FilterableListDisplay.java

package org.azavea.otm.ui;

import android.app.ListActivity;
import android.content.Intent;
import android.os.Bundle;
import android.text.Editable;
import android.text.TextWatcher;
import android.view.KeyEvent;
import android.view.View;
import android.widget.EditText;
import android.widget.ListView;

import com.google.common.base.Function;

import org.azavea.otm.R;
import org.azavea.otm.adapters.LinkedHashMapAdapter;
import org.azavea.otm.data.Model;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.LinkedHashMap;
import java.util.List;

import static org.azavea.otm.adapters.LinkedHashMapAdapter.Entry;

public abstract class FilterableListDisplay<T extends Model> extends ListActivity {

    /**
     * @return The Resource id of the hint text to show in the filter textbox
     */
    protected abstract int getFilterHintTextId();

    /**
     * @return The key used to store the model data in the intent result
     */
    protected abstract String getIntentDataKey();

    @Override
    public void onCreate(Bundle data) {
        super.onCreate(data);

        setContentView(R.layout.filterable_list_selector);

        EditText filterEditText = (EditText) findViewById(R.id.filter_text);
        filterEditText.setHint(getFilterHintTextId());
    }

    public void renderList(LinkedHashMapAdapter<T> adapter) {
        setListAdapter(adapter);
        setupFiltering(adapter);
    }

    private void setupFiltering(final LinkedHashMapAdapter<T> adapter) {
        EditText filterEditText = (EditText) findViewById(R.id.filter_text);
        setKeyboardChangeEvents(adapter, filterEditText);
        setTextWatcherEvents(adapter, filterEditText);
    }

    /**
     * Listen on events of the filter text box to pass along filter text
     * and invalidate the current view
     */
    private void setTextWatcherEvents(final LinkedHashMapAdapter<T> adapter,
                                      EditText filterEditText) {
        filterEditText.addTextChangedListener(new TextWatcher() {
            @Override
            public void onTextChanged(CharSequence s, int start, int before,
                                      int count) {
            }

            @Override
            public void afterTextChanged(Editable s) {
                adapter.getFilter().filter(s);
                adapter.notifyDataSetChanged();
            }

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

    /**
     * Listen on events the keyboard emits when finished editing
     * ('Done' and 'Next' are the ENTER event).
     * The Keyboard ENTER event on a ListActivity will re-render
     * the list, so the current view must be invalidated
     */
    private void setKeyboardChangeEvents(final LinkedHashMapAdapter<T> adapter,
                                         EditText filterEditText) {
        filterEditText.setOnKeyListener((v, keyCode, event) -> {
            if (event.getKeyCode() == KeyEvent.KEYCODE_ENTER) {
                adapter.notifyDataSetChanged();
            }
            return false;
        });
    }

    @Override
    protected void onListItemClick(ListView l, View v, int position, long id) {
        //noinspection unchecked
        Model selection = ((Entry<Model>) l.getItemAtPosition(position)).value;
        Intent result = new Intent();

        result.putExtra(getIntentDataKey(), selection.getData().toString());

        setResult(RESULT_OK, result);
        finish();
    }

    public LinkedHashMap<CharSequence, List<T>> groupListByKeyFirstLetter(T[] list, Function<T, String> getKey) {
        if (getKey == null) {
            throw new IllegalArgumentException("getKey cannot be null");
        }

        //noinspection ConstantConditions
        Arrays.sort(list, (a, b) -> getKey.apply(a).compareToIgnoreCase(getKey.apply(b)));

        LinkedHashMap<CharSequence, List<T>> itemSections = new LinkedHashMap<>(26);
        for (char c = 'A'; c <= 'Z'; c++) {
            itemSections.put(Character.toString(c), new ArrayList<>());
        }
        for (T item : list) {
            //noinspection ConstantConditions
            char firstChar = getKey.apply(item).toUpperCase().trim().charAt(0);
            if (firstChar < 'A' || firstChar > 'Z') {
                firstChar = 'A';
            }
            String key = Character.toString(firstChar);
            List<T> section = itemSections.get(key);
            section.add(item);
        }
        return itemSections;
    }
}