Android provides WifiManager API to manage all aspects of WIFI connectivity. We can instantiate this class by callinggetSystemService method. Its syntax is given below −

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

In order to scan a list of wireless networks, you also need to register your BroadcastReceiver. It can be registered using registerReceiver method with argument of your receiver class object. Its syntax is given below −

class WifiScanReceiver extends BroadcastReceiver {
   public void onReceive(Context c, Intent intent) {
   }
}
WifiScanReceiver wifiReciever = new WifiScanReceiver();
registerReceiver(wifiReciever, new IntentFilter(WifiManager.SCAN_RESULTS_AVAILABLE_ACTION));  

The wifi scan can be start by calling the startScan method of the WifiManager class. This method returns a list of ScanResult objects. You can access any object by calling the get method of list. Its syntax is given below −

List<ScanResult> wifiScanList = mainWifiObj.getScanResults();
String data = wifiScanList.get(0).toString();

Apart from just Scanning, you can have more control over your WIFI by using the methods defined in WifiManager class. They are listed as follows −

Sr.No	Method & Description
1	addNetwork(WifiConfiguration config) This method add a new network description to the set of configured networks.
2	createWifiLock(String tag) This method creates a new WifiLock.
3	disconnect() This method disassociate from the currently active access point.
4	enableNetwork(int netId, boolean disableOthers) This method allow a previously configured network to be associated with.
5	getWifiState() This method gets the Wi-Fi enabled state
6	isWifiEnabled() This method return whether Wi-Fi is enabled or disabled.
7	setWifiEnabled(boolean enabled) This method enable or disable Wi-Fi.
8	updateNetwork(WifiConfiguration config) This method update the network description of an existing configured network.

Example

Here is an example demonstrating the use of WIFI. It creates a basic application that scans a list of wireless networks and populate them in a list view.

To experiment with this example, you need to run this on an actual device on which wifi is turned on.

Steps	Description
1	You will use Android studio to create an Android application under a package com.example.sairamkrishna.myapplication. While creating this project, make sure you Target SDK and Compile With at the latest version of Android SDK to use higher levels of APIs.
2	Modify src/MainActivity.java file to add WebView code.
3	Modify the res/layout/activity_main to add respective XML components
4	Modify the AndroidManifest.xml to add the necessary permissions
5	Run the application and choose a running android device and install the application on it and verify the results.

Following is the content of the modified main activity file src/MainActivity.java.

package com.example.sairamkrishna.myapplication;

import android.app.Activity;
import android.content.BroadcastReceiver;

import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;

import android.graphics.Color;
import android.net.wifi.ScanResult;
import android.net.wifi.WifiManager;
import android.os.Bundle;

import android.view.Menu;
import android.view.MenuItem;
import android.view.View;

import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;

import java.util.List;

public class MainActivity extends Activity  {
   ListView lv;
   WifiManager wifi;
   String wifis[];
   WifiScanReceiver wifiReciever;
   
   @Override
   protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
      lv=(ListView)findViewById(R.id.listView);
      
      wifi=(WifiManager)getSystemService(Context.WIFI_SERVICE);
      wifiReciever = new WifiScanReceiver();
      wifi.startScan();
   }
   
   protected void onPause() {
      unregisterReceiver(wifiReciever);
      super.onPause();
   }
   
   protected void onResume() {
      registerReceiver(wifiReciever, new IntentFilter(WifiManager.SCAN_RESULTS_AVAILABLE_ACTION));
      super.onResume();
   }
   
   @Override
   public boolean onCreateOptionsMenu(Menu menu) {
      // Inflate the menu; this adds items to the action bar if it is present.
      getMenuInflater().inflate(R.menu.menu_main, menu);
      return true;
   }
   
   @Override
   public boolean onOptionsItemSelected(MenuItem item) {
      // Handle action bar item clicks here. The action bar will
      // automatically handle clicks on the Home/Up button, so long
      // as you specify a parent activity in AndroidManifest.xml.
      
      int id = item.getItemId();
      
      //noinspection SimplifiableIfStatement
      if (id == R.id.action_settings) {
         return true;
      }
      return super.onOptionsItemSelected(item);
   }
   
   private class WifiScanReceiver extends BroadcastReceiver{
      public void onReceive(Context c, Intent intent) {
         List<ScanResult> wifiScanList = wifi.getScanResults();
         wifis = new String[wifiScanList.size()];
         
         for(int i = 0; i < wifiScanList.size(); i++){
            wifis[i] = ((wifiScanList.get(i)).toString());
         }
         lv.setAdapter(new ArrayAdapter<String>(getApplicationContext(),android.R.layout.simple_list_item_1,wifis));
      }
   }
}

Following is the modified content of the xmlres/layout/activity_main.xml.

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
   xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
   android:layout_height="match_parent" android:paddingLeft="@dimen/activity_horizontal_margin"
   android:paddingRight="@dimen/activity_horizontal_margin"
   android:paddingTop="@dimen/activity_vertical_margin"
   android:paddingBottom="@dimen/activity_vertical_margin" tools:context=".MainActivity">
   
   <TextView android:text="Wifi" android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:id="@+id/textview"
      android:textSize="35dp"
      android:layout_alignParentTop="true"
      android:layout_centerHorizontal="true" />
      
   <TextView
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text="Tutorials point"
      android:id="@+id/textView"
      android:layout_below="@+id/textview"
      android:layout_centerHorizontal="true"
      android:textColor="#ff7aff24"
      android:textSize="35dp" />
      
   <mageView
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:id="@+id/imageView"
      android:src="@drawable/abc"
      android:layout_below="@+id/textView"
      android:layout_centerHorizontal="true" />
      
   <ListView
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:id="@+id/listView"
      android:layout_below="@+id/imageView"
      android:layout_alignParentLeft="true"
      android:layout_alignParentStart="true"
      android:background="#fff5d376" />

</RelativeLayout>

Following is the content of AndroidManifest.xml file.

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
   package="com.example.sairamkrishna.myapplication" >
   <uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
   <uses-permission android:name="android.permission.CHANGE_WIFI_STATE" />
   
   <application
      android:allowBackup="true"
      android:icon="@mipmap/ic_launcher"
      android:label="@string/app_name"
      android:theme="@style/AppTheme" >
      
      <activity
         android:name=".MainActivity"
         android:label="@string/app_name" >
         
         <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
         </intent-filter>
         
      </activity>
      
   </application>
</manifest>

Ref : http://www.tutorialspoint.com/android/android_wi_fi.htm