How to stop asynctask thread in Kotlin?

This example demonstrates how to stop an asynctask thread in Kotlin.

Step 1 − Create a new project in Android Studio, go to File ? New Project and fill all required details to create a new project.

Step 2 − Add the following code to res/layout/activity_main.xml.

Example

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools"
   android:layout_width="match_parent"
   android:layout_height="match_parent"
   tools:context=".MainActivity">
   <Button
      android:id="@+id/btnDo"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_above="@id/btnCancel"
      android:layout_centerInParent="true"
      android:layout_marginBottom="25sp"
      android:text="Do AsyncTask" />
   <Button
      android:id="@+id/btnCancel"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_above="@id/textView"
      android:layout_centerInParent="true"
      android:layout_marginBottom="20dp"
      android:text="Cancel" />
   <TextView
      android:id="@+id/textView"
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:layout_centerInParent="true"
      android:gravity="center_horizontal"
      android:textSize="20sp" />
</RelativeLayout>

Step 3 − Add the following code to src/MainActivity.kt

Example

import android.graphics.Color
import android.os.AsyncTask
import android.os.Bundle
import android.view.View
import android.widget.Button
import android.widget.TextView
import androidx.appcompat.app.AppCompatActivity
import java.util.*
class MainActivity : AppCompatActivity() {
   private lateinit var btnDo: Button
   private lateinit var btnCancel: Button
   private lateinit var textView: TextView
   private var myTask: AsyncTask<*, *, *>? = null
   override fun onCreate(savedInstanceState: Bundle?) {
      super.onCreate(savedInstanceState)
      setContentView(R.layout.activity_main)
      title = "KotlinApp"
      btnDo = findViewById(R.id.btnDo)
      btnCancel = findViewById(R.id.btnCancel)
      textView = findViewById(R.id.textView)
      btnDo.setOnClickListener(View.OnClickListener {
         textView.text = ""
         myTask = DownloadTask().execute("Task1", "Task2", "Task3", "Task4", "Task5")
      })
      btnCancel.setOnClickListener(View.OnClickListener { myTask!!.cancel(true) })
   }
   private open inner class DownloadTask :
   AsyncTask<String?, Int?, List<String>>() {
      override fun onPreExecute() {
         super.onPreExecute()
         textView.setTextColor(Color.BLUE)
         textView.text = textView.text.toString() + "
 Starting Task...."
      }
      override fun doInBackground(vararg params: String?): List<String>? {
         val count = params.size
         val taskList: MutableList<String> = ArrayList(count)
         for (i in 0 until count) {
            val currentTask = params[i]
            taskList.add(currentTask.toString())
            try {
               Thread.sleep(1000)
            } catch (e: InterruptedException) {
                  e.printStackTrace()
               }
               publishProgress(((i + 1) / count.toFloat() * 100).toInt())
               if (isCancelled) {
                  break
               }
            }
            return taskList
         }
         override fun onCancelled() {
            super.onCancelled()
            textView.setTextColor(Color.RED)
            textView.text = textView.text.toString() + "
 Operation is cancelled.."
         }
         override fun onProgressUpdate(vararg values: Int?) {
            super.onProgressUpdate(*values)
            textView.text = textView.text.toString() + "
 Completed:)" + values[0] + "%"
         }
      override fun onPostExecute(result: List<String>) {
         super.onPostExecute(result)
         textView.text = textView.text.toString() + "

 Done...."
         for (i in result.indices) {
            textView.text = textView.text.toString() + "
" +
            result[i]
         }
      }
   }
}

Step 4 − Add the following code to androidManifest.xml

Example

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="app.com.q10">
   <application
      android:allowBackup="true"
      android:icon="@mipmap/ic_launcher"
      android:label="@string/app_name"
      android:roundIcon="@mipmap/ic_launcher_round"
      android:supportsRtl="true"
      android:theme="@style/AppTheme">
      <activity android:name=".MainActivity">
         <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
         </intent-filter>
      </activity>
   </application>
</manifest>

Let's try to run your application. I assume you have connected your actual Android Mobile device with your computer. To run the app from android studio, open one of your project's activity files and click the Run icon from the toolbar. Select your mobile device as an option and then check your mobile device which will display your default screen

Updated on: 23-May-2020

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