how to create own download manager in android 2.2

Question

I know that we can use built-in download manager in Android 2.3 and above but my app is suitable for Android 2.2 and above.My question is how to create own download manager

Answer 1

please provide me some sample answer.

Step1 Look for Example on How to Download Files in Android

Step2 Look for Example on How to perform operations in AsyncTask.

Step3 Look for Example on How to Display Download Progress while Downloading.

Step4 Look for Example on How to send Custom Broadcast when Task is completed

Step5 Look for Example on How to Persist AsysncTask operation even on device rotation

Step6 Look for Example on How to Show Download Progress in Notification.

Below is example code.

1. Use AsyncTask and show the download progress in a dialog

// declare the dialog as a member field of your activity
ProgressDialog mProgressDialog;

// instantiate it within the onCreate method
mProgressDialog = new ProgressDialog(YourActivity.this);
mProgressDialog.setMessage("A message");
mProgressDialog.setIndeterminate(false);
mProgressDialog.setMax(100);
mProgressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);

// execute this when the downloader must be fired
DownloadFile downloadFile = new DownloadFile();
downloadFile.execute("the url to the file you want to download");

The AsyncTask will look like this:

// usually, subclasses of AsyncTask are declared inside the activity class.
// that way, you can easily modify the UI thread from here
private class DownloadFile extends AsyncTask<String, Integer, String> {
    @Override
    protected String doInBackground(String... sUrl) {
        try {
            URL url = new URL(sUrl[0]);
            URLConnection connection = url.openConnection();
            connection.connect();
            // this will be useful so that you can show a typical 0-100% progress bar
            int fileLength = connection.getContentLength();

            // download the file
            InputStream input = new BufferedInputStream(url.openStream());
            OutputStream output = new FileOutputStream("/sdcard/file_name.extension");

            byte data[] = new byte[1024];
            long total = 0;
            int count;
            while ((count = input.read(data)) != -1) {
                total += count;
                // publishing the progress....
                publishProgress((int) (total * 100 / fileLength));
                output.write(data, 0, count);
            }

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

The method above (doInBackground) runs always on a background thread. You shouldn't do any UI tasks there. On the other hand, the onProgressUpdate and onPreExecute run on the UI thread, so there you can change the progress bar:

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

    @Override
    protected void onProgressUpdate(Integer... progress) {
        super.onProgressUpdate(progress);
        mProgressDialog.setProgress(progress[0]);
    }
}

2. Download from Service

The big question here is: how do I update my activity from a service?. In the next example we are going to use two classes you may not be aware of: ResultReceiver and IntentService. ResultReceiver is the one that will allow us to update our thread from a service; IntentService is a subclass of Service which spawns a thread to do background work from there (you should know that a Service runs actually in the same thread of your app; when you extends Service, you must manually spawn new threads to run CPU blocking operations).

Download service can look like this:

public class DownloadService extends IntentService {
    public static final int UPDATE_PROGRESS = 8344;
    public DownloadService() {
        super("DownloadService");
    }
    @Override
    protected void onHandleIntent(Intent intent) {
        String urlToDownload = intent.getStringExtra("url");
        ResultReceiver receiver = (ResultReceiver) intent.getParcelableExtra("receiver");
        try {
            URL url = new URL(urlToDownload);
            URLConnection connection = url.openConnection();
            connection.connect();
            // this will be useful so that you can show a typical 0-100% progress bar
            int fileLength = connection.getContentLength();

            // download the file
            InputStream input = new BufferedInputStream(url.openStream());
            OutputStream output = new FileOutputStream("/sdcard/BarcodeScanner-debug.apk");

            byte data[] = new byte[1024];
            long total = 0;
            int count;
            while ((count = input.read(data)) != -1) {
                total += count;
                // publishing the progress....
                Bundle resultData = new Bundle();
                resultData.putInt("progress" ,(int) (total * 100 / fileLength));
                receiver.send(UPDATE_PROGRESS, resultData);
                output.write(data, 0, count);
            }

            output.flush();
            output.close();
            input.close();
        } catch (IOException e) {
            e.printStackTrace();
        }

        Bundle resultData = new Bundle();
        resultData.putInt("progress" ,100);
        receiver.send(UPDATE_PROGRESS, resultData);
    }
}

Add the service to your manifest:

<service android:name=".DownloadService"/>

And the activity will look like this:

// initialize the progress dialog like in the first example

// this is how you fire the downloader

mProgressDialog.show();
Intent intent = new Intent(this, DownloadService.class);
intent.putExtra("url", "url of the file to download");
intent.putExtra("receiver", new DownloadReceiver(new Handler()));
startService(intent);

Here is were ResultReceiver comes to play:

private class DownloadReceiver extends ResultReceiver{
    public DownloadReceiver(Handler handler) {
        super(handler);
    }

    @Override
    protected void onReceiveResult(int resultCode, Bundle resultData) {
        super.onReceiveResult(resultCode, resultData);
        if (resultCode == DownloadService.UPDATE_PROGRESS) {
            int progress = resultData.getInt("progress");
            mProgressDialog.setProgress(progress);
            if (progress == 100) {
                mProgressDialog.dismiss();
            }
        }
    }
}