Android中的Service

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Service

一、特点：

    Android四大组件之一    没有UI，后台处理耗时操作或者执行长期运行任务    会影响进程的优先级，从而影响内存进程被杀几率

二、与Thread区别
运行线程，service运行在UI线程，可以再起一个线程。
机制：Service作为远端全局工作，可以和任何Activity交互，Thread引用范围局限在Activity
优先级：Service会影响进程优先级，线程优先级跟进程无关。
生命周期：Service有生命周期方便管理。Thread无。
进程：Service可跨进程运行，Thread无。

三、Activity与Service交互

public class MainActivity extends Activity implements View.OnClickListener {    private static final String TAG = ">>>MainActivity";    private Handler mHandler = new Handler() {        @Override        public void handleMessage(Message msg) {            Log.d(TAG, "receive message:" + msg.what);        }    };    private ServiceConnection mSerCon = new ServiceConnection() {        @Override        public void onServiceConnected(ComponentName name, IBinder service) {//            自定义Binder//            TestService.MyBinder binder = (TestService.MyBinder) service;//            service回调//            binder.setCallback(new TestService.Callback() {//                @Override//                public void sendMessageToActivity(int what, int arg1, int arg2, Object object) {//                    Log.d(TAG, "service sendMessageToActivity:" + what);//                }//            });//            Activity调用Service//            Log.d(TAG, "onServiceConnected, count:" + binder.count(2, 3));            //使用Messenger，activity,service相互调用            Messenger myMessenger = new Messenger(service);            try {                myMessenger.send(Message.obtain(mHandler, 1, mHandler));            } catch (RemoteException e) {                e.printStackTrace();            }        }        @Override        public void onServiceDisconnected(ComponentName name) {            Log.d(TAG, "onServiceDisConnected");        }    };    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        findViewById(R.id.startService).setOnClickListener(this);        findViewById(R.id.stopService).setOnClickListener(this);        findViewById(R.id.bindService).setOnClickListener(this);        findViewById(R.id.unbindService).setOnClickListener(this);        findViewById(R.id.bindService2).setOnClickListener(this);    }    @Override    public void onClick(View v) {        switch (v.getId()) {            case R.id.startService:                Intent intent = new Intent(this, TestService.class);                intent.putExtra(TestService.INTENT_EXTRA.A, 8);                startService(intent);                intent.putExtra(TestService.INTENT_EXTRA.A, 9);                startService(intent);                break;            case R.id.stopService:                stopService(new Intent(this, TestService.class));                break;            case R.id.bindService:                bindService(new Intent(this, TestService.class), mSerCon, BIND_AUTO_CREATE);//表示绑定的时候如果service不存在则自动创建                break;            case R.id.unbindService:                unbindService(mSerCon);                break;            case R.id.bindService2:                startActivity(new Intent(this, AnotherActivity.class));                break;        }    }}

public class TestService extends Service {    private static final String TAG = ">>>TestService";    public static final class INTENT_EXTRA {        public static String A = "a";    }    private Callback mCallback;    private Handler mHandler = new Handler() {        @Override        public void handleMessage(Message msg) {            Handler clientHandler = (Handler) msg.obj;            Log.d(TAG, "receiver message:" + msg.what + "," + msg.obj);            //service回发消息            clientHandler.sendEmptyMessage(2);        }    };    @Nullable    @Override    public IBinder onBind(Intent intent) {        Log.d(TAG, "service onBind");//        return new MyBinder();自定义binder        return new Messenger(mHandler).getBinder();//使用Messenger，activity,service相互调用    }    @Override    public boolean onUnbind(Intent intent) {        boolean ret = super.onUnbind(intent);        Log.d(TAG, "service onUnbind, return:" + ret);        return ret;    }    @Override    public void onRebind(Intent intent) {        Log.d(TAG, "service onRebind");        super.onRebind(intent);    }    @Override    public void onCreate() {        Log.d(TAG, "service onCreate, looper:" + Looper.myLooper());        super.onCreate();//        mHandler.postDelayed(new Runnable() {//            @Override//            public void run() {//                停止service//                stopSelf();//                  根据id暂停service//                stopSelfResult()//            }//        }, 5000);    }    @Override    public int onStartCommand(Intent intent, int flags, int startId) {        Log.d(TAG, "service onStartCommand, looper:" + Looper.myLooper() + "," + intent);        if (intent != null) {            Log.d(TAG, "service arg:" + intent.getIntExtra(INTENT_EXTRA.A, 0));        }        if (mCallback != null) {            mCallback.sendMessageToActivity(88, 0, 0, null);        }        return START_REDELIVER_INTENT;    }    @Override    public void onDestroy() {        Log.d(TAG, "service onDestory");        super.onDestroy();    }    //Activity调用Binder方法    class MyBinder extends Binder {        public int count(int a, int b) {            return a + b;        }        //设置回调方法        public void setCallback(Callback callback) {            mCallback = callback;        }    }    interface Callback {        void sendMessageToActivity(int what, int arg1, int arg2, Object object);    }}

四、Service生命周期

这里写图片描述

五、onStartCommand返回值
START_STICKT 如果service被系统杀掉，会稍后被重启，但不会重传intent
START_NOT_STICKY 如果service被系统杀掉则不会被重启
START_REDELIVER_INTENT如果service被系统杀掉，会稍后被重启，且会重传intent

六、IntentService

    //单线程队列化执行，执行完后自动结束    class IntentTestService extends IntentService{        public IntentTestService(String name) {            super(name);        }        @Override        protected void onHandleIntent(Intent intent) {            //已经在一个线程里面了，可以做任何耗时操作        }    }

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