Async Task Example || Android Tutorial

When ever we try to implement a background task we need to implement it properly using a async task. In this tutorial we will discuss a simple example on android asynctask.

It’s a simple example to cover the concept of android asynctask by making use of a “Log” conditions.To make it much simple for even a beginner to understand what’s happening.

Android asynctask

Let us create a sample project and add a layout for it.

activity_test.xml

Let us declare a button by which we will call a async class on button click

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:gravity="center">


    <Button
        android:id="@+id/btn_click"
        android:layout_width="100dp"
        android:layout_height="wrap_content"
        android:text="Async"/>


</LinearLayout>

MainActivity.java

Now add the java code for android asynctask

Async Task contains four modules

1. onPreExecute
2. doInBackground
3. onProgressUpdate(optional)
4. onPostExecute

onPreExecute:

This method is invoked before android asynctask is started.We declare progress dialog here to alert user regarding the task going on in background.

doInBackground:

As per the name it does the work in background which gets executed immediately after onPreExecute.It might take some time for the computations to finish in this method. And the progress can be declared by using the third method i.e., onProgressUpdate.

onProgressUpdate(Optional):

This method gets called when publish Progress is called. It updates the user interface by showing the status in form of a progress bar or any other form while computation is running in background state.

Its again a optional method which can be used or not but its a good practice to make use of the feature and make user get to know the status of the work completed.

Example:

Downloading  a song or file we might be having the use of this android asynctask because of the size of the file it might take more time and user needs to have a progress with details of the process.

onPostExecute:

This is the final step / method of async task which is invoked after completion of task i.e., background computation.

And the final result is shown to the user.

A basic implementation is show as

private final class Async extends AsyncTask<Void,Void,String>{

    @Override
    protected void onPreExecute() {
        super.onPreExecute();

        Log.d("async"," 1 ");
    }

    @Override
    protected String doInBackground(Void... voids) {

        Log.d("async"," 2 ");

        publishProgress();

        return null;
    }

    @Override
    protected void onProgressUpdate(Void... values) {
        super.onProgressUpdate(values);

        Log.d("async"," 3 ");
    }

    @Override
    protected void onPostExecute(String s) {
        super.onPostExecute(s);

        Log.d("async"," 4 ");
    }

}

Now we will see how to call this async method

Initialize the button you may also use databinding here

Button btnClick = findViewById(R.id.btn_click);

then initialize the android asynctask class and with the help of object we will call

final Async async = new Async();

calling the class as

async.execute();

btnClick.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {

        async.execute();

    }
});

import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;

import androidx.appcompat.app.AppCompatActivity;

import com.abhishekapps.abhishek.mvvm.R;

public class TestActivity extends AppCompatActivity {

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_test);

        Button btnClick = findViewById(R.id.btn_click);

        final Async async = new Async();

        btnClick.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                async.execute();

            }
        });
    }

    private final class Async extends AsyncTask<Void,Void,String>{

        @Override
        protected void onPreExecute() {
            super.onPreExecute();

            Log.d("async"," 1 ");
        }

        @Override
        protected String doInBackground(Void... voids) {

            Log.d("async"," 2 ");

            publishProgress();

            return null;
        }

        @Override
        protected void onProgressUpdate(Void... values) {
            super.onProgressUpdate(values);

            Log.d("async"," 3 ");
        }

        @Override
        protected void onPostExecute(String s) {
            super.onPostExecute(s);

            Log.d("async"," 4 ");
        }

    }
}

Output:

The output depicting android asynctask flow

If you have any  query in this tutorial on android asynctask do let us know in the comment section below.If you like this tutorial do like and share us for more interesting updates.