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.cell.client; import com.google.gwt.dom.client.Element; import com.google.gwt.dom.client.NativeEvent; import com.google.gwt.safehtml.shared.SafeHtmlBuilder; import java.util.Set; /** * A light weight representation of a renderable object. * * <p> * <h3>Example</h3> * {@example com.google.gwt.examples.cell.CellExample} * </p> * * @param <C> the type that this Cell represents */ public interface Cell<C> { /** * Contains information about the context of the Cell. */ public static class Context { private final int column; private final int index; private final Object key; private final int subindex; /** * Create a new {@link Context}. * * @param index the absolute index of the value * @param column the column index of the cell, or 0 * @param key the unique key that represents the row value */ public Context(int index, int column, Object key) { this(index, column, key, 0); } /** * Create a new {@link Context}. * * @param index the absolute index of the value * @param column the column index of the cell, or 0 * @param key the unique key that represents the row value * @param subindex the child index */ public Context(int index, int column, Object key, int subindex) { this.index = index; this.column = column; this.key = key; this.subindex = subindex; } /** * Get the column index of the cell. If the view only contains a single * column, this method returns 0. * * @return the column index of the cell */ public int getColumn() { return column; } /** * Get the absolute index of the value. * * @return the index */ public int getIndex() { return index; } /** * Get the key that uniquely identifies the row object. * * @return the unique key */ public Object getKey() { return key; } /** * Get the sub index of the rendered row value. If the row value renders to * a single row element, the sub index is 0. If the row value renders to * more than one row element, the sub index may be greater than zero. */ public int getSubIndex() { return subindex; } } /** * Check if this cell depends on the selection state. * * @return true if dependent on selection, false if not */ boolean dependsOnSelection(); /** * Get the set of events that this cell consumes. The container that uses this * cell should only pass these events to * {@link #onBrowserEvent(Context, Element, Object, NativeEvent, ValueUpdater)} * when the event occurs. * * <p> * The returned value should not be modified, and may be an unmodifiable set. * Changes to the return value may not be reflected in the cell. * </p> * * @return the consumed events, or null if no events are consumed */ Set<String> getConsumedEvents(); /** * Check if this cell handles selection. If the cell handles selection, then * its container should not automatically handle selection. * * @return true if the cell handles selection, false if not */ boolean handlesSelection(); /** * Returns true if the cell is currently editing the data identified by the * given element and key. While a cell is editing, widgets containing the cell * may choose to pass keystrokes directly to the cell rather than using them * for navigation purposes. * * @param context the {@link Context} of the cell * @param parent the parent Element * @param value the value associated with the cell * @return true if the cell is in edit mode */ boolean isEditing(Context context, Element parent, C value); /** * Handle a browser event that took place within the cell. The default * implementation returns null. * * @param context the {@link Context} of the cell * @param parent the parent Element * @param value the value associated with the cell * @param event the native browser event * @param valueUpdater a {@link ValueUpdater}, or null if not specified */ void onBrowserEvent(Context context, Element parent, C value, NativeEvent event, ValueUpdater<C> valueUpdater); /** * Render a cell as HTML into a {@link SafeHtmlBuilder}, suitable for passing * to {@link Element#setInnerHTML(String)} on a container element. * * <p> * Note: If your cell contains natively focusable elements, such as buttons or * input elements, be sure to set the tabIndex to -1 so that they do not steal * focus away from the containing widget. * </p> * * @param context the {@link Context} of the cell * @param value the cell value to be rendered * @param sb the {@link SafeHtmlBuilder} to be written to */ void render(Context context, C value, SafeHtmlBuilder sb); /** * Reset focus on the Cell. This method is called if the cell has focus when * it is refreshed. * * @param context the {@link Context} of the cell * @param parent the parent Element * @param value the value associated with the cell * @return true if focus is taken, false if not */ boolean resetFocus(Context context, Element parent, C value); /** * This method may be used by cell containers to set the value on a single * cell directly, rather than using {@link Element#setInnerHTML(String)}. See * {@link AbstractCell#setValue(Context, Element, Object)} for a default * implementation that uses {@link #render(Context, Object, SafeHtmlBuilder)}. * * @param context the {@link Context} of the cell * @param parent the parent Element * @param value the value associated with the cell */ void setValue(Context context, Element parent, C value); }