Android Kotlin: How to convert drawable to bitmap

Android Kotlin: Converting Drawable to Bitmap

This code demonstrates how to convert a drawable resource referenced in the Android project to a Bitmap object in Kotlin. Bitmaps are a fundamental data structure for representing images in Android. They allow for pixel manipulation and various image processing tasks.

The code is implemented within the MainActivity.kt file, which is the main activity class for this example.

Code Breakdown

  1. Import Statements: Necessary classes for working with Bitmaps, Drawables, and resources are imported.
  2. Activity Class Definition: The MainActivity class inherits from AppCompatActivity.
  3. onCreate Method: This method is called when the activity is first created.
    • The layout (activity_main.xml) is inflated using setContentView.
    • Drawable to Bitmap Conversion:
      • ResourcesCompat.getDrawable(resources, R.drawable.flower, null) retrieves the drawable resource referenced by R.drawable.flower from the application resources.
      • The retrieved drawable is cast to a BitmapDrawable as this type of drawable holds a Bitmap internally.
      • Finally, the bitmap property of the BitmapDrawable is accessed to obtain the actual Bitmap object.
    • Setting Image Source: The setImageBitmap method of the imageView is called, passing the converted bitmap as its argument. This sets the image displayed by the ImageView to the converted drawable.

Summary

By converting the drawable resource to a Bitmap, the code gains the ability to manipulate the image data or perform further processing if needed. This approach is useful when you require more control over the image data compared to simply referencing a drawable resource directly in the layout.


MainActivity.kt 

package com.example.jetpack

import android.graphics.Bitmap
import android.graphics.drawable.BitmapDrawable
import android.os.Bundle
import androidx.appcompat.app.AppCompatActivity
import androidx.core.content.res.ResourcesCompat
import kotlinx.android.synthetic.main.activity_main.*


class MainActivity : AppCompatActivity() {

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

        // convert drawable to bitmap
        val bitmap:Bitmap = (ResourcesCompat.getDrawable(
            resources,R.drawable.flower,null)
                as BitmapDrawable).bitmap

        // set image view image source bitmap
        imageView.setImageBitmap(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/constraintLayout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <ImageView
        android:id="@+id/imageView"
        android:layout_width="0dp"
        android:layout_height="0dp"
        android:layout_marginStart="16dp"
        android:layout_marginTop="16dp"
        android:layout_marginEnd="16dp"
        android:layout_marginBottom="16dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        tools:srcCompat="@tools:sample/avatars" />

</androidx.constraintlayout.widget.ConstraintLayout>
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