每次更改选项卡时都会运行AsyncTask

Question

在我的班级中，

在我的onCreateView中定义了AsyncTask的执行，但当我切换标签并返回到运行此AsyncTask运行重载json请求的选项卡时

@Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                Bundle savedInstanceState) {

            View android = inflater.inflate(R.layout.android_frag, container, false);

        contactList = new ArrayList<HashMap<String, String>>();
        new GetContacts().execute();

        return android;
}

因为我可以在第一次使用该应用程序时让它继续运行吗？

类AsyncTask

private class GetContacts extends AsyncTask<Void, Void, Void> {

        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            // Showing progress dialog
            pDialog = new ProgressDialog(getActivity());
            pDialog.setMessage("Espere, cargando datos...");
            pDialog.setCancelable(false);
            pDialog.show();

        }

        @Override
        protected Void doInBackground(Void... arg0) {
            // Creating service handler class instance
            ServiceHandler sh = new ServiceHandler();

            // Making a request to url and getting response
            String jsonStr = sh.makeServiceCall(url, ServiceHandler.GET);

            Log.d("Response: ", "> " + jsonStr);

            if (jsonStr != null) {
                try {
                    JSONObject jsonObj = new JSONObject(jsonStr);

                    // Conseguir nodo matriz JSON
                    categories = jsonObj.getJSONArray(TAG_CONTACTS);

                    // bucle a través de todos las categorias
                    for (int i = 0; i < categories.length(); i++) {
                        JSONObject c = categories.getJSONObject(i);

                        String id = c.getString(TAG_ID);
                        String title = c.getString(TAG_title);
                        String slug = c.getString(TAG_slug);

                        String desc = c.getString(TAG_description);


                        // tmp hashmap para las ventanillas únicas
                        HashMap<String, String> contact = new HashMap<String, String>();

                        // adding each child node to HashMap key => value
                        contact.put(TAG_ID, id);
                        contact.put(TAG_title, title);
                        contact.put(TAG_slug, slug);
                        contact.put(TAG_description, desc);

                        // añadir categoria a la lista de categorias
                        contactList.add(contact);
                    }
                } catch (JSONException e) {
                    e.printStackTrace();
                }
            } else {
                Log.e("ServiceHandler", "no pudo obtener ningún dato de la url");
            }

            return null;
        }

        @Override
        protected void onPostExecute(Void result) {
            super.onPostExecute(result);
            // Dismiss the progress dialog
            if (pDialog.isShowing())
                pDialog.dismiss();
            /**
             * Actualización de datos analizados JSON en ListView
             * */
            ListView  vista = (ListView) getActivity().findViewById(R.id.list);
            ListAdapter adapter = new SimpleAdapter(
                    getActivity(), contactList,
                    R.layout.list_item, new String[]{TAG_title}, new int[]{R.id.name}
            );

            vista.setAdapter(adapter);
        }

    }

Answer 1

我不知道这对你有用，但这里有些东西可能会有用： 将json对象设为全局变量

boolean IsJsonObjectLoaded = false;
JSONObject jsonObj = null;

在odInBackgroud方法的AsyncTask中

odInBackgroud(object){
  // do not write anything here
  if(!IsJsonObjectLoaded){

  your all code here ....



  jsonObj = new JSONObject(jsonStr);
  IsJsonObjectLoaded  = true;
  }
}

将json对象设为全局变量

并在onCreateView方法中：

@Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {

        View android = inflater.inflate(R.layout.android_frag, container, false);

    // you code here ...
    if(!IsJsonObjectLoaded){
    new GetContacts().execute();
    )
    return android; 
}

我希望这会有所帮助。

Answer 2

只需设置一个标志，即在onPostExecute方法中设置为true的布尔值。使用此标志来确定是否应该运行AsyncTask。