Service服务相关（1）

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Service，服务，是android四大组件之一。使用场景：
1.一般用于执行长时间的事务。
2.可以在用户不可见的状态下处理事务。

使用：
1）通过 startService(intentS)方式启动服务：

package wy.bzt.com.phonehelper.service;import android.app.Service;import android.content.Intent;import android.os.IBinder;import android.support.annotation.Nullable;import android.util.Log;/** * Created by wuyong on 2016/7/18. */public class MyService extends Service {    @Nullable    @Override    public IBinder onBind(Intent intent) {        return null;    }    @Override    public void onCreate() {        super.onCreate();        Log.d("ss","service onCreate");    }    @Override    public int onStartCommand(Intent intent, int flags, int startId) {        Log.d("ss","service onStartCommand");        return super.onStartCommand(intent, flags, startId);    }    @Override    public void onDestroy() {        super.onDestroy();        Log.d("ss","service onDestroy");    }}

在activity中：

 intentS=new Intent(this, MyService.class);        startService(intentS);

第一次启动服务，调用onCreate，onStartCommand，之后再启动服务，只会调用onStartCommand；注销服务，只需要stopService(intentS)，或者在service中stopSelf（）。

2）通过bind方式启动服务

public class MyBindService extends Service {    @Override    public void onCreate() {        super.onCreate();        Log.d("bbb","onCreate");    }    @Nullable    @Override    public IBinder onBind(Intent intent) {        Log.d("bbb","onBind");        return new MyBinder();    }    @Override    public boolean onUnbind(Intent intent) {        Log.d("bbb","onUnbind");        return super.onUnbind(intent);    }    @Override    public void onDestroy() {        super.onDestroy();        Log.d("bbb","onDestroy");    }    public class MyBinder extends Binder{        public MyBindService getBindService(){            return MyBindService.this;        }    }}

在activity中：

MyServiceConnection myServiceConnection;    MyBindService.MyBinder myBinder;    MyBindService bindService;    Intent bindintent;    boolean bind;    class MyServiceConnection implements ServiceConnection {        @Override        public void onServiceConnected(ComponentName name, IBinder service) {            myBinder= (MyBindService.MyBinder) service;            bindService=myBinder.getBindService();            bind=true;        }        @Override        public void onServiceDisconnected(ComponentName name) {            bind=false;        }    }

 bindintent=new Intent(this,MyBindService.class);        bindService(bindintent,myServiceConnection,Context.BIND_AUTO_CREATE);

启动bindservice会调用onCreate，onBind方法，之后再启动的话，不会进行回调，调用unbindService(myServiceConnection)会触发onUnbind和onDestroy，事实上，用bind方式启动服务时，服务的生命周期会跟随activity的生命周期，activity结束，服务也自动结束。

一种常用的写法是：activity中启动服务，在服务中添加延时启动功能，到时候通过intent启动广播，广播中可以继续跳转至service（一般通过startservice方法），可以不断触发onStartCommand方法，达到某种目的；或者在activity中延时发送广播，在广播中启动服务，服务中开线程处理事务等等。

一个常用的类：intentservice
在studio中系统的例子：

public class MyIntentService extends IntentService {    // TODO: Rename actions, choose action names that describe tasks that this    // IntentService can perform, e.g. ACTION_FETCH_NEW_ITEMS    private static final String ACTION_FOO = "wy.bzt.com.phonehelper.service.action.FOO";    private static final String ACTION_BAZ = "wy.bzt.com.phonehelper.service.action.BAZ";    // TODO: Rename parameters    private static final String EXTRA_PARAM1 = "wy.bzt.com.phonehelper.service.extra.PARAM1";    private static final String EXTRA_PARAM2 = "wy.bzt.com.phonehelper.service.extra.PARAM2";    public MyIntentService() {        super("MyIntentService");    }    /**     * Starts this service to perform action Foo with the given parameters. If     * the service is already performing a task this action will be queued.     *     * @see IntentService     */    // TODO: Customize helper method    public static void startActionFoo(Context context, String param1, String param2) {        Intent intent = new Intent(context, MyIntentService.class);        intent.setAction(ACTION_FOO);        intent.putExtra(EXTRA_PARAM1, param1);        intent.putExtra(EXTRA_PARAM2, param2);        context.startService(intent);    }    /**     * Starts this service to perform action Baz with the given parameters. If     * the service is already performing a task this action will be queued.     *     * @see IntentService     */    // TODO: Customize helper method    public static void startActionBaz(Context context, String param1, String param2) {        Intent intent = new Intent(context, MyIntentService.class);        intent.setAction(ACTION_BAZ);        intent.putExtra(EXTRA_PARAM1, param1);        intent.putExtra(EXTRA_PARAM2, param2);        context.startService(intent);    }    @Override    protected void onHandleIntent(Intent intent) {        if (intent != null) {            final String action = intent.getAction();            if (ACTION_FOO.equals(action)) {                final String param1 = intent.getStringExtra(EXTRA_PARAM1);                final String param2 = intent.getStringExtra(EXTRA_PARAM2);                handleActionFoo(param1, param2);            } else if (ACTION_BAZ.equals(action)) {                final String param1 = intent.getStringExtra(EXTRA_PARAM1);                final String param2 = intent.getStringExtra(EXTRA_PARAM2);                handleActionBaz(param1, param2);            }        }    }    /**     * Handle action Foo in the provided background thread with the provided     * parameters.     */    private void handleActionFoo(String param1, String param2) {        // TODO: Handle action Foo        throw new UnsupportedOperationException("Not yet implemented");    }    /**     * Handle action Baz in the provided background thread with the provided     * parameters.     */    private void handleActionBaz(String param1, String param2) {        // TODO: Handle action Baz        throw new UnsupportedOperationException("Not yet implemented");    }}

其中需要注意的是：
1.onHandlerIntent默认在新的线程中运行，不需要再另外启动线程处理事务；
2.IntentService处理事务是按照队列一个个处理；
3.处理完成后，会自动结束service，不需要自己去关闭。

service的特点：
1.本身运行在所在进程的主线程，一般启动服务是为了处理长期事务，则需要在服务中启动线程处理，往往IntentService是更好的选择；

2.service 通过start方式启动后，如果不主动关闭，会一直在后台运行，很多时候会引起用户不满，所以最好在不需要的时候关掉它；

eg:
在activity中定时，一段时间后弹出个通知，点击通知，弹出个活动窗口；
关键代码：

    @Override    public int onStartCommand(Intent intent, int flags, int startId) {        Log.d("ss","service onStartCommand");        NotificationCompat.Builder mBuilder = new NotificationCompat.Builder(getApplicationContext())                .setSmallIcon(R.mipmap.ic_launcher)                .setContentTitle("new message")                .setContentText("aaaaaaaa");        mBuilder.setTicker("New message");//提示消息，显示在通知栏上，一会消失        mBuilder.setNumber(12);        //mBuilder.setLargeIcon();        mBuilder.setAutoCancel(true);//自己维护通知的消失        Intent resultIntent = new Intent(getApplicationContext(),MyActivity.class);        PendingIntent resultPendingIntent = PendingIntent.getActivity(                getApplicationContext(), 0, resultIntent,                PendingIntent.FLAG_UPDATE_CURRENT);        // 设置通知主题的意图        mBuilder.setContentIntent(resultPendingIntent);        //获取通知管理器对象        NotificationManager mNotificationManager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);        mNotificationManager.notify(0, mBuilder.build());        return super.onStartCommand(intent, flags, startId);    }

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