android kotlin - NumberPicker text size

MainActivity.kt


package com.cfsuman.kotlintutorials

import android.annotation.SuppressLint
import android.app.Activity
import android.content.Context
import android.graphics.Paint
import android.os.Bundle
import android.util.TypedValue
import android.widget.EditText
import android.widget.NumberPicker


class MainActivity : Activity() {
    private lateinit var numberPicker:NumberPicker

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        // get the context
        val context = this
        val textSize = 50F

        // get the widgets reference from XML layout
        numberPicker = findViewById(R.id.numberPicker)

        // set number picker minimum and maximum value
        numberPicker.minValue = 0
        numberPicker.maxValue = 10

        // set number picker text size to 50 sp or equivalent pixels
        if (android.os.Build.VERSION.SDK_INT >=
            android.os.Build.VERSION_CODES.Q) {
            // float: the text size in pixel units
            numberPicker.textSize = textSize.spToPixels(context)
        }else{
            numberPicker.changeTextSize(context,textSize)
        }
    }
}


// extension function to set number picker text size
@SuppressLint("SoonBlockedPrivateApi")
fun NumberPicker.changeTextSize(context: Context, textSize: Float) {
    try {
        val selectorWheelPaintField = javaClass
            .getDeclaredField("mSelectorWheelPaint")
        selectorWheelPaintField.isAccessible = true
        (selectorWheelPaintField[this] as Paint)
            .textSize = textSize.spToPixels(context)

    } catch (e: NoSuchFieldException) {
        // log exception here
    } catch (e: IllegalAccessException) {
        // log exception here
    } catch (e: IllegalArgumentException) {
        // log exception here
    }

    val count = childCount
    for (i in 0 until count) {
        val child = getChildAt(i)
        if (child is EditText) child
            .setTextSize(TypedValue.COMPLEX_UNIT_SP,textSize)
    }
    invalidate()
}


// extension function to convert sp to equivalent pixels
fun Float.spToPixels(context: Context): Float{
    return TypedValue.applyDimension(
        TypedValue.COMPLEX_UNIT_SP,
        this,
        context.resources.displayMetrics
    )
}

activity_main.xml


<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#DCDCDC"
    android:padding="32dp">

    <NumberPicker
        android:id="@+id/numberPicker"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="32dp"
        android:descendantFocusability="blocksDescendants"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>