service與runnable的應用

service不是啓動後就會持續在後臺運行的，雖然說是常駐在操作系統裏，但是它卻沒有反覆運行的能力，必須通過類似timer的機制來達成。這類技巧常用於需要向系統做常數監控，向網絡驗證數據，後臺同步數據等。

MainActivity類代碼：

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;
	@Override
	protected 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() {
			
			@Override
			public void onClick(View v) {
				// TODO Auto-generated method stub
				Intent service=new Intent(MainActivity.this, MyService.class);
				startService(service);
			}
		});
		
		btn2.setOnClickListener(new OnClickListener() {
			
			@Override
			public void onClick(View v) {
				// TODO Auto-generated method stub
				Intent service=new Intent(MainActivity.this, MyService.class);
				stopService(service);
			}
		});
		
	}
	

}

MyService類：

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() {
		
		@Override
		public void run() {
			// TODO Auto-generated method stub
			counter++;
			Log.i("service", "counter:"+counter);
			handler.postDelayed(runnable, 1000);
		}
	};
	public MyService() {
		// TODO Auto-generated constructor stub
	}
	
	@Override
	public void onCreate() {
		// TODO Auto-generated method stub
		super.onCreate();
		handler.postDelayed(runnable, 1000);
	}
	
	@Override
	public void onStart(Intent intent, int startId) {
		// TODO Auto-generated method stub
		super.onStart(intent, startId);
	}
	
	@Override
	public void onDestroy() {
		// TODO Auto-generated method stub
		super.onDestroy();
		handler.removeCallbacks(runnable);
	}
	@Override
	public IBinder onBind(Intent intent) {
		// TODO Auto-generated method stub
		return null;
	}

}

佈局文件：

<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="關閉系統服務" />

    <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="啓動系統服務" />

</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>