android 之 Service 播放音乐

Android里的Service 和 windows 里的Service功能差不多，就是一个不可见的进程在后台执行，避免被用户误关闭。因为android会在一定情况下关闭 未在前台显示的Activity， 所以如果要让一个功能一直在后台工作，不被系统关闭，就得用Service。比如闹钟，后台播放音乐。

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

<uses-sdk android:minSdkVersion="7" />

<application
android:icon="@drawable/ic_launcher"
android:label="@string/app_name" >
<activity
android:name=".ServiceDemoActivity"
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:enabled="true" android:name=".MyService"></service>
</application>

</manifest>

<?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" >

<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="@string/hello" />

<Button
android:id="@+id/button1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:gravity="center"
android:layout_gravity="center"
android:text="music" />

<Button
android:id="@+id/button2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:gravity="center"
android:layout_gravity="center"
android:text="stop" />

</LinearLayout>

package com.ethan.service;

import android.app.Activity;
import android.content.Intent;
import android.media.MediaPlayer;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;

public class ServiceDemoActivity extends Activity implements OnClickListener {
private static final String TAG = "ServicesDemo";
private Button buttonStart, buttonStop;

@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);

buttonStart = (Button) findViewById(R.id.button1);
buttonStop = (Button) findViewById(R.id.button2);

buttonStart.setOnClickListener(this);
buttonStop.setOnClickListener(this);
}

@Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.button1:
Log.d(TAG, "onClick: starting srvice");
startService(new Intent(this, MyService.class));
break;
case R.id.button2:
Log.d(TAG, "onClick: stopping srvice");
stopService(new Intent(this, MyService.class));
break;
}
}
}