MainActivity.java

package ir.smartlab.android.downloadasynctask;

import android.app.Activity;
import android.os.AsyncTask;
import android.os.Bundle;
import android.view.View;
import android.widget.ProgressBar;
import android.widget.TextView;
import android.widget.Toast;
import ir.smartlab.android.downloadasynctask.R;

public class MainActivity extends Activity {

    TextView downloadProgressTextView;
    ProgressBar downloadProgressBar;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        downloadProgressTextView = (TextView) findViewById(R.id.downloadProgressTextView);
        downloadProgressBar = (ProgressBar) findViewById(R.id.downloadProgressBar);
    }

    public void startDownload(View v) {
        DownloadTask downloadTask = new DownloadTask();
        downloadTask.execute("");
    }

    class DownloadTask extends AsyncTask<String, Integer, Boolean> {

        @Override
        protected void onPreExecute() {
            downloadProgressBar.setVisibility(View.VISIBLE);
        }

        @Override
        protected Boolean doInBackground(String... params) {
            for (int i = 0; i <= 100; i++) {
                try {
                    Thread.sleep(100);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                publishProgress(i);
            }
            return true;
        }

        @Override
        protected void onProgressUpdate(Integer... values) {
            downloadProgressTextView.setText(values[0] + "% downloaded...");
        }

        @Override
        protected void onPostExecute(Boolean result) {
            downloadProgressBar.setVisibility(View.INVISIBLE);
            if (result) {
                Toast.makeText(getApplicationContext(), "Download Completed.", Toast.LENGTH_LONG).show();
            } else {
                Toast.makeText(getApplicationContext(), "Download Error.", Toast.LENGTH_LONG).show();
            }
        }

    }
}