作为一款多任务操作系统，如果不能运行后台服务，显然说不过去，Android 当然提供了运行后台程序的方法。而且非常简单易用，只不过有一些小问题需要注意，这个主题分为两部分，第一部分是如何实现一个Service以及他的生命周期，第二部分是对于一个个后台服务应该注意的事项。我们开始吧！
创建服务类
所谓的服务，在Android里被称做 Service，只要继承 android.app.Service 这个抽象类，并且实现其中几个方法就可以了。
public class RoidingService extends android.app.Service {}
里边必须实现的一个方法是 onBind(Intent intent) ，他具体是做什么的我们下边讲。还有两个重要的回调函数需要覆盖，onCreate() 和 onDestroy()。跟 Actitivty 类似，在创建和销毁 Service 时回调这两个函数，达到初始化或退出前保存状态。
服务的生命周期
有了 Service 类我们如何启动他呢，有两种方法：
- Context.startService()
- Context.bindService()
在同一个应用任何地方调用 startService() 方法就能启动 Service 了，然后系统会回调 Service 类的 onCreate() 以及 onStart() 方法。这样启动的 Service 会一直运行在后台，直到 Context.stopService() 或者 selfStop() 方法被调用。另外如果一个 Service 已经被启动，其他代码再试图调用 startService() 方法，是不会执行 onCreate() 的，但会重新执行一次 onStart() 。
另外一种 bindService() 方法的意思是，把这个 Service 和调用 Service 的客户类绑起来，如果调用这个客户类被销毁，Service 也会被销毁。用这个方法的一个好处是，bindService() 方法执行后 Service 会回调上边提到的 onBind() 方发，你可以从这里返回一个实现了 IBind 接口的类，在客户端操作这个类就能和这个服务通信了，比如得到 Service 运行的状态或其他操作。如果 Service 还没有运行，使用这个方法启动 Service 就会 onCreate() 方法而不会调用 onStart()。
January 21st, 2010 at 10:36
有点深奥啊
January 21st, 2010 at 2:18
高深的理论。。
April 30th, 2010 at 1:06
Time Enter,maintain according play author box skill step energy display radio legislation belong bloody mental effective charge she review someone director expensive hill little occasion bar afterwards replace east thank depend data familiar may influence there effect resource following future within defendant agency car short beside come heat face natural east institute plenty death hour various announce himself but friend minute urban serious country draw supply cup assumption lean sure terms essential whether worker destroy accident soil letter education pupil interpretation argue successful marry hot design construction curriculum derive district mountain display corner water importance your cost
May 15th, 2010 at 5:23
Hey You
meself couldnt agree more, myself, but not everyone is as clever as you seem to be. Or as meself seem to be! HA! :-p
If you want to exchange links let me know.
May 19th, 2010 at 11:17
Greets
i like your site design. Looking forward to reading more down da road.
What do you know about assessment?
L8er
May 19th, 2010 at 11:18
Me am loving your posts. Found you on Twitter.
Please email me if you are interested
Sincerly
May 19th, 2010 at 11:19
Your posts are extremely helpful and informative. What brought you to put up your site ?
my homie cant wait for your next posts.
May 19th, 2010 at 11:22
Hey
Wow! thank you very much! my homie always wanted to write in my site something like that. Can my homie take part of your post to my blog?
Please email me if you are interested
May 19th, 2010 at 11:50
Hows It Going
How can start this work please tell me
Bye
June 5th, 2010 at 8:06
Hey
i am excited already as i know you always have pretty cool stuff.
June 5th, 2010 at 8:08
Good stuff i will try & get back to you thanks alot
June 6th, 2010 at 10:11
i am impressed by teh effort that went into your writing and teh way you managed to keep teh flow from Introduction of teh topic to teh summary. Do you think you might cover recent developments in over or what are your thoughts about that.
June 6th, 2010 at 11:02
Good Day
Very good video Lisa.
Would you be interested in exchanging site roll
June 6th, 2010 at 12:24
Realy cool stuff, myself managed to make my blog
my homie love dha site template
June 7th, 2010 at 10:18
Hi There
Hey yours truly came across your page by luck on ask while hunting for something totally irrelevant but yours truly am very glad that yours truly did, You have just captured yourself another subscriber.
Talk Later
June 16th, 2010 at 9:05
I love u Ye
June 18th, 2010 at 12:57
Hello
Your posts are extremely helpful and informative. What brought you to put up your site ?
June 18th, 2010 at 7:05
You would think that they world have OKd it at the beginning instead of allowing it to go so long without saying a thing and then bringing it back up when it was too late. My bro dont understand it at all.
Would you be interested in exchanging blogrolls links with my site?
Cu Later
June 18th, 2010 at 10:40
Hello thanks with regard to your page. My bro truly like your web site. Its quite informative. However My bro definitely want you to post how you put social bookmarking below your post. My bro like it due to the fact its a extremely thoroughly clean awesome blogger hack.
Cu Soon
June 24th, 2010 at 7:15
oh,how kind words.Like a balm to my heart…
June 28th, 2010 at 8:35
http://www.roiding.com is very the most informative. I enjoyed your blog a lot. Thank you.
July 1st, 2010 at 3:49
Hi
Me just stopped by your site and thought Me would say hello.
Talk Later
July 2nd, 2010 at 4:06
Added to my Google News Reader. Looking forward to reading more from you down teh road!
my homie discovered your homepage by coincidence.
July 2nd, 2010 at 10:47
wow powerful!
July 3rd, 2010 at 12:44
Hey my homie came across your page by luck on ask while hunting for something totally irrelevant but my homie am very glad that my homie did, You have just captured yourself another subscriber.
Very interesting posts and well written.
Buh Bye
July 3rd, 2010 at 12:44
Greets
Have you considered writing professionally? Like a periodical or something?
yours truly a blog owner too.
Bye
July 4th, 2010 at 3:17
Very nice site! is it yours too
July 11th, 2010 at 1:06
http://www.roiding.com is great! However it seems that as finances take center stage in the politics of this country it will only be a matter of time before payday loans become the target of scrutiny and lobbyists once again Certain states have already banned payday loans outright
July 19th, 2010 at 6:50
Even though it will not be here tomorrow, the effect of it will.
July 20th, 2010 at 4:36
i was reading someone elses site and saw you on their blogroll.
yours truly just wanted to drop you a comment to say keep up da good work.
Bye Bye
July 20th, 2010 at 7:27
Hey
A friend of mine just emailed me one of your articles from a while back. you read that one a few more.
Bye
July 22nd, 2010 at 8:57
Hello
thanks pal! this is so cool!! yea!!!
i cant wait for your next posts.
July 22nd, 2010 at 10:30
Hi Homie
Thanks meself found just the info meself already searched everywhere and just couldnt find. What a really tight website. Like this website this site is one of my favs.
Whats yer opinion on repeat?
Laters
July 24th, 2010 at 8:40
The thought of going on really appeals to me.
July 25th, 2010 at 12:55
Great site post.
Cu Later
July 25th, 2010 at 4:34
Hi Homie
Very good video Lisa.
Ciao
July 26th, 2010 at 9:09
IFnoeTQ