Android bluetooth get connected devices

Introduction

This article provides a comprehensive guide on how to discover and retrieve a list of Bluetooth devices connected to your Android device. We will explore the fundamental concepts and the necessary code snippets for implementing this functionality in your Android applications.

Prerequisites

Before we delve into the implementation, ensure you have the following in place:

• Android Studio installed on your system.
• Basic understanding of Android development concepts.
• A Bluetooth-enabled Android device for testing.

Core Concepts

Understanding the following concepts is crucial for working with Bluetooth in Android:

• BluetoothAdapter: Represents the local Bluetooth adapter. It allows you to interact with Bluetooth hardware and manage Bluetooth connections.
• BluetoothDevice: Represents a remote Bluetooth device. It provides information about the device, such as its name, address, and connection state.
• BluetoothManager: A central interface for managing Bluetooth. It provides methods to get the Bluetooth adapter and create Bluetooth connections.

Implementation Steps

1. Obtaining the Bluetooth Adapter

BluetoothManager bluetoothManager = (BluetoothManager) getSystemService(Context.BLUETOOTH_SERVICE);
BluetoothAdapter bluetoothAdapter = bluetoothManager.getAdapter();

2. Checking Bluetooth Availability

if (bluetoothAdapter == null) {
    // Bluetooth is not supported on this device
} else {
    // Bluetooth is supported
}

3. Enabling Bluetooth

if (!bluetoothAdapter.isEnabled()) {
    Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
    startActivityForResult(enableBtIntent, REQUEST_ENABLE_BT);
}

4. Discovering Devices

if (bluetoothAdapter.isDiscovering()) {
    bluetoothAdapter.cancelDiscovery();
}
bluetoothAdapter.startDiscovery();

5. Receiving Discovery Results

You can receive discovered devices by registering a BroadcastReceiver:

IntentFilter filter = new IntentFilter(BluetoothDevice.ACTION_FOUND);
registerReceiver(receiver, filter);

Define a BroadcastReceiver to handle the discovered devices:

private final BroadcastReceiver receiver = new BroadcastReceiver() {
    public void onReceive(Context context, Intent intent) {
        String action = intent.getAction();
        if (BluetoothDevice.ACTION_FOUND.equals(action)) {
            BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
            // Add the device to your list of connected devices
        }
    }
};

6. Getting Connected Devices

To retrieve a list of already connected devices, use the following code:

Set bondedDevices = bluetoothAdapter.getBondedDevices();
if (bondedDevices.size() > 0) {
    for (BluetoothDevice device : bondedDevices) {
        // Display device information (name, address)
    }
} else {
    // No connected devices
}

Example: Listing Connected Devices

The following code snippet demonstrates how to retrieve and display a list of connected Bluetooth devices:

package com.example.bluetoothconnecteddevices;

import androidx.appcompat.app.AppCompatActivity;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.bluetooth.BluetoothManager;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.os.Bundle;
import android.widget.TextView;
import java.util.Set;

public class MainActivity extends AppCompatActivity {

    private BluetoothAdapter bluetoothAdapter;
    private TextView connectedDevicesTextView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        connectedDevicesTextView = findViewById(R.id.connectedDevicesTextView);

        BluetoothManager bluetoothManager = (BluetoothManager) getSystemService(Context.BLUETOOTH_SERVICE);
        bluetoothAdapter = bluetoothManager.getAdapter();

        if (bluetoothAdapter == null) {
            connectedDevicesTextView.setText("Bluetooth not supported.");
            return;
        }

        if (!bluetoothAdapter.isEnabled()) {
            Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
            startActivityForResult(enableBtIntent, REQUEST_ENABLE_BT);
        } else {
            // Get connected devices
            Set bondedDevices = bluetoothAdapter.getBondedDevices();
            if (bondedDevices.size() > 0) {
                StringBuilder deviceList = new StringBuilder();
                for (BluetoothDevice device : bondedDevices) {
                    deviceList.append(device.getName()).append(" (").append(device.getAddress()).append(")\n");
                }
                connectedDevicesTextView.setText("Connected Devices:\n" + deviceList.toString());
            } else {
                connectedDevicesTextView.setText("No connected devices found.");
            }
        }
    }
}

Connected Devices:
MyBluetoothSpeaker (AA:BB:CC:DD:EE:FF)
MyBluetoothHeadset (11:22:33:44:55:66)

Conclusion

This article provided a comprehensive guide on discovering and retrieving connected Bluetooth devices in Android. By following the outlined steps and implementing the provided code snippets, you can seamlessly integrate Bluetooth functionality into your Android applications. Remember to handle permission requests appropriately and to gracefully manage potential errors during the process.