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

Class CellList<T>

  • Type Parameters:
    T - the data type of list items
    All Implemented Interfaces:
    HasAttachHandlers, HasHandlers, HasKeyboardPagingPolicy, HasKeyboardSelectionPolicy, EventListener, Focusable, HasVisibility, IsRenderable, IsWidget, HasCellPreviewHandlers<T>, HasData<T>, HasKeyProvider<T>, HasRows
    Direct Known Subclasses:
    CellBrowser.BrowserCellList
    public class CellList<T>
extends AbstractHasData<T>
    A single column list of cells.

    Examples

    Trivial example
    public class CellListExample implements EntryPoint {

  /**
   * The list of data to display.
   */
  private static final List<String> DAYS = Arrays.asList("Sunday", "Monday",
      "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday");

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

    // Create a CellList that uses the cell.
    CellList<String> cellList = new CellList<String>(textCell);
    cellList.setKeyboardSelectionPolicy(KeyboardSelectionPolicy.ENABLED);

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

    // 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.
    cellList.setRowCount(DAYS.size(), true);

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

    // Add it to the root panel.
    RootPanel.get().add(cellList);
  }
}
    Handling user input with ValueUpdater
    public class CellListValueUpdaterExample implements EntryPoint {

  /**
   * The list of data to display.
   */
  private static final List<String> DAYS = Arrays.asList("Sunday", "Monday",
      "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday");

  public void onModuleLoad() {
    // Create a cell that will interact with a value updater.
    TextInputCell inputCell = new TextInputCell();

    // Create a CellList that uses the cell.
    CellList<String> cellList = new CellList<String>(inputCell);

    // Create a value updater that will be called when the value in a cell
    // changes.
    ValueUpdater<String> valueUpdater = new ValueUpdater<String>() {
      public void update(String newValue) {
        Window.alert("You typed: " + newValue);
      }
    };

    // Add the value updater to the cellList.
    cellList.setValueUpdater(valueUpdater);

    // 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.
    cellList.setRowCount(DAYS.size(), true);

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

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

    • Constructor Detail

      • CellList

        public CellList​(Cell<T> cell)
        Construct a new CellList.
        Parameters:
        cell - the cell used to render each item

      • CellList

        public CellList​(Cell<T> cell,
                ProvidesKey<T> keyProvider)
        Construct a new CellList with the specified key provider.
        Parameters:
        cell - the cell used to render each item
        keyProvider - an instance of ProvidesKey, or null if the record object should act as its own key

      • CellList

        public CellList​(Cell<T> cell,
                CellList.Resources resources,
                ProvidesKey<T> keyProvider)
        Construct a new CellList with the specified CellList.Resources and key provider.
        Parameters:
        cell - the cell used to render each item
        resources - the resources used for this widget
        keyProvider - an instance of ProvidesKey, or null if the record object should act as its own key

    • Method Detail

      • getEmptyListWidget

        public Widget getEmptyListWidget()
        Get the widget displayed when the list has no rows.
        Returns:
        the empty list widget

      • getLoadingIndicator

        public Widget getLoadingIndicator()
        Get the widget displayed when the data is loading.
        Returns:
        the loading indicator

      • getRowElement

        public Element getRowElement​(int indexOnPage)
        Get the Element for the specified index. If the element has not been created, null is returned.
        Parameters:
        indexOnPage - the index on the page
        Returns:
        the element, or null if it doesn't exists
        Throws:
        java.lang.IndexOutOfBoundsException - if the index is outside of the current page

      • setEmptyListWidget

        public void setEmptyListWidget​(Widget widget)
        Set the widget to display when the list has no rows.
        Parameters:
        widget - the empty data widget

      • setLoadingIndicator

        public void setLoadingIndicator​(Widget widget)
        Set the widget to display when the data is loading.
        Parameters:
        widget - the loading indicator

      • setValueUpdater

        public void setValueUpdater​(ValueUpdater<T> valueUpdater)
        Set the value updater to use when cells modify items.
        Parameters:
        valueUpdater - the ValueUpdater

      • dependsOnSelection

        protected boolean dependsOnSelection()
        Description copied from class: AbstractHasData
        Check whether or not the cells in the view depend on the selection state.
        Specified by:
        dependsOnSelection in class AbstractHasData<T>
        Returns:
        true if cells depend on selection, false if not

      • doAttachChildren

        protected void doAttachChildren()
        Description copied from class: Widget
        If a widget contains one or more child widgets that are not in the logical widget hierarchy (the child is physically connected only on the DOM level), it must override this method and call Widget.onAttach() for each of its child widgets.
        Overrides:
        doAttachChildren in class Widget
        See Also:
        Widget.onAttach()

      • doDetachChildren

        protected void doDetachChildren()
        Description copied from class: Widget
        If a widget contains one or more child widgets that are not in the logical widget hierarchy (the child is physically connected only on the DOM level), it must override this method and call Widget.onDetach() for each of its child widgets.
        Overrides:
        doDetachChildren in class Widget
        See Also:
        Widget.onDetach()

      • fireEventToCell

        protected void fireEventToCell​(Cell.Context context,
                               Event event,
                               Element parent,
                               T value)
        Fire an event to the cell.
        Parameters:
        context - the Cell.Context of the cell
        event - the event that was fired
        parent - the parent of the cell
        value - the value of the cell

      • getCell

        protected Cell<T> getCell()
        Return the cell used to render each item.

      • getCellParent

        protected Element getCellParent​(Element item)
        Get the parent element that wraps the cell from the list item. Override this method if you add structure to the element.
        Parameters:
        item - the row element that wraps the list item
        Returns:
        the parent element of the cell

      • isKeyboardNavigationSuppressed

        protected boolean isKeyboardNavigationSuppressed()
        Description copied from class: AbstractHasData
        Check if keyboard navigation is being suppressed, such as when the user is editing a cell.
        Specified by:
        isKeyboardNavigationSuppressed in class AbstractHasData<T>
        Returns:
        true if suppressed, false if not

      • resetFocusOnCell

        protected boolean resetFocusOnCell()
        Description copied from class: AbstractHasData
        Reset focus on the currently focused cell.
        Specified by:
        resetFocusOnCell in class AbstractHasData<T>
        Returns:
        true if focus is taken, false if not

      • setKeyboardSelected

        protected void setKeyboardSelected​(int index,
                                   boolean selected,
                                   boolean stealFocus)
        Description copied from class: AbstractHasData
        Update an element to reflect its keyboard selected state.
        Specified by:
        setKeyboardSelected in class AbstractHasData<T>
        Parameters:
        index - the index of the element
        selected - true if selected, false if not
        stealFocus - true if the row should steal focus, false if not