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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}.
 * 

* A {@link Renderer Renderer} is used to get user-presentable strings to * display in the select element. * * @param the value type */ public class ValueListBox extends Composite implements HasConstrainedValue, IsEditor> { private final List values = new ArrayList(); private final Map valueKeyToIndex = new HashMap(); private final Renderer renderer; private final ProvidesKey keyProvider; private TakesValueEditor editor; private T value; public ValueListBox(Renderer renderer) { this(renderer, new SimpleKeyProvider()); } public ValueListBox(Renderer renderer, ProvidesKey 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 handler) { return addHandler(handler, ValueChangeEvent.getType()); } /** * Returns a {@link TakesValueEditor} backed by the ValueListBox. */ public TakesValueEditor asEditor() { if (editor == null) { editor = TakesValueEditor.of(this); } return editor; } public T getValue() { return value; } public void setAcceptableValues(Collection 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); } }





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