BluetoothActivity.java

import android.bluetooth.BluetoothDevice;
import android.os.Bundle;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.ListView;
import android.widget.Toast;

import java.util.ArrayList;
import java.util.List;

public class BluetoothActivity extends AppCompatActivity implements BluetoothHelper.BluetoothListener {

    private ListView listView;
    private Button btnScan;
    private List<BluetoothDevice> deviceList;
    private ArrayAdapter<String> adapter;
    private BluetoothHelper bluetoothHelper;

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

        listView = findViewById(R.id.listView);
        btnScan = findViewById(R.id.btnScan);

        deviceList = new ArrayList<>();
        adapter = new ArrayAdapter<>(this, android.R.layout.simple_list_item_1);
        listView.setAdapter(adapter);

        bluetoothHelper = new BluetoothHelper(this);
        bluetoothHelper.setListener(this);

        btnScan.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (btnScan.getText().toString().equals("Scan")) {
                    deviceList.clear();
                    adapter.clear();
                    bluetoothHelper.startDiscovery();
                    btnScan.setText("Stop");
                    Toast.makeText(BluetoothActivity.this, "Scanning...", Toast.LENGTH_SHORT).show();
                } else {
                    bluetoothHelper.stopDiscovery();
                    btnScan.setText("Scan");
                    Toast.makeText(BluetoothActivity.this, "Scan Stopped", Toast.LENGTH_SHORT).show();
                }
            }
        });
    }

    @Override
    public void onDeviceFound(List<BluetoothDevice> devices) {
        for (BluetoothDevice device : devices) {
            adapter.add(device.getName() + " - " + device.getAddress());
        }
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        bluetoothHelper.stopDiscovery();
    }
}