com.google.gwt.cell.client

Class AbstractEditableCell<C,V>

java.lang.Object

com.google.gwt.cell.client.AbstractCell<C>

com.google.gwt.cell.client.AbstractEditableCell<C,V>

Type Parameters:

C - the type that this Cell represents

V - the data type of the view data state

All Implemented Interfaces:

Cell<C>

Direct Known Subclasses:

AbstractInputCell, CheckboxCell, DatePickerCell, EditTextCell

public abstract class AbstractEditableCell<C,V>
extends AbstractCell<C>

A default implementation of the Cell interface used for editable cells that need to save view data state for specific values.

Example

public class EditableCellExample implements EntryPoint {

  /**
   * A simple data type that represents a contact.
   */
  private static class Contact {
    private final String address;
    private final String name;

    public Contact(String name, String address) {
      this.name = name;
      this.address = address;
    }
  }

  /**
   * A custom {@link Cell} used to render a {@link Contact}. We extend
   * {@link AbstractCell} because it provides reasonable implementations of
   * methods that work for most use cases.
   */
  private class ContactCell extends AbstractCell<Contact> {

    public ContactCell() {
      // Our cell responds to change events and keydown events.
      super("change", "keydown");
    }

    @Override
    public void onBrowserEvent(Context context, Element parent, Contact value,
        NativeEvent event, ValueUpdater<Contact> valueUpdater) {
      // Check that the value is not null.
      if (value == null) {
        return;
      }

      // Call the super handler, which handlers the enter key.
      super.onBrowserEvent(context, parent, value, event, valueUpdater);

      // Handle click events.
      if ("change".equals(event.getType())) {
        updateFavorites(parent, value);
        showCurrentFavorites();
      }
    }

    @Override
    public void render(Context context, Contact value, SafeHtmlBuilder sb) {
      /*
       * Always do a null check on the value. Cell widgets can pass null to
       * cells if the underlying data contains a null, or if the data arrives
       * out of order.
       */
      if (value == null) {
        return;
      }

      // Add a checkbox. If the contact is a favorite, the box will be checked.
      sb.appendHtmlConstant("<table><tr><td valign=\"top\">");
      if (favorites.contains(value)) {
        sb.appendHtmlConstant("<input type=\"checkbox\" checked=checked/>");
      } else {
        sb.appendHtmlConstant("<input type=\"checkbox\" />");
      }
      sb.appendHtmlConstant("</td><td>");

      // Display the name in big letters.
      sb.appendHtmlConstant("<div style=\"size:200%;font-weight:bold;\">");
      sb.appendEscaped(value.name);
      sb.appendHtmlConstant("</div>");

      // Display the address in normal text.
      sb.appendHtmlConstant("<div style=\"padding-left:10px;\">");
      sb.appendEscaped(value.address);
      sb.appendHtmlConstant("</div>");

      sb.appendHtmlConstant("</td></tr></table>");
    }

    /**
     * By convention, cells that respond to user events should handle the enter
     * key. This provides a consistent user experience when users use keyboard
     * navigation in the widget. Our cell will toggle the checkbox on Enter.
     */
    @Override
    protected void onEnterKeyDown(Context context, Element parent,
        Contact value, NativeEvent event, ValueUpdater<Contact> valueUpdater) {
      // Toggle the checkbox.
      InputElement input = getInputElement(parent);
      input.setChecked(!input.isChecked());

      // Update the favorites based on the new state.
      updateFavorites(parent, value);

      // Show the new list of favorites.
      showCurrentFavorites();
    }

    /**
     * Get the checkbox input element from the parent element that wraps our
     * cell.
     * 
     * @param parent the parent element
     * @return the checkbox
     */
    private InputElement getInputElement(Element parent) {
      // We need to navigate down to our input element.
      TableElement table = parent.getFirstChildElement().cast();
      TableRowElement tr = table.getRows().getItem(0);
      TableCellElement td = tr.getCells().getItem(0);
      InputElement input = td.getFirstChildElement().cast();
      return input;
    }

    /**
     * Update the favorites list based on the state of the input element.
     */
    private void updateFavorites(Element parent, Contact value) {
      // Get the input element.
      InputElement input = getInputElement(parent);

      // Update the favorites based on the checked state.
      if (input.isChecked()) {
        favorites.add(value);
      } else {
        favorites.remove(value);
      }
    }
  }

  /**
   * The list of data to display.
   */
  private static final List<Contact> CONTACTS = Arrays.asList(new Contact(
      "John", "123 Fourth Avenue"), new Contact("Joe", "22 Lance Ln"),
      new Contact("Michael", "1283 Berry Blvd"), new Contact("Sarah",
          "100 Hundred St."), new Contact("George", "1600 Pennsylvania Avenue"));

  /**
   * Our list of favorite contacts.
   */
  private final List<Contact> favorites = new ArrayList<EditableCellExample.Contact>();

  public void onModuleLoad() {
    // Create a cell to render each value.
    ContactCell contactCell = new ContactCell();

    // Use the cell in a CellList.
    CellList<Contact> cellList = new CellList<Contact>(contactCell);

    // Push the data into the widget.
    cellList.setRowData(0, CONTACTS);

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

  /**
   * Show the list of favorites.
   */
  private void showCurrentFavorites() {
    if (favorites.size() > 0) {
      String text = "You favorite contacts are ";
      boolean first = true;
      for (Contact contact : favorites) {
        if (!first) {
          text += ", ";
        } else {
          first = false;
        }
        text += contact.name;
      }
      Window.alert(text);
    } else {
      Window.alert("You have not selected any favorites.");
    }
  }
}

Nested Class Summary

Nested classes/interfaces inherited from interface com.google.gwt.cell.client.Cell

Cell.Context

Constructor Summary

Constructors

Constructor and Description
AbstractEditableCell(java.util.Set<java.lang.String> consumedEvents) Construct a new AbstractEditableCell with the specified consumed events.
AbstractEditableCell(java.lang.String... consumedEvents) Construct a new AbstractEditableCell with the specified consumed events.

Method Summary

Modifier and Type	Method and Description
void	clearViewData(java.lang.Object key) Clear the view data associated with the specified key.
V	getViewData(java.lang.Object key) Get the view data associated with the specified key.
abstract boolean	isEditing(Cell.Context context, Element parent, C value) Returns true if the cell is currently editing the data identified by the given element and key.
void	setViewData(java.lang.Object key, V viewData) Associate view data with the specified key.

Methods inherited from class com.google.gwt.cell.client.AbstractCell

dependsOnSelection, getConsumedEvents, handlesSelection, onBrowserEvent, onEnterKeyDown, render, resetFocus, setValue

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

AbstractEditableCell

public AbstractEditableCell(java.lang.String... consumedEvents)

Construct a new AbstractEditableCell with the specified consumed events.

Parameters:

consumedEvents - the events that this cell consumes

AbstractEditableCell

public AbstractEditableCell(java.util.Set<java.lang.String> consumedEvents)

Construct a new AbstractEditableCell with the specified consumed events.

Parameters:

consumedEvents - the events that this cell consumes

Method Detail

clearViewData

public void clearViewData(java.lang.Object key)

Clear the view data associated with the specified key.

Parameters:

key - the key identifying the row value

getViewData

public V getViewData(java.lang.Object key)

Get the view data associated with the specified key.

Parameters:

key - the key identifying the row object

Returns:

the view data, or null if none has been set

See Also:

setViewData(Object, Object)

isEditing

public abstract boolean isEditing(Cell.Context context,
                                  Element parent,
                                  C value)

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.

Specified by:

isEditing in interface Cell<C>

Overrides:

isEditing in class AbstractCell<C>

Parameters:

context - the Context of the cell

parent - the parent Element

value - the value associated with the cell

Returns:

true if the cell is in edit mode

setViewData

public void setViewData(java.lang.Object key,
                        V viewData)

Associate view data with the specified key. If the key is null, the view data will be ignored.

Parameters:

key - the key of the view data

viewData - the view data to associate

See Also:

getViewData(Object)