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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.cellview.client;

import com.google.gwt.cell.client.Cell;
import com.google.gwt.cell.client.Cell.Context;
import com.google.gwt.cell.client.FieldUpdater;
import com.google.gwt.cell.client.HasCell;
import com.google.gwt.cell.client.ValueUpdater;
import com.google.gwt.dom.client.Element;
import com.google.gwt.dom.client.NativeEvent;
import com.google.gwt.safehtml.shared.SafeHtmlBuilder;
import com.google.gwt.user.client.ui.HasAlignment;

/**
 * A representation of a column in a table.
 * 
 * @param  the row type
 * @param  the column type
 */
public abstract class Column implements HasCell, HasAlignment {

  /**
   * The {@link Cell} responsible for rendering items in the column.
   */
  private final Cell cell;

  private String cellStyleNames = null;

  /**
   * The {@link FieldUpdater} used for updating values in the column.
   */
  private FieldUpdater fieldUpdater;

  private boolean isDefaultSortAscending = true;
  private boolean isSortable = false;
  private String dataStoreName = null;
  private HorizontalAlignmentConstant hAlign = null;
  private VerticalAlignmentConstant vAlign = null;

  /**
   * Construct a new Column with a given {@link Cell}.
   * 
   * @param cell the Cell used by this Column
   */
  public Column(Cell cell) {
    this.cell = cell;
  }

  /**
   * Returns the {@link Cell} responsible for rendering items in the column.
   * 
   * @return a Cell
   */
  @Override
  public Cell getCell() {
    return cell;
  }

  /**
   * Get extra style names that should be applied to a cell in this column.
   * 
   * @param context the cell context
   * @param object the base object to be updated, or null if the row is empty
   * @return the extra styles of the given row in a space-separated list, or
   *         {@code null} if there are no extra styles for the cells in this
   *         column
   */
  public String getCellStyleNames(Context context, T object) {
    return cellStyleNames;
  }

  /**
   * @return the database name of the column, or null if it's never been set
   */
  public String getDataStoreName() {
    return dataStoreName;
  }

  /**
   * Returns the {@link FieldUpdater} used for updating values in the column.
   * 
   * @return an instance of FieldUpdater
   * @see #setFieldUpdater(FieldUpdater)
   */
  @Override
  public FieldUpdater getFieldUpdater() {
    return fieldUpdater;
  }

  @Override
  public HorizontalAlignmentConstant getHorizontalAlignment() {
    return hAlign;
  }
  
  /**
   * Returns the column value from within the underlying data object.
   */
  @Override
  public abstract C getValue(T object);

  @Override
  public VerticalAlignmentConstant getVerticalAlignment() {
    return vAlign;
  }

  /**
   * Check if the default sort order of the column is ascending or descending.
   * 
   * @return true if default sort is ascending, false if not
   */
  public boolean isDefaultSortAscending() {
    return isDefaultSortAscending;
  }

  /**
   * Check if the column is sortable.
   * 
   * @return true if sortable, false if not
   */
  public boolean isSortable() {
    return isSortable;
  }

  /**
   * Handle a browser event that took place within the column.
   * 
   * @param context the cell context
   * @param elem the parent Element
   * @param object the base object to be updated
   * @param event the native browser event
   */
  public void onBrowserEvent(Context context, Element elem, final T object, NativeEvent event) {
    final int index = context.getIndex();
    ValueUpdater valueUpdater = (fieldUpdater == null) ? null : new ValueUpdater() {
      @Override
      public void update(C value) {
        fieldUpdater.update(index, object, value);
      }
    };
    cell.onBrowserEvent(context, elem, getValue(object), event, valueUpdater);
  }

  /**
   * Render the object into the cell.
   * 
   * @param context the cell context
   * @param object the object to render
   * @param sb the buffer to render into
   */
  public void render(Context context, T object, SafeHtmlBuilder sb) {
    cell.render(context, getValue(object), sb);
  }

  /**
   * Set extra style names that should be applied to every cell.
   * 
   * 

* If you want to apply style names based on the row or cell value, override * {@link #getCellStyleNames(Context, Object)} directly. *

* * @param styleNames the extra style names to apply in a space-separated list, * or {@code null} if there are no extra styles for this cell */ public void setCellStyleNames(String styleNames) { this.cellStyleNames = styleNames; } /** * Sets a string that identifies this column in a data query. * * @param name name of the column from the data store's perspective */ public void setDataStoreName(String name) { this.dataStoreName = name; } /** * Set whether or not the default sort order is ascending. * * @param isAscending true to set the default order to ascending, false for * descending */ public void setDefaultSortAscending(boolean isAscending) { this.isDefaultSortAscending = isAscending; } /** * Set the {@link FieldUpdater} used for updating values in the column. * * @param fieldUpdater the field updater * @see #getFieldUpdater() */ public void setFieldUpdater(FieldUpdater fieldUpdater) { this.fieldUpdater = fieldUpdater; } /** * {@inheritDoc} * *

* The new horizontal alignment will apply the next time the table is * rendered. *

*/ @Override public void setHorizontalAlignment(HorizontalAlignmentConstant align) { this.hAlign = align; } /** * Set whether or not the column can be sorted. The change will take effect * the next time the table is redrawn. * * @param sortable true to make sortable, false to make unsortable */ public void setSortable(boolean sortable) { this.isSortable = sortable; } /** * {@inheritDoc} * *

* The new vertical alignment will apply the next time the table is rendered. *

*/ @Override public void setVerticalAlignment(VerticalAlignmentConstant align) { this.vAlign = align; } }




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