Question

请进来看下我这样使用ContentObserver为什么观察不到db的变动

Answer 1

项目需求：1当联系人更新时，本地表可以获取到更新的通知2程序退出后，仍然可以更新搜了网上很多文章，发现可以使用ContentObserver这个类实现需求1，对于需求2，当然是用Service实现了。代码如下：[java]viewplaincopyprint?publicclassDBUpdateServiceextendsService{protectedstaticfinalintLOCALCONTACTS_SYNC=1;privatefinalstaticintELAPSE_TIME=5000;//FIXME:Shouldremindthis//time./**SetanobservertolistentheLocalContacts'change.AstheDBofcontact*wouldbechangeaftermakeacallorsendamessage.Weshouldlistenthe*LogDBtoo.Ifitchange,webelievethecontactisnotchanged.It'snot*thebestway,justisatemporarysolution,butitcanhandlemanycases.*/publicContentObservermObserver=newContentObserver(newHandler()){@OverridepublicvoidonChange(booleanselfChange){super.onChange(selfChange);Log.i(TAG,"ContactonChange");mHandler.removeMessages(LOCALCONTACTS_SYNC);Log.v(TAG,"removeMessagesfinish.");mHandler.sendEmptyMessageDelayed(LOCALCONTACTS_SYNC,ELAPSE_TIME);}};protectedHandlermHandler=newHandler(){@OverridepublicvoidhandleMessage(Messagemsg){super.handleMessage(msg);Log.v(TAG,"++++handleMessage"+msg);switch(msg.what){caseLOCALCONTACTS_SYNC://dowhatyouwanttodobreak;default:break;}}};@OverridepublicvoidonCreate(){super.onCreate();getContentResolver().registerContentObserver(ContactsContract.Contacts.CONTENT_URI,true,mObserver);---------注册ContentObserver}@OverridepublicintonStartCommand(Intentintent,intflags,intstartId){returnSTART_STICKY;---------------这个可以使Service在需要运行时候自动运行，即使程序退出了}@OverridepublicvoidonDestroy(){getContentResolver().unregisterContentObserver(mObserver);-----------------------------------------------注销ContentObserver}}publicclassDBUpdateServiceextendsService{protectedstaticfinalintLOCALCONTACTS_SYNC=1;privatefinalstaticintELAPSE_TIME=5000;//FIXME:Shouldremindthis//time./**SetanobservertolistentheLocalContacts'change.AstheDBofcontact*wouldbechangeaftermakeacallorsendamessage.Weshouldlistenthe*LogDBtoo.Ifitchange,webelievethecontactisnotchanged.It'snot*thebestway,justisatemporarysolution,butitcanhandlemanycases.*/publicContentObservermObserver=newContentObserver(newHandler()){@OverridepublicvoidonChange(booleanselfChange){super.onChange(selfChange);Log.i(TAG,"ContactonChange");mHandler.removeMessages(LOCALCONTACTS_SYNC);Log.v(TAG,"removeMessagesfinish.");mHandler.sendEmptyMessageDelayed(LOCALCONTACTS_SYNC,ELAPSE_TIME);}};protectedHandlermHandler=newHandler(){@OverridepublicvoidhandleMessage(Messagemsg){super.handleMessage(msg);Log.v(TAG,"++++handleMessage"+msg);switch(msg.what){caseLOCALCONTACTS_SYNC://dowhatyouwanttodobreak;default:break;}}};@OverridepublicvoidonCreate(){super.onCreate();getContentResolver().registerContentObserver(ContactsContract.Contacts.CONTENT_URI,true,mObserver);---------注册ContentObserver}@OverridepublicintonStartCommand(Intentintent,intflags,intstartId){returnSTART_STICKY;---------------这个可以使Service在需要运行时候自动运行，即使程序退出了}@OverridepublicvoidonDestroy(){getContentResolver().unregisterContentObserver(mObserver);-----------------------------------------------注销ContentObserver}}参考：/questions/10431881/how-to-know-the-contact-is-updated-in-android/10432259#104322596985171更新：对于问题2，只需要注册了contentobserver就可以实现了，因为系统有一个ContentService会管理注册的observer。如果有数据修改，系统会自动向注册的observer发送通知。代码中需要实现两个onChange