android kotlin - Paint gradient circle

MainActivity.kt


package com.cfsuman.kotlintutorials

import android.app.Activity
import android.graphics.*
import android.os.Bundle
import android.widget.*
import kotlin.math.min


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

        // get the widgets reference from XML layout
        val imageView = findViewById<ImageView>(R.id.imageView)

        // show drawing on image view
        imageView.setImageBitmap(
            drawGradientCircle()
        )
    }
}



// function to draw gradient circle on canvas
fun drawGradientCircle(): Bitmap?{
    val bitmap = Bitmap.createBitmap(
        1500,
        850,
        Bitmap.Config.ARGB_8888
    )


    // canvas for drawing
    val canvas = Canvas(bitmap).apply {
        drawColor(Color.parseColor("#FEFEFA"))
    }


    // radius of circle and gradient
    val radius = min(canvas.width, canvas.height) / 2F - 25F


    // paint to draw radial gradient circle
    val paint = Paint().apply {
        isAntiAlias = true
        style = Paint.Style.FILL

        // radial gradient shader
        shader = RadialGradient(
            canvas.width / 2F, // center x
            canvas.height / 2F, // center y
            radius, // radius
            intArrayOf( // colors
                Color.parseColor("#E30022"),
                Color.parseColor("#F7E7CE"),
                Color.parseColor("#FFF600")
            ),
            // stops - may be null, valid values are between 0.0f and 1.0f
            null,
            Shader.TileMode.MIRROR // shader titling mode
        )
    }


    // finally, draw gradient circle on canvas
    canvas.drawCircle(
        canvas.width / 2F, // cx
        canvas.height / 2F, // cy
        radius, // radius
        paint // paint to draw
    )

    return bitmap
}

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"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/rootLayout"
    android:background="#DCDCDC"
    android:padding="24dp">

    <ImageView
        android:id="@+id/imageView"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>