Android Service 初探

简述：

Android 开发过程中，Service 作为重要的组件，起到了后台运行数据（包括请求、运算、响应等）功能，所以有必要写一个初级的模型来加深一下认识

设计:

想了一个简单的实现， 在主页面点击Run按钮，开始输出数字，使用定时器在Service定时更新当前页面的TextView, 点击Stop则停止这一更改。同时涉及到Handler的内存泄露问题的弱引用解决法

代码：

1. 项目结构

2. 基本配置和UI

Manifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.anialy.testproj"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="17" />

    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" >
    </uses-permission>
    <uses-permission android:name="android.permission.INTERNET" >
    </uses-permission>
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name=".part1.activity.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=".part1.service.MainService"
            android:enabled="true"
            android:exported="false" >
        </service>
    </application>

</manifest>

dimen.xml

<resources>

    <!-- Default screen margins, per the Android Design guidelines. -->
    <dimen name="activity_horizontal_margin">16dp</dimen>
    <dimen name="activity_vertical_margin">16dp</dimen>

</resources>

String.xml

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

    <string name="app_name">TestProj</string>
    <string name="action_settings">Settings</string>
    <string name="hello_world">Hello world!</string>

</resources>

主页

MainActivity.java

package com.anialy.testproj.part1.activity;

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;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;

import com.anialy.testproj.R;
import com.anialy.testproj.part1.service.MainService;
import com.anialy.testproj.part1.service.MainService.ServiceBinder;

public class MainActivity extends Activity {

	private static final String TAG = "MainActivity";
	
	
	/**
	 * service 定义实现绑定部分
	 */
	private MainService mService;
	
	private Intent intentService;
	
	private CustomizedEvent cusEvent;
	
	private boolean isStart = false;
	
	
	/**
	 * service连接监听
	 */
	private ServiceConnection serviceCon = new ServiceConnection() {
		@Override
		public void onServiceDisconnected(ComponentName name) {
			mService = null;
		}

		@Override
		public void onServiceConnected(ComponentName name, IBinder service) {
			if (mService == null) {
				mService = ((ServiceBinder) service).getService();
			}
			// 在service中诸如修改UI的实现cusEvent
			mService.setCusEvent(cusEvent);
		}
	};
	
	
	@Override
	protected void onPause() {
		super.onPause();
		Log.i(TAG, "onPause !");
		unbindService(serviceCon);
	}
	
	
	@Override
	protected void onResume() {
		Log.i(TAG, "onResume !");
		super.onResume();
	}
	
    //////////////////////////////////////////////////////////////////////////////
	/**
	 * 定义控件
	 */
	private Button btn;
	private TextView tv;

	
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		Log.i(TAG, "onCreate !");
		setContentView(R.layout.activity_main);
		initWidgets();
		initEvents();
	}


	private void initWidgets(){
		btn = (Button) findViewById(R.id.btn);
		tv = (TextView) findViewById(R.id.tv);
	}

	
	protected void initEvents(){
		// 定义修改UI的参数， 可以以接口实现的形式传到service， 在service中修改当前UI
		cusEvent = new CustomizedEvent() {
			private static final long serialVersionUID = -3269070363866254175L;

			@Override
			public void doSomething(int cnt) {
				tv.setText(tv.getText() + String.valueOf(cnt) + ", ");
			}
		};
		
		// 点击之后启动service
		btn.setOnClickListener(new OnClickListener() {
			@Override
			public void onClick(View v) {
		    	intentService = new Intent(MainActivity.this, MainService.class);
		    	startService(intentService);
			    if( !isStart ){
			    	bindService(intentService, serviceCon, Context.BIND_AUTO_CREATE);
			    	if(mService != null)
			    		mService.startTimer();
			    	btn.setText("Stop");
			    }else{
			    	mService.stopTimer();
			    	btn.setText("Run");
			    }
			    isStart = !isStart;
			}
		});
	}
}

主页配置文件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:id="@+id/btn"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:text="Run" /> 

    <TextView
        android:id="@+id/tv"
        android:layout_width="400dip"
        android:layout_height="300dip"
        android:layout_below="@+id/btn"
        android:layout_centerHorizontal="true"
        android:layout_marginLeft="24dp"
        android:layout_marginTop="20dp" />

</RelativeLayout>

3. 主页界面更改的接口

CustomizeEvent.java

package com.anialy.testproj.part1.activity;

import java.io.Serializable;

public interface CustomizedEvent extends Serializable {
	public void doSomething(int cnt);
}

4. service实现定时更新

package com.anialy.testproj.part1.service;

import java.lang.ref.WeakReference;
import java.util.Timer;
import java.util.TimerTask;

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

import com.anialy.testproj.part1.activity.CustomizedEvent;

public class MainService extends Service {
	private static final String TAG = "MainService";
	
	private CustomizedEvent cusEvent; //定义接口，用来传递MainActivity传来的函数
	
	private ServiceBinder serviceBinder = new ServiceBinder();
	
	public void setCusEvent(CustomizedEvent cusEvent) {
		this.cusEvent = cusEvent;
	}

	public MainService() {
    }

	
	/**
	 * 自定义binder类 返回当前的 service
	 * 
	 * @author Administrator
	 * 
	 */
	public class ServiceBinder extends Binder {
		public MainService getService() {
			return MainService.this;
		}
	}
    

	Timer timer = new Timer();
	TimerTask task;
	private static int cnt = 0;
	private static final int CHANGE_OK = 0x1;
	// 解决handler内存泄露
	private MyHandler handler = new MyHandler(this);
	private static class MyHandler extends Handler {
		WeakReference<MainService> mService;
		
		MyHandler(MainService mService){  
			this.mService = new WeakReference<MainService>(mService);  
		}
		
		public void handleMessage(Message msg) {
			switch(msg.what){
			case CHANGE_OK :
				mService.get().cusEvent.doSomething(++cnt);
			}
		};
	};
	// 开始定时发送
	public void startTimer() {
		task = new TimerTask(){
			@Override
			public void run() {
				Log.i(TAG, "timer begins !!!");
				handler.sendEmptyMessage(CHANGE_OK);
			}
		};
    	timer.schedule(task, 1000, 1000);
	}
	// 结束定时发送
	public void stopTimer(){
		task.cancel();
	}
	
	
    @Override
    public void onCreate() {
    	super.onCreate();
    	Log.i(TAG, " onCreate !");
    	startTimer();
    }
    
    
    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
    	Log.i(TAG, " onStart !");
    	return super.onStartCommand(intent, flags, startId);
    }
    
    
    @Override
    public IBinder onBind(Intent intent) {
    	Log.i(TAG, " onBind !");
        return serviceBinder;
    }
    
    
    @Override
    public boolean onUnbind(Intent intent) {
    	timer.cancel();
    	return super.onUnbind(intent);
    }
    
    
    @Override
    public void onDestroy() {
    	Log.i(TAG, " onDestroy !");
    	super.onDestroy();
    }

}

界面展示： 未开始前Run等待状态

点击Run开始service, 按钮变为Stop

点击Stop结束，按钮从Stop变为Run