Android WIFI 详解

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