[Android开发入门]初识Service

作者：sundroid

个人站点：sundroid.cn
邮箱： hfutsnjc@163.com 微博：http://weibo.com/Sundroid

Service是Android系统中类似Activity的一种组件，不能够自己启动，也不能与用户交互，只能运行于后台，主要适用于运行于后台的功能（比如请求网络，退出音乐程序后继续播放音乐），

Service和Activity一样也具有生命周期，其分别为onCreate()、onStart()和onDestory()。





从上图可见，Service的整个生命周期其实与onCreate()、终止于onDestory()。实现Service需要继承Service，其启动方法有两种，startService()和bindService(),相对应的结束方式分别为stopServie()和unbindService()。
startService()和bindService()两个方法都可以启动Service，但是两者的应用场合有所不同，使用startService()方法启动服务，调用者与服务之间没有关联，即使调用者退出了，服务仍然运行，使用bindService()方法启动服务，调用者与服务绑定在一起，调用者一旦退出，服务也就终止了。

倒计时方法一实现
MainActivity

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

public class MainActivity extends Activity {
private Button startService;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
startService = (Button) findViewById(R.id.startService);
//开启服务
startService.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent intent = new Intent(MainActivity.this,CountService.class);
startService(intent);
}
});
}

@Override
protected void onDestroy() {
super.onDestroy();
//程序结束后停止服务
Intent intent = new Intent(MainActivity.this,CountService.class);
stopService(intent);
}
}

CountService

import android.app.Service;
import android.content.Intent;
import android.os.IBinder;
import android.util.Log;

/**
* Created by sundroid on 2015/3/6.
*/
public class CountService extends Service{

private int seconds=60;
@Override
public IBinder onBind(Intent intent) {
return null;
}

@Override
public void onCreate() {
super.onCreate();
//新建线程
new Thread(new Runnable() {
@Override
public void run() {
while(seconds!=0){
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
Log.i("TIME","Time remain "+seconds);
seconds--;
}
Log.i("SERVICE","Time up");
}
}).start();

}

@Override
public void onDestroy() {
super.onDestroy();
}
}

倒计时方法二实现

MainActivity

import android.app.Activity;
import android.content.ComponentName;
import android.content.Context;
import android.content.Intent;
import android.content.ServiceConnection;
import android.os.Bundle;
import android.os.IBinder;

public class MainActivity extends Activity {

private CountService countService;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

Intent intent = new Intent(MainActivity.this,CountService.class);
//进入Activity时，开启服务
bindService(intent,conn, Context.BIND_AUTO_CREATE);
}

@Override
protected void onDestroy() {
super.onDestroy();
//程序结束后停止服务
this.unbindService(conn);    }
private ServiceConnection conn = new ServiceConnection() {
@Override
public void onServiceConnected(ComponentName name, IBinder service) {
countService = ((CountService.ServiceBinder)service).getService();
}

@Override
public void onServiceDisconnected(ComponentName name) {
countService=null;
}
};
}

CountService

import android.app.Service;
import android.content.Intent;
import android.os.Binder;
import android.os.IBinder;
import android.util.Log;

/**
* Created by sundroid on 2015/3/6.
*/
public class CountService extends Service{

private int seconds = 60;
private ServiceBinder serviceBinder;

@Override
public IBinder onBind(Intent intent) {
return serviceBinder;
}

@Override
public void onCreate() {
super.onCreate();
//新建一个线程
new Thread(new Runnable() {
@Override
public void run() {
while(seconds!=0){
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
Log.i("TIME","Time remain "+seconds);
seconds--;
}
Log.i("SERVICE","Time up");
}
}).start();
}

@Override
public void onDestroy() {
super.onDestroy();
}

class ServiceBinder extends Binder{
public CountService getService(){
return CountService.this;
}
}
}

manifest配置

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="cn.sundroid.androidreview" >

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

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

<service android:name=".CountService"></service>
</application>

</manifest>

BInder 的通信机制

运行结果

03-06 11:33:51.118    2359-2383/cn.sundroid.androidreview I/TIME﹕ Time remain 13
03-06 11:33:52.119    2359-2383/cn.sundroid.androidreview I/TIME﹕ Time remain 12
03-06 11:33:53.121    2359-2383/cn.sundroid.androidreview I/TIME﹕ Time remain 11
03-06 11:33:54.122    2359-2383/cn.sundroid.androidreview I/TIME﹕ Time remain 10
03-06 11:33:55.123    2359-2383/cn.sundroid.androidreview I/TIME﹕ Time remain 9
03-06 11:33:56.124    2359-2383/cn.sundroid.androidreview I/TIME﹕ Time remain 8
03-06 11:33:57.126    2359-2383/cn.sundroid.androidreview I/TIME﹕ Time remain 7
03-06 11:33:58.128    2359-2383/cn.sundroid.androidreview I/TIME﹕ Time remain 6
03-06 11:33:59.129    2359-2383/cn.sundroid.androidreview I/TIME﹕ Time remain 5
03-06 11:34:00.130    2359-2383/cn.sundroid.androidreview I/TIME﹕ Time remain 4
03-06 11:34:01.131    2359-2383/cn.sundroid.androidreview I/TIME﹕ Time remain 3
03-06 11:34:02.132    2359-2383/cn.sundroid.androidreview I/TIME﹕ Time remain 2
03-06 11:34:03.133    2359-2383/cn.sundroid.androidreview I/TIME﹕ Time remain 1
03-06 11:34:03.134    2359-2383/cn.sundroid.androidreview I/SERVICE﹕ Time up