Android Wifi How to scan wireless networks?

Scan for wireless networks in the current area: 

}ckage com.android.wifitester;

import java.util.List;

import android.app.Activity;

import android.content.BroadcastReceiver;

import android.content.Context;

import android.content.Intent;

import android.content.IntentFilter;

import android.net.wifi.ScanResult;

import android.net.wifi.WifiManager;

import android.os.Bundle;

import android.view.Menu;

import android.view.MenuItem;

import android.widget.TextView;

public class WifiTester extends Activity {

  TextView mainText;

  WifiManager mainWifi;

  WifiReceiver receiverWifi;

  List<ScanResult> wifiList;

  StringBuilder sb = new StringBuilder();

 

  public void onCreate(Bundle savedInstanceState) {

   super.onCreate(savedInstanceState);

   setContentView(R.layout.main);

   mainText = (TextView) findViewById(R.id.mainText);

   mainWifi = (WifiManager) getSystemService(Context.WIFI_SERVICE);

   receiverWifi = new WifiReceiver();

   registerReceiver(receiverWifi, new IntentFilter(

      WifiManager.SCAN_RESULTS_AVAILABLE_ACTION));

   mainWifi.startScan();

   mainText.setText("\nStarting Scan...\n");

  }

  public boolean onCreateOptionsMenu(Menu menu) {

    menu.add(0, 0, 0, "Refresh");

    return super.onCreateOptionsMenu(menu);

  }

  public boolean onMenuItemSelected(int featureId, MenuItem item) {

    mainWifi.startScan();

    mainText.setText("Starting Scan");

    return super.onMenuItemSelected(featureId, item);

  }

  protected void onPause() {

    unregisterReceiver(receiverWifi);

    super.onPause();

  }

  protected void onResume() {

    registerReceiver(receiverWifi, new IntentFilter(

       WifiManager.SCAN_RESULTS_AVAILABLE_ACTION));

    super.onResume();

  }

 

  class WifiReceiver extends BroadcastReceiver {

    public void onReceive(Context c, Intent intent) {

    sb = new StringBuilder();

    wifiList = mainWifi.getScanResults();

    for(int i = 0; i < wifiList.size(); i++){

      sb.append(new Integer(i+1).toString() + ".");

      sb.append((wifiList.get(i)).toString());

      sb.append("\n");

    }

    mainText.setText(sb);

    }

  }

}