Android WIFI 详解

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) {