Service

1. 概念
   是Context的子类，没有UI界面，是在后台运行的组件。
2. 生命周期
   (1) 使用context.startService()启动
   startService()–>onCreate()–>onStart()(可多次调用)–>Service running
   stopService()–>onDestory()–>Service stop
   (2) 使用context.bindService()启动
   context.bindService()–>onCreate()–>onBind()(只一次，不可多次绑定)–>Service running
   onUnbind()–>onDestory()–>Service stop
   （《第一行代码》）

/** * 自定义服务，四大组件都需要注册 *  * @author Administrator */public class MySercice extends Service {    private DownloadBinder mBinder = new DownloadBinder();    // 模拟下载    class DownloadBinder extends Binder {        public void startDownload() {            Log.d("MySerice", "startDownload executed");        }        public void getProgress() {            Log.d("MySerice", "getProgress executed");            return;        }    }    // 建立服务和活动的关系    @Override    public IBinder onBind(Intent intent) {        return mBinder;    }    // 服务创建时调用    @Override    public void onCreate() {        super.onCreate();        Notification notification = new Notification(R.drawable.ic_launcher, "Notification comes",                System.currentTimeMillis());        Intent notificationIntent = new Intent(this, MainActivity.class);        PendingIntent pendingIntent = PendingIntent.getActivity(this, 0, notificationIntent, 0);        notification.setLatestEventInfo(this, "This is title", "This is content", pendingIntent);        // 变为前台服务，并在系统状态栏显示出来        startForeground(1, notification);        Log.d("MySerice", "onCreate executed");    }    // 每次服务启动的时候调用    @Override    public int onStartCommand(Intent intent, int flags, int startId) {        Log.d("MySerice", "onStartCommand executed");        return super.onStartCommand(intent, flags, startId);    }    // 服务销毁的时候调用    @Override    public void onDestroy() {        super.onDestroy();        Log.d("MyService", "onDestory executed");    }}

MainActivity

package com.example.servicetest;import android.app.Activity;import android.content.ComponentName;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;public class MainActivity extends Activity implements OnClickListener {    private Button startService;    private Button stopService;    private Button bindService;    private Button unbindService;    private Button startIntentService;    private MySercice.DownloadBinder downloadBinder;    private ServiceConnection Connection = new ServiceConnection() {        // 服务解除绑定时调用        @Override        public void onServiceDisconnected(ComponentName name) {        }        // 服务成功绑定时调用        @Override        public void onServiceConnected(ComponentName name, IBinder service) {            downloadBinder = (MySercice.DownloadBinder) service;            downloadBinder.startDownload();            downloadBinder.getProgress();        }    };    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        startService = (Button) findViewById(R.id.start_service);        stopService = (Button) findViewById(R.id.stop_service);        startService.setOnClickListener(this);        stopService.setOnClickListener(this);        bindService = (Button) findViewById(R.id.bind_service);        unbindService = (Button) findViewById(R.id.unbind_service);        bindService.setOnClickListener(this);        unbindService.setOnClickListener(this);        startIntentService = (Button) findViewById(R.id.start_intent_service);        startIntentService.setOnClickListener(this);    }    @Override    public void onClick(View v) {        switch (v.getId()) {        case R.id.start_service:            Intent startintent = new Intent(this, MySercice.class);            startService(startintent);            break;        case R.id.stop_service:            Intent stopIntent = new Intent(this, MySercice.class);            stopService(stopIntent);        case R.id.bind_service:            Intent bindIntent = new Intent(this, MySercice.class);            bindService(bindIntent, Connection, BIND_AUTO_CREATE);            break;        case R.id.unbind_service:            unbindService(Connection);            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;        }    }}

使用IntentService:
防止出现ANR的情况

package com.example.servicetest;import android.app.IntentService;import android.content.Intent;import android.util.Log;public class MyIntentService extends IntentService {    // 调用父类的有参构造函数    public MyIntentService(String name) {        super("MyIntentService");    }    // 处理一些具体的逻辑，不用担心ANR问题    @Override    protected void onHandleIntent(Intent intent) {        // 打印当前线程的Id        Log.d("MyIntentService", "Thread id is " + Thread.currentThread().getId());    }    @Override    public void onDestroy() {        super.onDestroy();        // 证实服务是否停掉        Log.d("MyIntentService", "onDestory executed");    }}

3.Service和Thread的区分
Thread:是程序执行的最小单元，时分配CPU的基本单位，执行异步操作。
Service：是Android的一种机制。运行的时候如果是Local Service，则Service是运行在主线程的main线程上；如果是Remote，则是运行在独立进程的main线程上。
所以他俩没有任何关系。
4.判断Service是否存在的方法：

public static boolean isServiceExisted(Context context, String className) {        ActivityManager activityManager = (ActivityManager) context.getSystemService(Context.ACTIVITY_SERVICE);        List<ActivityManager.RunningServiceInfo> sList = activityManager.getRunningServices(Integer.MAX_VALUE);        if (!(sList.size() > 0)) {            return false;        }        for (int i = 0; i < sList.size(); i++) {            RunningServiceInfo serviceInfo = sList.get(i);            ComponentName serviceName = serviceInfo.service;            if (serviceName.getClassName().equals(className)) {                return true;            }        }        return false;    }