com.google.gwt.user.client.ui.ValueListBox.java Source code

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Here is the source code for com.google.gwt.user.client.ui.ValueListBox.java

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/*
 * Copyright 2010 Google Inc.
 * 
 * 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.gwt.user.client.ui;

import com.google.gwt.editor.client.IsEditor;
import com.google.gwt.editor.client.adapters.TakesValueEditor;
import com.google.gwt.event.dom.client.ChangeEvent;
import com.google.gwt.event.dom.client.ChangeHandler;
import com.google.gwt.event.logical.shared.ValueChangeEvent;
import com.google.gwt.event.logical.shared.ValueChangeHandler;
import com.google.gwt.event.shared.HandlerRegistration;
import com.google.gwt.text.shared.Renderer;
import com.google.gwt.view.client.ProvidesKey;
import com.google.gwt.view.client.SimpleKeyProvider;

import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

/**
 * Implementation of {@link HasConstrainedValue} based on a
 * {@link com.google.gwt.dom.client.SelectElement}.
 * <p>
 * A {@link Renderer Renderer<T>} is used to get user-presentable strings to
 * display in the select element.
 * 
 * @param <T> the value type
 */
public class ValueListBox<T> extends Composite implements HasConstrainedValue<T>, IsEditor<TakesValueEditor<T>> {

    private final List<T> values = new ArrayList<T>();
    private final Map<Object, Integer> valueKeyToIndex = new HashMap<Object, Integer>();
    private final Renderer<T> renderer;
    private final ProvidesKey<T> keyProvider;

    private TakesValueEditor<T> editor;
    private T value;

    public ValueListBox(Renderer<T> renderer) {
        this(renderer, new SimpleKeyProvider<T>());
    }

    public ValueListBox(Renderer<T> renderer, ProvidesKey<T> keyProvider) {
        this.keyProvider = keyProvider;
        this.renderer = renderer;
        initWidget(new ListBox());

        getListBox().addChangeHandler(new ChangeHandler() {
            public void onChange(ChangeEvent event) {
                int selectedIndex = getListBox().getSelectedIndex();

                if (selectedIndex < 0) {
                    return; // Not sure why this happens during addValue
                }
                T newValue = values.get(selectedIndex);
                setValue(newValue, true);
            }
        });
    }

    public HandlerRegistration addValueChangeHandler(ValueChangeHandler<T> handler) {
        return addHandler(handler, ValueChangeEvent.getType());
    }

    /**
     * Returns a {@link TakesValueEditor} backed by the ValueListBox.
     */
    public TakesValueEditor<T> asEditor() {
        if (editor == null) {
            editor = TakesValueEditor.of(this);
        }
        return editor;
    }

    public T getValue() {
        return value;
    }

    public void setAcceptableValues(Collection<T> newValues) {
        values.clear();
        valueKeyToIndex.clear();
        ListBox listBox = getListBox();
        listBox.clear();

        for (T nextNewValue : newValues) {
            addValue(nextNewValue);
        }

        updateListBox();
    }

    /**
     * Set the value and display it in the select element. Add the value to the
     * acceptable set if it is not already there.
     */
    public void setValue(T value) {
        setValue(value, false);
    }

    public void setValue(T value, boolean fireEvents) {
        if (value == this.value || (this.value != null && this.value.equals(value))) {
            return;
        }

        T before = this.value;
        this.value = value;
        updateListBox();

        if (fireEvents) {
            ValueChangeEvent.fireIfNotEqual(this, before, value);
        }
    }

    private void addValue(T value) {
        Object key = keyProvider.getKey(value);
        if (valueKeyToIndex.containsKey(key)) {
            throw new IllegalArgumentException("Duplicate value: " + value);
        }

        valueKeyToIndex.put(key, values.size());
        values.add(value);
        getListBox().addItem(renderer.render(value));
        assert values.size() == getListBox().getItemCount();
    }

    private ListBox getListBox() {
        return (ListBox) getWidget();
    }

    private void updateListBox() {
        Object key = keyProvider.getKey(value);
        Integer index = valueKeyToIndex.get(key);
        if (index == null) {
            addValue(value);
        }

        index = valueKeyToIndex.get(key);
        getListBox().setSelectedIndex(index);
    }
}