Downloading multiple files one by one using AsyncTask?

Question

I\'m trying to download multiple files one by one (file is downloaded, we start downloading the next file). Using this method I can keep track of the files being downloaded.

Answer 1

package com.ProgressDialogDemo1;

import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.URL;
import java.net.URLConnection;

import android.app.Activity;
import android.app.Dialog;
import android.app.ProgressDialog;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.Environment;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.ProgressBar;

public class ProgressDialogDemoActivity extends Activity {

    public static final int DIALOG_DOWNLOAD_PROGRESS = 0;
    private Button startBtn;
    private ProgressDialog mProgressDialog;
    ProgressBar prgBar1;
    ImageView imgv1;

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        imgv1 = (ImageView) findViewById(R.id.imgv1);
        startBtn = (Button)findViewById(R.id.startBtn);
        prgBar1 = (ProgressBar) findViewById(R.id.prgBar1);
        prgBar1.setMax(100);

        startBtn.setOnClickListener(new OnClickListener(){
            public void onClick(View v) {
                    startDownload();
            }
        });
    }

    private void startDownload() {
        String[] url = {"http://animal.discovery.com/birds/peacock/pictures/peacock-picture.jpg",
                    "http://www.funrocker.com/blog/wp-content/uploads/2010/04/Animals-Wild-Life-Jungle-FunRocker.Com-03.jpg",
                    "http://www.thewallpapers.org/photo/5790/Nature_Wallpapers-037.jpg",
                    "http://2.bp.blogspot.com/-j56yaqpfjVE/TnzTjcqnCjI/AAAAAAAAGPM/MzqmczFkC30/s1600/natural-pictures.jpg",
                    "http://www.fantasy-and-art.com/wp-content/gallery/nature-wallpapers/red-tree-wallpaper-hd.jpg",
                    "http://upload.wikimedia.org/wikipedia/commons/thumb/1/1a/Bachalpseeflowers.jpg/300px-Bachalpseeflowers.jpg"};
        DownloadFileAsync dloadFAsync = new DownloadFileAsync(url);
        dloadFAsync.execute(url);
    }
    @Override
    protected Dialog onCreateDialog(int id) {
        switch (id) {
        case DIALOG_DOWNLOAD_PROGRESS:
            mProgressDialog = new ProgressDialog(this);
            mProgressDialog.setCancelable(false);
            return mProgressDialog;
        default:
            return null;
        }
    }

    //              Async  Task
    class DownloadFileAsync extends AsyncTask<String, String, String> {
        int current=0;
        String[] paths;
        String fpath;
        boolean show = false;

        public DownloadFileAsync(String[] paths) {
            super();
            this.paths = paths;
            for(int i=0; i<paths.length; i++)
                System.out.println((i+1)+":  "+paths[i]);
        }

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

        @Override
        protected String doInBackground(String... aurl) {
            int rows = aurl.length;
                while(current < rows)
                {
                    int count;
                    try {
                        System.out.println("Current:  "+current+"\t\tRows: "+rows);
                        fpath = getFileName(this.paths[current]);
                        URL url = new URL(this.paths[current]);
                        URLConnection conexion = url.openConnection();
                        conexion.connect();
                        int lenghtOfFile = conexion.getContentLength();
                        InputStream input = new BufferedInputStream(url.openStream(), 512);
                        OutputStream output = new FileOutputStream("/sdcard/"+fpath);
                        byte data[] = new byte[512];
                        long total = 0;
                        while ((count = input.read(data)) != -1) {
                            total += count;
                            publishProgress(""+(int)((total*100)/lenghtOfFile));
                            output.write(data, 0, count);
                        }
                        show = true;
                        output.flush();
                        output.close();
                        input.close();
                        current++;
                    } catch (Exception e) {}
            }   //  while end
            return null;
        }

        @Override
        protected void onProgressUpdate(String... progress) {
            prgBar1.setProgress(Integer.parseInt(progress[0]));
            if(show) {
                File dir = Environment.getExternalStorageDirectory();
                File imgFile = new File(dir, getFileName(this.paths[(current-1)]));
                Bitmap bmp  = BitmapFactory.decodeFile(imgFile.getAbsolutePath());
                imgv1.setImageBitmap(bmp);
                show = false;
            }
        }

        @Override
        protected void onPostExecute(String unused) {
            System.out.println("unused: "+unused);
        }
    }

    public String getFileName(String wholePath)
    {
        String name=null;
        int start,end;
        start=wholePath.lastIndexOf('/');
        end=wholePath.length();     //lastIndexOf('.');
        name=wholePath.substring((start+1),end);
        name = "images/"+name;
        System.out.println("Start:"+start+"\t\tEnd:"+end+"\t\tName:"+name);
        return name;
    }
}

Answer 2

package com.example.androidhive;

import java.io.BufferedInputStream;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.URL;
import java.net.URLConnection;

import android.app.Activity;
import android.app.Dialog;
import android.app.ProgressDialog;
import android.graphics.drawable.Drawable;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.Environment;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;

public class AndroidDownloadFileByProgressBarActivity extends Activity {

    // button to show progress dialog
    Button btnShowProgress;

    // Progress Dialog
    private ProgressDialog pDialog;
    ImageView my_image;
    // Progress dialog type (0 - for Horizontal progress bar)
    public static final int progress_bar_type = 0;

    // File url to download
    String[] ur = {
            "http://www.funrocker.com/blog/wp-content/uploads/2010/04/Animals-Wild-Life-Jungle-FunRocker.Com-03.jpg",
            "http://2.bp.blogspot.com/-j56yaqpfjVE/TnzTjcqnCjI/AAAAAAAAGPM/MzqmczFkC30/s1600/natural-pictures.jpg",
            "http://www.fantasy-and-art.com/wp-content/gallery/nature-wallpapers/red-tree-wallpaper-hd.jpg" };

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

        // show progress bar button
        btnShowProgress = (Button) findViewById(R.id.btnProgressBar);
        // Image view to show image after downloading
        my_image = (ImageView) findViewById(R.id.my_image);
        /**
         * Show Progress bar click event
         * */
        btnShowProgress.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                // starting new Async Task
                new DownloadFileFromURL().execute(ur);
            }
        });
    }

    /**
     * Showing Dialog
     * */
    @Override
    protected Dialog onCreateDialog(int id) {
        switch (id) {
        case progress_bar_type:
            pDialog = new ProgressDialog(this);
            pDialog.setMessage("Downloading file. Please wait...");
            pDialog.setIndeterminate(false);
            pDialog.setMax(100);
            pDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
            pDialog.setCancelable(true);
            pDialog.show();
            return pDialog;
        default:
            return null;
        }
    }

    /**
     * Background Async Task to download file
     * */
    class DownloadFileFromURL extends AsyncTask<String, Integer, String> {

        /**
         * Before starting background thread Show Progress Bar Dialog
         * */
        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            showDialog(progress_bar_type);
        }

        /**
         * Downloading file in background thread
         * */
        @Override
        protected String doInBackground(String... f_url) {
            int count;
            try {

                for (int i = 0; i < f_url.length; i++) {
                    URL url = new URL(f_url[i]);
                    URLConnection conection = url.openConnection();
                    conection.connect();
                    // getting file length
                    int lenghtOfFile = conection.getContentLength();

                    // input stream to read file - with 8k buffer
                    InputStream input = new BufferedInputStream(
                            url.openStream(), 8192);
                    System.out.println("Data::" + f_url[i]);
                    // Output stream to write file
                    OutputStream output = new FileOutputStream(
                            "/sdcard/downloaded" + i + ".jpg");

                    byte data[] = new byte[1024];

                    long total = 0;

                    while ((count = input.read(data)) != -1) {
                        total += count;
                        // publishing the progress....
                        // After this onProgressUpdate will be called
                        publishProgress((int) ((total * 100)/lenghtOfFile));

                        // writing data to file
                        output.write(data, 0, count);
                    }

                    // flushing output
                    output.flush();

                    // closing streams
                    output.close();
                    input.close();
                }
            } catch (Exception e) {
                Log.e("Error: ", e.getMessage());
            }

            return null;
        }

        /**
         * Updating progress bar
         * */
        protected void onProgressUpdate(Integer... progress) {
            // setting progress percentage
            pDialog.setProgress(progress[0]);
        }

        /**
         * After completing background task Dismiss the progress dialog
         * **/
        @Override
        protected void onPostExecute(String file_url) {
            // dismiss the dialog after the file was downloaded
            dismissDialog(progress_bar_type);

            // Displaying downloaded image into image view
            // Reading image path from sdcard
            String imagePath = Environment.getExternalStorageDirectory()
                    .toString() + "/downloaded.jpg";
            // setting downloaded into image view
            // my_image.setImageDrawable(Drawable.createFromPath(imagePath));
        }

    }
}

Answer 3

If I understand correctly, you do not want to download all the files at the same tim e(simultaneously) but one by one (serially). In order to do so build a String array with the URLs to download, and call execute() with that array.

Example: Assuming that your DownloadFileAsync expects String as a parameter to it's doInBackground method, you would call to:

new DownloadFileAsync().execute(url1, url2, url3, url4, video1, video2, video3, video4);