Question

i have the following code to load a file from my website

class DownloadTT4FileTask extends AsyncTask<String, String, String> {

                    private Context mContext;
                    private String  mFilename;
                    private ProgressDialog progressDialog;
                    String  retString="";

                    public DownloadTT4FileTask(Context context, String filename) {
                        mContext=context;
                        mFilename=filename;
                    }

                    @Override
                    protected void onPreExecute() {
                        Log.d("DownloadTT4FileTask", "onPreExecute");
                        progressDialog = ProgressDialog.show(mContext, mFilename, "Loading. Please wait...");
                    }

                    protected String doInBackground(String... args) {

                        URL url;
                        try {
                            url = new URL(args[0]);
                            java.net.URLConnection con = url.openConnection();
                            con.connect();
                            //Log.d("DownloadTT4FileTask", "con.connect ok ");

                            java.io.BufferedReader in = new java.io.BufferedReader(new java.io.InputStreamReader(con.getInputStream()));
                            String line;
                            for (; (line = in.readLine()) != null; ) {
                                // just read the line and save it
                                retString += line+"\n";
                            }   

                        } catch (MalformedURLException e) {
                            // TODO Auto-generated catch block
                            e.printStackTrace();
                        } catch (IOException e) {
                            // TODO Auto-generated catch block
                            e.printStackTrace();
                        }

                        return retString;
                    }

                    protected void onPostExecute(String result) {
                        Log.d("DownloadTT4FileTask", "onPreExecute");
                        progressDialog.dismiss();
                    }
                };
                // loading from website
                filename = "http://2112design.com/tabs/"+band+"/"+song+".tt4";
                String fileContents = new DownloadTT4FileTask(context, filename).execute(filename).get(15L, TimeUnit.SECONDS);

                br = new BufferedReader(new StringReader(fileContents));

it loads fine (about 5 secs to load) but the progress dialog is a bit off. it doesn’t show up on the screen at the start of the download. it briefly flashes on screen at the end of the task.

i’ve seen many examples of how to use this and it looks like this is pretty normal code.

maybe the context is the issue? i get that from an onChildClick that running in a fragment which isn’t the main activity. i tried using the main activity context but that just crashed.

    @Override
public boolean onChildClick(ExpandableListView parent, View v, int groupPosition, int childPosition, long id) {
    Globals.mDoc.OpenTT4Document(parent.getContext(), band, song, mRemoteFilesThis==null ? Doc.SDCARD : Doc.WEBSITE);

    return false;
}

any ideas? thanks

Answer 1

as Doc says about AsyncTask.get() :

Waits if necessary for at most the given time for the computation to
complete, and then retrieves its result.

currently you are calling AsyncTask.get() on main UI thread and progress dialog not appeared . you will need to start AsyncTask without calling get() method as :

new DownloadTT4FileTask(context, filename).execute(filename);

and update UI after doInBackground completed inside onPostExecute as :

                protected void onPostExecute(String result) {
                    Log.d("DownloadTT4FileTask", "onPreExecute");
                    progressDialog.dismiss();
                     // get result here
                    br = new BufferedReader(new StringReader(result));
                }

EDIT :

if you want to call get method of AsyncTask then use a Thread to get result back and avoid freezing of UI as :

new Thread(new Runnable() {
  public void run() {
     try {
            Your_Activity.this.runOnUiThread(new Runnable() {
            public void run() {

               progressDialog = ProgressDialog.show(Your_Activity.this, 
                 mFilename, "Loading. Please wait...");
            }
           });
              // start AsyncTask here
              String fileContents = new DownloadTT4FileTask(context, filename)
                                     .execute(filename).get(15L, TimeUnit.SECONDS);

              Your_Activity.this.runOnUiThread(new Runnable() {
                 public void run() {
                    // update UI elements here
                     br = new BufferedReader(new StringReader(fileContents));
                       progressDialog.dismiss();
                  }
              });
          } catch (InterruptedException e) {
           // TODO Auto-generated catch block
            e.printStackTrace();
          } catch (ExecutionException e) {
             // TODO Auto-generated catch block
               e.printStackTrace();
          } catch (TimeoutException e) {
                    // TODO Auto-generated catch block
               e.printStackTrace();
          }
       }
 }).start();