Abstract Download AsyncTask

AbstractDownloadAsyncTask.java

import android.os.AsyncTask;
import android.text.TextUtils;
import android.util.Log;

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;

public abstract class AbstractDownloadAsyncTask extends AsyncTask<String, Integer, String> {
    @Override
    protected String doInBackground(String... params) {
        String path = "";
        if (params == null) {
            return path;
        }

        File file = getDestinationFile();
        if (file.exists()) {
            int i = 0;
            while (i <= 100) {
                super.publishProgress(i++);
                try {
                    Thread.sleep(10);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }

            path = file.getAbsolutePath();
            android.util.Log.i("Download", "is downloaded " + " size:" + file.length());
            return path;
        }

        InputStream input = null;
        OutputStream output = null;
        HttpURLConnection connection = null;
        try {
            String downloadUrl = params[0];
            URL url = new URL(downloadUrl);
            connection = (HttpURLConnection) url.openConnection();
            connection.setRequestMethod("GET");
            connection.setConnectTimeout(8000);
            connection.setDoInput(true);
            connection.connect();

            // Expect HTTP 200 OK, so we don't mistakenly save error report
            // instead of the file.
            if (connection.getResponseCode() != HttpURLConnection.HTTP_OK) {
                android.util.Log.i("Download", "Server returned HTTP " +
                        connection.getResponseCode() + " " + connection.getResponseMessage());
                path = "";
                return path;
            }

            // Download the file
            input = connection.getInputStream();
            output = new FileOutputStream(file);

            // This will be useful to display download percentage
            // might be -1: server did not report the length
            final int fileLength = connection.getContentLength();
            byte data[] = new byte[1024];
            long total = 0;
            int len;
            while ((len = input.read(data)) != -1) {
                total += len;
                // Publishing the progress.
                // Only if total length is known.
                if (fileLength > 0) {
                    super.publishProgress((int) (total * 100 / fileLength));
                }
                output.write(data, 0, len);
            }

            //Check whether the task been canceled.
            if (!isCancelled()) {
                //Assign the value to path if download completely success.
                path = file.getAbsolutePath();
            }
        } catch (IOException e) {
            e.printStackTrace();
            path = "";
        } finally {
            try {
                if (output != null) output.close();
                if (input != null) input.close();
            } catch (IOException ignored) {
            }

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

    @Override
    protected void onCancelled(String path) {
        super.onCancelled(path);
        File file = getDestinationFile();
        Log.d("AbstractDownload", "path when cancel--->" + path);
        Log.d("AbstractDownload", "destination file--->" + file);
        Log.d("AbstractDownload", "destination file exist--->" + file.exists());

        //Delete the previous existed and incomplete file if download canceled by user.
        if (TextUtils.isEmpty(path) && file.exists()) {
            file.delete();
        }
    }

    protected abstract File getDestinationFile();
}