com.google.collide.client.ui.dropdown.AutocompleteController.java Source code

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Here is the source code for com.google.collide.client.ui.dropdown.AutocompleteController.java

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// Copyright 2012 Google Inc. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package com.google.collide.client.ui.dropdown;

import com.google.collide.json.shared.JsonArray;
import com.google.gwt.user.client.Timer;

import elemental.events.Event;
import elemental.events.EventListener;
import elemental.events.KeyboardEvent;
import elemental.events.KeyboardEvent.KeyCode;
import elemental.html.InputElement;

/**
 * Provides autocomplete functionality for an input using simple list.
 * 
 */
public class AutocompleteController<M> {

    /*
     * hide long enough for the click to be caught by handlers but not long enough
     * to be noticable by the user.
     */
    private static final int HIDE_DELAY = 100;

    public static <M> AutocompleteController<M> create(InputElement inputBox, DropdownController<M> controller,
            AutocompleteHandler<M> callback) {
        return new AutocompleteController<M>(inputBox, controller, callback);
    }

    public interface AutocompleteHandler<M> {
        public JsonArray<M> doCompleteQuery(String query);

        public void onItemSelected(M item);
    }

    /**
     * The amount of time to wait after the user has finished typing before
     * updating autocompletion results.
     */
    private static final int AUTOCOMPLETE_DELAY = 30;

    private final InputElement inputBox;
    private final DropdownController<M> dropdown;
    private final AutocompleteHandler<M> callback;
    private int minimumCharactersBeforeCompletion = 1;

    public AutocompleteController(InputElement inputBox, DropdownController<M> dropdown,
            AutocompleteHandler<M> callback) {
        this.inputBox = inputBox;
        this.dropdown = dropdown;
        this.callback = callback;

        dropdown.preventDefaultOnMouseDown();
        attachHandlers();
    }

    public DropdownController<M> getDropdown() {
        return dropdown;
    }

    /**
     * Specifies the minimum number of characters to be typed in before completion
     * will take place.
     */
    public void setMinimumCharactersBeforeCompletion(int minimum) {
        minimumCharactersBeforeCompletion = minimum;
    }

    private void attachHandlers() {

        inputBox.addEventListener(Event.INPUT, new EventListener() {
            final Timer deferredShow = new Timer() {
                @Override
                public void run() {
                    JsonArray<M> items = callback.doCompleteQuery(inputBox.getValue());
                    if (items.size() > 0) {
                        dropdown.setItems(items);
                        dropdown.show();
                    } else {
                        dropdown.hide();
                    }
                }
            };

            @Override
            public void handleEvent(Event evt) {
                KeyboardEvent event = (KeyboardEvent) evt;

                if (inputBox.getValue().length() < minimumCharactersBeforeCompletion) {
                    dropdown.hide();
                } else {
                    deferredShow.cancel();
                    deferredShow.schedule(AUTOCOMPLETE_DELAY);
                }
            }
        }, false);

        inputBox.addEventListener(Event.BLUR, new EventListener() {
            @Override
            public void handleEvent(Event evt) {
                dropdown.hide();
            }
        }, false);

        inputBox.addEventListener(Event.KEYUP, new EventListener() {
            @Override
            public void handleEvent(Event evt) {
                KeyboardEvent event = (KeyboardEvent) evt;

                if (event.getKeyCode() == KeyCode.ESC) {
                    dropdown.hide();
                }
            }
        }, false);

    }
}