Question

在启动应用程序时，我想用数据库中的数据填充片段中的微调器。我从数据库中提取字符串列表，并希望在微调器中显示它。我已经有了填充列表，我相信在PostExecute中更改了ArrayAdapter，但是什么都没有显示。

片段代码

 public static class RegisterFragment extends Fragment{


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

     List<String> instituteList = new ArrayList<String>();
     View rootView = inflater.inflate(R.layout.fragment_register, container, false);
    if (instituteList.isEmpty()){ //list is null on app start-up
        Log.d("test","null list");
    }else{

    Spinner autoInstitute = (Spinner)getActivity(). findViewById(R.id.institute);
// Get the string array
    String[] institutes =  (String[]) instituteList.toArray(new String[instituteList.size()]);;
// Create the adapter and set it to the AutoCompleteTextView 
ArrayAdapter<String> instituteApapdter = 
        new ArrayAdapter<String>(getActivity(), android.R.layout.simple_list_item_1, institutes);
instituteApapdter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
    autoInstitute.setAdapter(instituteApapdter);
    }
       return rootView;
}

异步类

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

    @Override
    protected void onPreExecute() {

        super.onPreExecute();
        pDialog = new ProgressDialog(Login.this);
        pDialog.setMessage("Loading Institute List");
        pDialog.setIndeterminate(false);
        pDialog.setCancelable(true);
        pDialog.show();

    }
    @Override
    protected String doInBackground(String... params) {
                  //Get data and store in List
    }
protected void onPostExecute(String file_url) {
        // dismiss the dialog once done
        pDialog.dismiss();
        institutes_array =  (String[]) instituteList.toArray(new String[instituteList.size()]);;
        final ArrayAdapter<String> instituteApapdter = 
                new ArrayAdapter<String>(Login.this, android.R.layout.simple_list_item_1, institutes_array);
        instituteApapdter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
        runOnUiThread(new Runnable() {

            public void run() {

                instituteApapdter.notifyDataSetChanged();
            }
        //autoInstitute.setAdapter(instituteApapdter); // causes nullpointerexception   
        });
    }

Answer 1

写下这个：

Spinner autoInstitute = (Spinner)rootView. findViewById(R.id.institute);

取代这个：

Spinner autoInstitute = (Spinner)getActivity(). findViewById(R.id.institute);

此外，在AsyncTask类中，您已将Login.this写为ArrayAdapter()构造函数的第一个参数。将其更改为getActivity()

这应该是您完整的RegisterFragment类：

package com.bhavit.stackoverflow;

public static class RegisterFragment extends Fragment{

    Spinner autoInstitute;
     public View onCreateView(LayoutInflater inflater, ViewGroup container,
                Bundle savedInstanceState) {

         List<String> instituteList = new ArrayList<String>();
         View rootView = inflater.inflate(R.layout.fragment_register, container, false);

         if (instituteList.isEmpty()){ //list is null on app start-up
            Log.d("test","null list");
        }else{

        autoInstitute = (Spinner)getActivity(). findViewById(R.id.institute);

        GetInstitute obj = new GetInstitute();
        obj.execute();


        }
           return rootView;
    }


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

            @Override
            protected void onPreExecute() {

                super.onPreExecute();
                pDialog = new ProgressDialog(getActivity());
                pDialog.setMessage("Loading Institute List");
                pDialog.setIndeterminate(false);
                pDialog.setCancelable(true);
                pDialog.show();

            }
            @Override
            protected String doInBackground(String... params) {
                          //Get data and store in List
            }
        protected void onPostExecute(String file_url) {
                // dismiss the dialog once done
                pDialog.dismiss();
                institutes_array =  (String[]) instituteList.toArray(new String[instituteList.size()]);;
                final ArrayAdapter<String> instituteApapdter = 
                        new ArrayAdapter<String>(getActivity(), android.R.layout.simple_list_item_1, institutes_array);
                instituteApapdter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);

                    instituteApapdter.notifyDataSetChanged();

            autoInstitute.setAdapter(instituteApapdter); // causes nullpointerexception   

            }
     }

}

使用Async任务中的数据更新Spinner

1 个答案: