settings里的 wifi流程

Wifi启动流程

（1）使能Wifi

要想使用Wifi模块，必须首先使能Wifi，当你第一次按下Wifi使能按钮时，WirelessSettings会实例化一个WifiEnabler对象，实例化代码如下：

packages/apps/settings/src/com/android/settings/WirelessSettings.java

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

……

CheckBoxPreferencewifi = (CheckBoxPreference) findPreference(KEY_TOGGLE_WIFI);

mWifiEnabler= new WifiEnabler(this, wifi);

……

}

WifiEnabler类的定义大致如下，它实现了一个监听接口，当WifiEnabler对象被初始化后，它监听到你按键的动作，会调用响应函数 onPreferenceChange（），这个函数会调用WifiManager的setWifiEnabled（）函数。

public class WifiEnabler implementsPreference.OnPreferenceChangeListener {

……

public boolean onPreferenceChange(Preference preference,Object value) {

booleanenable = (Boolean) value;

……

if (mWifiManager.setWifiEnabled(enable) ) {

mCheckBox.setEnabled(false);

……

}

……

}

我们都知道Wifimanager只是个服务代理，所以它会调用WifiService的setWifiEnabled（）函数，而这个函数会调用 sendEnableMessage（）函数，了解android消息处理机制的都知道，这个函数最终会给自己发送一个 MESSAGE_ENABLE_WIFI的消息，被WifiService里面定义的handlermessage()函数处理，会调用 setWifiEnabledBlocking（）函数。下面是调用流程：

mWifiEnabler.onpreferencechange()=>mWifiManage.setWifienabled()=>mWifiService.setWifiEnabled()=>mWifiService.sendEnableMessage()=>mWifiService.handleMessage()=>mWifiService.setWifiEnabledBlocking().

在setWifiEnabledBlocking()函数中主要做如下工作：加载Wifi驱动，启动wpa_supplicant，注册广播接收器，启动WifiThread监听线程。代码如下：

……

if (enable) {

if (!mWifiStateTracker.loadDriver()) {

Slog.e(TAG, "Failed toload Wi-Fi driver.");

setWifiEnabledState(WIFI_STATE_UNKNOWN, uid);

return false;

}

if (!mWifiStateTracker.startSupplicant()) {

mWifiStateTracker.unloadDriver();

Slog.e(TAG, "Failed tostart supplicant daemon.");

setWifiEnabledState(WIFI_STATE_UNKNOWN, uid);

return false;

}

registerForBroadcasts();

mWifiStateTracker.startEventLoop();

……

至此，Wifi使能结束，自动进入扫描阶段。

(2) 扫描AP

当驱动加载成功后，如果配置文件的AP_SCAN = 1，扫描会自动开始，WifiMonitor将会从supplicant收到一个消息EVENT_DRIVER_STATE_CHANGED，调用 handleDriverEvent（），然后调用mWifiStateTracker.notifyDriverStarted()，该函数向消息队列添加EVENT_DRIVER_STATE_CHANGED，handlermessage()函数处理消息时调用scan()函数，并通过 WifiNative将扫描命令发送到wpa_supplicant。

Frameworks/base/wifi/java/android/net/wifi/WifiMonitor.java

private void handleDriverEvent(Stringstate) {

if (state == null) {

return;

}

if (state.equals("STOPPED")) {

mWifiStateTracker.notifyDriverStopped();

} else if (state.equals("STARTED")) {

mWifiStateTracker.notifyDriverStarted();

} else if (state.equals("HANGED")) {

mWifiStateTracker.notifyDriverHung();

}

}

Frameworks/base/wifi/java/android/net/wifi/WifiStateTracker.java

case EVENT_DRIVER_STATE_CHANGED:

switch(msg.arg1) {

case DRIVER_STARTED :

/**

*Set the number of allowed radio channels according

*to the system setting, since it gets reset by the

*driver upon changing to the STARTED state.

*/

setNumAllowedChannels();

synchronized (this) {

if (mRunState == RUN_STATE_STARTING) {

mRunState = RUN_STATE_RUNNING;

if (!mIsScanOnly) {

reconnectCommand();

} else {

// In somesituations, supplicant needs to be kickstarted to

// start thebackground scanning

scan(true);

}

}

}

break;

上面是启动Wifi时，自动进行的AP的扫描，用户当然也可以手动扫描AP，这部分实现在WifiService里面，WifiService通过startScan()接口函数发送扫描命令到supplicant。

Frameworks/base/wifi/java/android/net/wifi/WifiStateTracker.java

public boolean startScan(booleanforceActive) {

enforceChangePermission();

switch (mWifiStateTracker.getSupplicantState()) {

case DISCONNECTED:

case INACTIVE:

case SCANNING:

case DORMANT:

break;

default:

mWifiStateTracker.setScanResultHandling(

WifiStateTracker.SUPPL_SCAN_HANDLING_LIST_ONLY);

break;

}

return mWifiStateTracker.scan(forceActive);

}

然后下面的流程同上面的自动扫描，我们来分析一下手动扫描从哪里开始的。我们应该知道手动扫描是通过菜单键的扫描键来响应的，而响应该动作的应该是 WifiSettings类中Scanner类的handlerMessage()函数，它调用WifiManager的 startScanActive()，这才调用WifiService的startScan()。

packages/apps/Settings/src/com/android/settings/wifiwifisettings.java

public boolean onCreateOptionsMenu(Menu menu) {

menu.add(Menu.NONE, MENU_ID_SCAN, 0, R.string.wifi_menu_scan)

.setIcon(R.drawable.ic_menu_scan_network);

menu.add(Menu.NONE, MENU_ID_ADVANCED, 0, R.string.wifi_menu_advanced)

.setIcon(android.R.drawable.ic_menu_manage);

return super.onCreateOptionsMenu(menu);

}

当按下菜单键时，WifiSettings就会调用这个函数绘制菜单。如果选择扫描按钮，WifiSettings会调用onOptionsItemSelected()。

packages/apps/Settings/src/com/android/settings/wifiwifisettings.java

public booleanonOptionsItemSelected(MenuItem item) {

switch (item.getItemId()) {

case MENU_ID_SCAN:

if(mWifiManager.isWifiEnabled()) {

mScanner.resume();

}

return true;

case MENU_ID_ADVANCED:

startActivity(new Intent(this,AdvancedSettings.class));

return true;

}

return super.onOptionsItemSelected(item);

}

private class Scanner extends Handler {

private int mRetry = 0;

void resume() {

if (!hasMessages(0) ) {

sendEmptyMessage(0);

}

}

void pause() {

mRetry = 0;

mAccessPoints.setProgress(false);

removeMessages(0);

}

@Override

public void handleMessage(Message message) {

if (mWifiManager.startScanActive() ){

mRetry = 0;

} else if (++mRetry >= 3) {

mRetry = 0;

Toast.makeText(WifiSettings.this, R.string.wifi_fail_to_scan,

Toast.LENGTH_LONG).show();

return;

}

mAccessPoints.setProgress(mRetry != 0);

sendEmptyMessageDelayed(0, 6000);

}

}

这里的mWifiManager.startScanActive()就会调用WifiService里的startScan（）函数，下面的流程和上面的一样，这里不赘述。

当supplicant完成了这个扫描命令后，它会发送一个消息给上层，提醒他们扫描已经完成，WifiMonitor会接收到这消息，然后再发送给WifiStateTracker。

Frameworks/base/wifi/java/android/net/wifi/WifiMonitor.java

void handleEvent(int event, String remainder) {

switch (event) {

caseDISCONNECTED:

handleNetworkStateChange(NetworkInfo.DetailedState.DISCONNECTED,remainder);

break;

case CONNECTED:

handleNetworkStateChange(NetworkInfo.DetailedState.CONNECTED,remainder);

break;

case SCAN_RESULTS:

mWifiStateTracker.notifyScanResultsAvailable();

break;

case UNKNOWN:

break;

}

}

WifiStateTracker将会广播SCAN_RESULTS_AVAILABLE_ACTION消息：

Frameworks/base/wifi/java/android/net/wifi/WifiStateTracker.java

public voidhandleMessage(Message msg) {

Intent intent;

……

case EVENT_SCAN_RESULTS_AVAILABLE:

if(ActivityManagerNative.isSystemReady()) {

mContext.sendBroadcast(new Intent(WifiManager.SCAN_RESULTS_AVAILABLE_ACTION));

}

sendScanResultsAvailable();

/**

* On receiving the first scanresults after connecting to

* the supplicant, switch scanmode over to passive.

*/

setScanMode(false);

break;

……

｝

由于WifiSettings类注册了intent，能够处理SCAN_RESULTS_AVAILABLE_ACTION消息，它会调用handleEvent()，调用流程如下所示。

WifiSettings.handleEvent() =>WifiSettings.updateAccessPoints() => mWifiManager.getScanResults() => mService.getScanResults()=> mWifiStateTracker.scanResults() => WifiNative.scanResultsCommand()……

将获取AP列表的命令发送到supplicant，然后supplicant通过Socket发送扫描结果，由上层接收并显示。这和前面的消息获取流程基本相同。

(3)配置，连接AP

当用户选择一个活跃的AP时，WifiSettings响应打开一个对话框来配置AP，比如加密方法和连接AP的验证模式。配置好AP后，WifiService添加或更新网络连接到特定的AP。

packages/apps/settings/src/com/android/settings/wifi/WifiSetttings.java

public booleanonPreferenceTreeClick(PreferenceScreen screen, Preference preference) {

if (preference instanceof AccessPoint) {

mSelected = (AccessPoint) preference;

showDialog(mSelected, false);

} else if (preference == mAddNetwork) {

mSelected = null;

showDialog(null, true);

} else if (preference == mNotifyOpenNetworks) {

Secure.putInt(getContentResolver(),

Secure.WIFI_NETWORKS_AVAILABLE_NOTIFICATION_ON,

mNotifyOpenNetworks.isChecked() ? 1 : 0);

} else {

return super.onPreferenceTreeClick(screen, preference);

}

return true;

}

配置好以后，当按下“Connect Press”时，WifiSettings通过发送LIST_NETWORK命令到supplicant来检查该网络是否配置。如果没有该网络或没有配置它，WifiService调用addorUpdateNetwork（）函数来添加或更新网络，然后发送命令给supplicant，连接到这个网络。下面是从响应连接按钮到WifiService发送连接命令的代码：

packages/apps/settings/src/com/android/settings/wifi/WifiSetttings.java

public void onClick(DialogInterfacedialogInterface, int button) {

if (button == WifiDialog.BUTTON_FORGET && mSelected != null) {

forget(mSelected.networkId);

} else if (button == WifiDialog.BUTTON_SUBMIT && mDialog !=null) {

WifiConfiguration config = mDialog.getConfig();

if (config == null) {

if (mSelected != null&& !requireKeyStore(mSelected.getConfig())) {

connect(mSelected.networkId);

}

} else if (config.networkId != -1) {

if (mSelected != null) {

mWifiManager.updateNetwork(config);

saveNetworks();

}

} else {

int networkId =mWifiManager.addNetwork(config);

if (networkId != -1) {

mWifiManager.enableNetwork(networkId, false);

config.networkId =networkId;

if (mDialog.edit || requireKeyStore(config)){

saveNetworks();

} else {

connect(networkId);

}

}

}

}

}

Frameworks\base\wifi\java\android\net\wifi\WifiManager.java

public intupdateNetwork(WifiConfiguration config) {

if(config == null || config.networkId < 0) {

return -1;

}

return addOrUpdateNetwork(config);

}

private intaddOrUpdateNetwork(WifiConfiguration config) {

try {

return mService.addOrUpdateNetwork(config) ;

} catch (RemoteException e) {

return -1;

}

}

WifiService.addOrUpdateNetwork()通过调用mWifiStateTracker.setNetworkVariable()将连接命令发送到Wpa_supplicant。

（4）获取IP地址

当连接到supplicant后，WifiMonitor就会通知WifiStateTracker。

Frameworks/base/wifi/java/android/net/wifi/WifiMonitor.java

Public void Run(){

if (connectToSupplicant()) {

// Send a message indicatingthat it is now possible to send commands

// to the supplicant

mWifiStateTracker.notifySupplicantConnection();

} else {

mWifiStateTracker.notifySupplicantLost();

return;

}

……

}

WifiStateTracker发送EVENT_SUPPLICANT_CONNECTION消息到消息队列，这个消息有自己的handlermessage()函数处理，它会启动一个DHCP线程，而这个线程会一直等待一个消息事件，来启动DHCP协议分配IP地址。

frameworks/base/wifi/java/android/net/wifi/WifiStateTracker.java

void notifySupplicantConnection() {

sendEmptyMessage(EVENT_SUPPLICANT_CONNECTION);

}

public void handleMessage(Message msg) {

Intent intent;

switch (msg.what) {

case EVENT_SUPPLICANT_CONNECTION:

……

HandlerThread dhcpThread = newHandlerThread("DHCP Handler Thread");

dhcpThread.start();

mDhcpTarget = newDhcpHandler(dhcpThread.getLooper(), this);

……

……

}

当Wpa_supplicant连接到AP后，它会发送一个消息给上层来通知连接成功，WifiMonitor会接受到这个消息并上报给WifiStateTracker。

Frameworks/base/wifi/java/android/net/wifi/WifiMonitor.java

void handleEvent(int event, String remainder) {

switch (event) {

case DISCONNECTED:

handleNetworkStateChange(NetworkInfo.DetailedState.DISCONNECTED,remainder);

break;

case CONNECTED:

handleNetworkStateChange(NetworkInfo.DetailedState.CONNECTED,remainder);

break;

……

}

private voidhandleNetworkStateChange(NetworkInfo.DetailedState newState, String data) {

StringBSSID = null;

intnetworkId = -1;

if(newState == NetworkInfo.DetailedState.CONNECTED) {

Matcher match = mConnectedEventPattern.matcher(data);

if(!match.find()) {

if (Config.LOGD) Log.d(TAG, "Could not find BSSID in CONNECTEDevent string");

}else {

BSSID = match.group(1);

try {

networkId = Integer.parseInt(match.group(2));

} catch (NumberFormatException e) {

networkId = -1;

}

}

}

mWifiStateTracker.notifyStateChange(newState,BSSID, networkId);

}

void notifyStateChange(DetailedState newState, StringBSSID, int networkId) {

Messagemsg = Message.obtain(

this, EVENT_NETWORK_STATE_CHANGED,

newNetworkStateChangeResult(newState, BSSID, networkId));

msg.sendToTarget();

}

caseEVENT_NETWORK_STATE_CHANGED:

……

configureInterface();

……

private void configureInterface() {

checkPollTimer();

mLastSignalLevel = -1;

if(!mUseStaticIp) { //使用DHCP线程动态IP

if(!mHaveIpAddress && !mObtainingIpAddress) {

mObtainingIpAddress = true;

//发送启动DHCP线程获取IP

mDhcpTarget.sendEmptyMessage(EVENT_DHCP_START);

}

} else { //使用静态IP，IP信息从mDhcpInfo中获取

intevent;

if(NetworkUtils.configureInterface(mInterfaceName, mDhcpInfo)) {

mHaveIpAddress = true;

event = EVENT_INTERFACE_CONFIGURATION_SUCCEEDED;

if (LOCAL_LOGD) Log.v(TAG, "Static IP configurationsucceeded");

}else {

mHaveIpAddress = false;

event = EVENT_INTERFACE_CONFIGURATION_FAILED;

if (LOCAL_LOGD) Log.v(TAG, "Static IP configuration failed");

}

sendEmptyMessage(event); //发送IP获得成功消息事件

}

}

DhcpThread获取EVENT_DHCP_START消息事件后，调用handleMessage（）函数，启动DHCP获取IP地址的服务。

public void handleMessage(Message msg) {

intevent;

switch (msg.what) {

case EVENT_DHCP_START:

……

Log.d(TAG, "DhcpHandler: DHCP requeststarted");

//启动一个DHCPclient的精灵进程，为mInterfaceName请求分配一个IP地//址

if (NetworkUtils.runDhcp(mInterfaceName, mDhcpInfo) ) {

event= EVENT_INTERFACE_CONFIGURATION_SUCCEEDED;

if(LOCAL_LOGD) Log.v(TAG, "DhcpHandler: DHCP request succeeded");

} else {

event= EVENT_INTERFACE_CONFIGURATION_FAILED;

Log.i(TAG,"DhcpHandler: DHCP request failed: " +

NetworkUtils.getDhcpError());

}

……

}

这里调用了一个NetworkUtils.runDhcp（）函数，NetworkUtils类是一个网络服务的辅助类，它主要定义了一些本地接口，这些接口会通过他们的JNI层android_net_NetUtils.cpp文件和DHCP client通信，并获取IP地址。

至此，IP地址获取完毕，Wifi启动流程结束。