How to use BroadcastReceiver in Kotlin?

This example demonstrates how to use BroadcastReceiver in Kotlin .

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.

Example

<?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">
   <TextView
      android:id="@+id/textView"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_centerHorizontal="true"
      android:layout_marginTop="50dp"
      android:padding="8dp"
      android:text="Tutorials Point"
      android:textColor="@color/colorPrimaryDark"
      android:textSize="48sp"
      android:textStyle="bold" />
   <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.kt

Example

import android.content.BroadcastReceiver
import android.content.Context
import android.content.Intent
import android.content.IntentFilter
import android.net.wifi.WifiManager
import android.os.Bundle
import android.widget.Switch
import android.widget.Toast
import androidx.appcompat.app.AppCompatActivity
class MainActivity : AppCompatActivity() {
   lateinit var wifiSwitch: Switch
   lateinit var wifiManager: WifiManager
   override fun onCreate(savedInstanceState: Bundle?) {
      super.onCreate(savedInstanceState)
      setContentView(R.layout.activity_main)
      title = "KotlinApp"
      wifiSwitch = findViewById(R.id.wifiSwitch)
      wifiManager = applicationContext.getSystemService(Context.WIFI_SERVICE) as WifiManager
      wifiSwitch.setOnCheckedChangeListener { _, isChecked ->
         if (isChecked) {
            wifiManager.isWifiEnabled = true
            wifiSwitch.text = "WiFi is ON"
         } else {
            wifiManager.isWifiEnabled = false
            wifiSwitch.text = "WiFi is OFF"
         }
      }
   }
   override fun onStart() {
      super.onStart()
      val intentFilter = IntentFilter(WifiManager.WIFI_STATE_CHANGED_ACTION)
      registerReceiver(wifiStateReceiver, intentFilter)
   }
   override fun onStop() {
      super.onStop()
      unregisterReceiver(wifiStateReceiver)
   }
   private val wifiStateReceiver: BroadcastReceiver = object : BroadcastReceiver() {
      override fun onReceive(context: Context, intent: Intent) {
         when (intent.getIntExtra(WifiManager.EXTRA_WIFI_STATE,
         WifiManager.WIFI_STATE_UNKNOWN)) {
            WifiManager.WIFI_STATE_ENABLED -> {
               wifiSwitch.isChecked = true
               wifiSwitch.text = "WiFi is ON"
               Toast.makeText(this@MainActivity, "Wifi is On", Toast.LENGTH_SHORT).show()
            }
            WifiManager.WIFI_STATE_DISABLED -> {
               wifiSwitch.isChecked = false
               wifiSwitch.text = "WiFi is OFF"
               Toast.makeText(this@MainActivity, "Wifi is Off", Toast.LENGTH_SHORT).show()
            }
         }
      }
   }
}

Step 4 − Add the following code to androidManifest.xml

Example

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="app.com.q20">
<uses-permission android:name="android.permission.CHANGE_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 the Run icon from the toolbar. Select your mobile device as an option and then check your mobile device which will display your default screen