DownloadTask.java

package com.cafejeunesse.android.filemanager;

import android.content.Context;
import android.os.AsyncTask;
import android.os.PowerManager;

import com.cafejeunesse.android.fragment.Refreshable;
import com.cafejeunesse.android.navigationdrawer.R;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.Date;

// usually, subclasses of AsyncTask are declared inside the activity class.
// that way, you can easily modify the UI thread from here
public class DownloadTask extends AsyncTask<String, Integer, String> {

    private Context context;
    private PowerManager.WakeLock mWakeLock;
    private Refreshable mRefresh;

    public DownloadTask(Context context, Refreshable target) {
        this.context = context;
        this.mRefresh = target;
    }

    @Override
    protected String doInBackground(String... sUrl) {
        InputStream input = null;
        OutputStream output = null;
        HttpURLConnection connection = null;
        try {
            URL url = new URL(sUrl[0]);
            connection = (HttpURLConnection) url.openConnection();
            connection.connect();

            // expect HTTP 200 OK, so we don't mistakenly save error report
            // instead of the file
            if (connection.getResponseCode() != HttpURLConnection.HTTP_OK) {
                return context.getString(R.string.server_returned_http) + connection.getResponseCode()
                        + " " + connection.getResponseMessage();
            }

            // this will be useful to display download percentage
            // might be -1: server did not report the length
            int fileLength = connection.getContentLength();

            // download the file
            input = connection.getInputStream();
            String path = sUrl[1];
            output = new FileOutputStream(path);

            byte data[] = new byte[4096];
            long total = 0;
            int count;
            while ((count = input.read(data)) != -1) {
                // allow canceling with back button
                if (isCancelled()) {
                    input.close();
                    return null;
                }
                total += count;
                // publishing the progress....
                if (fileLength > 0) // only if total length is known
                    publishProgress((int) (total * 100 / fileLength));
                output.write(data, 0, count);
            }
        } catch (Exception e) {
            return e.toString();
        } finally {
            try {
                if (output != null)
                    output.close();
                if (input != null)
                    input.close();
            } catch (IOException ignored) {
            }

            if (connection != null)
                connection.disconnect();
        }
        return null;
    }

    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        // take CPU lock to prevent CPU from going off if the user
        // presses the power button during download
        PowerManager pm = (PowerManager) context.getSystemService(Context.POWER_SERVICE);
        mWakeLock = pm.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, getClass().getName());
        mWakeLock.acquire();
    }

    @Override
    protected void onPostExecute(String result) {
        mWakeLock.release();
        if (result == null)
            mRefresh.refresh();
    }

    public static void testAndDownload(String filepath, String url, Long timeBetweenDownloads, Context context, Refreshable refreshTarget) {

        // Téléchargement (si besoin) des calendriers
        File f = new File(filepath);

        // Si le fichier n'est pas présent ou qu'il est trop vieux
        if (!f.exists() || !f.isFile() || (new Date().getTime() - f.lastModified()) > timeBetweenDownloads)
            startDownload(url, filepath, context, refreshTarget);
    }

    public static void startDownload(String url, String fileName, Context context, Refreshable refreshTarget) {
        // execute this when the downloader must be fired
        final DownloadTask downloadTask = new DownloadTask(context, refreshTarget);
        downloadTask.execute(url, fileName);
    }
}