Kotlin Bluetooth Not Working on Some Devices

Bluetooth is one of the most essential features in Android applications, especially when developing apps that connect with IoT devices, external hardware, or wireless accessories. However, many developers face an issue where Kotlin Bluetooth not working on some devices even though the same code runs perfectly on other models. This article will guide you through the common causes, troubleshooting steps, and a full Kotlin code example to handle Bluetooth compatibility across different Android devices.

Why Bluetooth May Not Work on Some Devices

When building a Kotlin app with Bluetooth functionality, you may find that your app works smoothly on one smartphone brand but fails on another. The reasons behind this can include:

• Different Android Versions: Some devices may run Android 8 (Oreo), others Android 13 or higher. The Bluetooth API behavior has slightly changed over time.
• Manufacturer Customization: Brands like Samsung, Xiaomi, Oppo, and Vivo sometimes restrict background processes or require additional permissions.
• Permission Issues: From Android 12 onwards, you must request BLUETOOTH_CONNECT and BLUETOOTH_SCAN permissions.
• Hardware Incompatibility: Some devices simply don’t support certain Bluetooth profiles (e.g., BLE, A2DP).
• Battery Optimization: Aggressive power-saving settings can kill Bluetooth scanning in the background.

Step-by-Step Troubleshooting

Follow these steps to fix Bluetooth not working on some Android devices:

1. Check Permissions: Always declare the correct permissions in AndroidManifest.xml depending on the Android version.
2. Request Runtime Permissions: For Android 12+, request Bluetooth permissions at runtime.
3. Check if Bluetooth is Enabled: Use Kotlin code to verify if Bluetooth is turned on before scanning or connecting.
4. Handle Manufacturer Restrictions: Ask users to disable battery optimization for your app if necessary.
5. Use Compatible APIs: Ensure you use BluetoothAdapter and BluetoothLeScanner correctly.

Full Kotlin Code Example

Here’s a complete Kotlin example that handles Bluetooth initialization, permission requests, and device scanning. This code works for Android 12 and above while remaining backward-compatible.

import android.Manifest
import android.bluetooth.BluetoothAdapter
import android.bluetooth.BluetoothManager
import android.bluetooth.le.ScanCallback
import android.bluetooth.le.ScanResult
import android.content.Context
import android.content.pm.PackageManager
import android.os.Build
import androidx.activity.result.contract.ActivityResultContracts
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.util.Log
import androidx.core.app.ActivityCompat

class MainActivity : AppCompatActivity() {

    private lateinit var bluetoothAdapter: BluetoothAdapter

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        val bluetoothManager = getSystemService(Context.BLUETOOTH_SERVICE) as BluetoothManager
        bluetoothAdapter = bluetoothManager.adapter

        // Check Bluetooth availability
        if (bluetoothAdapter == null) {
            Log.e("Bluetooth", "Device does not support Bluetooth")
            return
        }

        // Request permissions depending on Android version
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.S) {
            ActivityCompat.requestPermissions(
                this,
                arrayOf(
                    Manifest.permission.BLUETOOTH_SCAN,
                    Manifest.permission.BLUETOOTH_CONNECT
                ),
                1
            )
        } else {
            ActivityCompat.requestPermissions(
                this,
                arrayOf(
                    Manifest.permission.BLUETOOTH,
                    Manifest.permission.BLUETOOTH_ADMIN,
                    Manifest.permission.ACCESS_FINE_LOCATION
                ),
                1
            )
        }

        // Check if Bluetooth is enabled
        if (!bluetoothAdapter.isEnabled) {
            Log.e("Bluetooth", "Bluetooth is disabled")
        } else {
            startScanning()
        }
    }

    private fun startScanning() {
        val scanner = bluetoothAdapter.bluetoothLeScanner
        scanner?.startScan(scanCallback)
    }

    private val scanCallback = object : ScanCallback() {
        override fun onScanResult(callbackType: Int, result: ScanResult?) {
            super.onScanResult(callbackType, result)
            result?.device?.let {
                Log.i("Bluetooth", "Device found: ${it.name} - ${it.address}")
            }
        }

        override fun onScanFailed(errorCode: Int) {
            super.onScanFailed(errorCode)
            Log.e("Bluetooth", "Scan failed with error: $errorCode")
        }
    }
}

Common Fixes for Specific Brands

Best Practices

• Always check for runtime permissions.
• Inform users when Bluetooth is required.
• Handle exceptions for devices without BLE support.
• Test on multiple device brands before release.

Conclusion

When facing the issue of Kotlin Bluetooth not working on some devices, the root causes are often related to permissions, Android version differences, and manufacturer customizations. By following the steps above and using the provided Kotlin code example, you can make your Bluetooth implementation more reliable and compatible across different devices.

If you want to explore more about Android Bluetooth development, you can check the official documentation from Android Developers Bluetooth Guide.