Progress bar and downloading a file sample program in Android

This sample android program shows you how to show Progress Bar in Android. In this program many concepts are explained. A button is shown and when clicked, a big file is downloaded from flickr. The downloaded file is saved to the sdcard in the android phone. While the download is still in progress, a progress bar is shown with the actual percentage of download. So the code below explains, downloading a file from a server, saving a file to the sdcard and showing a progress bar all in one android program.

The download.java file is as follows:

package com.javasamples;

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

public class download extends Activity {
   
    public static final int DIALOG_DOWNLOAD_PROGRESS = 0;
    private Button startBtn;
    private ProgressDialog mProgressDialog;
   
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        startBtn = (Button)findViewById(R.id.startBtn);
        startBtn.setOnClickListener(new OnClickListener(){
            public void onClick(View v) {
                startDownload();
            }
        });
    }

    private void startDownload() {
        String url = "http://farm1.static.flickr.com/114/298125983_0e4bf66782_b.jpg";
        new DownloadFileAsync().execute(url);
    }
    @Override
    protected Dialog onCreateDialog(int id) {
        switch (id) {
  case DIALOG_DOWNLOAD_PROGRESS:
   mProgressDialog = new ProgressDialog(this);
   mProgressDialog.setMessage("Downloading file..");
   mProgressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
   mProgressDialog.setCancelable(false);
   mProgressDialog.show();
   return mProgressDialog;
  default:
   return null;
        }
    }

class DownloadFileAsync extends AsyncTask<String, String, String> {
   
 @Override
 protected void onPreExecute() {
  super.onPreExecute();
  showDialog(DIALOG_DOWNLOAD_PROGRESS);
 }

 @Override
 protected String doInBackground(String... aurl) {
  int count;

 try {

 URL url = new URL(aurl[0]);
 URLConnection conexion = url.openConnection();
 conexion.connect();

 int lenghtOfFile = conexion.getContentLength();
 Log.d("ANDRO_ASYNC", "Lenght of file: " + lenghtOfFile);

 InputStream input = new BufferedInputStream(url.openStream());
 OutputStream output = new FileOutputStream("/sdcard/some_photo_from_gdansk_poland.jpg");

 byte data[] = new byte[1024];

 long total = 0;

  while ((count = input.read(data)) != -1) {
   total += count;
   publishProgress(""+(int)((total*100)/lenghtOfFile));
   output.write(data, 0, count);
  }

  output.flush();
  output.close();
  input.close();
 } catch (Exception e) {}
 return null;

 }
 protected void onProgressUpdate(String... progress) {
   Log.d("ANDRO_ASYNC",progress[0]);
   mProgressDialog.setProgress(Integer.parseInt(progress[0]));
 }

 @Override
 protected void onPostExecute(String unused) {
  dismissDialog(DIALOG_DOWNLOAD_PROGRESS);
 }
}
}

The output of this program will be as shown in the android emulator below.

The main.xml file in your res/layout folder is as follows:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
 xmlns:android="http://schemas.android.com/apk/res/android"
 android:orientation="vertical"
 android:layout_width="fill_parent"
 android:layout_height="fill_parent">
 <TextView
  android:layout_width="fill_parent"
  android:layout_height="wrap_content"
  android:text="@string/hello" />
 <Button
  android:text="Start long running task.."
  android:id="@+id/startBtn"
  android:layout_width="fill_parent"
  android:layout_height="wrap_content">
 </Button>
</LinearLayout>