Friday, July 3, 2020

android kotlin - Canvas draw circle

MainActivity.kt

package com.cfsuman.kotlintutorials

import android.app.Activity
import android.graphics.*
import android.os.Bundle
import android.widget.ImageView
import android.widget.TextView
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)
        val textView = findViewById<TextView>(R.id.textView)


        // draw circle on canvas and get bitmap
        val bitmap = drawCircle(
            color = Color.parseColor("#333399"),
            radius = 300f,
            canvasBackground = Color.parseColor("#A2A2D0")
        )


        // show drawing on image view
        imageView.setImageBitmap(bitmap)


        // about canvas drawing
        textView.text = "bitmap (${bitmap.width} px" +
                " * ${bitmap.height} px)"
        textView.append("\ncircle radius 300 px")
        textView.append("\ncircle color #333399")
        textView.append("\ncanvas color #A2A2D0")
    }
}



// function to draw circle on canvas
fun drawCircle(
    color:Int = Color.LTGRAY,
    bitmapWidth:Int = 1500,
    bitmapHeight:Int = 750,
    radius:Float = min(bitmapWidth, bitmapHeight) / 2f,
    cx:Float = bitmapWidth / 2f,
    cy:Float = bitmapHeight / 2f,
    canvasBackground:Int = Color.WHITE
):Bitmap{
    val bitmap = Bitmap.createBitmap(
        bitmapWidth, bitmapHeight, Bitmap.Config.ARGB_8888
    )


    // canvas to draw circle
    val canvas = Canvas(bitmap).apply {
        drawColor(canvasBackground)
    }


    // paint to draw on canvas
    val paint = Paint().apply {
        this.color = color
        isAntiAlias = true
    }


    // draw circle on canvas
    canvas.drawCircle(
        cx, // x-coordinate of the center of the circle
        cy, // y-coordinate of the center of the circle
        radius, // radius of the circle
        paint // paint used to draw the circle
    )

    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"
    xmlns:tools="http://schemas.android.com/tools"
    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="16dp"
        android:fontFamily="sans-serif"
        android:text="Canvas"
        android:textAlignment="center"
        android:textSize="22sp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/imageView" />

</androidx.constraintlayout.widget.ConstraintLayout>