분량 초과로 코드/로그캣 따로 보내드립니다. 죄송합니다.

Question

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <Button
        android:id="@+id/selectDeviceButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="bluetooth"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="20dp"/>

    <TextView
        android:id="@+id/postureTextView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="스트레칭을 따라하세요!"
        android:textSize="24sp"
        android:layout_below="@id/selectDeviceButton"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="30dp"/>

    <ImageView
        android:id="@+id/stretchImageView"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@id/postureTextView"
        android:layout_marginTop="20dp"
        android:scaleType="centerInside"
        android:src="@drawable/w25"/>

    <ListView
        android:id="@+id/paired_devices"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@id/stretchImageView"
        android:layout_marginTop="20dp"/>
</RelativeLayout>

package com.example.opensource;

import android.Manifest;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.bluetooth.BluetoothSocket;
import android.content.DialogInterface;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.os.Build;
import android.os.Bundle;
import android.os.CountDownTimer;
import android.os.Handler;
import android.os.Message;
import android.util.Log;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;

import androidx.annotation.NonNull;
import androidx.appcompat.app.AlertDialog;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.app.ActivityCompat;
import androidx.core.content.ContextCompat;

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

public class MainActivity extends AppCompatActivity {
    private static final int REQUEST_ENABLE_BT = 1;
    private static final int REQUEST_PERMISSIONS = 2;
    private static final String TAG = "MainActivity";

    private BluetoothAdapter bluetoothAdapter;
    private BluetoothSocket bluetoothSocket;
    private InputStream inputStream;
    private Handler handler;
    private TextView postureTextView;
    private ImageView stretchImageView;
    private Button selectDeviceButton;
    private ListView listView;
    private ArrayAdapter<String> pairedDevicesArrayAdapter;

    private final UUID MY_UUID = UUID.fromString("00001101-0000-1000-8000-00805F9B34FB");

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

        postureTextView = findViewById(R.id.postureTextView);
        stretchImageView = findViewById(R.id.stretchImageView);
        selectDeviceButton = findViewById(R.id.selectDeviceButton);
        listView = findViewById(R.id.paired_devices);

        bluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
        if (bluetoothAdapter == null) {
            Toast.makeText(this, "Bluetooth is not available", Toast.LENGTH_LONG).show();
            finish();
            return;
        }

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

        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.S) {
            if (ContextCompat.checkSelfPermission(this, Manifest.permission.BLUETOOTH_CONNECT) != PackageManager.PERMISSION_GRANTED) {
                ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.BLUETOOTH_CONNECT, Manifest.permission.BLUETOOTH_SCAN}, REQUEST_PERMISSIONS);
            }
        }

        selectDeviceButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                showPairedDevices();
            }
        });

        handler = new Handler(new Handler.Callback() {
            @Override
            public boolean handleMessage(Message msg) {
                String posture = msg.getData().getString("posture");
                Log.d(TAG, "Received posture data: " + posture);
                postureTextView.setText(posture);
                showStretchingImages(posture);
                return true;
            }
        });
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        if (requestCode == REQUEST_PERMISSIONS) {
            if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                showPairedDevices();
            } else {
                Toast.makeText(this, "Bluetooth permissions are required to use this application", Toast.LENGTH_LONG).show();
                finish();
            }
        }
    }

    private void showPairedDevices() {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.S) {
            if (ContextCompat.checkSelfPermission(this, Manifest.permission.BLUETOOTH_CONNECT) != PackageManager.PERMISSION_GRANTED) {
                ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.BLUETOOTH_CONNECT, Manifest.permission.BLUETOOTH_SCAN}, REQUEST_PERMISSIONS);
                return;
            }
        }