Development

Android BLE Development: From Scanning to Data Transfer

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Building BLE apps with Android's BLE API

  
  

    
    
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    2 분 읽기
    
  


  
  







  
  

    
    
      
      
  1. 
        Android BLE Development
      
    2. 
      
      
  2. 
        BluetoothLeScanner
      
    3. 
      
      
  3. 
        GATT Callback and Threading
      
    4. 
      
      
  4. 
        Common Issues
      
    5. 
      
      
  5. 
        Permissions (Android 12+)
      
    6. 
      
      
  6. 
        Best Practices
      
    7. 
      
    

  









  
  

  
  

    
    

      
Android BLE Development


Android's BLE API is stable from API 21+ but has well-documented pitfalls around connection management, threading, and MTU negotiation. This guide covers production-grade patterns.


BluetoothLeScanner


Always filter by service ATT">UUID to avoid processing irrelevant advertising packets:


val settings = ScanSettings.Builder()
    .setScanMode(ScanSettings.SCAN_MODE_LOW_LATENCY)
    .build()
val filter = ScanFilter.Builder()
    .setServiceUuid(ParcelUuid.fromString("6E400001-B5A3-F393-E0A9-E50E24DCCA9E"))
    .build()
bluetoothAdapter.bluetoothLeScanner.startScan(listOf(filter), settings, callback)



Use SCAN_MODE_LOW_POWER for background scanning. Android 12+ requires BLUETOOTH_SCAN with neverForLocation if scan results are not used for location.


GATT Callback and Threading


Android's GATT callbacks arrive on a Binder thread. Request MTU before service discovery, then chain operations through callbacks:


device.connectGatt(context, false, object : BluetoothGattCallback() {
    override fun onConnectionStateChange(gatt: BluetoothGatt, status: Int, newState: Int) {
        if (newState == BluetoothProfile.STATE_CONNECTED) gatt.requestMtu(512)
    }
    override fun onMtuChanged(gatt: BluetoothGatt, mtu: Int, status: Int) {
        gatt.discoverServices()
    }
    override fun onCharacteristicChanged(
        gatt: BluetoothGatt, char: BluetoothGattCharacteristic, value: ByteArray
    ) { /* API 33+ — value passed directly, no race */ }
})



Common Issues






Issue
Cause
Fix






STATUS_133 on connect
Android stack bug
Retry with exponential backoff




Characteristic reads stale
API < 33 value handling
Use API 33 onCharacteristicChanged(gatt, char, ByteArray)




Scan stops after 30 min
Background restriction
Use foreground service




Bonding loop
Incorrect CCCD write order
Write CCCD after discovery completes






Permissions (Android 12+)


<uses-permission android:name="android.permission.BLUETOOTH_SCAN"
    android:usesPermissionFlags="neverForLocation" />
<uses-permission android:name="android.permission.BLUETOOTH_CONNECT" />



Best Practices


    

  • Single GATT queue: Serialize all GATT operations — parallel calls cause STATUS_133
    • 

  • Bonding: Store peripheral MAC; use autoConnect=true for bonded devices
    • 

  • Reconnection: Exponential backoff on disconnect (100 ms → 200 ms → ... → 30 s cap)
    • 

  • Coroutines: Wrap callbacks with suspendCancellableCoroutine for clean async code
    • 



Use the GATT Profile Browser to verify service UUIDs during development. For iOS patterns, see iOS Core Bluetooth Guide.

    

    

    
    

    
    
    
    

    
    

      




  
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