ArrayAdapter need to be clear even i am creating a new one

问题

Hello I'm having problems understanding how the ArrayAdapter works. My code is working but I dont know how.(http://amy-mac.com/images/2013/code_meme.jpg)

I have my activity, inside it i have 2 private classes.:

public class MainActivity extends Activity {
    ...
    private void SomePrivateMethod(){
        autoCompleteTextView.setAdapter(new ArrayAdapter<String>(this,
            android.R.layout.simple_spinner_dropdown_item, new ArrayList<String>(Arrays.asList(""))));
        autoCompleteTextView.addTextChangedListener(new MyTextWatcher());
    }
    ...

    private class MyTextWatcher implements TextWatcher {
        ...
    }
    private class SearchAddressTask extends AsyncTask<String, Void, String[]> {
        ...
    }
}

Now inside my textwatcher class i call the search address task:

@Override
public void afterTextChanged(Editable s) {
    new SearchAddressTask().execute(s.toString());
}

So far so good.

In my SearchAddressTask I do some stuff on doInBackground() that returns the right array.

On the onPostExecute() method i try to just modify the AutoCompleteTextView adapter to add the values from the array obtained in doInBackground() but the adapter cannot be modified:

NOT WORKING CODE:

protected void onPostExecute(String[] addressArray) {
    ArrayAdapter<String> adapter = (ArrayAdapter<String>) autoCompleteDestination.getAdapter();
    adapter.clear();
    adapter.addAll(new ArrayList<String>(Arrays.asList(addressArray)));
    adapter.notifyDataSetChanged();
    Log.d("SearchAddressTask", "adapter isEmpty : " + adapter.isEmpty()); // Returns true!!??!
}

I dont get why this is not working. Even if i run it on UI Thread...

I kept investigating, if i recreate the arrayAdapter, is working in the UI (Showing the suggestions), but i still need to clear the old adapter:

WORKING CODE:

protected void onPostExecute(String[] addressArray) {
    ArrayAdapter<String> adapter = (ArrayAdapter<String>) autoCompleteDestination.getAdapter();
    adapter.clear();
    autoCompleteDestination.setAdapter(new ArrayAdapter<String>(NewDestinationActivity.this,android.R.layout.simple_spinner_dropdown_item, new ArrayList<String>(Arrays.asList(addressArray))));
    //adapter.notifyDataSetChanged(); // no needed
    Log.d("SearchAddressTask", "adapter isEmpty : " + adapter.isEmpty()); // keeps returning true!!??!
}

So my question is, what is really happening with this ArrayAdapter? why I cannot modify it in my onPostExecute()? Why is working in the UI if i am recreating the adapter? and why i need to clear the old adapter then?

I dont know there are so many questions that I need some help in here!!

Thanks!!

回答1:

I followed the recomendation of pskink, Thanks a lot!!

I switched all the responsability to the ArrayAdapter and implemented my own as filter.

import java.util.ArrayList;

import android.content.Context;
import android.widget.ArrayAdapter;
import android.widget.Filter;
import android.widget.Filterable;

import com.roisoftstudio.travelalarm.gui.utils.StreetListHelper;

public class AutoCompleteAdapter extends ArrayAdapter<String> implements Filterable {
    private ArrayList<String> mData;
    private Context context;

    public AutoCompleteAdapter(Context context, int textViewResourceId) {
        super(context, textViewResourceId);
        this.context = context;
        mData = new ArrayList<String>();
    }

    @Override
    public int getCount() {
        return mData.size();
    }

    @Override
    public String getItem(int index) {
    return mData.get(index);
    }

    @Override
    public Filter getFilter() {
        Filter myFilter = new Filter() {
            @Override
            protected FilterResults performFiltering(CharSequence constraint) {
                FilterResults filterResults = new FilterResults();
                if (constraint != null) {
                    mData = StreetListHelper.getStreetList(context, constraint.toString());
                    filterResults.values = mData;
                    filterResults.count = mData.size();
                }
                return filterResults;
            }

            @Override
            protected void publishResults(CharSequence constraint, FilterResults results) {
            }

        };
        return myFilter;
    }
}

来源：https://stackoverflow.com/questions/24096851/arrayadapter-need-to-be-clear-even-i-am-creating-a-new-one