从Activity调用时，另一个AsyncTask类中的ProgressDialog不显示

Question

I have a class called RestClient that gets some information from my webService and then return and I'm trying to make a Progress dialog run while it is accessing the internet. And as I use this class in more than one place I won't make in the Activity itself. Here is my RestClient class:

public class RestClient extends AsyncTask<URL, String, String> {

    private Context context;
    private String string;
public RestClient(Context context, String string)
{
    this.context = context;
    this.string = string;
}

@Override
protected void onPreExecute() {
    dialog = ProgressDialog.show(context, "Buscando seu Produto","Por favor, espere um momento...",true ,false);
    //I've already tried:
    /*ProgressDialog dialog = new ProgressDialog(context);
    dialog.setTitle("Buscando seu Produto");
    dialog.setMessage("Por favor, espere um momento...");
    dialog.setIndeterminate(true);
    dialog.setCancelable(false);*/

    dialog.show();
    super.onPreExecute();
}

@Override
protected String doInBackground(URL... params) {
    try {

        //Some WebService gets and Json conversions using my string variable
        //and some Thread.sleep that counts 2000 miliseconds to do all the queries

        dialog.dismiss();

    } catch (IOException | InterruptedException |JSONException e) {
        e.printStackTrace();

        dialog.dismiss();

        return e.getMessage();
    }
    return null;
}

@Override
protected void onPostExecute(String s) {
    super.onPostExecute(s);


   }
}

And in my activity I call the class RestClient when I click a button like this:

--- EDIT : I forgot to mention that I have an AlertDialog in this same activity that CAN be shown sometimes before and after the ProgressDialog ---

private Button buttonConfirm;
     private EditView evString;

     private String theString;
     private String returnFromExecute;

     private RestClient restClient;


     private AlertDialog.Builder dialog;

     @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_access_webservice);

            evString = (EditText) findViewById(R.id.editViewMyString);
            buttonConfirm = (Button) findViewById(R.id.buttonConfirm);

            dialog = new ProgressDialog(IdentificacaoDeProdutoActivity.this);
            dialog.setTitle("Error");
            dialog.setMessage("Please try again");
            dialog.setIndeterminate(true);
            dialog.setCancelable(false);


            buttonConfirmar.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v)  {                  
                    theString = evString.getText().toString();
                    if(!(theString!=null && theString.trim().length()>0)) //To check if theString is not null
                    {
                          dialog.show();
                    }

                    restClient = new RestClient(AccessWebserviceActivity.this, theString);

                    //Then I call execute and put a Thread.sleep a bit longer to compensate the ones I have in my doInBackground
                    restClient.execute();
                    try {
                        Thread.sleep(2050);

                    } catch (Exception e) {
                        dialog.show();
                        return;
                    }
                }
            }
        }

The problem is that my ProgressDialog never shows. I've already tried getParent() , getApplication() and getApplicationContext() instead of AccessWebserviceActivity.this but none have worked. Someone Have any idea what is happening and what should I do?

Answer 1

you have not created progress dialog try this.

ProgressDialog dialog;

 @Override
    protected void onPreExecute() {
        dialog= new ProgressDialog(context);
        dialog.setMessage("on Progress");
        dialog.show();
        super.onPreExecute();
    }

Answer 2

You need to call

dialog = ProgressDialog.show(context, "Buscando seu Produto","Por favor, espere um momento...",true ,false);

and remove

 dialog.show();

Also put your dialog.dismiss() ; method in onPostExecute (). This dialog.dismiss() method is good in catch block but what's its purpose if you are calling this method in try block. It will remove progress dialog as soon as you call this AsyncTask .

Answer 3

returnFromExecute = restClient.get();

Remove that statement. You have already:

restClient.execute();

That should do.

The result of doInBackground() you should handle in onPostExecute() . It cannot be handled or retrieved in onCreate() .

Answer 4

After a lot of researches about Threads and Process I found out that I had to encapsulate the all the code I have after my RestClient.execute in a

new Thread(new Runnable() { public void run() { // My code } });

so that the execution of the code happened in background as well as the WebService query.

EDIT:

Even if creating a new Thread works, it is not recommended! The right thing to do would be to create another class that extends AsyncTask to do job.