MainActivity.kt
package com.cfsuman.kotlinexamples
import android.content.Context
import android.os.AsyncTask
import android.support.v7.app.AppCompatActivity
import android.os.Bundle
import android.widget.Toast
import kotlinx.android.synthetic.main.activity_main.*
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
// Initialize a new instance of AsyncImageDownload class
val task = AsyncImageDownload(this,root_layout,progress_bar,text_view)
// Button to start multiple images download
button_start.setOnClickListener{
task.execute(
"https://images.freeimages.com/images/large-previews/310/spring-1-1405906.jpg",
"https://images.freeimages.com/images/large-previews/8f3/white-flower-power-1403046.jpg",
"https://images.freeimages.com/images/large-previews/81c/flower-1393311.jpg",
"https://images.freeimages.com/images/large-previews/7f7/statice-1406388.jpg",
"https://images.freeimages.com/images/large-previews/760/wedding-flower-1188350.jpg"
)
it.isEnabled = false
button_cancel.isEnabled = true
}
// Button to cancel the async task
button_cancel.setOnClickListener{
task.cancel(true)
it.isEnabled = false
}
// Set a click listener for root layout
root_layout.setOnClickListener{
// Get the async task status and show it using toast message
when(task.status){
AsyncTask.Status.RUNNING -> toast("Task running")
AsyncTask.Status.PENDING -> toast("Task pending")
AsyncTask.Status.FINISHED -> toast("Task finished")
else -> toast("Task status Unknown")
}
}
}
// Extension function to show toast message
fun Context.toast(message:String){
Toast.makeText(this,message,Toast.LENGTH_SHORT).show()
}
}
AsyncDownloads.kt
package com.cfsuman.kotlinexamples
import android.content.Context
import android.graphics.Bitmap
import android.graphics.BitmapFactory
import android.graphics.Color
import android.os.AsyncTask
import android.widget.*
import java.net.URL
class AsyncImageDownload(
val context: Context,
val rootLayout: LinearLayout,
val progressBar: ProgressBar,
val textView: TextView
)
: AsyncTask<String, Int, MutableList<Bitmap>>(){
// Before async task start
override fun onPreExecute() {
progressBar.progress = 0
textView.text = "Download started..."
super.onPreExecute()
}
// Manage background async task
override fun doInBackground(vararg params: String): ArrayList<Bitmap>{
val list = ArrayList<Bitmap>()
// Loop through the task and execute them
for( i in 0 until params.size){
val urlOfImage = URL(params[i])
try {
val inputStream = urlOfImage.openStream()
list.add(BitmapFactory.decodeStream(inputStream)!!)
} catch (e: Exception) { // Catch the download exception
e.printStackTrace()
}
// Publish the async task progress in percentage
publishProgress(((i + 1) / params.size.toFloat() * 100).toInt())
// If user cancel the task at runtime
if(isCancelled)break
}
return list
}
// Display the async tas progress
override fun onProgressUpdate(vararg values: Int?) {
progressBar.progress = values[0]!!
textView.text = "Download completed... ${values[0]}%"
Toast.makeText(context,"Downloaded ${values[0]} %",Toast.LENGTH_LONG).show()
super.onProgressUpdate(values[0])
}
// Manage completed task after user cancel async task
override fun onCancelled(result: MutableList<Bitmap>?) {
textView.text = "Task cancelled...\n ${result!!.size} files download success"
for (bitmap in result){
rootLayout.addView(newImageView(bitmap))
}
super.onCancelled(result)
}
// Manage result after completed async task
override fun onPostExecute(result: MutableList<Bitmap>?) {
textView.text = "Task finish...\n ${result?.size} files download success"
for (bitmap in result!!){
rootLayout.addView(newImageView(bitmap))
}
super.onPostExecute(result)
}
// Method to create a new ImageView instance
private fun newImageView(bitmap: Bitmap): ImageView {
val params = LinearLayout.LayoutParams(LinearLayout.LayoutParams.MATCH_PARENT, 300)
params.bottomMargin = 15
val imageView = ImageView(context)
imageView.layoutParams = params
imageView.setImageBitmap(bitmap)
imageView.setBackgroundColor(Color.LTGRAY)
imageView.setPadding(10,10,10,10)
return imageView
}
}
activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<ScrollView
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#92a692"
android:padding="16dp"
>
<LinearLayout
android:id="@+id/root_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
>
<Button
android:id="@+id/button_start"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Start Downloads"
/>
<Button
android:id="@+id/button_cancel"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Cancel Downloads"
android:textColor="#ff0400"
android:enabled="false"
/>
<ProgressBar
android:id="@+id/progress_bar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:indeterminate="false"
style="@style/Widget.AppCompat.ProgressBar.Horizontal"
/>
<TextView
android:id="@+id/text_view"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:textSize="20sp"
android:gravity="center"
android:textStyle="bold"
/>
</LinearLayout>
</ScrollView>
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