com.google.gwt.examples.view.KeyProviderExample.java Source code

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Here is the source code for com.google.gwt.examples.view.KeyProviderExample.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.examples.view;

import com.google.gwt.cell.client.AbstractCell;
import com.google.gwt.cell.client.Cell;
import com.google.gwt.core.client.EntryPoint;
import com.google.gwt.safehtml.shared.SafeHtmlBuilder;
import com.google.gwt.user.cellview.client.CellList;
import com.google.gwt.user.client.ui.RootPanel;
import com.google.gwt.view.client.ProvidesKey;
import com.google.gwt.view.client.SelectionModel;
import com.google.gwt.view.client.SingleSelectionModel;

import java.util.Arrays;
import java.util.List;

/**
 * Example of using a {@link ProvidesKey}.
 */
public class KeyProviderExample implements EntryPoint {

    /**
     * A simple data type that represents a contact.
     */
    private static class Contact {
        private static int nextId = 0;

        private final int id;
        private String name;

        public Contact(String name) {
            nextId++;
            this.id = nextId;
            this.name = name;
        }
    }

    /**
     * A custom {@link Cell} used to render a {@link Contact}.
     */
    private static class ContactCell extends AbstractCell<Contact> {
        @Override
        public void render(Context context, Contact value, SafeHtmlBuilder sb) {
            if (value != null) {
                sb.appendEscaped(value.name);
            }
        }
    }

    /**
     * The list of data to display.
     */
    private static final List<Contact> CONTACTS = Arrays.asList(new Contact("John"), new Contact("Joe"),
            new Contact("Michael"), new Contact("Sarah"), new Contact("George"));

    public void onModuleLoad() {
        /*
         * Define a key provider for a Contact. We use the unique ID as the key,
         * which allows to maintain selection even if the name changes.
         */
        ProvidesKey<Contact> keyProvider = new ProvidesKey<Contact>() {
            public Object getKey(Contact item) {
                // Always do a null check.
                return (item == null) ? null : item.id;
            }
        };

        // Create a CellList using the keyProvider.
        CellList<Contact> cellList = new CellList<Contact>(new ContactCell(), keyProvider);

        // Push data into the CellList.
        cellList.setRowCount(CONTACTS.size(), true);
        cellList.setRowData(0, CONTACTS);

        // Add a selection model using the same keyProvider.
        SelectionModel<Contact> selectionModel = new SingleSelectionModel<Contact>(keyProvider);
        cellList.setSelectionModel(selectionModel);

        /*
         * Select a contact. The selectionModel will select based on the ID because
         * we used a keyProvider.
         */
        Contact sarah = CONTACTS.get(3);
        selectionModel.setSelected(sarah, true);

        // Modify the name of the contact.
        sarah.name = "Sara";

        /*
         * Redraw the CellList. Sarah/Sara will still be selected because we
         * identify her by ID. If we did not use a keyProvider, Sara would not be
         * selected.
         */
        cellList.redraw();

        // Add the widgets to the root panel.
        RootPanel.get().add(cellList);
    }
}