本文介绍Wifi 分析线路二：在Setting中打开WiFi功能、扫描网络以及连接网络的流程。
WifiSettings 无线网络设置界面
WifiEnabler 相当于无线网络设置开关
WifiDialog 显示的无线网络配置信息由WifiConfigController 来控制和管理
Scanner 用于处理和无线网络扫描相关的工作
1、Settings 操作
无线网络设置界面UI 初始化过程中，WifiSettings 的onActivityCreated() 方法被调用：
public void onActivityCreated(Bundle savedInstanceState) { super.onActivityCreated(savedInstanceState); mWifiTracker = new WifiTracker(getActivity(), this, mBgThread.getLooper(), true, true, false); mWifiManager = mWifiTracker.getManager(); }
WifiTracker 构造函数调用：
WifiTracker(Context context, WifiListener wifiListener, Looper workerLooper, boolean includeSaved, boolean includeScans, boolean includePasspoints, WifiManager wifiManager, ConnectivityManager connectivityManager, Looper currentLooper) { //添加多个广播事件，在startTracker() 方法中进行注册 mFilter = new IntentFilter(); mFilter.addAction(WifiManager.WIFI_STATE_CHANGED_ACTION); mFilter.addAction(WifiManager.SCAN_RESULTS_AVAILABLE_ACTION); mFilter.addAction(WifiManager.NETWORK_IDS_CHANGED_ACTION); mFilter.addAction(WifiManager.SUPPLICANT_STATE_CHANGED_ACTION); mFilter.addAction(WifiManager.CONFIGURED_NETWORKS_CHANGED_ACTION); mFilter.addAction(WifiManager.LINK_CONFIGURATION_CHANGED_ACTION); mFilter.addAction(WifiManager.NETWORK_STATE_CHANGED_ACTION); mNetworkRequest = new NetworkRequest.Builder() .clearCapabilities() .addTransportType(NetworkCapabilities.TRANSPORT_WIFI) .build(); }
WifiSettings 的onStart() 方法创建WifiEnabler：
public void onStart() { // On/off switch is hidden for Setup Wizard (returns null) mWifiEnabler = createWifiEnabler(); } WifiEnabler createWifiEnabler() { final SettingsActivity activity = (SettingsActivity) getActivity(); return new WifiEnabler(activity, activity.getSwitchBar()); }
WifiEnabler 的构造函数，添加广播事件：
public WifiEnabler(Context context, SwitchBar switchBar) { mWifiManager = (WifiManager) context.getSystemService(Context.WIFI_SERVICE); //添加三个广播事件 mIntentFilter = new IntentFilter(WifiManager.WIFI_STATE_CHANGED_ACTION); // The order matters! We really should not depend on this. :( mIntentFilter.addAction(WifiManager.SUPPLICANT_STATE_CHANGED_ACTION); mIntentFilter.addAction(WifiManager.NETWORK_STATE_CHANGED_ACTION); setupSwitchBar(); }
WIFI_STATE_CHANGED_ACTION：反映WiFi 功能所对应的状态，包括WIFI_STATE_DISABLED(Wifi 功能已被关闭)、WIFI_STATE_DISABLING(Wifi 功能正在关闭中)、WIFI_STATE_ENABLED(Wifi 功能已被打开)、WIFI_STATE_ENABLING(Wifi 功能正在打开中)、WIFI_STATE_UNKNOWN(Wifi 功能状态未知)。
SUPPLICANT_STATE_CHANGED_ACTION：表示WPAS 的状态发生了变化。
NETWORK_STATE_CHANGED_ACTION：表示WIFI 连接状态发生变化，其携带的信息一般是NetworkInfo 对象。
WifiSettings 和 WifiEnabler 的设置的广播接收对象在onResume() 的方法中被注册：
public void onResume() { final Activity activity = getActivity(); if (mWifiEnabler != null) { mWifiEnabler.resume(activity); //调用WifiEnabler 类 } mWifiTracker.startTracking(); //调用framework WifiTracker 类 activity.invalidateOptionsMenu(); }
WifiEnabler 类的resume() 方法如下：
public void resume(Context context) { mContext = context; // Wi-Fi state is sticky, so just let the receiver update UI mContext.registerReceiver(mReceiver, mIntentFilter); //注册构造函数中添加的三个广播事件 if (!mListeningToOnSwitchChange) { mSwitchBar.addOnSwitchChangeListener(this); mListeningToOnSwitchChange = true; } }
WifiTracker 类的startTracking() 方法如下：
/** * Start tracking wifi networks. * Registers listeners and starts scanning for wifi networks. If this is not called * then forceUpdate() must be called to populate getAccessPoints(). */ public void startTracking() { resumeScanning(); if (!mRegistered) { mContext.registerReceiver(mReceiver, mFilter); //注册构造函数中添加的广播事件 // NetworkCallback objects cannot be reused. http://b/20701525 . mNetworkCallback = new WifiTrackerNetworkCallback(); mConnectivityManager.registerNetworkCallback(mNetworkRequest, mNetworkCallback); } }
WifiEnabler 处理较多的及时WIFI_STATE_CHANGED_ACTION 广播，根据此广播信息更新Switch 的界面。
2、启用WIFI 功能
WifiEnabler 实现了SwitchBar 的onSwitchChangeListener 接口，故用户点击事件将触发WifiEnabler 的onSwitchChanged() 方法：
public void onSwitchChanged(Switch switchView, boolean isChecked) { // Disable tethering if enabling Wifi if (mayDisableTethering(isChecked)) { mWifiManager.setWifiApEnabled(null, false); } }
WifiManager 的setWifiApEnabled() 方法将触发WifiService 开展一系列的动作，在此过程中，WifiManager 会通过发送广播的方法向外界发布一些信息，所以需重点关注广播事件的处理。
WifiTracker 的广播接收对象的处理：
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) || WifiManager.CONFIGURED_NETWORKS_CHANGED_ACTION.equals(action) || WifiManager.LINK_CONFIGURATION_CHANGED_ACTION.equals(action)) { mWorkHandler.sendEmptyMessage(WorkHandler.MSG_UPDATE_ACCESS_POINTS); //发送更新无线网络列表消息 } else if (WifiManager.NETWORK_STATE_CHANGED_ACTION.equals(action)) { NetworkInfo info = (NetworkInfo) intent.getParcelableExtra( WifiManager.EXTRA_NETWORK_INFO); mConnected.set(info.isConnected()); mMainHandler.sendEmptyMessage(MainHandler.MSG_CONNECTED_CHANGED); mWorkHandler.sendEmptyMessage(WorkHandler.MSG_UPDATE_ACCESS_POINTS); mWorkHandler.obtainMessage(WorkHandler.MSG_UPDATE_NETWORK_INFO, info) .sendToTarget(); } } };
WifiEnabler 的广播接收对象的处理：
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(intent.getIntExtra( WifiManager.EXTRA_WIFI_STATE, WifiManager.WIFI_STATE_UNKNOWN)); } 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()); } } };
1) 触发扫描
当WIFI 功能被启用时，将收到WIFI_STATE_CHANGED_ACTION 广播，该广播的处理函数是WifiTracker 的updateWifiState() 方法：
private void updateWifiState(int state) { mWorkHandler.obtainMessage(WorkHandler.MSG_UPDATE_WIFI_STATE, state, 0).sendToTarget(); } //向内部WrokHandler 对象发送消息
MSG_UPDATE_WIFI_STATE 的处理：
case MSG_UPDATE_WIFI_STATE: if (msg.arg1 == 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(); //启动扫描 } } else { mLastInfo = null; mLastNetworkInfo = null; if (mScanner != null) { mScanner.pause(); } } mMainHandler.obtainMessage(MainHandler.MSG_WIFI_STATE_CHANGED, msg.arg1, 0) .sendToTarget(); //向内部MainHandler 对象发送消息 break;
Scanner 也是WifiTracker 内部定义的一个Handler：
class Scanner extends Handler { static final int MSG_SCAN = 0; void resume() { if (!hasMessages(MSG_SCAN)) { sendEmptyMessage(MSG_SCAN); } } @Override public void handleMessage(Message message) { if (message.what != MSG_SCAN) return; if (mWifiManager.startScan()) { //发起扫描 mRetry = 0; } else if (++mRetry >= 3) { //扫描失败 mRetry = 0; if (mContext != null) { Toast.makeText(mContext, R.string.wifi_fail_to_scan, Toast.LENGTH_LONG).show(); } return; } sendEmptyMessageDelayed(0, WIFI_RESCAN_INTERVAL_MS); //每1秒发起一次扫描 } }
2) 更新AP 列表
如果WPAS 扫描完毕，则WifiTracker 将收到SCAN_RESULTS_AVAILABLE_ACTION 广播，发送消息MSG_UPDATE_ACCESS_POINTS，WorkHandler 对此消息的处理如下：
case MSG_UPDATE_ACCESS_POINTS: updateAccessPoints(); break;
继而调用updateAccessPoints() 方法：
private void updateAccessPoints() { final Collection<ScanResult> results = fetchScanResults(); //获取扫描结果 final List<WifiConfiguration> configs = mWifiManager.getConfiguredNetworks(); // Pre-sort accessPoints to speed preference insertion Collections.sort(accessPoints); //创建AP 列表 mMainHandler.sendEmptyMessage(MainHandler.MSG_ACCESS_POINT_CHANGED); //向MainHandler 发送MSG_ACCESS_POINT_CHANGED
3) 加入目标无线网络
从列表中选择加入某个无线网络，处理用户选择AP 事件的方法是WifiSettings 的onPreferenceTreeClick() 方法：
public boolean onPreferenceTreeClick(Preference preference) { if (preference instanceof LongPressAccessPointPreference) { mSelectedAccessPoint = ((LongPressAccessPointPreference) preference).getAccessPoint(); /** Bypass dialog for unsecured, unsaved, and inactive networks */ if (mSelectedAccessPoint.getSecurity() == AccessPoint.SECURITY_NONE && !mSelectedAccessPoint.isSaved() && !mSelectedAccessPoint.isActive()) { //对于没有安全设置的无线网络，直接连接它即可 mSelectedAccessPoint.generateOpenNetworkConfig(); connect(mSelectedAccessPoint.getConfig()); } else if (mSelectedAccessPoint.isSaved()) { showDialog(mSelectedAccessPoint, WifiConfigUiBase.MODE_VIEW); //弹出无线密码输入框 } else { showDialog(mSelectedAccessPoint, WifiConfigUiBase.MODE_CONNECT); } } else if (preference == mAddPreference) { onAddNetworkPressed(); } }
当用户设置完目标无线网络(例如设置密码)后，点击“连接”按钮，将触发WifiSettings 的submit() 方法被调用：
/* package */ void submit(WifiConfigController configController) { final WifiConfiguration config = configController.getConfig(); if (config == null) { ...... } else if (configController.getMode() == WifiConfigUiBase.MODE_MODIFY) { mWifiManager.save(config, mSaveListener); } else { mWifiManager.save(config, mSaveListener); if (mSelectedAccessPoint != null) { // Not an "Add network" connect(config); //连接目标无线网络 } } mWifiTracker.resumeScanning(); }
至此，后续的工作就是等待并处理广播事件，如果一切顺利，将接收一个NETWORK_STATE_CHANGED_ACTION 广播事件以告知手机成功加入目标无线网络。
和WifiManager 交互的几个重要函数以作下面分析重点：
setWifiEnabled()：启用WIFI 功能
startScanActive()：启动AP 扫描
connect()：连接至目标AP