一 前言

? ? ? ?這次接著講Wifi工程流程中的Wifi熱點查找過程，也是Wifi啟動的過程延續，Wifi啟動過程中會更新Wifi的狀態，框架層也有相應廣播發出，應用層接收到廣播后開始進行熱點的掃描。可以先看前面Wifi啟動的分析過程。

? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?Wifi模塊—源碼分析Wifi啟動1（Android P）

? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?Wifi模塊—源碼分析Wifi啟動2（Android P）

二 圖示調用流程

? ? ? 由于在 frameworks/base/packages/SettingsLib/src/com/android/settingslib/wifi/WifiTracker.java直接接收到框架層發出的wifi狀態改變的廣播WIFI_STATE_CHANGED_ACTION（這個在后面有交待），所以這里的圖示調用流程將從WifiTracker.java開始。

三 代碼具體流程

? ? ? ?我們先回顧一下之前wifi啟動過程的相關細節，wifi啟動過程會走到ClientModeStateMachine這個狀態機，具體看 Wifi模塊—源碼分析Wifi啟動1（Android P）。

frameworks/opt/net/wifi/service/java/com/android/server/wifi/ClientModeManager.java?

看ClientModeStateMachine的構造函數。

ClientModeStateMachine(Looper looper) {
? ? super(TAG, looper);
?
? ? addState(mIdleState);
? ? addState(mStartedState);
?
? ? setInitialState(mIdleState);
? ? start();
}
再看start()。

/**
* Start client mode.
*/
public void start() {
? ? mStateMachine.sendMessage(ClientModeStateMachine.CMD_START);
}
發送了一個消息ClientModeStateMachine.CMD_START。

private class IdleState extends State {
?
? ? @Override
? ? public void enter() {
? ? ? ? Log.d(TAG, "entering IdleState");
? ? ? ? mClientInterfaceName = null;
? ? ? ? mIfaceIsUp = false;
? ? }
?
? ? @Override
? ? public 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;
? ? }
}
在IdleState的狀態里接收到消息做相關處理updateWifiState，繼續看這個方法。

/**
? ? ?* 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 cleanup
? ? if (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 system
? ? ? ? return;
? ? }
?
? ? 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);
}
在這里發送了一個廣播sendStickyBroadcastAsUser,廣播具體是WifiManager.WIFI_STATE_CHANGED_ACTION。

? ? ? ? OK，上面的分析都屬于上次分析wifi啟動的部分，就是wifi在啟動過程中會更新wifi狀態并發送wifi狀態改變的廣播。不過。上次在分析wifi啟動過程中也沒有分析這個更新wifi狀態發送廣播的這個內容，這次作為一個補充也是開啟接下來的wifi熱點掃描的流程分析，接下來的wifi掃描過程是指打開wifi之后自動掃描過程而不是手動去刷新掃描。

1 應用層

1.1 packages/apps/Settings/src/com/android/settings/wifi/WifiSettings.java?

在WifiSettings.java里初始化WifiTracker。

@Override
public void onActivityCreated(Bundle savedInstanceState) {
? ? super.onActivityCreated(savedInstanceState);
?
? ? mWifiTracker = WifiTrackerFactory.create(
? ? ? ? ? ? getActivity(), this, getLifecycle(), true, true);
? ? mWifiManager = mWifiTracker.getManager();
? ? ...
}
? ?

1.2 packages/apps/Settings/src/com/android/settings/wifi/WifiEnabler.java

? ? ? ?應用層在掃描過程中貌似沒做什么事情但暫且提一下WifiEnabler也會接收到WifiManager.WIFI_STATE_CHANGED_ACTION廣播并會相關的處理。

private boolean mStateMachineEvent;
private final IntentFilter mIntentFilter;
private final BroadcastReceiver mReceiver = new BroadcastReceiver() {
? ? @Override
? ? public 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());
? ? ? ? }
? ? }
};
看handleWifiStateChanged。

private void handleWifiStateChanged(int state) {
? ? // Clear any previous state
? ? mSwitchWidget.setDisabledByAdmin(null);
?
? ? switch (state) {
? ? ? ? case WifiManager.WIFI_STATE_ENABLING:
? ? ? ? ? ? break;
? ? ? ? case WifiManager.WIFI_STATE_ENABLED:
? ? ? ? ? ? setSwitchBarChecked(true);
? ? ? ? ? ? mSwitchWidget.setEnabled(true);
? ? ? ? ? ? break;
? ? ? ? case WifiManager.WIFI_STATE_DISABLING:
? ? ? ? ? ? break;
? ? ? ? case WifiManager.WIFI_STATE_DISABLED:
? ? ? ? ? ? setSwitchBarChecked(false);
? ? ? ? ? ? mSwitchWidget.setEnabled(true);
? ? ? ? ? ? break;
? ? ? ? default:
? ? ? ? ? ? setSwitchBarChecked(false);
? ? ? ? ? ? mSwitchWidget.setEnabled(true);
? ? }
?
? ? if (RestrictedLockUtils.hasBaseUserRestriction(mContext,
? ? ? ? ? ? UserManager.DISALLOW_CONFIG_TETHERING, UserHandle.myUserId())) {
? ? ? ? mSwitchWidget.setEnabled(false);
? ? } else {
? ? ? ? final EnforcedAdmin admin = RestrictedLockUtils.checkIfRestrictionEnforced(mContext,
? ? ? ? ? ? UserManager.DISALLOW_CONFIG_TETHERING, UserHandle.myUserId());
? ? ? ? mSwitchWidget.setDisabledByAdmin(admin);
? ? }
}
根據wifi狀態，switchBar的狀態會變化。

2 java框架層

? ? ?真正的掃描過程從這里開始。framework/base/packages/SettingsLib。SettingsLib放在frameworks/base/packages/SettingsLib，因為SystemUi和開機向導中的藍牙WiFi流程也會用到對應的代碼。

2.1 frameworks/base/packages/SettingsLib/src/com/android/settingslib/wifi/WifiTracker.java

/**
* ?Receiver for handling broadcasts.
*
* ?This receiver is registered on the WorkHandler.
*/
@VisibleForTesting
final BroadcastReceiver mReceiver = new BroadcastReceiver() {
? ? @Override
? ? public void onReceive(Context context, Intent intent) {
? ? ? ? String action = intent.getAction();
?
? ? ? ? if (WifiManager.WIFI_STATE_CHANGED_ACTION.equals(action)) {
? ? ? ? ? ? updateWifiState(intent.getIntExtra(WifiManager.EXTRA_WIFI_STATE,
? ? ? ? ? ? ? ? ? ? ? ? ? ? WifiManager.WIFI_STATE_UNKNOWN));
? ? ? ? } else if (WifiManager.SCAN_RESULTS_AVAILABLE_ACTION.equals(action)) {
? ? ? ? ? ? mStaleScanResults = false;
?
? ? ? ? ? ? fetchScansAndConfigsAndUpdateAccessPoints();
? ? ? ? } else if (WifiManager.CONFIGURED_NETWORKS_CHANGED_ACTION.equals(action)
? ? ? ? ? ? ? ? || WifiManager.LINK_CONFIGURATION_CHANGED_ACTION.equals(action)) {
? ? ? ? ? ? fetchScansAndConfigsAndUpdateAccessPoints();
? ? ? ? } else if (WifiManager.NETWORK_STATE_CHANGED_ACTION.equals(action)) {
? ? ? ? ? ? // TODO(sghuman): Refactor these methods so they cannot result in duplicate
? ? ? ? ? ? // onAccessPointsChanged updates being called from this intent.
? ? ? ? ? ? NetworkInfo info = intent.getParcelableExtra(WifiManager.EXTRA_NETWORK_INFO);
? ? ? ? ? ? updateNetworkInfo(info);
? ? ? ? ? ? fetchScansAndConfigsAndUpdateAccessPoints();
? ? ? ? } else if (WifiManager.RSSI_CHANGED_ACTION.equals(action)) {
? ? ? ? ? ? NetworkInfo info =
? ? ? ? ? ? ? ? ? ? mConnectivityManager.getNetworkInfo(mWifiManager.getCurrentNetwork());
? ? ? ? ? ? updateNetworkInfo(info);
? ? ? ? }
? ? }
};
看updateWifiState。

/**
* Handles updates to WifiState.
*
* <p>If Wifi is not enabled in the enabled state, {@link #mStaleScanResults} will be set to
* true.
*/
private void updateWifiState(int state) {
? ? if (state == WifiManager.WIFI_STATE_ENABLED) {
? ? ? ? if (mScanner != null) {
? ? ? ? ? ? // We only need to resume if mScanner isn't null because
? ? ? ? ? ? // that means we want to be scanning.
? ? ? ? ? ? mScanner.resume();
? ? ? ? }
? ? } else {
? ? ? ? clearAccessPointsAndConditionallyUpdate();
? ? ? ? mLastInfo = null;
? ? ? ? mLastNetworkInfo = null;
? ? ? ? if (mScanner != null) {
? ? ? ? ? ? mScanner.pause();
? ? ? ? }
? ? ? ? mStaleScanResults = true;
? ? }
? ? mListener.onWifiStateChanged(state);
}
看mScanner.resume，其中Scanner是內部類。

@VisibleForTesting
class Scanner extends Handler {
? ? static final int MSG_SCAN = 0;
?
? ? private int mRetry = 0;
?
? ? void resume() {
? ? ? ? if (!hasMessages(MSG_SCAN)) {
? ? ? ? ? ? sendEmptyMessage(MSG_SCAN);
? ? ? ? }
? ? }
?
? ? void pause() {
? ? ? ? mRetry = 0;
? ? ? ? removeMessages(MSG_SCAN);
? ? }
?
? ? @VisibleForTesting
? ? boolean isScanning() {
? ? ? ? return hasMessages(MSG_SCAN);
? ? }
?
? ? @Override
? ? public void handleMessage(Message message) {
? ? ? ? if (message.what != MSG_SCAN) return;
? ? ? ? if (mWifiManager.startScan()) {
? ? ? ? ? ? mRetry = 0;
? ? ? ? } else if (++mRetry >= 3) {
? ? ? ? ? ? mRetry = 0;
? ? ? ? ? ? if (mContext != null) {
? ? ? ? ? ? ? ? Toast.makeText(mContext, R.string.wifi_fail_to_scan, Toast.LENGTH_LONG).show();
? ? ? ? ? ? }
? ? ? ? ? ? return;
? ? ? ? }
? ? ? ? sendEmptyMessageDelayed(MSG_SCAN, WIFI_RESCAN_INTERVAL_MS);
? ? }
}
? ? ? ?在resume方法里面發送消息MSG_SCAN,并接收該消息進行處理，看handleMessage。會調用mWifiManager.startScan，并且每隔10s再次進行掃描。

2.2 frameworks/base/wifi/java/android/net/wifi/WifiManager.java

* <p>
* To initiate a Wi-Fi scan, declare the
* {@link android.Manifest.permission#CHANGE_WIFI_STATE}
* permission in the manifest, and perform these steps:
* </p>
* <ol style="1">
* <li>Invoke the following method:
* {@code ((WifiManager) getSystemService(WIFI_SERVICE)).startScan()}</li>
* <li>
* Register a BroadcastReceiver to listen to
* {@code SCAN_RESULTS_AVAILABLE_ACTION}.</li>
* <li>When a broadcast is received, call:
* {@code ((WifiManager) getSystemService(WIFI_SERVICE)).getScanResults()}</li>
* </ol>
* @return {@code true} if the operation succeeded, i.e., the scan was initiated.
* @deprecated The ability for apps to trigger scan requests will be removed in a future
* release.
*/
@Deprecated
public boolean startScan() {
? ? return startScan(null);
}
?
/** @hide */
@SystemApi
@RequiresPermission(android.Manifest.permission.UPDATE_DEVICE_STATS)
public boolean startScan(WorkSource workSource) {
? ? try {
? ? ? ? String packageName = mContext.getOpPackageName();
? ? ? ? return mService.startScan(packageName);
? ? } catch (RemoteException e) {
? ? ? ? throw e.rethrowFromSystemServer();
? ? }
}
看mService.startScan。這個mService是遠程的服務端WifiService,其實現類為WifiServiceImpl，這個過程也是跨進程調用。

2.3 ?frameworks/opt/net/wifi/service/java/com/android/server/wifi/wifiServiceImpl.java

/**
* See {@link android.net.wifi.WifiManager#startScan}
*
* @param packageName Package name of the app that requests wifi scan.
*/
@Override
public boolean startScan(String packageName) {
? ? if (enforceChangePermission(packageName) != MODE_ALLOWED) {
? ? ? ? return false;
? ? }
?
? ? int callingUid = Binder.getCallingUid();
? ? long ident = Binder.clearCallingIdentity();
? ? mLog.info("startScan uid=%").c(callingUid).flush();
? ? synchronized (this) {
? ? ? ? if (mInIdleMode) {
? ? ? ? ? ? // Need to send an immediate scan result broadcast in case the
? ? ? ? ? ? // caller is waiting for a result ..
?
? ? ? ? ? ? // TODO: investigate if the logic to cancel scans when idle can move to
? ? ? ? ? ? // WifiScanningServiceImpl. ?This will 1 - clean up WifiServiceImpl and 2 -
? ? ? ? ? ? // avoid plumbing an awkward path to report a cancelled/failed scan. ?This will
? ? ? ? ? ? // be sent directly until b/31398592 is fixed.
? ? ? ? ? ? sendFailedScanBroadcast();
? ? ? ? ? ? mScanPending = true;
? ? ? ? ? ? return false;
? ? ? ? }
? ? }
? ? try {
? ? ? ? mWifiPermissionsUtil.enforceCanAccessScanResults(packageName, callingUid);
? ? ? ? Mutable<Boolean> scanSuccess = new Mutable<>();
? ? ? ? boolean runWithScissorsSuccess = mWifiInjector.getWifiStateMachineHandler()
? ? ? ? ? ? ? ? .runWithScissors(() -> {
? ? ? ? ? ? ? ? ? ? scanSuccess.value = mScanRequestProxy.startScan(callingUid, packageName);
? ? ? ? ? ? ? ? }, RUN_WITH_SCISSORS_TIMEOUT_MILLIS);
? ? ? ? if (!runWithScissorsSuccess) {
? ? ? ? ? ? Log.e(TAG, "Failed to post runnable to start scan");
? ? ? ? ? ? sendFailedScanBroadcast();
? ? ? ? ? ? return false;
? ? ? ? }
? ? ? ? if (!scanSuccess.value) {
? ? ? ? ? ? Log.e(TAG, "Failed to start scan");
? ? ? ? ? ? return false;
? ? ? ? }
? ? } catch (SecurityException e) {
? ? ? ? return false;
? ? } finally {
? ? ? ? Binder.restoreCallingIdentity(ident);
? ? }
? ? return true;
}
繼續看mScanRequestProxy.startScan。

2.4 ?frameworks/opt/net/wifi/service/java/com/android/server/wifi/ScanRequestProxy.java

/**
* Initiate a wifi scan.
*
* @param callingUid The uid initiating the wifi scan. Blame will be given to this uid.
* @return true if the scan request was placed or a scan is already ongoing, false otherwise.
*/
public boolean startScan(int callingUid, String packageName) {
? ? if (!retrieveWifiScannerIfNecessary()) {
? ? ? ? Log.e(TAG, "Failed to retrieve wifiscanner");
? ? ? ? sendScanResultFailureBroadcastToPackage(packageName);
? ? ? ? return false;
? ? }
? ? boolean fromSettingsOrSetupWizard =
? ? ? ? ? ? mWifiPermissionsUtil.checkNetworkSettingsPermission(callingUid)
? ? ? ? ? ? ? ? ? ? || mWifiPermissionsUtil.checkNetworkSetupWizardPermission(callingUid);
? ? // Check and throttle scan request from apps without NETWORK_SETTINGS permission.
? ? if (!fromSettingsOrSetupWizard
? ? ? ? ? ? && shouldScanRequestBeThrottledForApp(callingUid, packageName)) {
? ? ? ? Log.i(TAG, "Scan request from " + packageName + " throttled");
? ? ? ? sendScanResultFailureBroadcastToPackage(packageName);
? ? ? ? return false;
? ? }
? ? // Create a worksource using the caller's UID.
? ? WorkSource workSource = new WorkSource(callingUid);
?
? ? // Create the scan settings.
? ? WifiScanner.ScanSettings settings = new WifiScanner.ScanSettings();
? ? // Scan requests from apps with network settings will be of high accuracy type.
? ? if (fromSettingsOrSetupWizard) {
? ? ? ? settings.type = WifiScanner.TYPE_HIGH_ACCURACY;
? ? }
? ? // always do full scans
? ? settings.band = WifiScanner.WIFI_BAND_BOTH_WITH_DFS;
? ? settings.reportEvents = WifiScanner.REPORT_EVENT_AFTER_EACH_SCAN
? ? ? ? ? ? | WifiScanner.REPORT_EVENT_FULL_SCAN_RESULT;
? ? if (mScanningForHiddenNetworksEnabled) {
? ? ? ? // retrieve the list of hidden network SSIDs to scan for, if enabled.
? ? ? ? List<WifiScanner.ScanSettings.HiddenNetwork> hiddenNetworkList =
? ? ? ? ? ? ? ? mWifiConfigManager.retrieveHiddenNetworkList();
? ? ? ? settings.hiddenNetworks = hiddenNetworkList.toArray(
? ? ? ? ? ? ? ? new WifiScanner.ScanSettings.HiddenNetwork[hiddenNetworkList.size()]);
? ? }
? ? mWifiScanner.startScan(settings, new ScanRequestProxyScanListener(), workSource);
? ? mIsScanProcessingComplete = false;
? ? return true;
}
看mWifiScanner.startScan

2.5 ?frameworks/base/wifi/java/android/net/wifi/WifiScanner.java

/**
* starts a single scan and reports results asynchronously
* @param settings specifies various parameters for the scan; for more information look at
* {@link ScanSettings}
* @param listener specifies the object to report events to. This object is also treated as a
* ? ? ? ? ? ? ? ?key for this scan, and must also be specified to cancel the scan. Multiple
* ? ? ? ? ? scans should also not share this object.
*/
@RequiresPermission(android.Manifest.permission.LOCATION_HARDWARE)
public void startScan(ScanSettings settings, ScanListener listener) {
? ? startScan(settings, listener, null);
}
?
/**
* starts a single scan and reports results asynchronously
* @param settings specifies various parameters for the scan; for more information look at
* {@link ScanSettings}
* @param workSource WorkSource to blame for power usage
* @param listener specifies the object to report events to. This object is also treated as a
* ? ? ? ? ? ? ? ? key for this scan, and must also be specified to cancel the scan. Multiple
* ? ? ? ? ? ? ? ? scans should also not share this object.
*/
@RequiresPermission(android.Manifest.permission.LOCATION_HARDWARE)
public void startScan(ScanSettings settings, ScanListener listener, WorkSource workSource) {
? ? Preconditions.checkNotNull(listener, "listener cannot be null");
? ? int key = addListener(listener);
? ? if (key == INVALID_KEY) return;
? ? validateChannel();
? ? Bundle scanParams = new Bundle();
? ? scanParams.putParcelable(SCAN_PARAMS_SCAN_SETTINGS_KEY, settings);
? ? scanParams.putParcelable(SCAN_PARAMS_WORK_SOURCE_KEY, workSource);
? ? mAsyncChannel.sendMessage(CMD_START_SINGLE_SCAN, 0, key, scanParams);
? ??
}
? ? ? ? Android P和Android O框架層代碼改變不是很大，不過Android O的操作基本都是經過WifiStateMachine狀態機，而Android P很多操作都不再經過WifiStateMachine狀態機,在這里是為了把scan功能獨立分開出來。而和Android O之前的代碼相比則有很大區別，這里接下來使用到了雙向異步通道的方式，mAsyncChannel.sendMessage。AsyncChannel處理兩個handler之間消息異步傳遞的問題，這兩個handler可以在一個進程也可以處于不同的進程。?

2.6 ?frameworks/opt/net/wifi/service/java/com/android/server/wifi/scanner/WifiScanningServiceImpl.java

private class ClientHandler extends WifiHandler {
?
? ? ClientHandler(String tag, Looper looper) {
? ? ? ? super(tag, looper);
? ? }
?
? ? @Override
? ? public void handleMessage(Message msg) {
? ? ? ? super.handleMessage(msg);
? ? ? ? ...
? ? ? ? switch (msg.what) {
? ? ? ? ? ? case WifiScanner.CMD_START_BACKGROUND_SCAN:
? ? ? ? ? ? case WifiScanner.CMD_STOP_BACKGROUND_SCAN:
? ? ? ? ? ? ? ? mBackgroundScanStateMachine.sendMessage(Message.obtain(msg));
? ? ? ? ? ? ? ? break;
? ? ? ? ? ? case WifiScanner.CMD_START_PNO_SCAN:
? ? ? ? ? ? case WifiScanner.CMD_STOP_PNO_SCAN:
? ? ? ? ? ? ? ? mPnoScanStateMachine.sendMessage(Message.obtain(msg));
? ? ? ? ? ? ? ? break;
? ? ? ? ? ? case WifiScanner.CMD_START_SINGLE_SCAN:
? ? ? ? ? ? case WifiScanner.CMD_STOP_SINGLE_SCAN:
? ? ? ? ? ? ? ? mSingleScanStateMachine.sendMessage(Message.obtain(msg));
? ? ? ? ? ? ? ? break;
? ? ? ? ? ? ...
? ? ? ? }
? ? }
}
? ?ClientHandler接收到CMD_START_SINGLE_SCAN消息并處理也就是向狀態機發送這個消息，mSingleScanStateMachine.sendMessage(Message.obtain(msg))。SingleScanStateMachine是個處理熱點掃描的狀態機。

/**
* State machine that holds the state of single scans. Scans should only be active in the
* ScanningState. The pending scans and active scans maps are swapped when entering
* ScanningState. Any requests queued while scanning will be placed in the pending queue and
* executed after transitioning back to IdleState.
*/
class WifiSingleScanStateMachine extends StateMachine implements WifiNative.ScanEventHandler {
? ? /**
? ? * Maximum age of results that we return from our cache via
? ? * {@link WifiScanner#getScanResults()}.
? ? * This is currently set to 3 minutes to restore parity with the wpa_supplicant's scan
? ? * result cache expiration policy. (See b/62253332 for details)
? ? */
? ? @VisibleForTesting
? ? public static final int CACHED_SCAN_RESULTS_MAX_AGE_IN_MILLIS = 180 * 1000;
?
? ? private final DefaultState mDefaultState = new DefaultState();
? ? private final DriverStartedState mDriverStartedState = new DriverStartedState();
? ? private final IdleState ?mIdleState ?= new IdleState();
? ? private final ScanningState ?mScanningState ?= new ScanningState();
?
? ? private WifiNative.ScanSettings mActiveScanSettings = null;
? ? private RequestList<ScanSettings> mActiveScans = new RequestList<>();
? ? private RequestList<ScanSettings> mPendingScans = new RequestList<>();
?
? ? // Scan results cached from the last full single scan request.
? ? private final List<ScanResult> mCachedScanResults = new ArrayList<>();
?
? ? WifiSingleScanStateMachine(Looper looper) {
? ? ? ? super("WifiSingleScanStateMachine", looper);
?
? ? ? ? setLogRecSize(128);
? ? ? ? setLogOnlyTransitions(false);
?
? ? ? ? // CHECKSTYLE:OFF IndentationCheck
? ? ? ? addState(mDefaultState);
? ? ? ? ? ? addState(mDriverStartedState, mDefaultState);
? ? ? ? ? ? ? ? addState(mIdleState, mDriverStartedState);
? ? ? ? ? ? ? ? addState(mScanningState, mDriverStartedState);
? ? ? ? ? ? // CHECKSTYLE:ON IndentationCheck
?
? ? ? ? ? ? setInitialState(mDefaultState);
? ? }
? ? ...
}
狀態機有四個狀態，初始狀態為默認狀態。在DriverStarted對CMD_START_SINGLE_SCAN消息進行處理。

/**
* State representing when the driver is running. This state is not meant to be transitioned
* directly, but is instead intended as a parent state of ScanningState and IdleState
* to hold common functionality and handle cleaning up scans when the driver is shut down.
*/
class DriverStartedState extends State {
? ? ...
?
? ? @Override
? ? public boolean processMessage(Message msg) {
? ? ? ? ClientInfo ci = mClients.get(msg.replyTo);
?
? ? ? ? switch (msg.what) {
? ? ? ? ? ? case CMD_DRIVER_LOADED:
? ? ? ? ? ? ? ? // Ignore if we're already in driver loaded state.
? ? ? ? ? ? ? ? return HANDLED;
? ? ? ? ? ? case WifiScanner.CMD_START_SINGLE_SCAN:
? ? ? ? ? ? ? ? mWifiMetrics.incrementOneshotScanCount();
? ? ? ? ? ? ? ? int handler = msg.arg2;
? ? ? ? ? ? ? ? Bundle scanParams = (Bundle) msg.obj;
? ? ? ? ? ? ? ? if (scanParams == null) {
? ? ? ? ? ? ? ? ? ? logCallback("singleScanInvalidRequest", ?ci, handler, "null params");
? ? ? ? ? ? ? ? ? ? replyFailed(msg, WifiScanner.REASON_INVALID_REQUEST, "params null");
? ? ? ? ? ? ? ? ? ? return HANDLED;
? ? ? ? ? ? ? ? }
? ? ? ? ? ? ? ? scanParams.setDefusable(true);
? ? ? ? ? ? ? ? ScanSettings scanSettings =
? ? ? ? ? ? ? ? ? ? ? ? ? ? scanParams.getParcelable(WifiScanner.SCAN_PARAMS_SCAN_SETTINGS_KEY);
? ? ? ? ? ? ? ? WorkSource workSource =
? ? ? ? ? ? ? ? ? ? ? ? ? ? scanParams.getParcelable(WifiScanner.SCAN_PARAMS_WORK_SOURCE_KEY);
? ? ? ? ? ? ? ? if (validateScanRequest(ci, handler, scanSettings)) {
? ? ? ? ? ? ? ? ? ? ? ? ? ? logScanRequest("addSingleScanRequest", ci, handler, workSource,
? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? scanSettings, null);
? ? ? ? ? ? ? ? ? ? replySucceeded(msg);
?
? ? ? ? ? ? ? ? ? ? // If there is an active scan that will fulfill the scan request then
? ? ? ? ? ? ? ? ? ? // mark this request as an active scan, otherwise mark it pending.
? ? ? ? ? ? ? ? ? ? // If were not currently scanning then try to start a scan. Otherwise
? ? ? ? ? ? ? ? ? ? // this scan will be scheduled when transitioning back to IdleState
? ? ? ? ? ? ? ? ? ? // after finishing the current scan.
? ? ? ? ? ? ? ? ? ? if (getCurrentState() == mScanningState) {
? ? ? ? ? ? ? ? ? ? ? ? if (activeScanSatisfies(scanSettings)) {
? ? ? ? ? ? ? ? ? ? ? ? ? ? mActiveScans.addRequest(ci, handler, workSource, scanSettings);
? ? ? ? ? ? ? ? ? ? ? ? } else {
? ? ? ? ? ? ? ? ? ? ? ? ? ? mPendingScans.addRequest(ci, handler, workSource, scanSettings);
? ? ? ? ? ? ? ? ? ? ? ? }
? ? ? ? ? ? ? ? ? ? } else {
? ? ? ? ? ? ? ? ? ? ? ? mPendingScans.addRequest(ci, handler, workSource, scanSettings);
? ? ? ? ? ? ? ? ? ? ? ? tryToStartNewScan();
? ? ? ? ? ? ? ? ? ? }
? ? ? ? ? ? ? ? } else {
? ? ? ? ? ? ? ? ...
? ? ? ? ? ? ? ? } ? ?
? ? ? ? }
? ? } ??
}
看調用的tryToStartNewScan。

void tryToStartNewScan() {
? ? if (mPendingScans.size() == 0) { // no pending requests
? ? ? ? return;
? ? }
? ? ...
? ? if (mScannerImpl.startSingleScan(settings, this)) {
? ? ? ? // store the active scan settings
? ? ? ? mActiveScanSettings = settings;
? ? ? ? // swap pending and active scan requests
? ? ? ? RequestList<ScanSettings> tmp = mActiveScans;
? ? ? ? mActiveScans = mPendingScans;
? ? ? ? mPendingScans = tmp;
? ? ? ? // make sure that the pending list is clear
? ? ? ? mPendingScans.clear();
? ? ? ? transitionTo(mScanningState);
? ? } else {
? ? ? ? mWifiMetrics.incrementScanReturnEntry(
? ? ? ? ? ? ? ? WifiMetricsProto.WifiLog.SCAN_UNKNOWN, mPendingScans.size());
? ? ? ? // notify and cancel failed scans
? ? ? ? sendOpFailedToAllAndClear(mPendingScans, WifiScanner.REASON_UNSPECIFIED,
? ? ? ? ? ? ? ? "Failed to start single scan");
? ? }
}
看mScannerImpl.startSingleScan。

2.7 ?frameworks/opt/net/wifi/service/java/com/android/server/wifi/scanner/WifiScannerImpl.java

/**
* Start a one time scan. This method should only be called when there is no scan going on
* (after a callback indicating that the previous scan succeeded/failed).
* @return if the scan paramaters are valid
* Note this may return true even if the parameters are not accepted by the chip because the
* scan may be scheduled async.
*/
public abstract boolean startSingleScan(WifiNative.ScanSettings settings,
? ? ? ? ? ? ? ? ?WifiNative.ScanEventHandler eventHandler);
?

2.8 ?frameworks/opt/net/wifi/service/java/com/android/server/wifi/scanner/WificondScannerImpl.java

WificondScannerImpl.java繼承抽象類WifiScannerImpl.java，所以復寫了startSingleScan。

@Override
public boolean startSingleScan(WifiNative.ScanSettings settings,
? ? ? ? WifiNative.ScanEventHandler eventHandler) {
? ? ...
? ? if (!allFreqs.isEmpty()) {
? ? ? ? freqs = allFreqs.getScanFreqs();
? ? ? ? success = mWifiNative.scan(
? ? ? ? ? ? ? ? ? ? ? ? mIfaceName, settings.scanType, freqs, hiddenNetworkSSIDSet);
? ? ? ? if (!success) {
? ? ? ? ? ? Log.e(TAG, "Failed to start scan, freqs=" + freqs);
? ? ? ? }
? ? } else {
? ? ? ? // There is a scan request but no available channels could be scanned for.
? ? ? ? // We regard it as a scan failure in this case.
? ? ? ? Log.e(TAG, "Failed to start scan because there is no available channel to scan");
? ? }
? ? if (success) {
? ? ? ? if (DBG) {
? ? ? ? ? ? Log.d(TAG, "Starting wifi scan for freqs=" + freqs);
? ? ? ? }
?
? ? ? ? mScanTimeoutListener = new AlarmManager.OnAlarmListener() {
? ? ? ? ? ? @Override public void onAlarm() {
? ? ? ? ? ? ? ? handleScanTimeout();
? ? ? ? ? ? }
? ? ? ? };
?
? ? ? ? mAlarmManager.set(AlarmManager.ELAPSED_REALTIME_WAKEUP,
? ? ? ? ? ? ? ? ? ? mClock.getElapsedSinceBootMillis() + SCAN_TIMEOUT_MS,
? ? ? ? ? ? ? ? ? ? ? ? TIMEOUT_ALARM_TAG, mScanTimeoutListener, mEventHandler);
? ? ? ? } else {
? ? ? ? ? ? // indicate scan failure async
? ? ? ? ? ? mEventHandler.post(new Runnable() {
? ? ? ? ? ? ? ? @Override public void run() {
? ? ? ? ? ? ? ? ? ? reportScanFailure();
? ? ? ? ? ? ? ? }
? ? ? ? ? ? });
? ? ? ? }
?
? ? ? ? return true;
? ? }
}
看 mWifiNative.scan，java框架層最終還是會調用到native層。

2.9 ?frameworks/opt/net/wifi/service/java/com/android/server/wifi/WifiNative.java

/**
* Start a scan using wificond for the given parameters.
* @param ifaceName Name of the interface.
* @param scanType Type of scan to perform. One of {@link ScanSettings#SCAN_TYPE_LOW_LATENCY},
* {@link ScanSettings#SCAN_TYPE_LOW_POWER} or {@link ScanSettings#SCAN_TYPE_HIGH_ACCURACY}.
* @param freqs list of frequencies to scan for, if null scan all supported channels.
* @param hiddenNetworkSSIDs List of hidden networks to be scanned for.
* @return Returns true on success.
*/
public boolean scan(@NonNull String ifaceName, int scanType, Set<Integer> freqs,
? ? ? ? ? ? Set<String> hiddenNetworkSSIDs) {
? ? return mWificondControl.scan(ifaceName, scanType, freqs, hiddenNetworkSSIDs);
}
看mWificondControl.scan。

2.10 ?frameworks/opt/net/wifi/service/java/com/android/server/wifi/WificondControl.java

/**
* Start a scan using wificond for the given parameters.
* @param ifaceName Name of the interface.
* @param scanType Type of scan to perform.
* @param freqs list of frequencies to scan for, if null scan all supported channels.
* @param hiddenNetworkSSIDs List of hidden networks to be scanned for.
* @return Returns true on success.
*/
public boolean scan(@NonNull String ifaceName,
? ? ? ? ? ? ? ? ? ? int scanType,
? ? ? ? ? ? ? ? ? ? Set<Integer> freqs,
? ? ? ? ? ? ? ? ? ? Set<String> hiddenNetworkSSIDs) {
? ? IWifiScannerImpl scannerImpl = getScannerImpl(ifaceName);
? ? if (scannerImpl == null) {
? ? ? ? Log.e(TAG, "No valid wificond scanner interface handler");
? ? ? ? return false;
? ? }
? ? SingleScanSettings settings = new SingleScanSettings();
? ? try {
? ? ? ? settings.scanType = getScanType(scanType);
? ? } catch (IllegalArgumentException e) {
? ? ? ? Log.e(TAG, "Invalid scan type ", e);
? ? ? ? return false;
? ? }
? ? settings.channelSettings ?= new ArrayList<>();
? ? settings.hiddenNetworks ?= new ArrayList<>();
?
? ? if (freqs != null) {
? ? ? ? for (Integer freq : freqs) {
? ? ? ? ? ? ChannelSettings channel = new ChannelSettings();
? ? ? ? ? ? channel.frequency = freq;
? ? ? ? ? ? settings.channelSettings.add(channel);
? ? ? ? }
? ? }
? ? if (hiddenNetworkSSIDs != null) {
? ? ? ? for (String ssid : hiddenNetworkSSIDs) {
? ? ? ? ? ? HiddenNetwork network = new HiddenNetwork();
? ? ? ? ? ? try {
? ? ? ? ? ? ? ? network.ssid = NativeUtil.byteArrayFromArrayList(NativeUtil.decodeSsid(ssid));
? ? ? ? ? ? } catch (IllegalArgumentException e) {
? ? ? ? ? ? ? ? Log.e(TAG, "Illegal argument " + ssid, e);
? ? ? ? ? ? ? ? continue;
? ? ? ? ? ? }
? ? ? ? ? ? settings.hiddenNetworks.add(network);
? ? ? ? }
? ? }
?
? ? try {
? ? ? ? return scannerImpl.scan(settings);
? ? } catch (RemoteException e1) {
? ? ? ? Log.e(TAG, "Failed to request scan due to remote exception");
? ? }
? ? return false;
}
又調到scannerImpl.scan了，看getScannerImpl。

/** Helper function to look up the scanner impl handle using name */
private IWifiScannerImpl getScannerImpl(@NonNull String ifaceName) {
? ? return mWificondScanners.get(ifaceName);
}
看mWificondScanners怎么來的，從下面可以看到wificondScanner = clientInterface.getWifiScannerImpl()。

/**
* Setup interface for client mode via wificond.
* @return An IClientInterface as wificond client interface binder handler.
* Returns null on failure.
*/
public IClientInterface setupInterfaceForClientMode(@NonNull String ifaceName) {
? ? Log.d(TAG, "Setting up interface for client mode");
? ? if (!retrieveWificondAndRegisterForDeath()) {
? ? ? ? return null;
? ? }
?
? ? IClientInterface clientInterface = null;
? ? try {
? ? ? ? clientInterface = mWificond.createClientInterface(ifaceName);
? ? } catch (RemoteException e1) {
? ? ? ? Log.e(TAG, "Failed to get IClientInterface due to remote exception");
? ? ? ? return null;
? ? }
?
? ? if (clientInterface == null) {
? ? ? ? Log.e(TAG, "Could not get IClientInterface instance from wificond");
? ? ? ? return null;
? ? }
? ? Binder.allowBlocking(clientInterface.asBinder());
?
? ? // Refresh Handlers
? ? mClientInterfaces.put(ifaceName, clientInterface);
? ? try {
? ? ? ? IWifiScannerImpl wificondScanner = clientInterface.getWifiScannerImpl();
? ? ? ? if (wificondScanner == null) {
? ? ? ? ? ? Log.e(TAG, "Failed to get WificondScannerImpl");
? ? ? ? ? ? return null;
? ? ? ? }
? ? ? ? mWificondScanners.put(ifaceName, wificondScanner);
? ? ? ? Binder.allowBlocking(wificondScanner.asBinder());
? ? ? ? ScanEventHandler scanEventHandler = new ScanEventHandler(ifaceName);
? ? ? ? mScanEventHandlers.put(ifaceName, ?scanEventHandler);
? ? ? ? wificondScanner.subscribeScanEvents(scanEventHandler);
? ? ? ? PnoScanEventHandler pnoScanEventHandler = new PnoScanEventHandler(ifaceName);
? ? ? ? mPnoScanEventHandlers.put(ifaceName, ?pnoScanEventHandler);
? ? ? ? wificondScanner.subscribePnoScanEvents(pnoScanEventHandler);
? ? } catch (RemoteException e) {
? ? ? ? Log.e(TAG, "Failed to refresh wificond scanner due to remote exception");
? ? }
?
? ? return clientInterface;
}
看retrieveWificondAndRegisterForDeath。

/**
* Helper method to retrieve the global wificond handle and register for
* death notifications.
*/
private boolean retrieveWificondAndRegisterForDeath() {
? ? if (mWificond != null) {
? ? ? ? if (mVerboseLoggingEnabled) {
? ? ? ? ? ? Log.d(TAG, "Wificond handle already retrieved");
? ? ? ? }
? ? ? ? // We already have a wificond handle.
? ? ? ? return true;
? ? }
? ? mWificond = mWifiInjector.makeWificond();
? ? if (mWificond == null) {
? ? ? ? Log.e(TAG, "Failed to get reference to wificond");
? ? ? ? return false;
? ? }
? ? try {
? ? ? ? mWificond.asBinder().linkToDeath(this, 0);
? ? } catch (RemoteException e) {
? ? ? ? Log.e(TAG, "Failed to register death notification for wificond");
? ? ? ? // The remote has already died.
? ? ? ? return false;
? ? }
? ? return true;
}
看mWiifInjector.makeWificond。

2.11 ?frameworks/opt/net/wifi/service/java/com/android/server/wifi/WifiInjector.java

public IWificond makeWificond() {
? ? // We depend on being able to refresh our binder in WifiStateMachine, so don't cache it.
? ? IBinder binder = ServiceManager.getService(WIFICOND_SERVICE_NAME);
? ? return IWificond.Stub.asInterface(binder);
}
再往下走就是C++層了。往下的部分以后有機會再繼續深入。

四 總結

?wifi框架層從Android O版本開始變化還是挺大的，Android P是延續Android O 的改變做了一些不怎么大的變化：

? ? ? (1) 與其他Android版本相比，整體架構還好，多了wificond跟底層通信，framework整個修改比較大；

? ? ?(2) Android O ?scan、scan_results命令不再通過wpa_supplicant下發到kernel，而是直接由wificond傳送到kernel，而scan results的結果也是直接由kernel傳給wificond，再由wificond傳送給上層去顯示；

? ? ? (3) wifi direct的p2p find還是通過wpa-supplicant通信 ；

? ? ? (4) wifi的連接等操作，還是通過wpa_supplicant進行。
————————————————
版權聲明：本文為CSDN博主「BrighterLi」的原創文章，遵循CC 4.0 BY-SA版權協議，轉載請附上原文出處鏈接及本聲明。
原文鏈接：https://blog.csdn.net/weixin_42093428/article/details/82682804

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