How to turn on flashlight programmatically in Android using Kotlin?

This example demonstrates how to turn on flashlight programmatically in Android using 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="https://schemas.android.com/apk/res/android"
   android:layout_width="match_parent"
   android:layout_height="match_parent"
   android:orientation="vertical">
<TextView
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:layout_centerHorizontal="true"
   android:layout_marginTop="50dp"
   android:text="Tutorials Point"
   android:textAlignment="center"
   android:textColor="@android:color/holo_green_dark"
   android:textSize="32sp"
   android:textStyle="bold" />
<ToggleButton
   android:id="@+id/onOffFlashlight"
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:layout_centerInParent="true"
   android:checked="false"
   android:text="Turn On/Off Camera LED/ Flashlight Android"
   android:textOff="Turn On"
   android:textOn="Turn Off" />
</RelativeLayout>

Step 3 − Add the following code to src/MainActivity.kt

import android.content.Context
import android.content.DialogInterface
import android.content.pm.PackageManager
import android.hardware.camera2.CameraAccessException
import android.hardware.camera2.CameraManager
import android.os.Build
import android.os.Bundle
import android.widget.ToggleButton
import androidx.appcompat.app.AlertDialog
import androidx.appcompat.app.AppCompatActivity
class MainActivity : AppCompatActivity() {
   private lateinit var cameraManager: CameraManager
   private lateinit var cameraId: String
   private lateinit var toggleButton: ToggleButton
   override fun onCreate(savedInstanceState: Bundle?) {
      super.onCreate(savedInstanceState)
      setContentView(R.layout.activity_main)
      title = "KotlinApp"
      val isFlashAvailable = applicationContext.packageManager
      .hasSystemFeature(PackageManager.FEATURE_CAMERA_FRONT)
      if (!isFlashAvailable) {
         showNoFlashError()
      }
      cameraManager = getSystemService(Context.CAMERA_SERVICE) as CameraManager
      try {
         cameraId = cameraManager.cameraIdList[0]
      } catch (e: CameraAccessException) {
         e.printStackTrace()
      }
      toggleButton = findViewById(R.id.onOffFlashlight)
      toggleButton.setOnCheckedChangeListener { _, isChecked -> switchFlashLight(isChecked) }
   }
   private fun showNoFlashError() {
      val alert = AlertDialog.Builder(this)
      .create()
      alert.setTitle("Oops!")
      alert.setMessage("Flash not available in this device...")
      alert.setButton(DialogInterface.BUTTON_POSITIVE, "OK") { _, _ -> finish() }
      alert.show()
   }
   private fun switchFlashLight(status: Boolean) {
      try {
         if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            cameraManager.setTorchMode(cameraId, status)
         }
      } catch (e: CameraAccessException) {
         e.printStackTrace()
      }
   }
}

Step 4 − Add the following code to androidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="https://schemas.android.com/apk/res/android" package="com.example.q11">
   <uses-permission android:name="android.permission.CAMERA" />
   <uses-feature android:name="android.hardware.camera.flash" />
   <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

NOTE: TRY THIS IS REAL DEVICE FOR BETTER RESULTS