android - changing Activity UI from application class

Question

I extended the Application class in order to create singleton-like object in android.

in this object I have all the HTTP work with my server, and all the other activities can access it and call methods to GET, POST etc.

Code:

public class HttpManagerInstance extends Application {
    private HttpClient httpClient;
    private HttpGet get;

    @Override
    public void onCreate() {
        httpClient = new DefaultHttpClient();
        get = new HttpGet("http://10.100.102.9:8000/users/");
        super.onCreate();

    }


    public Void getUsers() throws Exception {
        new executeRequest().execute(get);
        return null;
    }

    private class executeRequest extends AsyncTask<HttpRequest, Void, Integer> {

        @Override
        protected Integer doInBackground(HttpRequest... params) {
            // TODO Auto-generated method stub
            HttpRequest request = params[0];
            HttpResponse response;
            String result="";
            try {
                response = httpClient.execute((HttpUriRequest) request);
            } catch (ClientProtocolException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            return responseCode;
        }

        @Override
        protected void onPostExecute(Integer result) {
            // TODO Auto-generated method stub
            switch (result) {
            case HttpStatus.SC_OK:
                // request was fine

                // Here I want to updated the GUI of the activity that called this method.
                break;
            }
        }

    }

}

This is how I call the method from the Activity:

HttpManagerInstance sampleApp = (HttpManagerInstance)getApplicationContext();
sampleApp.getUsers();

Again - I want to access the UI of the Activity that called the method to put an REQUEST ACCEPTED message.

Maybe pass a context? any ideas?

mmark · Accepted Answer · 2015-05-25T16:05:53.270

I'd create a listener:

public class HttpManagerInstance extends Application {
    private HttpClient httpClient;
    private HttpGet get;

    public interface ResponseListener{
      public void onSuccess(Object data);
    }


    @Override
    public void onCreate() {
        httpClient = new DefaultHttpClient();
        get = new HttpGet("http://10.100.102.9:8000/users/");
        super.onCreate();

    }


    public Void getUsers(ResponseListener listener) throws Exception {
        new executeRequest(listener).execute(get);
        return null;
    }

    private class executeRequest extends AsyncTask<HttpRequest, Void, Integer> {

        private ResponseListener mListener;

        public executeRequest(ResponseListener listener){
         this.mListener = listener;
        }

        @Override
        protected Integer doInBackground(HttpRequest... params) {
            // TODO Auto-generated method stub
            HttpRequest request = params[0];
            HttpResponse response;
            String result="";
            try {
                response = httpClient.execute((HttpUriRequest) request);
            } catch (ClientProtocolException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            return responseCode;
        }

        @Override
        protected void onPostExecute(Integer result) {
            // TODO Auto-generated method stub
            switch (result) {
            case HttpStatus.SC_OK:
                // request was fine

                // Here I want to updated the GUI of the activity that called this method.
                if(this.mListener != null) mListener.onSuccess(whatEverDataYouWant);
                break;
            }
        }

    }

}

Then, in your activity:

    HttpManagerInstance sampleApp = (HttpManagerInstance)getApplicationContext();
    sampleApp.getUsers(new ResponseListener(){
       public void onSuccess(Object data){
         //update your ui!
       }

});

thanks for your answer. it looks really good, I will try it. BTW - I think that you had a small mistake - in the Activity code there is ResponseListener which is the Interface and in the AsyncTask you wrote RequestListener which doesn't exist. Thanks again! — Ofek Agmon, May 25 '15 at 15:53
@OfekAgmon thanks for the correction! i just fixed it! Let me know how it went. You're welcome! — mmark, May 25 '15 at 16:07

score 0 · Answer 2 · edited May 23 '17 at 12:24

0

The short answer is you can't directly reference to the UI from another activity. My advice would be for you to set up a callback on your Application class and call in on executeRequest#onPostExecute then implement that callback on your Activity and update your UI from there.

If you need help to implement the callback check this question

edited May 23 '17 at 12:24

Community

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1

answered May 25 '15 at 15:37

Carlos J

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Merlí Escarpenter Pérez · Answer 3 · 2015-05-25T16:00:51.410

If you need to show message is good option the Dialog Class or the Toast Class, you can see more info are here: Dialogs: http://developer.android.com/guide/topics/ui/dialogs.html Toasts: http://developer.android.com/guide/topics/ui/notifiers/toasts.html

But if you want to access or modify a control in your actual activity, then use Runnable class, and context.runOnUiThread() method if you work inside AsyncTask. The real problem is that you can't change UI in a AsyncTask using declaration of the controls. You need to throw a Runnable process to communicate with activity!!. For example:

context.runOnUiThread(new Runnable() {
                public void run() {
                    //Declaration of variables
                    TextView MyTextView = (TextView) context.findViewById(R.id.txtvMyControl);

                    MyTextView.setText("My title");
                }
}

If I can helps you say me, good luck!

android - changing Activity UI from application class

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