上文講到WIFI的啓動流程，當然接着便掃描熱點（AP），然後顯示掃描到的AP、配置AP（填寫IP地址等信息）、連接AP、獲取IP地址、最後就是想要的上網咯！
一、掃描熱點（AP）
上文啓動WIFI成功後：// Success!
setWifiEnabledState(eventualWifiState, uid);
private void setWifiEnabledState(int wifiState, int uid) {
// Broadcast
final Intent intent = new Intent(WifiManager.WIFI_STATE_CHANGED_ACTION);
}
當使能成功後，會廣播發送WIFI_STATE_CHANGED_ACTION 這個Intent 通知外界WIFI已經成功使能了。WifiLayer 創建的時候就會向Android 註冊接收WIFI_STATE_CHANGED_ACTION，因此它會收到該Intent，從而開始掃描。
WifiSetting.java:
protected void onCreate(Bundle savedInstanceState) {
mWifiLayer.onCreate();
}
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
WifiLayer.java:
public void onCreate() {
mWifiManager = (WifiManager) mContext.getSystemService(Context.WIFI_SERVICE);
mIntentFilter = new IntentFilter();
mIntentFilter.addAction(WifiManager.NETWORK_STATE_CHANGED_ACTION);
mIntentFilter.addAction(WifiManager.SCAN_RESULTS_AVAILABLE_ACTION);
mIntentFilter.addAction(WifiManager.WIFI_STATE_CHANGED_ACTION);
}
public void onResume() {
mContext.registerReceiver(mReceiver, mIntentFilter);
if (isWifiEnabled()) {
// Kick start the continual scan
queueContinuousScan();
}
}
以上就是WifiLayer.java註冊接收的部分事件。接收部分事件處理有：
private BroadcastReceiver mReceiver = new BroadcastReceiver() {
private BroadcastReceiver mReceiver = new BroadcastReceiver() {
public void onReceive(Context context, Intent intent) {
final String action = intent.getAction();
if (action.equals(WifiManager.NETWORK_STATE_CHANGED_ACTION)) {
handleNetworkStateChanged(
(NetworkInfo) intent.getParcelableExtra(WifiManager.EXTRA_NETWORK_INFO),
intent.getStringExtra(WifiManager.EXTRA_BSSID));
} else if (action.equals(WifiManager.SCAN_RESULTS_AVAILABLE_ACTION)) {
handleScanResultsAvailable();
} ……
else if (action.equals(WifiManager.WIFI_STATE_CHANGED_ACTION)) {
handleWifiStateChanged(intent.getIntExtra(WifiManager.EXTRA_WIFI_STATE,
WifiManager.WIFI_STATE_UNKNOWN));
}
}
};
從可接受的事件看，當WIFI_STATE_CHANGED_ACTION時，對應的處理函數有：
handleWifiStateChanged(intent.getIntExtra(WifiManager.EXTRA_WIFI_STATE,
WifiManager.WIFI_STATE_UNKNOWN));
private void handleWifiStateChanged(int wifiState) {
attemptScan();
…………
}
public void attemptScan() {
if (!mWifiManager.startScanActive()) {
postAttemptScan();
}
}
WifiManager.java:
public boolean startScanActive() {
return mService.startScan(true);
}
-------AIDL-------------------------------------------------------------------------------------------------------------------------------------------------------------------------
WifiService.java:
public boolean startScan(boolean forceActive) {
…………
return WifiNative.scanCommand(forceActive);
}
---------JNI---------------------------------------------------------------------------------------------------------------------------------------------------------------------------
android_net_wifi_wifi.cpp:
{ "scanCommand", "(Z)Z", (void*) android_net_wifi_scanCommand },
static jboolean android_net_wifi_scanCommand(JNIEnv* env, jobject clazz, jboolean forceActive)
{
…………
result = doBooleanCommand("SCAN", "OK");
}
static jboolean doBooleanCommand(const char *cmd, const char *expect)
{
if (doCommand(cmd, reply, sizeof(reply)) != 0) {
return (jboolean)JNI_FALSE;
}
}
static int doCommand(const char *cmd, char *replybuf, int replybuflen)
{
if (::wifi_command(cmd, replybuf, &reply_len) != 0)
return -1;
…………
}
-------HAL------------------------------------------------------------------------------------------------------------------------------------------------------------------------
wifi.c:
int wifi_command(const char *command, char *reply, size_t *reply_len)
{
return wifi_send_command(ctrl_conn, command, reply, reply_len);
}
int wifi_send_command(struct wpa_ctrl *ctrl, const char *cmd, char *reply, size_t *reply_len)
{
ret = wpa_ctrl_request(ctrl, cmd, strlen(cmd), reply, reply_len, NULL);
…………
}
wpa_ctrl.c:
int wpa_ctrl_request()在wpa_ctrl.c中其實就是執行SCAN命令。
二、顯示掃描的AP
當掃描成後，WifiMonitor 中的MonitorThread 會被執行來出來這個事件：
void handleEvent(int event, String remainder) {
switch (event) {
case SCAN_RESULTS:
mWifiStateTracker.notifyScanResultsAvailable();
->sendEmptyMessage(EVENT_SCAN_RESULTS_AVAILABLE);
break;
}
WifiStateTracker.java
public void handleMessage(Message msg) {
switch (msg.what) {
case EVENT_SCAN_RESULTS_AVAILABLE:
if (ActivityManagerNative.isSystemReady()) {
mContext.sendBroadcast(new Intent(WifiManager.SCAN_RESULTS_AVAILABLE_ACTION));
}
}
WifiLayer註冊接收SCAN_RESULTS_AVAILABLE_ACTION這個Intent：
private BroadcastReceiver mReceiver = new BroadcastReceiver() {
@Override
public void onReceive(Context context, Intent intent) {
else if (action.equals(WifiManager.SCAN_RESULTS_AVAILABLE_ACTION))
{
handleScanResultsAvailable();
}
handleScanResultsAvailable();
-> list = mWifiManager.getScanResults();
-> mCallback.onAccessPointSetChanged(ap, true);
handleScanResultsAvailable()中首先會去拿到SCAN的結果（最終是往wpa_supplicant中發送SCAN_RESULT命令並讀取返回值來實現的），對每一個掃描返回的AP，WifiLayer會回調WifiSetting的onAccessPointSetChanged函數，從而最終把該AP加到GUI顯示列表中。
三、配置AP
當用戶在 WifiSettings 界面上選擇了一個AP 後，會顯示配置AP 參數的一個對話框：
public boolean onPreferenceTreeClick()
->showAccessPointDialog(state, AccessPointDialog.MODE_INFO);
->AccessPointDialog dialog =
new AccessPointDialog(this, mWifiLayer);
showDialog(dialog);
當用戶在AccessPointDialog中選擇好加密方式和輸入密鑰之後，再點擊連接按鈕，Android就會去連接這個AP。
四、連接AP
在AccessPointDialog.java中點擊連接後會執行：
public void onClick(DialogInterface dialog, int which) {
handleConnect();
-> mWifiLayer.connectToNetwork(mState);
-> // Need WifiConfiguration for the AP
WifiConfiguration config = findConfiguredNetwork(state);
config = addConfiguration(state, 0);
managerEnableNetwork(state, false)
->mWifiManager.enableNetwork()
->mService.enalbeNetwork()
->WifiNative.enableNetworkCommand()
接下去就JNI { "enableNetworkCommand", "(IZ)Z", (void*) android_net_wifi_enableNetworkCommand },最終就是向wpa_supplicant發送連接命令
五、獲取IP地址
當wpa_supplicant成功連接上AP之後,它會向控制通道發送事件通知連接上AP了,從而wifi_wait_for_event函數會接收到該事件，由此WifiMonitor中的MonitorThread會被執行來出來這個事件:
void handleEvent(int event, String remainder) {
switch (event) {
case CONNECTED:
handleNetworkStateChange();
-> mWifiStateTracker.notifyStateChange(newState, BSSID, networkId);
->msg.sendToTarget();
break;
}
WifiStateTracker.java
public void handleMessage(Message msg) {
switch (msg.what) {
case EVENT_NETWORK_STATE_CHANGED:
sendNetworkStateChangeBroadcast(mWifiInfo.getBSSID());
}
}
WifiStateTracker中註冊的對Wifi相關數據庫的觀察者if(changed) 則啓動：
private void configureInterface()
-> mDhcpTarget.sendEmptyMessage();
private class DhcpHandler extends Handler
handleMessage()
->switch (msg.what) {
case EVENT_DHCP_START:
Target.sendEmptyMessage(event);
DhcpHandler會發送EVENT_DHCP_START消息啓動DHCP去獲取IP地址，當DHCP拿到IP地址之後，會發送EVENT_INTERFACE_CONFIGURATION_SUCCEEDED的消息，然後WifiStateTacker中的handleMessage會處理這樣的消息
case EVENT_INTERFACE_CONFIGURATION_SUCCEEDED:
sendNetworkStateChangeBroadcast(mWifiInfo.getBSSID());
-> Intent intent = new Intent(WifiManager.NETWORK_STATE_CHANGED_ACTION);
-> mContext.sendStickyBroadcast(intent);
這次帶上完整的IP地址信息。WifiLayer中註冊了此Intent的接受者，會調用handleNetworkStateChanged進行處理。最後就可以自由的上網了
