android笔记：Service

服务：在后台运行，没有界面的组件。

服务生命周期如下：

两种启动方式：

1、startService(): onCreate()-->onStartCommand()-->onDestroy().
2、bindService(): onCreate()-->onBind()-->onUnbind()-->onDestroy().

一、定义一个服务，得做到以下：

1.继承Service，重写onBind()、onCreate()、onStartCommand()和 onDestroy();

2.在AndroidManifest里面注册才能生效.

二、启动服务：

Intent startIntent=new Intent(this,MyService.class);

startService(startIntent);

三、停止服务：

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

四、绑定服务：

1.onBind()方法返回Binder对象；

2.创建了ServiceConnection 的匿名类，重写onServiceConnected()方法和 onServiceDisconnected()方法；

3.用bindService()方法将 Activity 和 Service 进行绑定。

bindService()方法接收三个参数，第一个参数就是 Intent 对象，第二个参数是ServiceConnection 的实例，第三个
参数则是一个标志位，可以传入 BIND_AUTO_CREATE 表示在活动和服务进行绑定后自动创建服务。

示例如下：

Intent bindIntent = new Intent(this, MyService.class);
bindService(bindIntent, connection, BIND_AUTO_CREATE);

五、解绑服务：

unbindService(connection);

六、使用IntentService

优点：

1.异步，可以在子线程处理耗时操作

2.执行完毕自动停止

代码示例如下：

MainActivity.java

package com.example.servicedemo;

import android.os.Bundle;
import android.os.IBinder;
import android.app.Activity;
import android.content.ComponentName;
import android.content.Intent;
import android.content.ServiceConnection;
import android.util.Log;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;

public class MainActivity extends Activity implements OnClickListener {
    private Button startService;
    private Button stopService;
    private Button bindService;
    private Button unbindService;
    private MyService.DownloadBinder downloadBinder;
    private Button startIntentService;
    private boolean mIsBound =false;
    private ServiceConnection connection = new ServiceConnection() {
        @Override
        public void onServiceConnected(ComponentName name, IBinder service) {
            // TODO Auto-generated method stub
            downloadBinder=(MyService.DownloadBinder)service;
            downloadBinder.startDownload();
            downloadBinder.getProgress();
        }

        @Override
        public void onServiceDisconnected(ComponentName name) {
            // TODO Auto-generated method stub
        }
    };
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        startService=(Button)findViewById(R.id.start);
        stopService=(Button)findViewById(R.id.stop);
        bindService = (Button) findViewById(R.id.bind_service);
        unbindService = (Button) findViewById(R.id.unbind_service);
        startIntentService = (Button) findViewById(R.id.start_intent_service);
        startIntentService.setOnClickListener(this);
        startService.setOnClickListener(this);
        stopService.setOnClickListener(this);
        bindService.setOnClickListener(this);
        unbindService.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        // TODO Auto-generated method stub
        switch(v.getId()) {
          case R.id.start:
              Intent startIntent=new Intent(this,MyService.class);
              startService(startIntent);
              
             break;
          case R.id.stop:  
              Intent stopIntent=new Intent(this,MyService.class);
              stopService(stopIntent);
             break;
          case R.id.bind_service:   
              Intent bindIntent = new Intent(this, MyService.class);
              bindService(bindIntent,connection,BIND_AUTO_CREATE);//绑定服务
              mIsBound = true;
              break;
          case R.id.unbind_service:  
              if(mIsBound) {
                 unbindService(connection);  //解绑服务
                 Log.d("MainActivity","UnbindService");
                 mIsBound=false;
              }
             
              break;
          case R.id.start_intent_service:
                Log.d("MainActivity","Thread id is "+Thread.currentThread().getId());
                Intent intentService=new Intent(this,MyIntentService.class);
                startService(intentService);
                break;
          default:
              break;
        }
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }
   
}

MyService.java：

package com.example.servicedemo;

import android.app.Service;

import android.content.Intent;

import android.os.Binder;

import android.os.IBinder;

import android.util.Log;

public class MyService extends Service{

    private DownloadBinder mBinder = new DownloadBinder();

    //继承Binder的内部类，一个方法开始下载，另一个方法获取进度

    class DownloadBinder extends Binder {

      public void startDownload() {

        Log.d("MyService", "startDownload executed");

      }

      public int getProgress() {

        Log.d("MyService", "getProgress executed");

        return 0;

    }

  }

    @Override

    public IBinder onBind(Intent intent) {

        // TODO Auto-generated method stub

        return mBinder;

    }

    public void onCreate(){

        super.onCreate();

        Log.d("MyService","onCreate executed");

    }

    public int onStartCommand(Intent intent,int flags,int startId){

        Log.d("MyService","onStartCommand executed");

        return super.onStartCommand(intent,flags,startId);

    }

    public void onDestroy(){

        Log.d("MyService","onDestroy executed");

        super.onDestroy();

    }

}

MyIntentService.java:

package com.example.servicedemo;

import android.app.IntentService;

import android.content.Intent;

import android.util.Log;

public class MyIntentService extends IntentService{

    public MyIntentService() {

        super("MyIntentService");

        // TODO Auto-generated constructor stub

    }

    @Override

    protected void onHandleIntent(Intent intent) {

        // TODO Auto-generated method stub

        Log.d("MyIntentService", "Thread id is " + Thread.currentThread().

                getId());

    }

    public void onDestroy() {

        super.onDestroy();

        Log.d("MyIntentService", "onDestroy executed");

        }

}

activity_main.xml

<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=".MainActivity" >

   <Button

       android:layout_width="match_parent"

       android:layout_height="wrap_content"

       android:id="@+id/start"

       android:text="start service"

       />

      <Button

       android:layout_width="match_parent"

       android:layout_height="wrap_content"

       android:id="@+id/stop"

       android:text="stop service"

       android:layout_below="@id/start"

       />

      <Button

         android:id="@+id/bind_service"

         android:layout_width="match_parent"

         android:layout_height="wrap_content"

         android:text="Bind Service"

         android:layout_below="@id/stop"  />

      <Button

         android:id="@+id/unbind_service"

         android:layout_width="match_parent"

         android:layout_height="wrap_content"

         android:text="Unbind Service"

         android:layout_below="@id/bind_service" />

      <Button

       android:id="@+id/start_intent_service"

       android:layout_width="match_parent"

       android:layout_height="wrap_content"

       android:text="Start IntentService"

       android:layout_below="@id/unbind_service"  />

</RelativeLayout>

AndroidManifest.xml

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

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

    package="com.example.servicedemo"

    android:versionCode="1"

    android:versionName="1.0" >

    <uses-sdk

        android:minSdkVersion="8"

        android:targetSdkVersion="17" />

    <application

        android:allowBackup="true"

        android:icon="@drawable/ic_launcher"

        android:label="@string/app_name"

        android:theme="@style/AppTheme" >

        <activity

            android:name="com.example.servicedemo.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=".MyService"

            ></service>

       <service android:name=".MyIntentService"></service>

    </application>

</manifest>