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Overview

The DeviceLocationScreen provides functionality for users to retrieve their device’s current location. It displays both human-readable address information and precise GPS coordinates, with features to speak the location aloud using text-to-speech and copy location data to the clipboard. File Location: com.demodogo.ev_sum_2.ui.location.DeviceLocationScreen.kt:46

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Function Signature

@Composable
fun DeviceLocationScreen(
    onBack: () -> Unit
)

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Parameters

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onBack
() -> Unit
required
Callback function invoked when the user clicks the “Volver” (Back) button. Typically navigates back to the previous screen.

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State Management

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Location Data State

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address
String?
Stores the human-readable address obtained from reverse geocoding. Null if not yet retrieved or unavailable.
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lat
Double?
Stores the latitude coordinate of the device’s location.
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lon
Double?
Stores the longitude coordinate of the device’s location.

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UI Feedback State

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isLoading
Boolean
Indicates whether a location fetch operation is currently in progress.
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error
String?
Stores error messages to display to the user (e.g., permission denied, location unavailable).
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info
String?
Stores informational messages to display to the user (e.g., “Ubicación actualizada”, “Copiado al portapapeles”).

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Services & Controllers

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LocationService

Handles location operations:
  • getLocationWithAddress() - Retrieves GPS coordinates and performs reverse geocoding to get address
  • hasPermission() - Checks if location permissions are granted

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TextToSpeechController

Provides text-to-speech functionality:
  • speak(text: String) - Speaks the provided location information aloud
  • destroy() - Cleans up TTS resources

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User Interactions

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Retrieving Location

The location fetch process handles permissions and errors gracefully:
DeviceLocationScreen.kt:88-105
fun fetchLocation() {
    scope.launch {
        isLoading = true
        error = null
        info = null
        try {
            val result = service.getLocationWithAddress()
            lat = result.coords.latitude
            lon = result.coords.longitude
            address = result.address
            info = "Ubicación actualizada."
        } catch (e: Exception) {
            error = e.message ?: "Error obteniendo ubicación."
        } finally {
            isLoading = false
        }
    }
}
When user clicks “Obtener ubicación”:
  1. Check if location permissions are granted
  2. If not granted, request permissions
  3. If granted, fetch location with address
  4. Display results or error message

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Permission Handling

The screen requests location permissions when needed:
DeviceLocationScreen.kt:107-119
val permissionLauncher = rememberLauncherForActivityResult(
    ActivityResultContracts.RequestMultiplePermissions()
) { perms ->
    val ok = (perms[Manifest.permission.ACCESS_FINE_LOCATION] == true) ||
            (perms[Manifest.permission.ACCESS_COARSE_LOCATION] == true)

    if (!ok) {
        error = "Permiso de ubicación denegado."
        info = null
    } else {
        fetchLocation()
    }
}

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Text-to-Speech Location

The screen can speak the location information:
DeviceLocationScreen.kt:72-77
fun spokenText(): String {
    val a = address?.takeIf { it.isNotBlank() }
    return if (a != null) "Tu ubicación actual es: $a"
    else if (lat != null && lon != null) "Tu ubicación actual es latitud ${"%.5f".format(lat)} y longitud ${"%.5f".format(lon)}"
    else "Aún no tengo tu ubicación."
}

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Copy to Clipboard

Users can copy location data in a formatted string:
DeviceLocationScreen.kt:79-86
fun copyText(): String {
    val a = address?.takeIf { it.isNotBlank() }
    return if (a != null && lat != null && lon != null)
        "Ubicación: $a (lat=${"%.6f".format(lat)}, lon=${"%.6f".format(lon)})"
    else if (lat != null && lon != null)
        "Ubicación: lat=${"%.6f".format(lat)}, lon=${"%.6f".format(lon)}"
    else "Ubicación no disponible."
}
DeviceLocationScreen.kt:66-70
fun copy(text: String) {
    clipboard.setText(AnnotatedString(text))
    info = "Copiado al portapapeles."
    error = null
}

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UI Components

The DeviceLocationScreen uses Material 3 components:
  • Surface - Root container with background color
  • Column - Main vertical layout with spacing
  • Card - Display containers for location data, errors, and info messages
  • Button - Primary action to obtain location
  • OutlinedButton - Secondary actions (speak, copy, back)
  • LinearProgressIndicator - Loading state indicator
  • Icon - Visual indicators (MyLocation, VolumeUp, ContentCopy)
  • Row - Horizontal layout for action buttons

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Permissions

The screen requests the following Android permissions:
  • Manifest.permission.ACCESS_FINE_LOCATION - For precise GPS coordinates
  • Manifest.permission.ACCESS_COARSE_LOCATION - For approximate location
The screen accepts either FINE or COARSE location permission. If the user grants only COARSE, the location will be less precise but still functional.

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Location Data Display

The location information is displayed in a card:
DeviceLocationScreen.kt:128-142
Card(
    shape = RoundedCornerShape(16.dp),
    colors = CardDefaults.cardColors(containerColor = MaterialTheme.colorScheme.primary.copy(alpha = 0.06f))
) {
    Column(modifier = Modifier.padding(16.dp), verticalArrangement = Arrangement.spacedBy(8.dp)) {
        Text("Dirección:", style = MaterialTheme.typography.titleMedium)
        Text(address ?: "—", style = MaterialTheme.typography.bodyLarge)

        Text("Coordenadas:", style = MaterialTheme.typography.titleMedium)
        Text(
            if (lat != null && lon != null) "lat=${"%.6f".format(lat)}, lon=${"%.6f".format(lon)}" else "—",
            style = MaterialTheme.typography.bodyLarge
        )
    }
}
The display shows:
  • Dirección - Full address string or ”—” if unavailable
  • Coordenadas - Latitude and longitude with 6 decimal places or ”—” if unavailable

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Error and Info Messages

Feedback messages are displayed in styled cards:
DeviceLocationScreen.kt:146-158
if (error != null) {
    Card(
        shape = RoundedCornerShape(16.dp),
        colors = CardDefaults.cardColors(containerColor = MaterialTheme.colorScheme.error.copy(alpha = 0.10f))
    ) { Text(error!!, modifier = Modifier.padding(14.dp)) }
}

if (info != null) {
    Card(
        shape = RoundedCornerShape(16.dp),
        colors = CardDefaults.cardColors(containerColor = MaterialTheme.colorScheme.primary.copy(alpha = 0.10f))
    ) { Text(info!!, modifier = Modifier.padding(14.dp)) }
}

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Example Usage

NavHost(navController = navController, startDestination = "home") {
    composable("location") {
        DeviceLocationScreen(
            onBack = {
                navController.popBackStack()
            }
        )
    }
}

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Action Buttons

The screen provides three action buttons:
  1. Obtener ubicación - Fetches current location (disabled while loading)
  2. Hablar - Speaks location using TTS
  3. Copiar - Copies formatted location to clipboard
  4. Volver - Returns to previous screen
DeviceLocationScreen.kt:160-177
Button(
    onClick = {
        if (service.hasPermission()) fetchLocation()
        else permissionLauncher.launch(
            arrayOf(
                Manifest.permission.ACCESS_FINE_LOCATION,
                Manifest.permission.ACCESS_COARSE_LOCATION
            )
        )
    },
    enabled = !isLoading,
    modifier = Modifier.fillMaxWidth(),
    shape = RoundedCornerShape(16.dp)
) {
    Icon(Icons.Default.MyLocation, contentDescription = null)
    Spacer(Modifier.width(10.dp))
    Text("Obtener ubicación")
}

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Best Practices

  1. Resource Cleanup - TTS controller is destroyed in DisposableEffect to prevent memory leaks
  2. Graceful Degradation - Shows coordinates even if address lookup fails
  3. User Feedback - Clear loading states and error messages
  4. Accessibility - Text-to-speech support for reading location aloud
  5. Permission Handling - Gracefully requests and handles permission denials
  6. State Persistence - Location data preserved with rememberSaveable across configuration changes

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