Can't change editText input from string to float

Issue

package com.example.tipcalculator

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.widget.Button
import android.widget.EditText
import android.widget.TextView
import kotlin.text.toFloat as kotlinTextToFloat


class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        supportActionBar?.hide()
        val tenPerTip: Button =       findViewById(R.id.tenPerTipButton)
        val fifteenPerTip: Button =   findViewById(R.id.fifteenPerTipButton)
        val twentyPerTip: Button =    findViewById(R.id.twentyPerTipButton)
        val customTip: Button =       findViewById(R.id.customTipSubmit)
        val sumRaw: EditText =        findViewById(R.id.billEnter)
        val tipOnlyResult: TextView = findViewById(R.id.tipOnlyResult)
        val totalResult: TextView =   findViewById(R.id.totalResult)
        val sumString = sumRaw.toString()
        val sumInput = sumString.toInt()

        tenPerTip.setOnClickListener{
            val sumTotal = sumInput * 1.1
            val tipOnly = sumInput * 0.1
            tipOnlyResult.text = tipOnly.toString()
            totalResult.text = sumTotal.toString()
        }
        fifteenPerTip.setOnClickListener{

        }
        twentyPerTip.setOnClickListener{

        }
        customTip.setOnClickListener{

        }
    }
}

I was trying to switch the EditText input to a string and from there to a float so that I can do calculations on it. On the line with val sumInput = sumString.toInt() the code breaks. It will compile, but when I try to run an emulator it casts error codes about the toInt declaration. The code is using toInt in this because I was trying to see if the emulator would like that. Also whenever I declare that toInt it highlights in a light yellow italic font, which I haven't seen before.

Solution

I have Edited your code. Changes to the code is explained with the comments below.

class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        supportActionBar?.hide()
        val tenPerTip: Button = findViewById(R.id.tenPerTipButton)
        val fifteenPerTip: Button = findViewById(R.id.fifteenPerTipButton)
        val twentyPerTip: Button = findViewById(R.id.twentyPerTipButton)
        val customTip: Button = findViewById(R.id.customTipSubmit)
        val sumRaw: EditText = findViewById(R.id.billEnter)
        val tipOnlyResult: TextView = findViewById(R.id.tipOnlyResult)
        val totalResult: TextView = findViewById(R.id.totalResult)

        /** if you put sumString and sumInput here, what happens is when your app
         *  is created and the onCreate method is called sumString is initialized
         *  here without using .text, i.e., sumRaw.text command what happens is sumString
         *  will be initialized with sumRaw value (i guess maybe sumRaw id) and you will 
         *  get error.
         *  Also, this is only called once when all the other variable are initialized.
         *  If you want to use it outside use a TextWatcher and change the variable as
         *  soon as it is updated in the EditText.
         *  A work-around would be initializing this value inside OnClickListener, what
         *  happens here is whenever you click tenPerTip Button sumString is Initialized
         *  with current values in sumRaw EditText.
         *  
         *  Do use .text else it will give errors.
         */
        

        tenPerTip.setOnClickListener {

            val sumString = sumRaw.text.toString()
            
            // what happens here is sumString is converted to Double if it has valid pattern
            // else it will return null
            // And then the elvis operator will check for null. If its null, it will not
            // not proceed further and will get out the listener. 
            
            val sumInput = sumString.toDoubleOrNull() ?: return@setOnClickListener

            val sumTotal = sumInput * 1.1
            val tipOnly = sumInput * 0.1
            tipOnlyResult.text = tipOnly.toString()
            totalResult.text = sumTotal.toString()
        }
        fifteenPerTip.setOnClickListener {

        }
        twentyPerTip.setOnClickListener {

        }
        customTip.setOnClickListener {

        }
    }
}

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