🔧 Build a Flashlight in Jetpack Compose

 // Dependency to request hardware permission
 implementation ("com.google.accompanist:accompanist-permissions:0.32.0")

 <uses-feature
   android:name="android.hardware.camera"
   android:required="false" />
 <uses-permission android:name="android.permission.CAMERA" />

fun toggleFlashLight(cameraManager: CameraManager, cameraId: String, isFlashOn: Boolean) {
    try {
        cameraManager.setTorchMode(cameraId, isFlashOn)
    } catch (e: Exception) {
        e.printStackTrace()
    }
}

fun handlePermissionDenied(context: Context) {
    Toast.makeText(context, "Please grant camera permission", Toast.LENGTH_LONG).show()
}

fun handlePermissionRationale(context: Context) {
    Toast.makeText(context, "Camera permission is needed", Toast.LENGTH_LONG).show()
}

@OptIn(ExperimentalPermissionsApi::class)
fun handleLogic(
    cameraPermissionState: PermissionState,
    context: Context,
    cameraManager: CameraManager,
    cameraId: String,
    isFlashOn: Boolean,
    updateState: (Boolean) -> Unit,
) {
    if (cameraPermissionState.status.isGranted) {
        val newState = !isFlashOn
        updateState(newState)
        toggleFlashLight(cameraManager, cameraId, newState)
    } else if (cameraPermissionState.status.shouldShowRationale) {
        handlePermissionRationale(context)
        cameraPermissionState.launchPermissionRequest()
    } else {
        handlePermissionDenied(context)
        cameraPermissionState.launchPermissionRequest()
    }
}

import android.Manifest
import android.content.Context
import android.hardware.camera2.CameraManager
import android.os.Bundle
import android.widget.Toast
import androidx.activity.ComponentActivity
import androidx.activity.compose.setContent
import androidx.activity.enableEdgeToEdge
import androidx.compose.foundation.layout.Arrangement
import androidx.compose.foundation.layout.Column
import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.foundation.layout.height
import androidx.compose.foundation.layout.padding
import androidx.compose.material3.Button
import androidx.compose.material3.ButtonColors
import androidx.compose.material3.ButtonDefaults
import androidx.compose.material3.Scaffold
import androidx.compose.material3.Text
import androidx.compose.runtime.Composable
import androidx.compose.runtime.getValue
import androidx.compose.runtime.mutableStateOf
import androidx.compose.runtime.remember
import androidx.compose.runtime.saveable.rememberSaveable
import androidx.compose.runtime.setValue
import androidx.compose.ui.Alignment
import androidx.compose.ui.Modifier
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.platform.LocalContext
import androidx.compose.ui.text.style.TextAlign
import androidx.compose.ui.tooling.preview.Preview
import androidx.compose.ui.unit.dp
import androidx.compose.ui.unit.sp
import com.example.kotlin_articles.ui.theme.KotlinarticlesTheme
import com.google.accompanist.permissions.ExperimentalPermissionsApi
import com.google.accompanist.permissions.PermissionState
import com.google.accompanist.permissions.isGranted
import com.google.accompanist.permissions.rememberPermissionState
import com.google.accompanist.permissions.shouldShowRationale


class MainActivity : ComponentActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        enableEdgeToEdge()
        setContent {
            KotlinarticlesTheme {
                Scaffold(modifier = Modifier.fillMaxSize()) { innerPadding ->
                    Greeting(
                        modifier = Modifier.padding(innerPadding)
                    )
                }
            }
        }
    }
}

@OptIn(ExperimentalPermissionsApi::class)
@Composable
fun Greeting(modifier: Modifier = Modifier) {
    val context: Context = LocalContext.current
    val cameraPermissionState = rememberPermissionState(permission = Manifest.permission.CAMERA)
    var isFlashOn: Boolean by rememberSaveable {
        mutableStateOf(false)
    }
    val cameraManager: CameraManager = remember {
        context.getSystemService(Context.CAMERA_SERVICE) as CameraManager
    }
    val cameraId: String = rememberSaveable {
        try {
            cameraManager.cameraIdList[0]
        } catch (e: Exception) {
            "0"
        }
    }

    Column(
        modifier = Modifier
            .fillMaxSize(),
        horizontalAlignment = Alignment.CenterHorizontally,
        verticalArrangement = Arrangement.Center,
    ) {
        Button(
            modifier = Modifier.height(50.dp),
            onClick = {
                handleLogic(
                    cameraPermissionState,
                    context,
                    cameraManager,
                    cameraId,
                    isFlashOn
                ) { isFlashOn = it }
            },
        ) {
            Text(
                text = "Turn flashlight ${if (isFlashOn) "Off" else "On"} !",
                fontSize = 16.sp,
                textAlign = TextAlign.Center
            )
        }
    }
}

fun toggleFlashLight(cameraManager: CameraManager, cameraId: String, isFlashOn: Boolean) {
    try {
        cameraManager.setTorchMode(cameraId, isFlashOn)
    } catch (e: Exception) {
        e.printStackTrace()
    }
}

fun handlePermissionDenied(context: Context) {
    Toast.makeText(context, "Please grant camera permission", Toast.LENGTH_LONG).show()
}

fun handlePermissionRationale(context: Context) {
    Toast.makeText(context, "Camera permission is needed", Toast.LENGTH_LONG).show()
}

@OptIn(ExperimentalPermissionsApi::class)
fun handleLogic(
    cameraPermissionState: PermissionState,
    context: Context,
    cameraManager: CameraManager,
    cameraId: String,
    isFlashOn: Boolean,
    updateState: (Boolean) -> Unit,
) {
    if (cameraPermissionState.status.isGranted) {
        val newState = !isFlashOn
        updateState(newState)
        toggleFlashLight(cameraManager, cameraId, newState)
    } else if (cameraPermissionState.status.shouldShowRationale) {
        handlePermissionRationale(context)
        cameraPermissionState.launchPermissionRequest()
    } else {
        handlePermissionDenied(context)
        cameraPermissionState.launchPermissionRequest()
    }
}