bluetooth.md

Here's an example of a simple Bluetooth Android application in Java. This example demonstrates how to discover nearby Bluetooth devices and establish a connection with one of them.

import android.app.Activity;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.bluetooth.BluetoothSocket;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.ListView;
import android.widget.Toast;

import java.io.IOException;
import java.util.ArrayList;
import java.util.Set;
import java.util.UUID;

public class BluetoothActivity extends Activity {
    private BluetoothAdapter bluetoothAdapter;
    private ArrayAdapter<String> discoveredDevicesArrayAdapter;
    private ArrayList<BluetoothDevice> discoveredDevices;
    private BluetoothSocket bluetoothSocket = null;
    private static final UUID MY_UUID = UUID.fromString("00001101-0000-1000-8000-00805F9B34FB"); // UUID for SPP (Serial Port Profile)
    private static final int REQUEST_ENABLE_BT = 1;

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

        // Initialize Bluetooth adapter
        bluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
        if (bluetoothAdapter == null) {
            Toast.makeText(this, "Bluetooth is not supported on this device", Toast.LENGTH_SHORT).show();
            finish();
            return;
        }

        // Check if Bluetooth is enabled, and request to enable it if not
        if (!bluetoothAdapter.isEnabled()) {
            Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
            startActivityForResult(enableBtIntent, REQUEST_ENABLE_BT);
        }

        // Initialize UI components
        Button discoverButton = findViewById(R.id.discoverButton);
        ListView discoveredDevicesListView = findViewById(R.id.discoveredDevicesListView);
        discoveredDevicesArrayAdapter = new ArrayAdapter<>(this, android.R.layout.simple_list_item_1);
        discoveredDevices = new ArrayList<>();
        discoveredDevicesListView.setAdapter(discoveredDevicesArrayAdapter);

        // Register for broadcasts when a device is discovered
        IntentFilter filter = new IntentFilter(BluetoothDevice.ACTION_FOUND);
        registerReceiver(discoveryReceiver, filter);

        // Set up item click listener for discovered devices list
        discoveredDevicesListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> adapterView, View view, int position, long id) {
                // Connect to the selected device
                BluetoothDevice selectedDevice = discoveredDevices.get(position);
                connectToDevice(selectedDevice);
            }
        });

        // Set up discover button click listener
        discoverButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                discoverDevices();
            }
        });
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        // Unregister the broadcast receiver
        unregisterReceiver(discoveryReceiver);
    }

    // Discover nearby Bluetooth devices
    private void discoverDevices() {
        if (bluetoothAdapter.isDiscovering()) {
            bluetoothAdapter.cancelDiscovery();
        }
        bluetoothAdapter.startDiscovery();
    }

    // Connect to a Bluetooth device
    private void connectToDevice(BluetoothDevice device) {
        try {
            bluetoothSocket = device.createRfcommSocketToServiceRecord(MY_UUID);
            bluetoothSocket.connect();
            // You can now send/receive data through the BluetoothSocket
            // For example, use InputStream and OutputStream to communicate with the device
            Toast.makeText(this, "Connected to " + device.getName(), Toast.LENGTH_SHORT).show();
        } catch (IOException e) {
            e.printStackTrace();
            Toast.makeText(this, "Failed to connect to " + device.getName(), Toast.LENGTH_SHORT).show();
        }
    }

    // Broadcast receiver for handling device discovery
    private final BroadcastReceiver discoveryReceiver = new BroadcastReceiver() {
        public void onReceive(Context context, Intent intent) {
            String action = intent.getAction();
            if (BluetoothDevice.ACTION_FOUND.equals(action)) {
                // A Bluetooth device has been discovered
                BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
                if (device != null) {
                    discoveredDevices.add(device);
                    discoveredDevicesArrayAdapter.add(device.getName() + "\n" + device.getAddress());
                }
            }
        }
    };
}

In this example, we create an Android application that can discover nearby Bluetooth devices, display them in a list, and establish a connection with the selected device when an item in the list is clicked.

Make sure to add the necessary Bluetooth permissions to your AndroidManifest.xml file:

<uses-permission android:name="android.permission.BLUETOOTH"/>
<uses-permission android:name="android.permission.BLUETOOTH_ADMIN"/>
<uses-permission android:name="android.permission.BLUETOOTH_CONNECT"/>

Additionally, you should have appropriate layout XML files (e.g., activity_bluetooth.xml) and add Bluetooth-related UI elements to them.

Remember that Bluetooth programming can be complex, and this is just a basic example to get you started. You will need to handle error cases, manage Bluetooth state changes, and implement data communication as per your specific requirements.