service与runnable的应用

service不是启动后就会持续在后台运行的，虽然说是常驻在操作系统里，但是它却没有反复运行的能力，必须通过类似timer的机制来达成。这类技巧常用于需要向系统做常数监控，向网络验证数据，后台同步数据等。

MainActivity类代码：

package com.example.service_and_runnable;import android.support.v7.app.ActionBarActivity;import android.support.v7.app.ActionBar;import android.support.v4.app.Fragment;import android.os.Bundle;import android.view.LayoutInflater;import android.view.Menu;import android.view.MenuItem;import android.view.View;import android.view.View.OnClickListener;import android.view.ViewGroup;import android.widget.Button;import android.content.Intent;import android.os.Build;public class MainActivity extends ActionBarActivity {private Button btn1,btn2;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.fragment_main);btn1=(Button) findViewById(R.id.button1);btn2=(Button) findViewById(R.id.button2);btn1.setOnClickListener(new OnClickListener() {@Overridepublic void onClick(View v) {// TODO Auto-generated method stubIntent service=new Intent(MainActivity.this, MyService.class);startService(service);}});btn2.setOnClickListener(new OnClickListener() {@Overridepublic void onClick(View v) {// TODO Auto-generated method stubIntent service=new Intent(MainActivity.this, MyService.class);stopService(service);}});}}

MyService类：

package com.example.service_and_runnable;import android.app.Service;import android.content.Intent;import android.os.Handler;import android.os.IBinder;import android.util.Log;public class MyService extends Service {private Handler handler=new Handler();private int counter=0;private Runnable runnable=new Runnable() {@Overridepublic void run() {// TODO Auto-generated method stubcounter++;Log.i("service", "counter:"+counter);handler.postDelayed(runnable, 1000);}};public MyService() {// TODO Auto-generated constructor stub}@Overridepublic void onCreate() {// TODO Auto-generated method stubsuper.onCreate();handler.postDelayed(runnable, 1000);}@Overridepublic void onStart(Intent intent, int startId) {// TODO Auto-generated method stubsuper.onStart(intent, startId);}@Overridepublic void onDestroy() {// TODO Auto-generated method stubsuper.onDestroy();handler.removeCallbacks(runnable);}@Overridepublic IBinder onBind(Intent intent) {// TODO Auto-generated method stubreturn null;}}

布局文件：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:tools="http://schemas.android.com/tools"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:paddingBottom="@dimen/activity_vertical_margin"    android:paddingLeft="@dimen/activity_horizontal_margin"    android:paddingRight="@dimen/activity_horizontal_margin"    android:paddingTop="@dimen/activity_vertical_margin"    tools:context="com.example.service_and_runnable.MainActivity$PlaceholderFragment" >    <Button        android:id="@+id/button2"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:layout_alignRight="@+id/button1"        android:layout_below="@+id/button1"        android:layout_marginTop="47dp"        android:text="关闭系统服务" />    <Button        android:id="@+id/button1"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:layout_alignParentLeft="true"        android:layout_alignParentTop="true"        android:layout_marginLeft="28dp"        android:layout_marginTop="25dp"        android:text="启动系统服务" /></RelativeLayout>

AndroidManifest.xml:

<?xml version="1.0" encoding="utf-8"?><manifest xmlns:android="http://schemas.android.com/apk/res/android"    package="com.example.service_and_runnable"    android:versionCode="1"    android:versionName="1.0" >    <uses-sdk        android:minSdkVersion="8"        android:targetSdkVersion="19" />    <application        android:allowBackup="true"        android:icon="@drawable/ic_launcher"        android:label="@string/app_name"        android:theme="@style/AppTheme" >        <activity            android:name="com.example.service_and_runnable.MainActivity"            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="com.example.service_and_runnable.MyService"             android:exported="true" android:process=":remote">                    </service>    </application></manifest>