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