Receiving data from arduino to android application

Question

I have been struggling for a long time with receiving data from the arduino. I know how to send data to arduino but I don't know how to receive it. My android application is very simple, once launched it connects directly to arduino. The code on the arduino side is working fine, I tested it with the Bluetooth Transfer app ready. Please help.

import androidx.appcompat.app.AppCompatActivity;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.bluetooth.BluetoothSocket;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.UUID;


public class MainActivity extends AppCompatActivity {

    static final UUID mUUID = UUID.fromString("00001101-0000-1000-8000-00805F9B34FB");
    Button buttonON, buttonOFF;
    TextView tV_received;
    BluetoothSocket btSocket = null;

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

        buttonON = (Button)findViewById(R.id.button_on);
        buttonOFF = (Button)findViewById(R.id.button_off);
        tV_received = (TextView) findViewById(R.id.tV_received);

        BluetoothAdapter btAdapter = BluetoothAdapter.getDefaultAdapter();
        System.out.println(btAdapter.getBondedDevices());

        BluetoothDevice hc05 = btAdapter.getRemoteDevice("00:21:13:03:CC:90");
        System.out.println(hc05.getName());


        int counter = 0;

        do {
            try {
                btSocket = hc05.createRfcommSocketToServiceRecord(mUUID);
                System.out.println(btSocket);
                btSocket.connect();
                System.out.println(btSocket.isConnected());
            } catch (IOException e) {
                e.printStackTrace();
            }
            counter++;
        } while(!btSocket.isConnected() && counter < 3);

        try {
            OutputStream outputStream = btSocket.getOutputStream();
            outputStream.write(48);
        } catch (IOException e) {
            e.printStackTrace();
        }

        InputStream inputStream = null;

        try {
            inputStream = btSocket.getInputStream();
            inputStream.skip(inputStream.available());

           
                byte b = (byte) inputStream.read();
                System.out.println((char) b);
         
        } catch (IOException e) {
            e.printStackTrace();
        }

    }

    public void clickON (View view) {

        if (btSocket!=null)
        {
            try
            {
                btSocket.getOutputStream().write("1".toString().getBytes());
            }
            catch (IOException e)
            {

            }
        }

    }

    public void clickOFF (View view) {

        if (btSocket!=null)
        {
            try
            {
                btSocket.getOutputStream().write("0".toString().getBytes());
            }
            catch (IOException e)
            {

            }
        }

    }
    
}