Question

I’m creating a thread in android for a time consuming operation. I want the main screen to show a progress dialog with a message informing that the operation is in progress, but I want that dialog to dismiss once the thread is done. I’ve tried with join but it locks the thread and doesn’t show the dialog. I tried using:

dialog.show();
mythread.start();
dialog.dismiss(); 

but then the dialog doesn’t show. How can I make that sequence but wait for the thread to end without locking the main thread?

This is as far as I got:

public class syncDataElcanPos extends AsyncTask<String, Integer, Void> {
    ProgressDialog pDialog;
    Context cont;
    public syncDataElcanPos(Context ctx) {
        cont=ctx;
    }

    protected void onPreExecute() {
    pDialog = ProgressDialog.show(cont,cont.getString(R.string.sync), cont.getString(R.string.sync_complete), true);
}

protected Void doInBackground(String... parts) {        
   // blablabla...
   return null;
}

protected void onProgressUpdate(Integer... item) {
    pDialog.setProgress(item[0]); // just for possible bar in a future.
}

protected void onPostExecute(Void unused) {
    pDialog.dismiss();
}

But when I try to execute it, it gives me an exception: “Unable to add window”.

Answer 1

To do that there is two ways to do it , ( and i prefer the first second one : AsyncTask ) :

First : you display your alertDialog , and then on the method run() you should do like this

@override
public void run(){
//the code of your method run 
//....
.
.
.
//at the end of your method run() , dismiss the dialog
YourActivity.this.runOnUiThread(new Runnable() {
public void run() {
        dialog.dismiss();
    }
});

}

Second : Using an AsyncTask like this :

class AddTask extends AsyncTask<Void, Item, Void> {

    protected void onPreExecute() {
//create and display your alert here 
    pDialog = ProgressDialog.show(MyActivity.this,"Please wait...", "Downloading data ...", true);
}

protected Void doInBackground(Void... unused) {

    // here is the thread's work ( what is on your method run()
    items = parser.getItems();

    for (Item it : items) {
        publishProgress(it);
    }
    return(null);
}

protected void onProgressUpdate(Item... item) {
    adapter.add(item[0]);
}

protected void onPostExecute(Void unused) {
    //dismiss the alert here where the thread has finished his work
    pDialog.dismiss();
}
  }