".Servicetest"
            android:label="@string/app_name">
        </service>
    </application>

</manifest>

參考資料:
http://www.kfsoft.info/article-40-9--%E5%BB%BA%E7%AB%8BService.html
http://www.jollen.org/blog/2009/01/jollen-android-programming-8.html