Java tutorial
/* * 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.cellview.client; import com.google.gwt.cell.client.Cell; import com.google.gwt.cell.client.Cell.Context; import com.google.gwt.cell.client.ValueUpdater; import com.google.gwt.dom.client.Document; import com.google.gwt.dom.client.Element; import com.google.gwt.dom.client.Style.Unit; import com.google.gwt.editor.client.IsEditor; import com.google.gwt.editor.client.LeafValueEditor; import com.google.gwt.editor.client.adapters.TakesValueEditor; 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.resources.client.CommonResources; import com.google.gwt.safehtml.shared.SafeHtmlBuilder; import com.google.gwt.user.client.Event; import com.google.gwt.user.client.ui.HasValue; import com.google.gwt.user.client.ui.Widget; import com.google.gwt.view.client.HasKeyProvider; import com.google.gwt.view.client.ProvidesKey; /** * A {@link Widget} that wraps a {@link Cell}. * * @param <C> the type that the Cell represents */ public class CellWidget<C> extends Widget implements HasKeyProvider<C>, HasValue<C>, IsEditor<LeafValueEditor<C>> { /** * Create the default element used to wrap the Cell. The default element is a * div with display set to inline-block. * * @return the default wrapper element */ private static Element createDefaultWrapperElement() { Element div = Document.get().createDivElement(); div.setClassName(CommonResources.getInlineBlockStyle()); return div; } /** * The cell being wrapped. */ private final Cell<C> cell; /** * For use with the editor framework. */ private LeafValueEditor<C> editor; /** * The key provider for the value. */ private final ProvidesKey<C> keyProvider; /** * The current cell value. */ private C value; /** * The {@link ValueUpdater} used to trigger value update events. */ private final ValueUpdater<C> valueUpdater = new ValueUpdater<C>() { public void update(C value) { // no need to redraw, the Cell took care of it setValue(value, true, false); } }; /** * Construct a new {@link CellWidget} with the specified cell and an initial * value of <code>null</code>. * * @param cell the cell to wrap */ public CellWidget(Cell<C> cell) { this(cell, null, null); } /** * Construct a new {@link CellWidget} with the specified cell and key * provider, and an initial value of <code>null</code>. * * @param cell the cell to wrap * @param keyProvider the key provider used to get keys from values */ public CellWidget(Cell<C> cell, ProvidesKey<C> keyProvider) { this(cell, null, keyProvider); } /** * Construct a new {@link CellWidget} with the specified cell and initial * value. * * @param cell the cell to wrap * @param initialValue the initial value of the Cell */ public CellWidget(Cell<C> cell, C initialValue) { this(cell, initialValue, null); } /** * Construct a new {@link CellWidget} with the specified cell, initial value, * and key provider. * * @param cell the cell to wrap * @param initialValue the initial value of the Cell * @param keyProvider the key provider used to get keys from values */ public CellWidget(Cell<C> cell, C initialValue, ProvidesKey<C> keyProvider) { this(cell, initialValue, keyProvider, createDefaultWrapperElement()); } /** * Creates a {@link CellWidget} with the specified cell, initial value, key * provider, using the specified element as the wrapper around the cell. * * @param cell the cell to wrap * @param initialValue the initial value of the Cell * @param keyProvider the key provider used to get keys from values * @param elem the browser element to use */ protected CellWidget(Cell<C> cell, C initialValue, ProvidesKey<C> keyProvider, Element elem) { this.cell = cell; this.keyProvider = keyProvider; setElement(elem); CellBasedWidgetImpl.get().sinkEvents(this, cell.getConsumedEvents()); setValue(initialValue); } public HandlerRegistration addValueChangeHandler(ValueChangeHandler<C> handler) { return addHandler(handler, ValueChangeEvent.getType()); } public LeafValueEditor<C> asEditor() { if (editor == null) { editor = TakesValueEditor.of(this); } return editor; } /** * Get the {@link Cell} wrapped by this widget. * * @return the {@link Cell} being wrapped */ public Cell<C> getCell() { return cell; } public ProvidesKey<C> getKeyProvider() { return keyProvider; } public C getValue() { return value; } @Override public void onBrowserEvent(Event event) { CellBasedWidgetImpl.get().onBrowserEvent(this, event); super.onBrowserEvent(event); // Forward the event to the cell. String eventType = event.getType(); if (cell.getConsumedEvents().contains(eventType)) { cell.onBrowserEvent(createContext(), getElement(), value, event, valueUpdater); } } /** * Redraw the widget. */ public void redraw() { SafeHtmlBuilder sb = new SafeHtmlBuilder(); cell.render(createContext(), value, sb); getElement().setInnerHTML(sb.toSafeHtml().asString()); /* * The rendered Cell should fill the root element so height and width styles * applied to the widget also apply to the Cell. If there is exactly one * child element, the height and width are set to 100% to fill the parent. */ Element child = getElement().getFirstChildElement(); if (child != null && child.getNextSiblingElement() == null) { child.getStyle().setHeight(100, Unit.PCT); child.getStyle().setWidth(100, Unit.PCT); } } /** * {@inheritDoc} * <p> * This method will redraw the widget if the new value does not equal the * existing value. * </p> */ public void setValue(C value) { setValue(value, false, true); } /** * {@inheritDoc} * <p> * This method will redraw the widget if the new value does not equal the * existing value. * </p> */ public void setValue(C value, boolean fireEvents) { setValue(value, fireEvents, true); } /** * Sets this object's value and optionally redraw the widget. Fires * {@link com.google.gwt.event.logical.shared.ValueChangeEvent} when * fireEvents is true and the new value does not equal the existing value. * Redraws the widget when redraw is true and the new value does not equal the * existing value. * * @param value the object's new value * @param fireEvents fire events if true and value is new * @param redraw redraw the widget if true and value is new */ public void setValue(C value, boolean fireEvents, boolean redraw) { C oldValue = getValue(); if (value != oldValue && (oldValue == null || !oldValue.equals(value))) { this.value = value; if (redraw) { redraw(); } if (fireEvents) { ValueChangeEvent.fire(this, value); } } } /** * Get the {@link Context} for the cell. */ private Context createContext() { return new Context(0, 0, getKey(value)); } /** * Get the key for the specified value. * * @param value the value * @return the key */ private Object getKey(C value) { return (keyProvider == null || value == null) ? value : keyProvider.getKey(value); } }