СПИСОК WIFI НЕ НАЙДЕН

Question

Не могу получить список wifi.Почему не работает?

Я использую приведенный ниже код, но он не работает.

      receiverWifi = new WifiReceiver();
        registerReceiver(receiverWifi, new IntentFilter(
                WifiManager.SCAN_RESULTS_AVAILABLE_ACTION));
        wifiManager.startScan();

Эта функция запуска списка Wi-Fi для использования BroadcastReceiver () ...

public class MainActivity extends AppCompatActivity {
    private static final String TAG = "MainActivity";

    // Intent request codes
    private final static int PERMISSIONS_REQUEST_CODE = 100;
    Handler handler;
    Button wifisetting_btn;
    TextView wifi_ssid;
    EditText send_data;
    Button send_btn;

    OutputStream os;
    Socket socket;
    WifiManager wifiManager;


    Button wifi_scan;
    ListView listViwProvider;

    WifiReceiver receiverWifi;
    List<ScanResult> wifiList;
    List<String> listOfProvider;
    ListAdapter adapter;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);    


        send_btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                netthread thread = new netthread();
                thread.start();
                String stringdata="1234568"+send_data.getText().toString();
                           }
        });

             wifi_scan.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                scaning();
            }
        });

        listViwProvider.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view,
                                    int position, long id) {
                ImportDialog action = new ImportDialog(MainActivity.this, (wifiList.get(position)).toString());
                action.showDialog();
            }
        });
    }

    private void scaning() {
        receiverWifi = new WifiReceiver();
        registerReceiver(receiverWifi, new IntentFilter(
                WifiManager.SCAN_RESULTS_AVAILABLE_ACTION));
        wifiManager.startScan();

    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        try{
            unregisterReceiver(receiverWifi);
            unregisterReceiver(mReceiver);
        }catch(IllegalArgumentException e){}
    }

    class WifiReceiver extends BroadcastReceiver {

        public void onReceive(Context c, Intent intent) {
            wifiList = wifiManager.getScanResults();
            Collections.sort(wifiList, new Comparator<ScanResult>() {
                @Override
                public int compare(ScanResult lhs, ScanResult rhs) {
                    return (lhs.level > rhs.level ? -1
                            : (lhs.level == rhs.level ? 0 : 1));
                }
            });
            listOfProvider.clear();
                      String providerName;
            for (int i = 0; i < wifiList.size(); i++) {
                providerName = (wifiList.get(i).SSID).toString()
                        +"\n"+(wifiList.get(i).BSSID).toString();
                listOfProvider.add(providerName);
                           }
            adapter = new ListAdapter(MainActivity.this, listOfProvider);
            listViwProvider.setAdapter(adapter);
            adapter.notifyDataSetChanged();
        }
    }

}