Download Manager Class

Here a simple Download Manager Class.

Use like this:

  DownloadManager DM = new DownloadManager();
  DM.init(....);
  DM.execute();

Here the Class:

import android.os.AsyncTask;
import java.io.File;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.PrintWriter;
import java.net.HttpURLConnection;
import java.net.URL;

public class DownloadManager extends AsyncTask<Void, Void, Void> {
    /////////////////////////////////////////////////
    // Needed class Variables
    File apkStorage = null;
    File outputFile = null;
    private String downloadUrl = "", downloadFileName = "";
    String FilePath =   null;
    boolean isValid;
    boolean isExisting;

    /////////////////////////////////////////////////
    // Initialise the Download
    void initDownload(String IntFilePath, String downloadUrl, String filename, boolean checkExistingState)  {
        this.FilePath = IntFilePath;
        this.downloadUrl = downloadUrl;
        this.downloadFileName = filename;
        this.isExisting =   checkExistingState;
    }

    /////////////////////////////////////////////////
    // Check if a Downloaded Process is Valid
    boolean getValidity() {
        return isValid;
    }

    /////////////////////////////////////////////////
    // Rename a Ready File
    private void renameFile(String inputFile) {
        try {
            File tmpFile = new File(this.FilePath , "file.temp");
            if(new File(this.FilePath, inputFile).exists()) {
                if(new File(this.FilePath, inputFile).delete()) {
                    if (!tmpFile.renameTo(new File(this.FilePath, inputFile))) {
                        isValid = false;
                    }

                }
            } else {
                if (!tmpFile.renameTo(new File(this.FilePath, inputFile))) {
                    isValid = false;
                }
            }

        }
        catch (Exception ignored) {
            isValid = false;
        }
    }

    /////////////////////////////////////////////////
    // Background Download
    @Override
    protected Void doInBackground(Void... arg0) {
        try {
            //////////////////////////////
            // Stop if File Exists
            File checkFile = new File(new File(this.FilePath + "/"), downloadFileName);
            if (isExisting) {
                if (checkFile.exists()) {
                    isValid =   true;
                    return null;
                }
            }

            //////////////////////////////
            // Start Download Operations
            URL url = new URL(downloadUrl);
            HttpURLConnection c = (HttpURLConnection) url.openConnection();
            c.setRequestMethod("GET");
            c.connect();

            //////////////////////////////
            // Return Null if HTTP Request Misbehave
            if (c.getResponseCode() != HttpURLConnection.HTTP_OK) {
                isValid =   false;
                return null;
            }

            //////////////////////////////
            // Create Files Variable
            apkStorage = new File(this.FilePath + "/");

            //////////////////////////////
            // Create Directory if Needed
            if (!apkStorage.exists()) {
                if(!apkStorage.mkdir()) {
                    isValid = false;
                    return null;
                }
            }

            //////////////////////////////
            // Write Temp Output File
            outputFile = new File(apkStorage, "file.temp");

            //////////////////////////////////////////////////////////////////////////////////////////////////////
            // Start Writing the File and CHeck for Existens of Real File / Reset the File if Overwrite Enabled
            if (!outputFile.exists()) {
                if(!outputFile.createNewFile()) {
                    isValid = false;
                    return null;
                }
            } else {
                ////////////////////////////////
                // Create Empty File
                PrintWriter writer = new PrintWriter(outputFile);
                writer.print("");
                writer.close();
            }

            //////////////////////////////////////////////////////////////////////////////////////////////////////
            // File Operations
            FileOutputStream fos = new FileOutputStream(outputFile);

            InputStream is = c.getInputStream();

            byte[] buffer = new byte[1024];
            int len1;
            while ((len1 = is.read(buffer)) != -1) {
                //Write A New File
                fos.write(buffer, 0, len1);
            }
            fos.close();
            is.close();

        } catch (Exception e) {
            //////////////////////////////
            // Return Null to Outputfile if Exception Occurs
            outputFile = null;
        }

        try {
            ///// Check if Download Successfull
            isValid = outputFile != null;
        } catch (Exception e) { isValid = false; }

        ///// Move the File to its Final Location if Download Successfull
        if (isValid) { renameFile(downloadFileName); }

        return null;
    }

    /////////////////////////////////////////////////
    // On Post Execute Function
    @Override
    protected void onPostExecute(Void result) {
        super.onPostExecute(result);
    }

    /////////////////////////////////////////////////
    // On Pre Execute Function
    @Override
    protected void onPreExecute() {
        super.onPreExecute();
    }

}