Change
btnShowProgress.setOnClickListener(new View.OnClickListener()
{
@Override
public void onClick(View v)
{
new DownloadFileFromURL().execute(file_url);
}
});
to
btnShowProgress.setOnClickListener(new View.OnClickListener()
{
@Override
public void onClick(View v)
{
if(!new File(Environment.getExternalStorageDirectory().toString() + "/downloadedfile.jpg").exists())
new DownloadFileFromURL().execute(file_url);
else
{
AlertDialog.Builder dialogBuilder = new AlertDialog.Builder(Main.this);
dialogBuilder.setMessage("This file has already been downloaded")
AlertDialog dialog = dialogBuilder.create();
dialog.show();
}
}
});