安卓軟件開發(fā)android中wifi原理詳解轉(zhuǎn)

二：Wifi在SystemServerConnectivityServicetryLog.i(TAG,"StartingConnectivityService.");ServiceManager.addService(Context.CONNECTIVITY_SERVICE,new}catch(Throwablee)Log.e(TAG,"FailurestartingConnectivityService",}ConnectivityServiceWifiService，if(DBG)Log.v(TAG,"StartingWifiService.");mWifiStateTracker=newWifiStateTracker(context,handler);WifiServicewifiService=newWifiService(context,mWifiStateTracker);ServiceManager.addService(Context.WIFI_SERVICE,wifiService);WifiStateTracker會創(chuàng)建WifiMonitor接收來自底層的，WifiService和WifiMonitor是整個模塊的。WifiService負責(zé)啟動關(guān)閉 _supplicant、啟動關(guān)閉WifiMonitor監(jiān)視線程 _supplicant，而WifiMonitor則負責(zé)從 _supplicant接收通知。第三部分：Wifi（使能WirelessSettingsWifiEnablerWifiprivatevoidinitToggles(){mWifiEnabler=newWifiEnabler(this,

(WifiManager)getSystemService(WIFI_SERVICE),(CheckBoxPreference)findPreference(KEY_TOGGLE_WIFI));Wifi，AndroidWifiEnableronPreferenceChange，WifiEnablerWifiManagersetWifiEnabledAIDL，WifiService的setWifiEnabled函數(shù)，WifiServiceMESSAGE_ENABLE_WIFI消息，在處理該消息的代碼中做真正的使能工作：首先裝載WIFI內(nèi)核模塊（該模塊的位置硬編碼為"/system/lib/modules/wlan.ko"），然后啟動 _supplicant（配置文件硬編碼為 _supplicant.conf"），再通過WifiStateTracker來啟動WifiMonitor中的監(jiān)視privatebooleansetWifiEnabledBlocking(booleanenable)finalinteventualWifiState=enable?WIFI_STATE_ENABLED:WIFI_STATE_DISABLED;updateWifiState(enable?WIFI_STATE_ENABLING:WIFI_STATE_DISABLING);if(enable)if(!WifiNative.loadDriver())Log.e(TAG,"FailedtoloadWi-Fidriver.");return}if(!WifiNative.startSupplicant())Log.e(TAG,"Failedtostartsupplicantdaemon.");return}}//Success!returntrue;}WIFI_STATE_CHANGED_ACTIONIntentWIFI已經(jīng)成功使能了。WifiEnabler創(chuàng)建的時候就會向Android接收WIFI_STATE_CHANGED_ACTIONIntent，從而開始掃描。privatevoidhandleWifiStateChanged(intwifiState){if(wifiState==WIFI_STATE_ENABLED){}具體流程 程圖所示第四部分：查找熱點上一節(jié)（第三部分：Wifi開啟）中講到Wifi模塊開啟后會對外發(fā)送WIFI_STATE_CHANGED_ACTION。WifiLayer中了ActionReceiverWifiLayerActionscan _supplicant處理完SCAN命令后，它會向控制通道發(fā) 通知掃描完成，從wifi_wait_for_event函數(shù)會接收