How to use BroadcastReceiver in Android?

This example demonstrates how do I use BroadcastReceiver in android.
Step 1 − Create a new project in Android Studio, go to File ⇒ New Project and fill all required details to create a new project.
Step 2 − Add the following code to res/layout/activity_main.xml.
<?xml version="1.0" encoding="utf-8"?>
<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"
   tools:context=".MainActivity">
   <Switch
      android:id="@+id/wifiSwitch"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_centerInParent="true"/>
</RelativeLayout>
Step 3 − Add the following code to src/MainActivity.java
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.net.wifi.WifiManager;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.CompoundButton;
import android.widget.Switch;
import android.widget.Toast;
public class MainActivity extends AppCompatActivity {
   Switch wifiSwitch;
   WifiManager wifiManager;
   @Override
   protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
      wifiSwitch = findViewById(R.id.wifiSwitch);
      wifiManager = (WifiManager) getApplicationContext().getSystemService(Context.WIFI_SERVICE);
      wifiSwitch.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
         @Override
         public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
            if (isChecked) {
               wifiManager.setWifiEnabled(true);
               wifiSwitch.setText("WiFi is ON");
            } else {
               wifiManager.setWifiEnabled(false);
               wifiSwitch.setText("WiFi is OFF");
            }
         }
      });
   }
   @Override
   protected void onStart() {
      super.onStart();
      IntentFilter intentFilter = new IntentFilter(WifiManager.WIFI_STATE_CHANGED_ACTION);
      registerReceiver(wifiStateReceiver, intentFilter);
   }
   @Override
   protected void onStop() {
      super.onStop();
      unregisterReceiver(wifiStateReceiver);
   }
   private BroadcastReceiver wifiStateReceiver = new BroadcastReceiver() {
      @Override
      public void onReceive(Context context, Intent intent) {
         int wifiStateExtra = intent.getIntExtra(WifiManager.EXTRA_WIFI_STATE, WifiManager.WIFI_STATE_UNKNOWN);
         switch (wifiStateExtra) {
            case WifiManager.WIFI_STATE_ENABLED:
               wifiSwitch.setChecked(true);
               wifiSwitch.setText("WiFi is ON");
               Toast.makeText(MainActivity.this, "Wifi is On", Toast.LENGTH_SHORT).show();
               break;
            case WifiManager.WIFI_STATE_DISABLED:
               wifiSwitch.setChecked(false);
               wifiSwitch.setText("WiFi is OFF");
               Toast.makeText(MainActivity.this, "Wifi is Off", Toast.LENGTH_SHORT).show();
               break;
         }
      }
   };
}
Step 4 − Add the following code to androidManifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="app.com.sample">
   <uses-permission android:name="android.permission.CHANGE_WIFI_STATE" />
   <uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
   <application
      android:allowBackup="true"
      android:icon="@mipmap/ic_launcher"
      android:label="@string/app_name"
      android:roundIcon="@mipmap/ic_launcher_round"
      android:supportsRtl="true"
      android:theme="@style/AppTheme">
      <activity android:name=".MainActivity">
         <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
         </intent-filter>
      </activity>
   </application>
</manifest>
Let's try to run your application. I assume you have connected your actual Android Mobile device with your computer. To run the app from android studio, open one of your project's activity files and click Run  icon from the toolbar. Select your mobile device as an option and then check your mobile device which will display your default screen –
Click here to download the project code.