duplicate SSID in scanning wifi result - wifi

Question

i'm trying to make an app that can create a list of available wifi access point. here's part of the code i used:
x = new BroadcastReceiver()
{
#Override
public void onReceive(Context c, Intent intent)
{
results = wifi.getScanResults();
size = results.size();
if (results != null) {
for (int i=0; i<size; i++){
ScanResult scanresult = wifi.getScanResults().get(i);
String ssid = scanresult.SSID;
int rssi = scanresult.level;
String rssiString = String.valueOf(rssi);
textStatus.append(ssid + "," + rssiString);
textStatus.append("\n");
}
unregisterReceiver(x); //stops the continuous scan
textState.setText("Scanning complete!");
} else {
unregisterReceiver(x);
textState.setText("Nothing is found. Please make sure you are under any wifi coverage");
}
}
};
both textStatus and textState is a TextView.
i can get this to work but sometimes the result shows duplicate SSID but with different signal level, in a single scan. there might be 3-4 same SSIDs but with different signal level.
is it really different SSIDs and what differs them? can anyone explain?

Answer 1

Are you having several router modems for the same network? For example: A company has a big wireless network with multiple router modems installed in several places so every room has Wifi. If you do that scan you will get a lot of results with the same SSIDs but with different acces points, and thus different signal level.
EDIT:
According to Walt's comment you can also have multiple results despite having only one access point if your modem is dual-band.

Answer 2

use below code to to remove duplicate ssids with highest signal strength
public void onReceive(Context c, Intent intent) {
ArrayList<ScanResult> mItems = new ArrayList<>();
List<ScanResult> results = wifiManager.getScanResults();
wifiListAdapter = new WifiListAdapter(ConnectToInternetActivity.this, mItems);
lv.setAdapter(wifiListAdapter);
int size = results.size();
HashMap<String, Integer> signalStrength = new HashMap<String, Integer>();
try {
for (int i = 0; i < size; i++) {
ScanResult result = results.get(i);
if (!result.SSID.isEmpty()) {
String key = result.SSID + " "
+ result.capabilities;
if (!signalStrength.containsKey(key)) {
signalStrength.put(key, i);
mItems.add(result);
wifiListAdapter.notifyDataSetChanged();
} else {
int position = signalStrength.get(key);
ScanResult updateItem = mItems.get(position);
if (calculateSignalStength(wifiManager, updateItem.level) >
calculateSignalStength(wifiManager, result.level)) {
mItems.set(position, updateItem);
wifiListAdapter.notifyDataSetChanged();
}
}
}
}
} catch (Exception e) {
e.printStackTrace();
}
}

Answer 3

This is my simple Solution please and it is work for me
private void scanWifiListNew() {
wifiManager.startScan();
List<ScanResult> wifiList = wifiManager.getScanResults();
mWiFiList = new ArrayList<>();
for(ScanResult result: wifiList){
checkItemExists(mWiFiList, result);
}
setAdapter(mWiFiList);
}
private void printList(List<ScanResult> list){
for(ScanResult result: list){
int level = WifiManager.calculateSignalLevel(result.level, 100);
System.out.println(result.SSID + " Level is " + level + " out of 100");
}
}
private void checkItemExists(List<ScanResult> newWiFiList, ScanResult resultNew){
int indexToRemove = -1;
if(newWiFiList.size() > 0) {
for (int i = 0; i < newWiFiList.size(); i++) {
ScanResult resultCurrent = newWiFiList.get(i);
if (resultCurrent.SSID.equals(resultNew.SSID)) {
int levelCurrent = WifiManager.calculateSignalLevel(resultCurrent.level, 100);
int levelNew = WifiManager.calculateSignalLevel(resultNew.level, 100);
if (levelNew > levelCurrent) {
indexToRemove = i;
break;
}else indexToRemove = -2;
}
}
if(indexToRemove > -1){
newWiFiList.remove(indexToRemove);
newWiFiList.add(indexToRemove,resultNew);
}else if(indexToRemove == -1)newWiFiList.add(resultNew);
} else newWiFiList.add(resultNew);
}
private void setAdapter(List<ScanResult> list) {
listAdapter = new WifiListAdapter(getActivity().getApplicationContext(), list);
wifiListView.setAdapter(listAdapter);
}