Question

Alright, so I’m new to Android programming, so far my experience has been quite interesting and challenging. But I fear I have now encountered the first problem I’m not able to overcome on my own.

Simply put, all I want to do is have 2 Spinners:
1 for country selection
1 for province/state selection

What I want to accomplish is that when the user selects his/her country the province/state Spinner is updated with the correct adapter. Currently I’m only using 2 country for testing purposes.

When I launch the Activity, I get an exception and my app crashes.

Here’s my code, any pointers would be appreciated !

    public class ManageAccountActivity extends Activity {

    final ArrayAdapter<CharSequence> adapterSexe = ArrayAdapter.createFromResource(ManageAccountActivity.this, R.array.sex_array_fr, android.R.layout.simple_spinner_item);
    final ArrayAdapter<CharSequence> adapterProvince = ArrayAdapter.createFromResource(ManageAccountActivity.this, R.array.province_array_fr, android.R.layout.simple_spinner_item);
    final ArrayAdapter<CharSequence> adapterStates = ArrayAdapter.createFromResource(ManageAccountActivity.this, R.array.state_array_fr, android.R.layout.simple_spinner_item);
    final ArrayAdapter<CharSequence> adapterCountry = ArrayAdapter.createFromResource(ManageAccountActivity.this, R.array.country_array_fr, android.R.layout.simple_spinner_item);

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

        Spinner spinSexe = (Spinner) findViewById(R.id.spin_sex);
        Spinner spinProvince = (Spinner) findViewById(R.id.spin_province);
        Spinner spinCountry = (Spinner) findViewById(R.id.spin_country);

        adapterSexe.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
        adapterProvince.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
        adapterStates.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
        adapterCountry.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);

        spinSexe.setAdapter(adapterSexe);
        spinProvince.setAdapter(adapterProvince);
        spinCountry.setAdapter(adapterCountry);

        spinCountry.setOnItemSelectedListener(new CountryOnItemSelectedListener());   
    }   

    public class CountryOnItemSelectedListener implements OnItemSelectedListener {
        public void onItemSelected(AdapterView<?> parent, View view, int pos, long id) {
            setContentView(R.layout.account_management);
            Spinner spinProvince = (Spinner) view.findViewById(R.id.spin_province);

            if (parent.getItemAtPosition(pos).toString().equals("Canada")) {
                spinProvince.setAdapter(adapterProvince);
            } else {
                spinProvince.setAdapter(adapterStates);
            }
        }

        public void onNothingSelected(AdapterView parent) {
          // Do nothing.
        }
    }
}

Here’s the LogCat message I’m getting.

01-10 20:41:01.024: E/AndroidRuntime(1275):
java.lang.RuntimeException: Unable to instantiate activity
ComponentInfo{gggolf.android.minutegolf/gggolf.android.minutegolf.ManageAccountActivity}:
java.lang.NullPointerException

Answer 1

You cannot instantiate your ArrayAdapter directly on class attribut, because createFromResource() use Context, and it’s not exists at this time, do it in onCreate() methode instead.

In addition, you get spin province wrong in your listener, you can’t call findViewById on view local variable, because it’s not your layout, but an inflate of android.R.layout.simple_spinner_item

The good way:

public void onItemSelected(AdapterView<?> parent, View view, int pos, long id) {
        Spinner spinProvince = (Spinner) findViewById(R.id.spin_province);

        if (parent.getItemAtPosition(pos).toString().equals("Canada")) {
            spinProvince.setAdapter(adapterProvince);
        } else {
            spinProvince.setAdapter(adapterStates);
        }
    }