How to get an item from an ArrayList?

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How to get an item from an ArrayList?

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#1 by (1 votes)

1

The problem I have is trying to recover a item of a ArrayList that I filled with data from Mysql , because when I try to get it with the get() it tells me the following:

java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.Object java.util.ArrayList.get (int)' on a null object reference

LoadSpinner method:

 public void CargarSpinner(JSONArray jsonArray){
    ListaSpinner = new ArrayList<>();
    for(int i=0;i<jsonArray.length();i++){
        try {
            JSONObject hijo = jsonArray.getJSONObject(i);
            ListaPadres.add(hijo.getString("email_padre"));
            ListaSpinner.add(hijo.getString("nombre_hijo"));
        } catch (JSONException e) {
            e.printStackTrace();
        }
    }
    adaptador = new ArrayAdapter<String>(getContext(), android.R.layout.simple_spinner_item, ListaSpinner);
    estudiantes.setAdapter(adaptador);
}

Here is where I try to get the ListArray item:

estudiantes = (Spinner)view.findViewById(R.id.spinner_estudiantes);
    estudiantes.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
        @Override
        public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
            Toast.makeText(getActivity(), estudiantes.getSelectedItem().toString(), Toast.LENGTH_LONG).show();
            String email_padre = ListaSpinner.get(0).toString(); //Aqui es
        }

        @Override
        public void onNothingSelected(AdapterView<?> parent) {

        }
    });

What I'm doing is using a ArrayList to fill the Spinner with the names and the other ArrayList to save your emails, but I already probe to get an item from both lists but the application stops.

android arraylist

asked by Rosyec Parrado 06.03.2018 в 00:09

source

1 answer

validate if a variable is of type date Problems grouping with ArrayList

score 1 · Accepted Answer

Within onItemSelected() you can get an object, and get its value:

Object item = parent.getItemAtPosition(position);
String email_padre = item.toString();

This would be the code:

estudiantes = (Spinner)view.findViewById(R.id.spinner_estudiantes);
    estudiantes.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
        @Override
        public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
            Toast.makeText(getActivity(), estudiantes.getSelectedItem().toString(), Toast.LENGTH_LONG).show();
            Object item = parent.getItemAtPosition(position);
            String email_padre = item.toString();        
        }

        @Override
        public void onNothingSelected(AdapterView<?> parent) {

        }
    });

You can also use the variable position to get the value within the list:

estudiantes = (Spinner)view.findViewById(R.id.spinner_estudiantes);
    estudiantes.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
        @Override
        public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {

            String email_padre = ListaSpinner.get(position).toString();            
        }

        @Override
        public void onNothingSelected(AdapterView<?> parent) {

        }
    });