Android WIFI 详解

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。