NullPointerException on dynamic AutoCompleteTextView

Question

Some users are reporting this error:

java.lang.NullPointerException
at android.widget.ArrayAdapter.getCount(ArrayAdapter.java:291)
at android.widget.AutoCompleteTextView$PopupDataSetObserver$1.run(AutoCompleteTextView.java:1670)
at android.os.Handler.handleCallback(Handler.java:587)
at android.os.Handler.dispatchMessage(Handler.java:92)
at android.os.Looper.loop(Looper.java:123)
at android.app.ActivityThread.main(ActivityThread.java:3687)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:507)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:842)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:600)
at dalvik.system.NativeStart.main(Native Method)

Here is my code snippet:

    private List<City> autoCompleteCities = new ArrayList<City>();
    private List<City> autoCompleteCitiesOld = new ArrayList<City>();
    private ArrayAdapter<String> autoCompleteAdapter;
    private AutoCompleteTextView cityView;

    ...

    autoCompleteAdapter = new ArrayAdapter<String>(this, android.R.layout.simple_dropdown_item_1line);
    autoCompleteAdapter.setNotifyOnChange(true);

    cityView = (AutoCompleteTextView) findViewById(R.id.city);      

    cityView.setAdapter(autoCompleteAdapter);
    cityView.addTextChangedListener(new TextWatcher() {

        @Override
        public void onTextChanged(CharSequence s, int start, int before, int count) {
            LogUtil.i("!!!!!!!!!!!!! ontextchanged", s.toString());
            autoCompleteAdapter.clear();
            autoCompleteCitiesOld = autoCompleteCities;
            if (s.toString().length() > 2) {
                autoCompleteCities = search(s.toString());
                for (City city : autoCompleteCities) {
                    autoCompleteAdapter.add(city.getDisplayName());
                }
            }
        }

        @Override
        public void beforeTextChanged(CharSequence s, int start, int count, int after) {
        }

        @Override
        public void afterTextChanged(Editable s) {
        }
    });

It doesnt happen for me, but I have enough error reports to know it happens for several users. Any idea what is wrong? Why does this happen to only a handful of users?

I found this post but putting the fetching of new autocomplete values in an AsyncTask meant that the results always were one character behind what the user had entered.

Answer 1

Where are you passing the ArrayList to the ArrayAdapter. The NullPointerException throws while counting the list lenght in ArrayAdapter. But the list is not passed to Adapter, so the list object in default Adapter contains null.