Downloading a single file with AsyncTask

Issue

I'm a beginner in Android development. I'm trying to learn multi-threading and working with the internet so I'm doing that by downloading a PDF file from a link through the background thread using AsyncTask. I have confusions about what the best way is to go about it.

Do I create the URI and other necessary connectivity objects in the onCreate or in the doInBackground method of the AsyncTask class?

To download just a single PDF file, what sort of objects do I need to call?

I have checked the documentation but I couldn't really understand it. I'd appreciate a layman's explanation and possibly pseudo-code.

Here is the code I have so far:

public class MainActivity extends AppCompatActivity {
    Button downloadPDF;
    DownloadingClass downPDF;
    private static final String TAG = "omar.asynctaskdemo;";

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

        String urlExample = "https://doc.lagout.org/programmation/Actionscript%20-%20Flash%20-%20Flex%20-%20Air/Flash%20Development%20for%20Android%20Cookbook%20-%20Labrecque%20-%20Packt%20%282011%29/Flash%20Development%20for%20Android%20Cookbook%20-%20Labrecque%20-%20Packt%20%282011%29.pdf");

        downloadPDF = findViewById(R.id.download_pdf);
        downPDF = new DownloadingClass();

        downloadPDF.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                downPDF.execute();
            }
        });
    }

    private class DownloadingClass extends AsyncTask<String, Integer, Void>{
        @Override
        protected Void doInBackground(String... strings) {
            return null;
        }
    }
}

Solution

AsyncTask just runs your code in the background thread. To download a pdf file is like any other file.

You will require to use HttpUrlConnection, Create a FileOutputStream and write the inputstream. Refer this

Have the above code executed in doInBackground of AsyncTask class and better pass the url in the constructor and do everything inside the doInBackground method. Since you don't want to block the UI thread.

Answered By - Binary Baba