Update City Spinner with notifyDataSetChanged after state is selected

问题

How do I update my city spinner once the user selects a state?

Both fields are populated using a DataCall.class that returns JSON data and parses the info into an array for the spinner.

My code below sets the city adapter to a defualt "Select State" value and once the user gets selects the state it should use notifyDataSetChanged since the default array for the city spinner is updated with the new city names. The errors I am getting are commented in my code below.

public class SearchActivity extends Activity{
       private static final String TAG = "MyApp";
       ArrayAdapter<String> adapter2;
       String city_values[] = new String[]{"Please select a state."};

       @Override
       public void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.search_layout);

            final Spinner zipspinner = (Spinner) findViewById(R.id.zipspinner);
            final Spinner cityspinner = (Spinner) findViewById(R.id.cityspinner);       

            adapter2 = new ArrayAdapter<String> (this,android.R.layout.simple_spinner_item, city_values);
            adapter2.setDropDownViewResource(R.layout.city_spinner_layout);
            cityspinner.setAdapter(adapter2);

            JSONArray jsonArray;
            try {
                String spinnerContentType = "state";
                String spinnerURL = "getStoreState.php";
                String spinner_data =  DataCall.getJSON(spinnerURL,spinnerContentType); 
                Log.d(TAG, spinner_data);
                jsonArray = new JSONArray(spinner_data);

                final String[] array_spinner = new String[jsonArray.length()]; 
                for (int i=0; i<jsonArray.length(); i++) {   
                String styleValue = jsonArray.getJSONArray(i).getString(0);    
                    Log.d(TAG, styleValue);
                    array_spinner[i] = styleValue;
                }

                ArrayAdapter<String> adapter = new ArrayAdapter<String> (this, 
                                  android.R.layout.simple_spinner_item,array_spinner);
                adapter.setDropDownViewResource(R.layout.state_spinner_layout);
                zipspinner.setAdapter(adapter);
                zipspinner.setOnItemSelectedListener(new OnItemSelectedListener() {
                      public void onItemSelected(AdapterView<?> parent,View view, int pos, long id) {
                            int item = zipspinner.getSelectedItemPosition();
                            if(item != 0){

                                String item_value = array_spinner[item];
                                String spinnerContentType = "city";
                                String spinnerURL = "getStoreCity.php?state=" + item_value;
                                Log.d(TAG, spinnerURL);
                                String city_data =  DataCall.getJSON(spinnerURL,spinnerContentType); 
                                Log.d(TAG, city_data);

                                JSONArray cityArray = null;
                                try {
                                    cityArray = new JSONArray(city_data);
                                } catch (JSONException e) {
                                     e.printStackTrace();
                                }       
                                final String[] city_spinner = new String[cityArray.length()]; 

                                for (int i=0; i<cityArray.length(); i++){                       
                                    String styleValue = null;
                                    try {
                                        styleValue = cityArray.getJSONArray(i).getString(0);
                                        Log.d(TAG, styleValue);
                                    } catch (JSONException e) {
                                        e.printStackTrace();
                                    }              
                                    city_spinner[i] = styleValue;                               
                                }

                                city_values = city_spinner; 
                                adapter2.notifyDataSetChanged();

                                String test_string = "NOTIFY UPDATE";
                                Log.d(TAG, test_string);
                            } else {
                               // finish();
                            }
                        }
                        public void onNothingSelected(AdapterView parent) {
                          // Do nothing.
                        }
                   });

                   cityspinner.setOnItemSelectedListener(new OnItemSelectedListener() {
                        public void onItemSelected(AdapterView<?> parent,View view, int pos, long id) {
                            int item = zipspinner.getSelectedItemPosition();
                            if(item != 0){

                            }else{

                            }

                        }

                        public void onNothingSelected(AdapterView parent) {
                          // Do nothing.
                        }
                  });   
          }catch (JSONException e) {
                e.printStackTrace();
          }
     }
}

回答1:

public class SearchActivity extends Activity {
    ArrayAdapter<String> adapter2;
    String city_values[];

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.search_layout);

        final Spinner zipspinner = (Spinner) findViewById(R.id.zipspinner);
        final Spinner cityspinner = (Spinner) findViewById(R.id.cityspinner);

        String city_values[] = new String[]{"Please select a state."};
        adapter2 = new ArrayAdapter<String>(this, android.R.layout.simple_spinner_item, city_values);
        adapter2.setDropDownViewResource(R.layout.city_spinner_layout);
        cityspinner.setAdapter(adapter2);

        JSONArray jsonArray;
        final JSONArray cityArray;

        try {
            String spinnerContentType = "state";
            String spinnerURL = "getStoreState.php";
            String spinner_data = DataCall.getJSON(spinnerURL, spinnerContentType);

            jsonArray = new JSONArray(spinner_data);

            final String[] array_spinner = new String[jsonArray.length()];

            for (int i = 0; i < jsonArray.length(); i++) {
                String styleValue = jsonArray.getJSONArray(i).getString(0);
                array_spinner[i] = styleValue;
            }

            ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, android.R.layout.simple_spinner_item, array_spinner);
            adapter.setDropDownViewResource(R.layout.state_spinner_layout);
            zipspinner.setAdapter(adapter);
            zipspinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {

                public void onItemSelected(AdapterView<?> parent, View view, int pos, long id) {
                    int item = zipspinner.getSelectedItemPosition();
                    String item_value = array_spinner[item];
                    String spinnerContentType = "city";
                    String spinnerURL = "getStoreCity.php?state=" + item_value;
                    String city_data = DataCall.getJSON(spinnerURL, spinnerContentType);
                    cityArray = new JSONArray(city_data);               //The final local variable cityArray cannot be assigned, since it is defined in an enclosing type

                    final String[] city_spinner = new String[cityArray.length()];


                    for (int i = 0; i < cityArray.length(); i++) {
                        String styleValue = cityArray.getJSONArray(i).getString(0); //Unhandled exception type JSONException                
                        city_spinner[i] = styleValue;
                    }

                    city_values = city_spinner; //Unhandled exception type JSONException
                    adapter2.notifyDataSetChanged();
                }

                public void onNothingSelected(AdapterView parent {
                    // Do nothing.
                }
            });
        } catch (JSONException e) {
            e.printStackTrace();
        }
    }
}

now try

回答2:

Well, this is how I will suggest,

First of all check that you are getting values in city_values. Then, notify the adapter.... adapter2.notifyDataSetChanged(); And finally cityspinner.setSelection(0);

UPDATE:

I would suggest to trake ArrayList<String> instead of String[]

Thanks...

回答3:

Declare the city_array variable at the place where you assign a new JSONArray(). Anyways you are using it temporarily. Just set the adapter again.

来源：https://stackoverflow.com/questions/7370107/update-city-spinner-with-notifydatasetchanged-after-state-is-selected