CO2-APP/app/src/main/java/com/example/co2sense_app/MainActivity.java

package com.example.co2sense_app;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.annotation.RequiresApi;
import androidx.appcompat.app.AppCompatActivity;
import androidx.appcompat.widget.Toolbar;

import android.bluetooth.BluetoothGatt;
import android.bluetooth.BluetoothGattCallback;
import android.bluetooth.BluetoothGattCharacteristic;
import android.content.Context;
import android.content.Intent;
import android.content.SharedPreferences;
import android.os.Build;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;

public class MainActivity extends AppCompatActivity {
    CO2Sensor sensor;

    @RequiresApi(api = Build.VERSION_CODES.S)
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        Toolbar myToolbar = (Toolbar) findViewById(R.id.toolbar);
        myToolbar.showContextMenu();
        myToolbar.showOverflowMenu();
        setSupportActionBar(myToolbar);
        getSupportActionBar().setDisplayShowTitleEnabled(false);

        SharedPreferences sharedPref = getSharedPreferences(
                getString(R.string.main_shared_pref),Context.MODE_PRIVATE);
        String targetDeviceMAC = sharedPref.getString("target_device_mac", null);
        Log.d("MAIN", "onCreate: "+targetDeviceMAC);
        Log.d("MAIN", "onCreate: "+sharedPref.hashCode());

        sensor = new CO2Sensor(this);

        if(targetDeviceMAC != null) {
            sensor.setDeviceFromMAC(targetDeviceMAC);
            sensor.startConnectOnBTStart(true);
            sensor.startBT();
        }

        ESWidget CO2_widget = findViewById(R.id.CO2_ES);
        ESWidget temp_widget = findViewById(R.id.TEMP_ES);
        ESWidget hum_widget = findViewById(R.id.HUM_ES);
        ESWidget batt_widget = findViewById(R.id.BATT_ES);

        sensor.setGattEventCallback(new BluetoothGattCallback() {
            @Override
            public void onCharacteristicChanged(BluetoothGatt gatt, BluetoothGattCharacteristic characteristic) {
                super.onCharacteristicChanged(gatt, characteristic);
                Log.d("UI_update", "onCharacteristicChanged: "+characteristic.getUuid()+";\n"+sensor.CHAR_TEMP_UUID+"\n");
                if(characteristic.getUuid().equals(sensor.CHAR_CO2_UUID)){
                    Log.d("UI_update", "onCharacteristicChanged: co2");
                    int value = characteristic.getIntValue(BluetoothGattCharacteristic.FORMAT_UINT16, 0);
                    CO2_widget.setValue(value);
                }
                else if(characteristic.getUuid().equals(sensor.CHAR_TEMP_UUID)){
                    Log.d("UI_update", "onCharacteristicChanged: temp");
                    int value = characteristic.getIntValue(BluetoothGattCharacteristic.FORMAT_SINT16, 0);
                    temp_widget.setValue(value/100.0f);
                }
                else if(characteristic.getUuid().equals(sensor.CHAR_HUM_UUID)){
                    Log.d("UI_update", "onCharacteristicChanged: hum");
                    int value = characteristic.getIntValue(BluetoothGattCharacteristic.FORMAT_SINT16, 0);
                    hum_widget.setValue(value/100.0f);
                }
            }

            @RequiresApi(api = Build.VERSION_CODES.TIRAMISU)
            @Override
            public void onCharacteristicRead(@NonNull BluetoothGatt gatt, @NonNull BluetoothGattCharacteristic characteristic, int status) {
                super.onCharacteristicRead(gatt, characteristic, status);
                Log.d("UI_update", "onCharacteristicRead: ");
                if(characteristic.getUuid().equals(sensor.CHAR_BATT_LEVEL_UUID)){
                    Log.d("UI_update", "onCharacteristicChanged: batt");
                    int val = characteristic.getIntValue(BluetoothGattCharacteristic.FORMAT_UINT8, 0);
                    batt_widget.setValue(val);
                }
            }
        });
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        sensor.disconnect();
    }

    @RequiresApi(api = Build.VERSION_CODES.S)
    @Override
    protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        sensor.onActivityResult(requestCode, resultCode, data);
    }

    @RequiresApi(api = Build.VERSION_CODES.S)
    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        sensor.onRequestPermissionsResult(requestCode, permissions, grantResults);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.toolbar, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
            case R.id.select_target:
                Intent myIntent = new Intent(this, search_ble_devices_activity.class);
                startActivity(myIntent);
                return true;

            default:
                // If we got here, the user's action was not recognized.
                // Invoke the superclass to handle it.
                return super.onOptionsItemSelected(item);

        }
    }
}