Android 启动后台运行程序(Service)

Android开发中，当需要创建在后台运行的程序的时候，就要使用到Service。Service 可以分为有无限生命和有限生命两种。特别需要注意的是Service跟Activities是不同的（简单来说可以理解为后台与前台的区别），例如，如果需要使用Service的话，需要调用startService(),从而利用startService()去调用Service中的OnCreate()和onStart()方法来启动一个后台的Service。
启动一个Service的过程如下：context.startService() ->onCreate()- >onStart()->Service running其中onCreate()可以进行一些服务的初始化工作，onStart()则启动服务。
停止一个Service的过程如下：context.stopService() | ->onDestroy() ->Service stop
接下来的实例是一个利用后台服务播放音乐的小例子，点击start运行服务，点击stop停止服务。
ServicesDemo.java（是一个Activity）

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package com.android.myservice;

import android.app.Activity;

import android.content.Intent;

import android.os.Bundle;

import android.util.Log;

import android.view.View;

import android.view.View.OnClickListener;

import android.widget.Button;

public class ServiceDemo extends Activity implements OnClickListener {

private static final String TAG = "ServiceDemo";

Button buttonStart, buttonStop;

@Override

public void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.main);

buttonStart = (Button) findViewById(R.id.buttonStart);

buttonStop = (Button) findViewById(R.id.buttonStop);

buttonStart.setOnClickListener(this);

buttonStop.setOnClickListener(this);

}

public void onClick(View src) {

switch (src.getId()) {

case R.id.buttonStart:

Log.i(TAG, "onClick: starting service");

startService(new Intent(this, MyService.class));

break;

case R.id.buttonStop:

Log.i(TAG, "onClick: stopping service");

stopService(new Intent(this, MyService.class));

break;

}

}

}

除此之外还要在Manifest里面声明服务:(AndroidManifest.xml)

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<?xml version="1.0" encoding="utf-8"?>

<manifest xmlns:android="http://schemas.android.com/apk/res/android"

package="com.android.myservice">

<application android:label="@string/app_name">

<activity android:name=".ServiceDemo" 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"/>

</application>

</manifest>

定义Service(MyService.java)

[java] view plain copy

package com.android.myservice;

import android.app.Service;

import android.content.Intent;

import android.media.MediaPlayer;

import android.os.IBinder;

import android.util.Log;

import android.widget.Toast;

public class MyService extends Service {

private static final String TAG = "MyService";

MediaPlayer player;

@Override

public IBinder onBind(Intent intent) {

return null;

}

@Override

public void onCreate() {

Toast.makeText(this, "My Service created", Toast.LENGTH_LONG).show();

Log.i(TAG, "onCreate");

player = MediaPlayer.create(this, R.raw.braincandy);

player.setLooping(false);

}

@Override

public void onDestroy() {

Toast.makeText(this, "My Service Stoped", Toast.LENGTH_LONG).show();

Log.i(TAG, "onDestroy");

player.stop();

}

@Override

public void onStart(Intent intent, int startid) {

Toast.makeText(this, "My Service Start", Toast.LENGTH_LONG).show();

Log.i(TAG, "onStart");

player.start();

}

}

layout文件夹中是main.xml

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<?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"

android:gravity="center">

<TextView

android:layout_width="fill_parent"

android:layout_height="wrap_content" android:text="@string/services_demo" android:gravity="center" android:textSize="20sp" android:padding="20dp"/>

<Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:id="@+id/buttonStart" android:text="@string/start"></Button>

<Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@string/stop" android:id="@+id/buttonStop"></Button>

</LinearLayout>

values 文件夹中是strings.xml

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<?xml version="1.0" encoding="utf-8"?>

<resources>

<string name="start">Start</string>

<string name="stop">Stop</string>

<string name="services_demo">Service Demo</string>

</resources>