Re: [android-developers] How to scan Access Points and select strongest signal?

Hi,

 

1. Regarding duplicates. Android maintains a list of "known" networks - for each, it stores the SSID, encryption configuration, along with the password, if necessary. Each known network also has a unique numeric ID.

 

You can only connect to networks on this "known" list, because, as you correctly figured out, connecting to a network is done by its id.

 

However, it's not necessary to add the network to this list if it's already been added (by Android or by your application).

 

You can get the list of known networks from the WifiManager:

 

http://developer.android.com/reference/android/net/wifi/WifiManager.html#getConfiguredNetworks()

 

You can match these networks to your live scan results using their SSIDs. If the network is already in the known list, just use its numeric id. If not, you get the numeric ID back from addNetwork().

 

2. Once you have the numeric ID, call enableNetwork(networkId, true) to connect. The second parameter means "disconnect from others", not "forget all other network" as its name might seem to imply.

 

-- Kostya Vasilyev

 

2010/5/13 draffo3@gmail.com <draffo3@gmail.com>

I am currently trying to write a class in Android that will Scan for
access points, calculate which access point has the best signal and
then connect to that access point.


So the application will be able to scan on the move and attach to new
access points on the go.

I have the scanning and calculation of the best signal working.

But when it comes to attaching to the best access point I am having
trouble.

It appears that enableNetwork(netid, othersTrueFalse) is the only
method for attaching to an Access point but this causes problems as
from my Scan Results I am not able to get the id of the access point
with the strongest signal.

This is my code:

---

   public void doWifiScan(){

         scanTask = new TimerTask() {
     public void run() {
         handler.post(new Runnable() {
             public void run() {
                  sResults = wifiManager.scan(getBaseContext());
                  if(sResults!=null)
                  Log.d("TIMER", "sResults count" + sResults.size());
                  ScanResult scan =
wifiManager.calculateBestAP(sResults);
                  wifiManager.addNewAccessPoint(scan);
              }
          });
       }};

       t.schedule(scanTask, 3000, 30000);
   }


---

   public ScanResult calculateBestAP(List<ScanResult> sResults){

                ScanResult bestSignal = null;
                   for (ScanResult result : sResults) {
                     if (bestSignal == null
                         || WifiManager.compareSignalLevel(bestSignal.level,
result.level) < 0)
                       bestSignal = result;
                   }

                   String message = String.format("%s networks found. %s is the
strongest. %s is the bsid",
                           sResults.size(), bestSignal.SSID, bestSignal.BSSID);

                   Log.d("sResult", message);
                   return bestSignal;
       }


---

   public void addNewAccessPoint(ScanResult scanResult){

               WifiConfiguration wc = new WifiConfiguration();
               wc.SSID = '\"' + scanResult.SSID + '\"';
               //wc.preSharedKey  = "\"password\"";
               wc.hiddenSSID = true;
               wc.status = WifiConfiguration.Status.ENABLED;
               wc.allowedGroupCiphers.set(WifiConfiguration.GroupCipher.TKIP);
               wc.allowedGroupCiphers.set(WifiConfiguration.GroupCipher.CCMP);
               wc.allowedKeyManagement.set(WifiConfiguration.KeyMgmt.WPA_PSK);

wc.allowedPairwiseCiphers.set(WifiConfiguration.PairwiseCipher.TKIP);

wc.allowedPairwiseCiphers.set(WifiConfiguration.PairwiseCipher.CCMP);
               wc.allowedProtocols.set(WifiConfiguration.Protocol.RSN);
               int res = mainWifi.addNetwork(wc);
               Log.d("WifiPreference", "add Network returned " + res );
               boolean b = mainWifi.enableNetwork(res, false);
               Log.d("WifiPreference", "enableNetwork returned " + b );

       }


---

When I try to use addNewAccessPoint(ScanResult scanResult) it just
adds another AP to the list in the settings application with the same
name as the one with the best signal, so I end up with loads of
duplicates and not actually attaching to them.

Can anyone point me in the direction of a better solution?

--
You received this message because you are subscribed to the Google
Groups "Android Developers" group.
To post to this group, send email to android-developers@googlegroups.com
To unsubscribe from this group, send email to
android-developers+unsubscribe@googlegroups.com
For more options, visit this group at
http://groups.google.com/group/android-developers?hl=en

--
You received this message because you are subscribed to the Google
Groups "Android Developers" group.
To post to this group, send email to android-developers@googlegroups.com
To unsubscribe from this group, send email to
android-developers+unsubscribe@googlegroups.com
For more options, visit this group at
http://groups.google.com/group/android-developers?hl=en