android - 通过android从网络服务器下载pdf文件、音频和视频文件

Question

我创建了一个安卓应用程序。这需要将 pdf、音频和视频文件从我的 asp.net web api 下载到我的 android 应用程序。但我不知道我的 web api 代码会是什么样子，我的 pdf、音频文件和视频文件的 android 下载代码会是什么样子。感谢您的细读。

Answer 1

You can customize and use this, you will need the wakelock permission to prevent interruption

@SuppressLint("Wakelock")
public class DownloadTask extends AsyncTask<String, Integer, String>
{

    private Context context;

    public DownloadTask(Context context ,Dialog dialog, ProgressBar progressBar ,TextView progressTextView , String destinationPath ,String fileName , JSONObject jObject )
    {
        this.context = context;
    }

    @SuppressWarnings("resource")
    @Override 
    protected String doInBackground(String... sUrl)
    {
        String directory = sUrl[0];
        String fileName = sUrl[1];


        //prevent CPU from going off if the user presses the power button during download
        PowerManager pm = (PowerManager) context.getSystemService(Context.POWER_SERVICE);
        PowerManager.WakeLock wl = pm.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, getClass().getName());
        wl.acquire();

        //download
        try
        {
            new File(directory).mkdirs();
            InputStream input = null;
            OutputStream output = null;
            HttpURLConnection connection = null;
            try
            {
                //connect to url
                URL url = new URL(sUrl[2]);
                connection = (HttpURLConnection) url.openConnection();
                connection.connect();


                // check for http_ok (200)
                if (connection.getResponseCode() != HttpURLConnection.HTTP_OK)
                    return "Server returned HTTP "
                            + connection.getResponseCode() + " "
                            + connection.getResponseMessage();


                int fileLength = connection.getContentLength();
                // download the file
                input = connection.getInputStream();
                output = new FileOutputStream(directory+"/"+fileName+".mp3");//change extension

                //copying
                byte data[] = new byte[4096];
                long total = 0;
                int count;
                while ((count = input.read(data)) != -1)
                {
                    // allow canceling
                    if (isCancelled())
                    {
                        new File(directory+"/"+fileName+".mp3").delete();//delete partially downloaded file
                        return null;
                    }
                    total += count;
                    if (fileLength > 0 ) //publish progress only if total length is known
                        publishProgress( (int)(total/1024) , fileLength/1024 );//(int) (total * 100 / fileLength));
                    output.write(data, 0, count);
                }
            }
            catch (Exception e)
            {
                return e.toString();
            }
            finally //closing streams and connection
            {
                try
                {
                    if (output != null)
                        output.close();
                    if (input != null)
                        input.close();
                }
                catch (IOException ignored)
                {
                }

                if (connection != null)
                    connection.disconnect();
            }
        }
        finally
        {
            wl.release(); // release the lock screen
        }
        return null;
    }

    @Override // onPreExecute and onProgressUpdate run on ui thread so you can update ui from here
    protected void onPreExecute()
    {
        super.onPreExecute();
    }

    @Override
    protected void onProgressUpdate(Integer... progress)
    {
        super.onProgressUpdate(progress);
    }

    @Override
    protected void onPostExecute(String result)
    {
        if (result != null)
            Toast.makeText(context, "Download error: " + result,Toast.LENGTH_SHORT).show();
        else
        {
                Toast.makeText(context, " download complete ",Toast.LENGTH_SHORT).show();

        }
    }
}

and then call it from main

new DownloadTask(this).execute( dirPath , fileName , urlToDownload );