Android WiFi 打开关闭流程

本文简单介绍下WiFi打开与关闭流程，参考源码Android P。

一、WiFi 开机自动打开流程

系统服务启动的时候会启动WifiService，在SystemService.PHASE_SYSTEM_SERVICES_READY的时候，会调用 WifiServiceImpl#checkAndStartWifi()，获取Wi-Fi开关，持久化存储的值。

然后判断是否需要打开WiFi。

    /*** Check if we are ready to start wifi.** First check if we will be restarting system services to decrypt the device. If the device is* not encrypted, check if Wi-Fi needs to be enabled and start if needed** This function is used only at boot time.*/public void checkAndStartWifi() {// First check if we will end up restarting WifiServiceif (mFrameworkFacade.inStorageManagerCryptKeeperBounce()) {Log.d(TAG, "Device still encrypted. Need to restart SystemServer.  Do not start wifi.");return;}// Check if wi-fi needs to be enabledboolean wifiEnabled = mSettingsStore.isWifiToggleEnabled();........// If we are already disabled (could be due to airplane mode), avoid changing persist// state hereif (wifiEnabled) {try {setWifiEnabled(mContext.getPackageName(), wifiEnabled);} catch (RemoteException e) {/* ignore - local call */}}}

二、系统设置主动开启WiFi

1. WiFi开关切换，在WifiEnabler的SwitchToggled中会调用WifiManager.setWifiEnabled方法。

    @Overridepublic boolean onSwitchToggled(boolean isChecked) {//Do nothing if called as a result of a state machine eventif (mStateMachineEvent) {return true;}// Show toast message if Wi-Fi is not allowed in airplane modeif (isChecked && !WirelessUtils.isRadioAllowed(mContext, Settings.Global.RADIO_WIFI)) {Toast.makeText(mContext, R.string.wifi_in_airplane_mode, Toast.LENGTH_SHORT).show();// Reset switch to off. No infinite check/listener loop.mSwitchWidget.setChecked(false);return false;}if (isChecked) {mMetricsFeatureProvider.action(mContext, MetricsEvent.ACTION_WIFI_ON);} else {// Log if user was connected at the time of switching off.mMetricsFeatureProvider.action(mContext, MetricsEvent.ACTION_WIFI_OFF,mConnected.get());}if (!mWifiManager.setWifiEnabled(isChecked)) {// ErrormSwitchWidget.setEnabled(true);Toast.makeText(mContext, R.string.wifi_error, Toast.LENGTH_SHORT).show();}return true;}

2. WifiManager中通过AIDL接口调用WifiService的方法。

    /*** Enable or disable Wi-Fi.* <p>* Applications must have the {@link android.Manifest.permission#CHANGE_WIFI_STATE}* permission to toggle wifi.** @param enabled {@code true} to enable, {@code false} to disable.* @return {@code false} if the request cannot be satisfied; {@code true} indicates that wifi is*         either already in the requested state, or in progress toward the requested state.* @throws  {@link java.lang.SecurityException} if the caller is missing required permissions.*/public boolean setWifiEnabled(boolean enabled) {try {return mService.setWifiEnabled(mContext.getOpPackageName(), enabled);} catch (RemoteException e) {throw e.rethrowFromSystemServer();}}

3. WiFiManager.aidl中提供了setWifiEnabled()接口。

boolean setWifiEnabled(String packageName, boolean enable);

4. WifiServiceImpl中实现WifiManager的接口，在setWifiEnabled函数中会先调用WifiSettingsStore将WiFi开关值进行持久化存储。

然后WifiController发消息CMD_WIFI_TOGGLED 去打开WiFi。

    /*** see {@link android.net.wifi.WifiManager#setWifiEnabled(boolean)}* @param enable {@code true} to enable, {@code false} to disable.* @return {@code true} if the enable/disable operation was*         started or is already in the queue.*/@Overridepublic synchronized boolean setWifiEnabled(String packageName, boolean enable)throws RemoteException {........try {if (! mSettingsStore.handleWifiToggled(enable)) {// Nothing to do if wifi cannot be toggledreturn true;}} finally {Binder.restoreCallingIdentity(ident);}........mWifiController.sendMessage(CMD_WIFI_TOGGLED);return true;}

5. WifiController中对CMD_WIFI_TOGGLED消息进行处理，从初始状态StaDisabledState（如果没有开启wifi_scan_always_enabled功能）切换到DeviceActiveState状态。

    class StaDisabledState extends State {private int mDeferredEnableSerialNumber = 0;private boolean mHaveDeferredEnable = false;private long mDisabledTimestamp;@Overridepublic void enter() {mWifiStateMachinePrime.disableWifi();// Supplicant can't restart right away, so note the time we switched offmDisabledTimestamp = SystemClock.elapsedRealtime();mDeferredEnableSerialNumber++;mHaveDeferredEnable = false;mWifiStateMachine.clearANQPCache();}@Overridepublic boolean processMessage(Message msg) {switch (msg.what) {case CMD_WIFI_TOGGLED:if (mSettingsStore.isWifiToggleEnabled()) {if (doDeferEnable(msg)) {if (mHaveDeferredEnable) {//  have 2 toggles now, inc serial number and ignore bothmDeferredEnableSerialNumber++;}mHaveDeferredEnable = !mHaveDeferredEnable;break;}transitionTo(mDeviceActiveState);} else if (checkScanOnlyModeAvailable()) {// only go to scan mode if we aren't in airplane modeif (mSettingsStore.isAirplaneModeOn()) {transitionTo(mStaDisabledWithScanState);}}break;........}}/*** Parent: StaEnabledState** TODO (b/79209870): merge DeviceActiveState and StaEnabledState into a single state*/class DeviceActiveState extends State {@Overridepublic void enter() {mWifiStateMachinePrime.enterClientMode();mWifiStateMachine.setHighPerfModeEnabled(false);}@Overridepublic boolean processMessage(Message msg) {if (msg.what == CMD_USER_PRESENT) {// TLS networks can't connect until user unlocks keystore. KeyStore// unlocks when the user punches PIN after the reboot. So use this// trigger to get those networks connected.if (mFirstUserSignOnSeen == false) {mWifiStateMachine.reloadTlsNetworksAndReconnect();}mFirstUserSignOnSeen = true;return HANDLED;} else if (msg.what == CMD_RECOVERY_RESTART_WIFI) {final String bugTitle;final String bugDetail;if (msg.arg1 < SelfRecovery.REASON_STRINGS.length && msg.arg1 >= 0) {bugDetail = SelfRecovery.REASON_STRINGS[msg.arg1];bugTitle = "Wi-Fi BugReport: " + bugDetail;} else {bugDetail = "";bugTitle = "Wi-Fi BugReport";}if (msg.arg1 != SelfRecovery.REASON_LAST_RESORT_WATCHDOG) {(new Handler(mWifiStateMachineLooper)).post(() -> {mWifiStateMachine.takeBugReport(bugTitle, bugDetail);});}return NOT_HANDLED;}return NOT_HANDLED;}}

进入DeviceActiveState，执行enter()函数，执行enterClientMode，给ModeStateMachine状态机发送CMD_START_CLIENT_MODE消息。

    /*** Method to switch wifi into client mode where connections to configured networks will be* attempted.*/public void enterClientMode() {changeMode(ModeStateMachine.CMD_START_CLIENT_MODE);}private class ModeStateMachine extends StateMachine {........private boolean checkForAndHandleModeChange(Message message) {switch(message.what) {case ModeStateMachine.CMD_START_CLIENT_MODE:Log.d(TAG, "Switching from " + getCurrentMode() + " to ClientMode");mModeStateMachine.transitionTo(mClientModeActiveState);break;case ModeStateMachine.CMD_START_SCAN_ONLY_MODE:Log.d(TAG, "Switching from " + getCurrentMode() + " to ScanOnlyMode");mModeStateMachine.transitionTo(mScanOnlyModeActiveState);break;case ModeStateMachine.CMD_DISABLE_WIFI:Log.d(TAG, "Switching from " + getCurrentMode() + " to WifiDisabled");mModeStateMachine.transitionTo(mWifiDisabledState);break;default:return NOT_HANDLED;}return HANDLED;}........}

6. 进入ClientModeActiveState，执行enter()函数，WifiInjector创建一个 ClientModeManager，并start。

    class ClientModeActiveState extends ModeActiveState {@Overridepublic void enter() {Log.d(TAG, "Entering ClientModeActiveState");mListener = new ClientListener();mManager = mWifiInjector.makeClientModeManager(mListener);mManager.start();mActiveModeManagers.add(mManager);updateBatteryStatsWifiState(true);}}

    /*** Create a ClientModeManager** @param listener listener for ClientModeManager state changes* @return a new instance of ClientModeManager*/public ClientModeManager makeClientModeManager(ClientModeManager.Listener listener) {return new ClientModeManager(mContext, mWifiStateMachineHandlerThread.getLooper(),mWifiNative, listener, mWifiMetrics, mScanRequestProxy, mWifiStateMachine);}

ClientModeManager 中去启动客户端模式，发送消息CMD_START，进去到IdleState继续处理，处理完毕进入StartedState。

    /*** Start client mode.*/public void start() {mStateMachine.sendMessage(ClientModeStateMachine.CMD_START);}

        private class IdleState extends State {@Overridepublic void enter() {Log.d(TAG, "entering IdleState");mClientInterfaceName = null;mIfaceIsUp = false;}@Overridepublic boolean processMessage(Message message) {switch (message.what) {case CMD_START:updateWifiState(WifiManager.WIFI_STATE_ENABLING,WifiManager.WIFI_STATE_DISABLED);mClientInterfaceName = mWifiNative.setupInterfaceForClientMode(false /* not low priority */, mWifiNativeInterfaceCallback);if (TextUtils.isEmpty(mClientInterfaceName)) {Log.e(TAG, "Failed to create ClientInterface. Sit in Idle");updateWifiState(WifiManager.WIFI_STATE_UNKNOWN,WifiManager.WIFI_STATE_ENABLING);updateWifiState(WifiManager.WIFI_STATE_DISABLED,WifiManager.WIFI_STATE_UNKNOWN);break;}sendScanAvailableBroadcast(false);mScanRequestProxy.enableScanningForHiddenNetworks(false);mScanRequestProxy.clearScanResults();transitionTo(mStartedState);break;default:Log.d(TAG, "received an invalid message: " + message);return NOT_HANDLED;}return HANDLED;}}

7. 接下来看下WifiNative 中setupInterfaceForClientMode，在其中做了HAL部分的启动（包含check驱动是否已经准备ok，HAL部分是否成功启动），之后再进行wpa_supplicant进程的启动，状态检测进程的启动startMonitoring。

    /*** Setup an interface for Client mode operations.** This method configures an interface in STA mode in all the native daemons* (wificond, wpa_supplicant & vendor HAL).** @param lowPrioritySta The requested STA has a low request priority (lower probability of*                       getting created, higher probability of getting destroyed).* @param interfaceCallback Associated callback for notifying status changes for the iface.* @return Returns the name of the allocated interface, will be null on failure.*/public String setupInterfaceForClientMode(boolean lowPrioritySta,@NonNull InterfaceCallback interfaceCallback) {synchronized (mLock) {if (!startHal()) {Log.e(TAG, "Failed to start Hal");mWifiMetrics.incrementNumSetupClientInterfaceFailureDueToHal();return null;}if (!startSupplicant()) {Log.e(TAG, "Failed to start supplicant");mWifiMetrics.incrementNumSetupClientInterfaceFailureDueToSupplicant();return null;}Iface iface = mIfaceMgr.allocateIface(Iface.IFACE_TYPE_STA);if (iface == null) {Log.e(TAG, "Failed to allocate new STA iface");return null;}iface.externalListener = interfaceCallback;iface.name = createStaIface(iface, lowPrioritySta);if (TextUtils.isEmpty(iface.name)) {Log.e(TAG, "Failed to create STA iface in vendor HAL");mIfaceMgr.removeIface(iface.id);mWifiMetrics.incrementNumSetupClientInterfaceFailureDueToHal();return null;}if (mWificondControl.setupInterfaceForClientMode(iface.name) == null) {Log.e(TAG, "Failed to setup iface in wificond on " + iface);teardownInterface(iface.name);mWifiMetrics.incrementNumSetupClientInterfaceFailureDueToWificond();return null;}if (!mSupplicantStaIfaceHal.setupIface(iface.name)) {Log.e(TAG, "Failed to setup iface in supplicant on " + iface);teardownInterface(iface.name);mWifiMetrics.incrementNumSetupClientInterfaceFailureDueToSupplicant();return null;}iface.networkObserver = new NetworkObserverInternal(iface.id);if (!registerNetworkObserver(iface.networkObserver)) {Log.e(TAG, "Failed to register network observer on " + iface);teardownInterface(iface.name);return null;}mWifiMonitor.startMonitoring(iface.name);// Just to avoid any race conditions with interface state change callbacks,// update the interface state before we exit.onInterfaceStateChanged(iface, isInterfaceUp(iface.name));initializeNwParamsForClientInterface(iface.name);Log.i(TAG, "Successfully setup " + iface);return iface.name;}}

8. 在ClientModeManager中进行状态的更新，广播WiFi状态改变消息。

    /*** Update Wifi state and send the broadcast.* @param newState new Wifi state* @param currentState current wifi state*/private void updateWifiState(int newState, int currentState) {if (!mExpectedStop) {mListener.onStateChanged(newState);} else {Log.d(TAG, "expected stop, not triggering callbacks: newState = " + newState);}// Once we report the mode has stopped/failed any other stop signals are redundant// note: this can happen in failure modes where we get multiple callbacks as underlying// components/interface stops or the underlying interface is destroyed in cleanupif (newState == WifiManager.WIFI_STATE_UNKNOWN|| newState == WifiManager.WIFI_STATE_DISABLED) {mExpectedStop = true;}if (newState == WifiManager.WIFI_STATE_UNKNOWN) {// do not need to broadcast failure to systemreturn;}mWifiStateMachine.setWifiStateForApiCalls(newState);final Intent intent = new Intent(WifiManager.WIFI_STATE_CHANGED_ACTION);intent.addFlags(Intent.FLAG_RECEIVER_REGISTERED_ONLY_BEFORE_BOOT);intent.putExtra(WifiManager.EXTRA_WIFI_STATE, newState);intent.putExtra(WifiManager.EXTRA_PREVIOUS_WIFI_STATE, currentState);mContext.sendStickyBroadcastAsUser(intent, UserHandle.ALL);}

9. 系统设置在WifiEnabler中会监听WiFi的状态。

    private final BroadcastReceiver mReceiver = new BroadcastReceiver() {@Overridepublic void onReceive(Context context, Intent intent) {String action = intent.getAction();if (WifiManager.WIFI_STATE_CHANGED_ACTION.equals(action)) {handleWifiStateChanged(mWifiManager.getWifiState());} else if (WifiManager.SUPPLICANT_STATE_CHANGED_ACTION.equals(action)) {if (!mConnected.get()) {handleStateChanged(WifiInfo.getDetailedStateOf((SupplicantState)intent.getParcelableExtra(WifiManager.EXTRA_NEW_STATE)));}} else if (WifiManager.NETWORK_STATE_CHANGED_ACTION.equals(action)) {NetworkInfo info = (NetworkInfo) intent.getParcelableExtra(WifiManager.EXTRA_NETWORK_INFO);mConnected.set(info.isConnected());handleStateChanged(info.getDetailedState());}}};

三、WiFi关闭流程

与打开流程一样，只是在WifiController中收到CMD_WIFI_TOGGLED消息，会从StaEnabledState切换到mStaDisabledState（如果没有启用wifi_scan_always_enabled功能）。

    class StaDisabledState extends State {private int mDeferredEnableSerialNumber = 0;private boolean mHaveDeferredEnable = false;private long mDisabledTimestamp;@Overridepublic void enter() {mWifiStateMachinePrime.disableWifi();// Supplicant can't restart right away, so note the time we switched offmDisabledTimestamp = SystemClock.elapsedRealtime();mDeferredEnableSerialNumber++;mHaveDeferredEnable = false;mWifiStateMachine.clearANQPCache();}

会调用WifiStateMachinePrime.disableWifi() 发送消息CMD_DISABLE_WIFI 。

    /*** Method to disable wifi in sta/client mode scenarios.** This mode will stop any client/scan modes and will not perform any network scans.*/public void disableWifi() {changeMode(ModeStateMachine.CMD_DISABLE_WIFI);}

WifiStateMachinePrime中则会由ClientModeActiveState切换到WifiDisabled，会执行ClientModeActiveState的exit()函数，其调用ModeActiveState的exit()，调用mManager.stop()，最终会将wifi最新状态设置到WifiStateMachine。

        class ModeActiveState extends State {ActiveModeManager mManager;@Overridepublic boolean processMessage(Message message) {// handle messages for changing modes herereturn NOT_HANDLED;}@Overridepublic void exit() {// Active states must have a mode manager, so this should not be null, but it isn't// obvious from the structure - add a null check here, just in case this is missed// in the futureif (mManager != null) {mManager.stop();mActiveModeManagers.remove(mManager);}updateBatteryStatsWifiState(false);}}

        private boolean checkForAndHandleModeChange(Message message) {switch(message.what) {case ModeStateMachine.CMD_START_CLIENT_MODE:Log.d(TAG, "Switching from " + getCurrentMode() + " to ClientMode");mModeStateMachine.transitionTo(mClientModeActiveState);break;case ModeStateMachine.CMD_START_SCAN_ONLY_MODE:Log.d(TAG, "Switching from " + getCurrentMode() + " to ScanOnlyMode");mModeStateMachine.transitionTo(mScanOnlyModeActiveState);break;case ModeStateMachine.CMD_DISABLE_WIFI:Log.d(TAG, "Switching from " + getCurrentMode() + " to WifiDisabled");mModeStateMachine.transitionTo(mWifiDisabledState);break;default:return NOT_HANDLED;}return HANDLED;}

ClientModeManager中也会从StartedState切换到IdleState，在启exit()函数中调用mWifiNative.teardownInterface。

        private class StartedState extends State {private void onUpChanged(boolean isUp) {if (isUp == mIfaceIsUp) {return;  // no change}mIfaceIsUp = isUp;if (isUp) {Log.d(TAG, "Wifi is ready to use for client mode");sendScanAvailableBroadcast(true);mWifiStateMachine.setOperationalMode(WifiStateMachine.CONNECT_MODE,mClientInterfaceName);updateWifiState(WifiManager.WIFI_STATE_ENABLED,WifiManager.WIFI_STATE_ENABLING);} else {if (mWifiStateMachine.isConnectedMacRandomizationEnabled()) {// Handle the error case where our underlying interface went down if we// do not have mac randomization enabled (b/72459123).return;}// if the interface goes down we should exit and go back to idle state.Log.d(TAG, "interface down!");updateWifiState(WifiManager.WIFI_STATE_UNKNOWN,WifiManager.WIFI_STATE_ENABLED);mStateMachine.sendMessage(CMD_INTERFACE_DOWN);}}/*** Clean up state, unregister listeners and update wifi state.*/@Overridepublic void exit() {mWifiStateMachine.setOperationalMode(WifiStateMachine.DISABLED_MODE, null);if (mClientInterfaceName != null) {mWifiNative.teardownInterface(mClientInterfaceName);mClientInterfaceName = null;mIfaceIsUp = false;}updateWifiState(WifiManager.WIFI_STATE_DISABLED,WifiManager.WIFI_STATE_DISABLING);// once we leave started, nothing else to do...  stop the state machinemStateMachine.quitNow();}}

WifiNactive中后续则会调用到mWifiMonitor.stopMonitoring()，stopSupplicantIfNecessary(),stopHalAndWificondIfNecessary()，去停止监测，停止wpa_supplicant，停止hal服务等。

    /** Helper method invoked to teardown client iface and perform necessary cleanup */private void onClientInterfaceDestroyed(@NonNull Iface iface) {synchronized (mLock) {mWifiMonitor.stopMonitoring(iface.name);if (!unregisterNetworkObserver(iface.networkObserver)) {Log.e(TAG, "Failed to unregister network observer on " + iface);}if (!mSupplicantStaIfaceHal.teardownIface(iface.name)) {Log.e(TAG, "Failed to teardown iface in supplicant on " + iface);}if (!mWificondControl.tearDownClientInterface(iface.name)) {Log.e(TAG, "Failed to teardown iface in wificond on " + iface);}stopSupplicantIfNecessary();stopHalAndWificondIfNecessary();}}

Android 的WiFi打开关闭流程大致如此，不足之处后续会继续完善。

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