How can I use the same variable in different activities in Android Studio (kotlin)?

Question

So I'm making a fitness/health app and I need to make some user inputs public such that I can use their values on other screens(activities). I have looked online on how to do this and the closest I got was a companion object. But this is not working as Kotlin is not allowing me to use findViewByID inside a variable inside the class. All the other solutions I have found are for Java and I'm using Kotlin.

I tried making the user inputs a companion object inside the activity's class, but this didn't work after I used findViewByID to grab the user input and put it inside the variable to begin with.

Here is my code, hopefully it's not too long:

package com.example.optilife

import android.content.Intent
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.widget.Button
import android.widget.EditText
import com.google.firebase.database.DatabaseReference


class LogIn1stTimeActivity : AppCompatActivity() {
    companion object {
        val userHeight = findViewById<EditText>(R.id.et_UserHeight) //so this doesn't work because it doesn't allow me to use findViewByID
    }
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_log_in1st_time)
        val welcomeButton = findViewById<Button>(R.id.welcomeButton)
        val userHeight = findViewById<EditText>(R.id.et_UserHeight)
        val userWeight = findViewById<EditText>(R.id.et_UserWeight)
        val userAge = findViewById<EditText>(R.id.et_UserAge)

        welcomeButton.setOnClickListener { var recommendedCalories = 66 + 13.7*userWeight.text.toString().toInt() + 5*userHeight.text.toString().toInt() - 6.8*userAge.text.toString().toInt()

            println("$recommendedCalories")

            val intent = Intent(this, WelcomeActivity::class.java)
            startActivity(intent)}
    }
} 

So I want to calculate recommendedCalories on another screen and I need the user inputs on that screen. Any help would be appreciated, thanks.

Answer 1

You can just use the intent.putExtra with intent and pass the "recommendedCalories" data.

welcomeButton.setOnClickListener  
{ 
  var recommendedCalories = 66 + 13.7*userWeight.text.toString().toInt() + 
        5*userHeight.text.toString().toInt() - 6.8*userAge.text.toString().toInt()

        println("$recommendedCalories")

         val intent = Intent(this@LogIn1stTimeActivity,WelcomeActivity::class.java)
         intent.putExtra("Calories", recommendedCalories)
         startActivity(intent)
 }

Get values in WelcomeActivity.class and store them in one variable.

    val resultIntent = intent.extras

    if (resultIntent != null) {
        val calories= resultIntent.getDouble("Calories")
    }