android kotlin - Canvas draw point

MainActivity.kt


package com.cfsuman.kotlintutorials

import android.app.Activity
import android.graphics.*
import android.os.Bundle
import android.widget.CheckBox
import android.widget.ImageView
import android.widget.SeekBar
import android.widget.TextView


class MainActivity : Activity() {
    lateinit var imageView:ImageView
    lateinit var seekBarWidth:SeekBar
    lateinit var seekBarX:SeekBar
    lateinit var seekBarY:SeekBar
    lateinit var textView:TextView
    lateinit var checkBox:CheckBox

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

        // get the widgets reference from XML layout
        imageView = findViewById(R.id.imageView)
        seekBarWidth = findViewById(R.id.seekBarWidth)
        seekBarX = findViewById(R.id.seekBarX)
        seekBarY = findViewById(R.id.seekBarY)
        textView = findViewById(R.id.textView)
        checkBox = findViewById(R.id.checkBox)


        // initial settings
        seekBarX.max = 1500
        seekBarY.max = 850
        seekBarWidth.max = 100


        seekBarX.progress = 750
        seekBarY.progress = 425
        seekBarWidth.progress = 30


        setSeekBarListener(seekBarWidth)
        setSeekBarListener(seekBarX)
        setSeekBarListener(seekBarY)


        checkBox.setOnCheckedChangeListener {
                buttonView, isChecked ->
            updateDrawing()
        }

        // show initial drawing on image view
        updateDrawing()
    }



    private fun setSeekBarListener(seekBar: SeekBar){
        seekBar.setOnSeekBarChangeListener(
            object : SeekBar.OnSeekBarChangeListener{
                override fun onProgressChanged(
                    seekBar: SeekBar?, progress: Int,
                    fromUser: Boolean) {
                    updateDrawing()
                }

                override fun onStartTrackingTouch(seekBar: SeekBar?) {
                }

                override fun onStopTrackingTouch(seekBar: SeekBar?) {
                }
            })
    }



    // function to update drawing
    private fun updateDrawing(){
        val bitmap= drawPoint(
            seekBarX.progress.toFloat(),
            seekBarY.progress.toFloat(),
            seekBarWidth.progress + 20F,
            checkBox.isChecked
        )


        textView.text = "Width : ${seekBarWidth.progress + 20} px"

        textView.append(" (X:${seekBarX.progress}, " +
                "Y:${seekBarY.progress})")


        imageView.setImageBitmap(bitmap)
    }
}



// function to draw point / dot on canvas
fun drawPoint(
    x : Float = 500F,
    y : Float = 200F,
    strokeWidth : Float = 50F,
    isRound:Boolean = false
):Bitmap?{
    val bitmap = Bitmap.createBitmap(
        1500,
        850,
        Bitmap.Config.ARGB_8888
    )


    // canvas for drawing
    val canvas = Canvas(bitmap).apply {
        drawColor(Color.parseColor("#A2A2D0"))
    }


    // paint to draw point / dot on canvas
    val paint = Paint().apply {
        isAntiAlias = true
        color = Color.parseColor("#333399")

        // point / dot width
        this.strokeWidth = strokeWidth
        style = Paint.Style.STROKE

        // make it round or square shape
        strokeCap = if (isRound){
            Paint.Cap.ROUND
        }else{
            Paint.Cap.SQUARE
        }
    }


    // finally, draw point / dot on canvas
    canvas.drawPoint(
        x,
        y,
        paint
    )

    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:id="@+id/rootLayout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    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" />

    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="8dp"
        android:text="TextView"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/imageView" />

    <CheckBox
        android:id="@+id/checkBox"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="8dp"
        android:text="Round?"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView" />

    <SeekBar
        android:id="@+id/seekBarWidth"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="24dp"
        android:layout_marginEnd="24dp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/checkBox" />

    <SeekBar
        android:id="@+id/seekBarX"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="8dp"
        android:layout_marginTop="24dp"
        android:layout_marginEnd="8dp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/seekBarWidth" />

    <SeekBar
        android:id="@+id/seekBarY"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="8dp"
        android:layout_marginEnd="8dp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/seekBarX" />

</androidx.constraintlayout.widget.ConstraintLayout>