Android - How to download a file from a webserver
Using Async task
call when you want to download file : new DownloadFileFromURL().execute(file_url);
public class MainActivity extends Activity {
// Progress Dialog
private ProgressDialog pDialog;
public static final int progress_bar_type = 0;
// File url to download
private static String file_url = "http://www.qwikisoft.com/demo/ashade/20001.kml";
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
new DownloadFileFromURL().execute(file_url);
}
/**
* Showing Dialog
* */
@Override
protected Dialog onCreateDialog(int id) {
switch (id) {
case progress_bar_type: // we set this to 0
pDialog = new ProgressDialog(this);
pDialog.setMessage("Downloading file. Please wait...");
pDialog.setIndeterminate(false);
pDialog.setMax(100);
pDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
pDialog.setCancelable(true);
pDialog.show();
return pDialog;
default:
return null;
}
}
/**
* Background Async Task to download file
* */
class DownloadFileFromURL extends AsyncTask<String, String, String> {
/**
* Before starting background thread Show Progress Bar Dialog
* */
@Override
protected void onPreExecute() {
super.onPreExecute();
showDialog(progress_bar_type);
}
/**
* Downloading file in background thread
* */
@Override
protected String doInBackground(String... f_url) {
int count;
try {
URL url = new URL(f_url[0]);
URLConnection connection = url.openConnection();
connection.connect();
// this will be useful so that you can show a tipical 0-100%
// progress bar
int lenghtOfFile = connection.getContentLength();
// download the file
InputStream input = new BufferedInputStream(url.openStream(),
8192);
// Output stream
OutputStream output = new FileOutputStream(Environment
.getExternalStorageDirectory().toString()
+ "/2011.kml");
byte data[] = new byte[1024];
long total = 0;
while ((count = input.read(data)) != -1) {
total += count;
// publishing the progress....
// After this onProgressUpdate will be called
publishProgress("" + (int) ((total * 100) / lenghtOfFile));
// writing data to file
output.write(data, 0, count);
}
// flushing output
output.flush();
// closing streams
output.close();
input.close();
} catch (Exception e) {
Log.e("Error: ", e.getMessage());
}
return null;
}
/**
* Updating progress bar
* */
protected void onProgressUpdate(String... progress) {
// setting progress percentage
pDialog.setProgress(Integer.parseInt(progress[0]));
}
/**
* After completing background task Dismiss the progress dialog
* **/
@Override
protected void onPostExecute(String file_url) {
// dismiss the dialog after the file was downloaded
dismissDialog(progress_bar_type);
}
}
}
if not working in 4.0 then add:
StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
StrictMode.setThreadPolicy(policy);
Simple kotlin version
fun download(link: String, path: String) {
URL(link).openStream().use { input ->
FileOutputStream(File(path)).use { output ->
input.copyTo(output)
}
}
}
is there anyway to get the download progress or downloaded size from this method ?
This is the same realization as defined in InputStream.copyTo
, but with progress
/*inline*/ fun download(link: String, path: String, progress: ((Long, Long) -> Unit)? = null): Long {
val url = URL(link)
val connection = url.openConnection()
connection.connect()
val length = if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) connection.contentLengthLong else
connection.contentLength.toLong()
url.openStream().use { input ->
FileOutputStream(File(path)).use { output ->
val buffer = ByteArray(DEFAULT_BUFFER_SIZE)
var bytesRead = input.read(buffer)
var bytesCopied = 0L
while (bytesRead >= 0) {
output.write(buffer, 0, bytesRead)
bytesCopied += bytesRead
progress?.invoke(bytesCopied, length)
bytesRead = input.read(buffer)
}
return bytesCopied
}
}
}
An example of usage:
val handler = object : Handler(Looper.getMainLooper()) {
override fun handleMessage(msg: Message) {
// length may be negative because it is based on http header
val (progress, length) = msg.obj as Pair<Long, Long>
}
}
// call this outside of main thread
val totalSize = download("http://example.site/path/to/file", "path/to/file") { progress, length ->
// handling the result on main thread
handler.sendMessage(handler.obtainMessage(0, progress to length))
}