Package com.google.gwt.user.cellview.client

Class CellTable<T>

java.lang.Object
com.google.gwt.user.client.ui.UIObject
com.google.gwt.user.client.ui.Widget
com.google.gwt.user.client.ui.Composite
com.google.gwt.user.cellview.client.AbstractHasData<T>
com.google.gwt.user.cellview.client.AbstractCellTable<T>
com.google.gwt.user.cellview.client.CellTable<T>
Type Parameters:
T - the data type of each row
All Implemented Interfaces:
HasAttachHandlers, HasHandlers, AbstractCellTable.TableSectionChangeHandler, HasKeyboardPagingPolicy, HasKeyboardSelectionPolicy, EventListener, Focusable, HasVisibility, IsRenderable, IsWidget, HasCellPreviewHandlers<T>, HasData<T>, HasKeyProvider<T>, HasRows
public class CellTable<T> extends AbstractCellTable<T> implements AbstractCellTable.TableSectionChangeHandler
A tabular view that supports paging and columns.

Columns

The Column class defines the Cell used to render a column. Implement Column.getValue(Object) to retrieve the field value from the row object that will be rendered in the Cell.

Headers and Footers

A Header can be placed at the top (header) or bottom (footer) of the CellTable. You can specify a header as text using AbstractCellTable.addColumn(Column, String), or you can create a custom Header that can change with the value of the cells, such as a column total. The Header will be rendered every time the row data changes or the table is redrawn. If you pass the same header instance (==) into adjacent columns, the header will span the columns.

Examples

Trivial example
public class CellTableExample implements EntryPoint {

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

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

  /**
   * The list of data to display.
   */
  private static final List<Contact> CONTACTS = Arrays.asList(
      new Contact("John", new Date(80, 4, 12), "123 Fourth Avenue"),
      new Contact("Joe", new Date(85, 2, 22), "22 Lance Ln"),
      new Contact("George", new Date(46, 6, 6), "1600 Pennsylvania Avenue"));

  public void onModuleLoad() {
    // Create a CellTable.
    CellTable<Contact> table = new CellTable<Contact>();
    table.setKeyboardSelectionPolicy(KeyboardSelectionPolicy.ENABLED);

    // Add a text column to show the name.
    TextColumn<Contact> nameColumn = new TextColumn<Contact>() {
      @Override
      public String getValue(Contact object) {
        return object.name;
      }
    };
    table.addColumn(nameColumn, "Name");

    // Add a date column to show the birthday.
    DateCell dateCell = new DateCell();
    Column<Contact, Date> dateColumn = new Column<Contact, Date>(dateCell) {
      @Override
      public Date getValue(Contact object) {
        return object.birthday;
      }
    };
    table.addColumn(dateColumn, "Birthday");

    // Add a text column to show the address.
    TextColumn<Contact> addressColumn = new TextColumn<Contact>() {
      @Override
      public String getValue(Contact object) {
        return object.address;
      }
    };
    table.addColumn(addressColumn, "Address");

    // Add a selection model to handle user selection.
    final SingleSelectionModel<Contact> selectionModel = new SingleSelectionModel<Contact>();
    table.setSelectionModel(selectionModel);
    selectionModel.addSelectionChangeHandler(new SelectionChangeEvent.Handler() {
      public void onSelectionChange(SelectionChangeEvent event) {
        Contact selected = selectionModel.getSelectedObject();
        if (selected != null) {
          Window.alert("You selected: " + selected.name);
        }
      }
    });

    // Set the total row count. This isn't strictly necessary, but it affects
    // paging calculations, so its good habit to keep the row count up to date.
    table.setRowCount(CONTACTS.size(), true);

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

    // Add it to the root panel.
    RootPanel.get().add(table);
  }
}
Handling user input with trivial FieldUpdater example
public class CellTableFieldUpdaterExample implements EntryPoint {

  /**
   * A simple data type that represents a contact with a unique ID.
   */
  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;
    }
  }

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

  /**
   * The key provider that allows us to identify Contacts even if a field
   * changes. We identify contacts by their unique ID.
   */
  private static final ProvidesKey<Contact> KEY_PROVIDER =
      new ProvidesKey<CellTableFieldUpdaterExample.Contact>() {
        @Override
        public Object getKey(Contact item) {
          return item.id;
        }
      };

  @Override
  public void onModuleLoad() {
    // Create a CellTable with a key provider.
    final CellTable<Contact> table = new CellTable<Contact>(KEY_PROVIDER);

    // Add a text input column to edit the name.
    final TextInputCell nameCell = new TextInputCell();
    Column<Contact, String> nameColumn = new Column<Contact, String>(nameCell) {
      @Override
      public String getValue(Contact object) {
        // Return the name as the value of this column.
        return object.name;
      }
    };
    table.addColumn(nameColumn, "Name");

    // Add a field updater to be notified when the user enters a new name.
    nameColumn.setFieldUpdater(new FieldUpdater<Contact, String>() {
      @Override
      public void update(int index, Contact object, String value) {
        // Inform the user of the change.
        Window.alert("You changed the name of " + object.name + " to " + value);

        // Push the changes into the Contact. At this point, you could send an
        // asynchronous request to the server to update the database.
        object.name = value;

        // Redraw the table with the new data.
        table.redraw();
      }
    });

    // Push the data into the widget.
    table.setRowData(CONTACTS);

    // Add it to the root panel.
    RootPanel.get().add(table);
  }
}
Handling user input with complex FieldUpdater example
public class CellTableFieldUpdaterExampleComplex implements EntryPoint {

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

    private final int id;
    private final String address;
    private Date birthday;
    private String name;

    public Contact(String name, Date birthday, String address) {
      nextId++;
      this.id = nextId;
      this.name = name;
      this.birthday = birthday;
      this.address = address;
    }
  }

  /**
   * The list of data to display.
   */
  private static final List<Contact> CONTACTS = Arrays.asList(
      new Contact("John", new Date(80, 4, 12), "123 Fourth Avenue"),
      new Contact("Joe", new Date(85, 2, 22), "22 Lance Ln"),
      new Contact("George", new Date(46, 6, 6), "1600 Pennsylvania Avenue"));

  /**
   * The key provider that allows us to identify Contacts even if a field
   * changes. We identify contacts by their unique ID.
   */
  private static final ProvidesKey<Contact> KEY_PROVIDER = new ProvidesKey<CellTableFieldUpdaterExampleComplex.Contact>() {
    @Override
    public Object getKey(Contact item) {
      return item.id;
    }
  };

  @Override
  public void onModuleLoad() {
    // Create a CellTable with a key provider.
    final CellTable<Contact> table = new CellTable<Contact>(KEY_PROVIDER);
    table.setKeyboardSelectionPolicy(KeyboardSelectionPolicy.ENABLED);

    // Add a text input column to edit the name.
    final TextInputCell nameCell = new TextInputCell();
    Column<Contact, String> nameColumn = new Column<Contact, String>(nameCell) {
      @Override
      public String getValue(Contact object) {
        return object.name;
      }
    };
    table.addColumn(nameColumn, "Name");

    // Add a field updater to be notified when the user enters a new name.
    nameColumn.setFieldUpdater(new FieldUpdater<Contact, String>() {
      @Override
      public void update(int index, Contact object, String value) {
        // Validate the data.
        if (value.length() < 3) {
          Window.alert("Names must be at least three characters long.");

          /*
           * Clear the view data. The view data contains the pending change and
           * allows the table to render with the pending value until the data is
           * committed. If the data is committed into the object, the view data
           * is automatically cleared out. If the data is not committed because
           * it is invalid, you must delete.
           */
          nameCell.clearViewData(KEY_PROVIDER.getKey(object));

          // Redraw the table.
          table.redraw();
          return;
        }

        // Inform the user of the change.
        Window.alert("You changed the name of " + object.name + " to " + value);

        // Push the changes into the Contact. At this point, you could send an
        // asynchronous request to the server to update the database.
        object.name = value;

        // Redraw the table with the new data.
        table.redraw();
      }
    });

    // Add a date column to show the birthday.
    Column<Contact, Date> dateColumn = new Column<Contact, Date>(
        new DatePickerCell()) {
      @Override
      public Date getValue(Contact object) {
        return object.birthday;
      }
    };
    table.addColumn(dateColumn, "Birthday");

    // Add a field updater to be notified when the user enters a new birthday.
    dateColumn.setFieldUpdater(new FieldUpdater<Contact, Date>() {
      @Override
      public void update(int index, Contact object, Date value) {
        Window.alert("You changed the birthday of "
            + object.name
            + " to "
            + DateTimeFormat.getFormat(PredefinedFormat.DATE_LONG).format(value));

        // Push the changes into the Contact.
        object.birthday = value;

        // Redraw the table with the new data.
        table.redraw();
      }
    });
    // Add a text column to show the address.
    TextColumn<Contact> addressColumn = new TextColumn<Contact>() {
      @Override
      public String getValue(Contact object) {
        return object.address;
      }
    };
    table.addColumn(addressColumn, "Address");

    // Set the total row count. This isn't strictly necessary, but it affects
    // paging calculations, so its good habit to keep the row count up to date.
    table.setRowCount(CONTACTS.size(), true);

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

    // Add it to the root panel.
    RootPanel.get().add(table);
  }
}
Pushing data with List Data Provider (backed by List)
public class ListDataProviderExample implements EntryPoint {

  public void onModuleLoad() {
    // Create a CellList.
    CellList<String> cellList = new CellList<String>(new TextCell());

    // Create a list data provider.
    final ListDataProvider<String> dataProvider = new ListDataProvider<String>();

    // Add the cellList to the dataProvider.
    dataProvider.addDataDisplay(cellList);

    // Create a form to add values to the data provider.
    final TextBox valueBox = new TextBox();
    valueBox.setText("Enter new value");
    Button addButton = new Button("Add value", new ClickHandler() {
      public void onClick(ClickEvent event) {
        // Get the value from the text box.
        String newValue = valueBox.getText();

        // Get the underlying list from data dataProvider.
        List<String> list = dataProvider.getList();

        // Add the value to the list. The dataProvider will update the cellList.
        list.add(newValue);
      }
    });

    // Add the widgets to the root panel.
    VerticalPanel vPanel = new VerticalPanel();
    vPanel.add(valueBox);
    vPanel.add(addButton);
    vPanel.add(cellList);
    RootPanel.get().add(vPanel);
  }
}
Pushing data asynchronously with Async Data Provider
public class AsyncDataProviderExample implements EntryPoint {

  /**
   * A custom {@link AsyncDataProvider}.
   */
  private static class MyDataProvider extends AsyncDataProvider<String> {
    /**
     * {@link #onRangeChanged(HasData)} is called when the table requests a new
     * range of data. You can push data back to the displays using
     * {@link #updateRowData(int, List)}.
     */
    @Override
    protected void onRangeChanged(HasData<String> display) {
      // Get the new range.
      final Range range = display.getVisibleRange();

      /*
       * Query the data asynchronously. If you are using a database, you can
       * make an RPC call here. We'll use a Timer to simulate a delay.
       */
      new Timer() {
        @Override
        public void run() {
          // We are creating fake data. Normally, the data will come from a
          // server.
          int start = range.getStart();
          int length = range.getLength();
          List<String> newData = new ArrayList<String>();
          for (int i = start; i < start + length; i++) {
            newData.add("Item " + i);
          }

          // Push the data to the displays. AsyncDataProvider will only update
          // displays that are within range of the data.
          updateRowData(start, newData);
        }
      }.schedule(3000);
    }
  }

  public void onModuleLoad() {
    // Create a CellList.
    CellList<String> cellList = new CellList<String>(new TextCell());

    // Create a data provider.
    MyDataProvider dataProvider = new MyDataProvider();

    // Add the cellList to the dataProvider.
    dataProvider.addDataDisplay(cellList);

    // Create paging controls.
    SimplePager pager = new SimplePager();
    pager.setDisplay(cellList);

    // Add the widgets to the root panel.
    VerticalPanel vPanel = new VerticalPanel();
    vPanel.add(pager);
    vPanel.add(cellList);
    RootPanel.get().add(vPanel);
  }
}
Writing a custom data provider
public class RangeChangeHandlerExample implements EntryPoint {

  @Override
  public void onModuleLoad() {
    // Create a CellList.
    final CellList<String> cellList = new CellList<String>(new TextCell());

    // Add a range change handler.
    cellList.addRangeChangeHandler(new RangeChangeEvent.Handler() {
      @Override
      public void onRangeChange(RangeChangeEvent event) {
        Range range = event.getNewRange();
        int start = range.getStart();
        int length = range.getLength();

        // Create the data to push into the view. At this point, you could send
        // an asynchronous RPC request to a server.
        List<String> data = new ArrayList<String>();
        for (int i = start; i < start + length; i++) {
          data.add("Item " + i);
        }

        // Push the data into the list.
        cellList.setRowData(start, data);
      }
    });

    // Force the cellList to fire an initial range change event.
    cellList.setVisibleRangeAndClearData(new Range(0, 25), true);

    // Create paging controls.
    SimplePager pager = new SimplePager();
    pager.setDisplay(cellList);

    // Add the widgets to the root panel.
    VerticalPanel vPanel = new VerticalPanel();
    vPanel.add(pager);
    vPanel.add(cellList);
    RootPanel.get().add(vPanel);
  }
}
Using a key provider to track objects as they change
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);
  }
}