Thursday, July 16, 2020

android kotlin - Coroutines url to bitmap

MainActivity.kt

package com.example.coroutine

import android.graphics.Bitmap
import android.graphics.BitmapFactory
import android.os.Bundle
import androidx.appcompat.app.AppCompatActivity
import kotlinx.android.synthetic.main.activity_main.*
import kotlinx.coroutines.*
import java.io.IOException
import java.net.URL


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

        // url of image
        val urlImage:URL = URL("https://images.pexels.com/photos/954129/" +
                "pexels-photo-954129.jpeg?" +
                "auto=compress&cs=tinysrgb&dpr=3&h=750&w=1260")

        button.setOnClickListener {
            it.isEnabled = false // disable button

            // async task to get bitmap from url
            val result: Deferred<Bitmap?> = GlobalScope.async {
                urlImage.toBitmap()
            }

            GlobalScope.launch(Dispatchers.Main) {
                // show bitmap on image view when available
                imageView.setImageBitmap(result.await())

                it.isEnabled = true // enable button
            }
        }
    }
}


// extension function to get bitmap from url
fun URL.toBitmap(): Bitmap?{
    return try {
        BitmapFactory.decodeStream(openStream())
    }catch (e:IOException){
        null
    }
}
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="#B2BEB5"
    tools:context=".MainActivity">

    <com.google.android.material.button.MaterialButton
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:backgroundTint="#E52B50"
        android:text="Show Bitmap"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <ImageView
        android:id="@+id/imageView"
        android:layout_width="0dp"
        android:layout_height="350dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="12dp"
        android:layout_marginEnd="8dp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/button"
        tools:srcCompat="@tools:sample/avatars" />

</androidx.constraintlayout.widget.ConstraintLayout>
build.gradle (app) [dependencies]

// kotlin coroutine
implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-core:1.3.7'
implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-android:1.3.7'