Why is the flashlight blinking not starting when running the application from the phone?

It does start on the phone when I'm running the application through android studio and it's building and installing it to the phone then the blinking start. but if I start the application from the phone not from android studio then it does nothing.

The goal is to make the flashlight on the phone start blinking when starting the application either from the android studio or from the phone itself but it's working only from android studio.

package com.example.myflashlight
import android.content.Context
import android.hardware.camera2.CameraAccessException
import android.hardware.camera2.CameraCharacteristics.FLASH_INFO_AVAILABLE
import android.hardware.camera2.CameraManager
import android.os.Build
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.os.Handler
import android.os.Looper
import androidx.annotation.RequiresApi
class MainActivity : AppCompatActivity() {
private lateinit var cameraManager: CameraManager
private lateinit var cameraId: String
private lateinit var handler: Handler
private var isFlashOn = false
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
cameraManager = getSystemService(Context.CAMERA_SERVICE) as CameraManager
try {
cameraId = cameraManager.cameraIdList[0]
} catch (e: CameraAccessException) {
e.printStackTrace()
}
handler = Handler(Looper.getMainLooper())
handler.post(blinkRunnable)
}
private val blinkRunnable = object : Runnable {
@RequiresApi(Build.VERSION_CODES.M)
override fun run() {
if (isFlashOn) {
turnFlashOff()
} else {
turnFlashOn()
}
handler.postDelayed(this, 1000)
}
}
@RequiresApi(Build.VERSION_CODES.M)
private fun turnFlashOn() {
try {
cameraManager.setTorchMode(cameraId, true)
isFlashOn = true
} catch (e: CameraAccessException) {
e.printStackTrace()
}
}
@RequiresApi(Build.VERSION_CODES.M)
private fun turnFlashOff() {
try {
cameraManager.setTorchMode(cameraId, false)
isFlashOn = false
} catch (e: CameraAccessException) {
e.printStackTrace()
}
}
@RequiresApi(Build.VERSION_CODES.M)
override fun onPause() {
super.onPause()
handler.removeCallbacks(blinkRunnable)
if (isFlashOn) {
turnFlashOff()
}
}
}

If you're clearing the Handler in onPause, then you should start the first runnable in onResume (instead of onCreate) for symmetry. onCreate() might not be getting called when you reopen an app on Android SDK 30+ because it might just be resuming the same Activity instance.

The reason it might be working when launched through Android Studio is that it's probably forcing a complete restart of the whole application which would guarantee a new Activity instance and new call to onCreate().