ListBoxCell.java

/*
 * 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.sample.webapp.client;

import com.google.gwt.cell.client.AbstractInputCell;
import com.google.gwt.cell.client.Cell;
import com.google.gwt.cell.client.ValueUpdater;
import com.google.gwt.core.client.GWT;
import com.google.gwt.dom.client.BrowserEvents;
import com.google.gwt.dom.client.Element;
import com.google.gwt.dom.client.NativeEvent;
import com.google.gwt.dom.client.SelectElement;
import com.google.gwt.safehtml.client.SafeHtmlTemplates;
import com.google.gwt.safehtml.shared.SafeHtml;
import com.google.gwt.safehtml.shared.SafeHtmlBuilder;

import java.util.HashMap;
import java.util.Map;

/**
 * A {@link Cell} used to render a drop-down list.
 */
public class ListBoxCell extends AbstractInputCell<String, ListBoxCell.HasKey> {
    public interface HasKey {
        String getKey();
        String getText();
    }

    interface Template extends SafeHtmlTemplates {
        @Template("<option value=\"{0}\">{1}</option>")
        SafeHtml deselected(String key, String value);

        @Template("<option value=\"{0}\" selected=\"selected\">{1}</option>")
        SafeHtml selected(String key, String value);
    }

    private static Template template;

    public final Map<String, HasKey> options;

    public void addOptions(HasKey value) {
        options.put(value.getKey(), value);
    }
    /**
     * Construct a new {@link ListBoxCell} with the specified options.
     *
     * @param options the options in the cell
     */
    public ListBoxCell(Map<String, HasKey> options) {
        super(BrowserEvents.CHANGE);
        if (template == null) {
            template = GWT.create(Template.class);
        }
        this.options = options;
    }

    @Override
    public void onBrowserEvent(Context context, Element parent, String value,
                               NativeEvent event, ValueUpdater<String> valueUpdater) {
        super.onBrowserEvent(context, parent, value, event, valueUpdater);
        String type = event.getType();
        if (BrowserEvents.CHANGE.equals(type)) {
            Object key = context.getKey();
            SelectElement select = parent.getFirstChild().cast();
            HasKey newValue = options.get(select.getValue());
            setViewData(key, newValue);
            finishEditing(parent, newValue.getText(), key, valueUpdater);
            if (valueUpdater != null) {
                valueUpdater.update(newValue.getKey());
            }
        }
    }

    @Override
    public void render(Context context, String value, SafeHtmlBuilder sb) {
        // Get the view data.
        Object key = context.getKey();
        HasKey viewData = getViewData(key);
        if (viewData != null && viewData.equals(value)) {
            clearViewData(key);
            viewData = null;
        }

        String key2 = viewData == null ? value : viewData.getKey();
        sb.appendHtmlConstant("<select tabindex=\"-1\">");
        int index = 0;
        for (Map.Entry<String, HasKey> entry : options.entrySet()) {
            if (entry.getKey().equals(key2)) {
                sb.append(template.selected(entry.getKey(), entry.getValue().getText()));
            } else {
                sb.append(template.deselected(entry.getKey(), entry.getValue().getText()));
            }
        }
        sb.appendHtmlConstant("</select>");
    }
}