GXT combo with multiple checkbox for GXT 4.0.3

InputCheckboxCell.java

package com.sencha.gxt.test.client.combo_multi_checkselect4;
import com.google.gwt.cell.client.AbstractCell;
import com.google.gwt.cell.client.ValueUpdater;
import com.google.gwt.dom.client.Element;
import com.google.gwt.dom.client.InputElement;
import com.google.gwt.dom.client.NativeEvent;
import com.google.gwt.safehtml.shared.SafeHtmlBuilder;
import com.google.gwt.safehtml.shared.SafeHtmlUtils;
import com.sencha.gxt.core.client.dom.XElement;

/**
 * A simple native input checkbox.
 * @since 4.0.3
 */
public class InputCheckboxCell extends AbstractCell<Boolean> {

  public InputCheckboxCell() {
    super("click", "touchstart");
  }

  /**
   * Allow selection when clicked.
   */
  @Override
  public boolean handlesSelection() {
    return true;
  }

  @Override
  public void onBrowserEvent(Context context, Element parent, Boolean value, NativeEvent event,
      ValueUpdater<Boolean> valueUpdater) {
    super.onBrowserEvent(context, parent, value, event, valueUpdater);

    XElement targetEl = event.getEventTarget().cast();
    if (targetEl != null && targetEl.getTagName().equalsIgnoreCase("input")) {
      InputElement input = targetEl.cast();
      if (input != null) {
        valueUpdater.update(input.isChecked());
      }
    }
  }

  @Override
  public void render(Context context, Boolean value, SafeHtmlBuilder sb) {
    String checked = "";
    if (value) {
      checked = "checked";
    }
    String s = "<input type='checkbox' " + checked + " style='" + getStyle(context, value) + "' class='"
        + getStyleName(context, value) + "' />";

    sb.append(SafeHtmlUtils.fromTrustedString(s));
  }

  /**
   * Provide the input with a style attribute.
   * @param value the checked value
   * @param context the cell context
   * 
   * @return styles
   */
  protected String getStyle(Context context, Boolean value) {
    return "";
  }

  /**
   * Provide the input with a class attribute.
   * @param value the checked value
   * @param context the cell context
   * 
   * @return the class attribute
   */
  protected String getStyleName(Context context, Boolean value) {
    return "";
  }

}

MultiSelectCombo.java

import java.util.List;

import com.google.gwt.user.client.Event;
import com.sencha.gxt.data.shared.LabelProvider;
import com.sencha.gxt.data.shared.ListStore;
import com.sencha.gxt.widget.core.client.form.TriggerField;

public class MultiSelectComboBox<T> extends TriggerField<List<T>> {

  /**
   * Create an instance of the multiple select combo.
   * 
   * @param listStore the possible values for selection.
   * @param labelProvider the item label renderer.
   */
  public MultiSelectComboBox(ListStore<T> listStore, LabelProvider<T> labelProvider) {
    this(new MultiSelectComboBoxCell<T>(listStore, labelProvider));
  }

  /**
   * Create an instance of the mutlti select combo with your own cell and property editor.
   * 
   * @param cell a multi select combobox cell.
   * @param propertyEditor a multi select combobox property editor.
   */
  public MultiSelectComboBox(MultiSelectComboBoxCell<T> cell) {
    super(cell, cell.getPropertyEditor());
  }

  @Override
  protected void onResize(int width, int height) {
    super.onResize(width, height);

    getCell().syncListViewWidth(getElement());
  }

  @Override
  public void onBrowserEvent(Event event) {
    super.onBrowserEvent(event);
    
    // on key down
  }

  /**
   * Sets the panel's expand state.
   * 
   * @param expand true to expand
   */
  public void setExpanded(boolean expand) {
    if (expand) {
      getCell().expand(getElement(), getValue());
    } else {
      getCell().collapse();
    }
  }
  
  @Override
  public MultiSelectComboBoxCell<T> getCell() {
    return (MultiSelectComboBoxCell<T>) super.getCell();
  }

}

MultiSelectComboBoxCell.java

package com.sencha.gxt.test.client.combo_multi_checkselect4;

import java.text.ParseException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

import com.google.gwt.cell.client.Cell;
import com.google.gwt.cell.client.CompositeCell;
import com.google.gwt.cell.client.FieldUpdater;
import com.google.gwt.cell.client.HasCell;
import com.google.gwt.cell.client.TextCell;
import com.google.gwt.cell.client.ValueUpdater;
import com.google.gwt.core.client.GWT;
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.Event;
import com.google.gwt.user.client.Event.NativePreviewEvent;
import com.google.gwt.user.client.ui.RootPanel;
import com.sencha.gxt.cell.core.client.form.TriggerFieldCell;
import com.sencha.gxt.core.client.IdentityValueProvider;
import com.sencha.gxt.core.client.Style.Anchor;
import com.sencha.gxt.core.client.Style.AnchorAlignment;
import com.sencha.gxt.core.client.Style.HideMode;
import com.sencha.gxt.core.client.Style.SelectionMode;
import com.sencha.gxt.core.client.ValueProvider;
import com.sencha.gxt.core.client.dom.XDOM;
import com.sencha.gxt.core.client.dom.XElement;
import com.sencha.gxt.core.client.util.BaseEventPreview;
import com.sencha.gxt.data.shared.LabelProvider;
import com.sencha.gxt.data.shared.ListStore;
import com.sencha.gxt.widget.core.client.ListView;
import com.sencha.gxt.widget.core.client.ListViewSelectionModel;
import com.sencha.gxt.widget.core.client.event.XEvent;
import com.sencha.gxt.widget.core.client.form.PropertyEditor;
import com.sencha.gxt.widget.core.client.selection.SelectionChangedEvent;
import com.sencha.gxt.widget.core.client.selection.SelectionChangedEvent.SelectionChangedHandler;

public class MultiSelectComboBoxCell<T> extends TriggerFieldCell<List<T>> {

  /**
   * Render and parse values to and from the input.
   */
  public static class MultiComboPropertyEditor<T> extends PropertyEditor<List<T>> {
    protected MultiSelectComboBoxCell<T> cell;
    protected LabelProvider<T> labelProvider;

    public MultiComboPropertyEditor(MultiSelectComboBoxCell<T> cell, LabelProvider<T> labelProvider) {
      this.cell = cell;
      this.labelProvider = labelProvider;
    }

    /**
     * Used to render the values into the input
     */
    @Override
    public String render(List<T> objects) {
      if (objects == null) {
        return "";
      }
      StringBuffer sb = new StringBuffer();
      for (int i = 0; i < objects.size(); i++) {
        T item = objects.get(i);
        String label = labelProvider.getLabel(item);
        sb.append(label);
        if (i < objects.size() - 1) {
          sb.append(getItemSeparator());
        }
      }

      return sb.toString();
    }

    /**
     * Used to parse the values from the inputs. Instead use the cells selected list values.
     */
    @Override
    public List<T> parse(CharSequence text) throws ParseException {
      return cell.getValues();
    }

    protected String getItemSeparator() {
      return ", ";
    }
  }

  public class ItemCheckBoxCellHasCell<T> implements HasCell<T, Boolean> {
    private ListViewSelectionModel<T> selectionModel;

    public ItemCheckBoxCellHasCell(ListViewSelectionModel<T> selectionModel) {
      this.selectionModel = selectionModel;
    }

    @Override
    public Cell<Boolean> getCell() {
      return new InputCheckboxCell();
    }

    @Override
    public FieldUpdater<T, Boolean> getFieldUpdater() {
      return new FieldUpdater<T, Boolean>() {
        @Override
        public void update(int index, T object, Boolean value) {
          if (value) {
            selectionModel.select(object, true);
          } else {
            selectionModel.deselect(object);
          }
        }
      };
    }

    @Override
    public Boolean getValue(T item) {
      return selectionModel.isSelected(item);
    }
  }

  public class ItemTextHasCell<T> implements HasCell<T, String> {
    protected TextCell cell = new TextCell();
    protected LabelProvider<T> labelProvider;

    public ItemTextHasCell(LabelProvider<T> labelProvider) {
      this.labelProvider = labelProvider;
    }

    @Override
    public Cell<String> getCell() {
      return cell;
    }

    @Override
    public FieldUpdater<T, String> getFieldUpdater() {
      return new FieldUpdater<T, String>() {
        @Override
        public void update(int index, T object, String value) {
        }
      };
    }

    @Override
    public String getValue(T object) {
      return labelProvider.getLabel(object);
    }
  }

  public static class ListViewSelectionModelExt<T> extends ListViewSelectionModel<T> {
    public ListViewSelectionModelExt() {
      super();
      setSelectionMode(SelectionMode.MULTI);
    }

    @Override
    protected void doSelect(List<T> models, boolean keepExisting, boolean suppressEvent) {
      // always keep existing
      super.doSelect(models, true, suppressEvent);
    }

    @Override
    protected void onMouseDown(NativeEvent event) {
      XEvent e = event.<XEvent>cast();
      XElement target = e.getEventTargetEl();
      int selIndex = listView.findElementIndex(target);

      if (selIndex == -1 || isLocked()) {
        return;
      }

      T sel = listStore.get(selIndex);
      if (sel == null) {
        return;
      }

      boolean isSelected = isSelected(sel);
      if (isSelected) {
        doDeselect(Collections.singletonList(sel), false);
        selected.remove(sel);
      } else {
        doSelect(Collections.singletonList(sel), true, false);
      }
    }
  }

  public static class ListViewExt<T, N> extends ListView<T, N> {
    public ListViewExt(ListStore<T> store, ValueProvider<? super T, N> valueProvider, Cell<N> cell) {
      super(store, valueProvider, cell);
    }

    @Override
    public void onBrowserEvent(Event event) {
      super.onBrowserEvent(event);

      switch (event.getTypeInt()) {
      case Event.ONCLICK:
        onMouseDown(event);
        break;
      }
    }

    @Override
    protected void onMouseOver(Event ce) {
      // don't highlight on mouse over
      // super.onMouseOver(ce);
    }
  }

  protected ListViewExt<T, T> listView;
  protected ListStore<T> store;
  protected LabelProvider<T> labelProvider;
  protected BaseEventPreview basePreviewEvent;
  protected int listViewMaxHeight = 300;
  protected ListViewSelectionModelExt<T> selectionModel;
  protected List<T> showListSelectedValues;
  protected boolean expanded;

  public MultiSelectComboBoxCell(ListStore<T> store, LabelProvider<T> labelProvider) {
    super(GWT.<TriggerFieldAppearance>create(TriggerFieldAppearance.class));

    this.store = store;
    this.labelProvider = labelProvider;
    this.propertyEditor = initPropertyEditor(labelProvider);
  }

  protected PropertyEditor<List<T>> initPropertyEditor(LabelProvider<T> labelProvider) {
    return new MultiComboPropertyEditor<T>(this, labelProvider);
  }

  @Override
  protected void onTriggerClick(Context context, XElement parent, NativeEvent event, List<T> values,
      ValueUpdater<List<T>> updater) {
    super.onTriggerClick(context, parent, event, values, updater);

    if (!expanded) {
      saveContext(context, parent, event, updater, values);
      expand(parent, values);
    } else {
      collapse();
    }
  }

  /**
   * Show the list view with the selected values.
   * 
   * @param parent widget consuming this cell.
   * @param values to be selected.
   */
  public void expand(XElement parent, List<T> values) {
    this.showListSelectedValues = values;

    if (!expanded) {
      configureListView();
      showListView();
    }
  }

  /**
   * Set the selected values.
   * 
   * @param values to be selected.
   */
  public void setValues(List<T> values) {
    selectionModel.setSelection(values);
  }

  /**
   * Returns the selected values. 
   * 
   * @return the selected values.
   */
  public List<T> getValues() {
    return selectionModel.getSelection();
  }

  /**
   * Sets the max height of the expanded list view.
   * 
   * @param listViewMaxHeight sets the max height of the view.
   */
  public void setListViewMaxHeight(int listViewMaxHeight) {
    this.listViewMaxHeight = listViewMaxHeight;
  }

  /**
   * Sync width to a parent widget.
   * 
   * @param syncWidthToParentWidgetElement the widget to sync the width to.
   */
  public void syncListViewWidth(XElement syncWidthToParentWidgetElement) {
    if (!expanded) {
      return;
    }
    listView.setWidth(getListViewWidth(syncWidthToParentWidgetElement));
  }

  /**
   * Initialize the list view.
   */
  protected void configureListView() {
    if (listView != null) {
      return;
    }

    selectionModel = new ListViewSelectionModelExt<>();
    selectionModel.addSelectionChangedHandler(new SelectionChangedHandler<T>() {
      @Override
      public void onSelectionChanged(SelectionChangedEvent<T> event) {
        listView.refresh();
        
        List<T> selectedItems = event.getSelection();
        updateSelectedItems(selectedItems);
      }
    });

    listView = initListView();

    basePreviewEvent = new BaseEventPreview() {
      @Override
      protected boolean onPreview(NativePreviewEvent event) {
        Element target = event.getNativeEvent().getEventTarget().cast();

        switch (event.getTypeInt()) {
        case Event.ONSCROLL:
        case Event.ONMOUSEWHEEL:
        case Event.ONMOUSEDOWN:
          // collapse if the mouse down is not on list or parent widget
          if (listView != null && lastParent != null && !listView.getElement().isOrHasChild(target) && !lastParent.isOrHasChild(target)) { 
            collapse();
          }
          break;
        }
        return true;
      }
    };
    basePreviewEvent.setAutoHide(false);
  }

  protected void updateSelectedItems(List<T> selectedItems) {
    if (lastValueUpdater == null) {
      return;
    }
    
    lastValueUpdater.update(selectedItems);
    String renderedValues = getPropertyEditor().render(selectedItems);
    setText(lastParent, renderedValues);
  }

  protected ListViewExt<T, T> initListView() {
    List<HasCell<T, ?>> cells = new ArrayList<HasCell<T, ?>>();
    cells.add(initCheckBoxCell(selectionModel));
    cells.add(initTextCell(labelProvider));

    // add two cells to layout a checkbox and label - [] label
    CompositeCell<T> listViewCell = initCompositeCell(cells);

    listView = new ListViewExt<T, T>(store, new IdentityValueProvider<T>(XDOM.getUniqueId()), listViewCell) {
      @Override
      protected void onAfterFirstAttach() {
        super.onAfterFirstAttach();
       
        // This can cause a lock up if called over and over
        selectionModel.select(showListSelectedValues, false);
      }
    };
    listView.setSelectionModel(selectionModel);
    listView.setHideMode(HideMode.OFFSETS);
    listView.setSelectOnOver(false);
    listView.setVisible(false);
    listView.setBorders(true);

    return listView;
  }

  protected CompositeCell<T> initCompositeCell(List<HasCell<T, ?>> cells) {
    return new CompositeCell<T>(cells) {
      @Override
      protected <X> void render(Context context, T value, SafeHtmlBuilder sb, HasCell<T, X> hasCell) {
        // draw the cells in a line
        Cell<X> cell = hasCell.getCell();
        sb.appendHtmlConstant("<span style='display: inline-block; vertical-align:middle;'>");
        cell.render(context, hasCell.getValue(value), sb);
        sb.appendHtmlConstant("</span>&nbsp;");
      }
    };
  }

  protected HasCell<T, ?> initCheckBoxCell(ListViewSelectionModelExt<T> selectionModel) {
    return new ItemCheckBoxCellHasCell<T>(selectionModel);
  }

  protected HasCell<T, ?> initTextCell(LabelProvider<T> labelProvider) {
    return new ItemTextHasCell<T>(labelProvider);
  }

  protected void showListView() {
    expanded = true;

    RootPanel.get().add(listView);

    listView.getElement().getStyle().setProperty("maxHeight", getListViewMaxHeight(lastParent));
    listView.setWidth(getListViewWidth(lastParent));
    listView.getElement().makePositionable(true);
    listView.setVisible(true);
    basePreviewEvent.add();

    AnchorAlignment anchorAlignment = new AnchorAlignment(Anchor.TOP_LEFT, Anchor.BOTTOM_LEFT, true);
    listView.getElement().alignTo(lastParent, anchorAlignment, 0, 0);
  }

  protected int getListViewWidth(XElement parent) {
    return parent.getOffsetWidth();
  }

  protected String getListViewMaxHeight(XElement parent) {
    return listViewMaxHeight + "px";
  }

  protected void collapse() {
    doTriggerBlur();

    basePreviewEvent.remove();
    listView.setVisible(false);
    clearContext();
    RootPanel.get().remove(listView);
    
    expanded = false;
  }

  protected void doTriggerBlur() {
    doTriggerBlur(lastContext, lastParent, lastValue, lastValueUpdater);
  }

  protected void doTriggerBlur(Context context, XElement parent, List<T> value, ValueUpdater<List<T>> valueUpdater) {
    triggerBlur(context, parent, value, valueUpdater);
    onBlur(context, parent, value, null, valueUpdater);
  }

  @Override
  protected void saveContext(Context context, Element parent, NativeEvent event, ValueUpdater<List<T>> valueUpdater,
      List<T> value) {
    super.saveContext(context, parent, event, valueUpdater, value);
  }
  
  @Override
  protected void clearContext() {
    if (expanded) {
      return;
    }
    super.clearContext();
  }
  
  @Override
  protected void onFocus(Context context, XElement parent, List<T> value, NativeEvent event,
      ValueUpdater<List<T>> valueUpdater) {
    super.onFocus(context, parent, value, event, valueUpdater);
    
    saveContext(context, parent, event, valueUpdater, value);
  }
  
}

MultiSelectComboTest4.java

import java.util.ArrayList;
import java.util.List;

import com.google.gwt.core.client.EntryPoint;
import com.google.gwt.user.client.ui.RootPanel;
import com.sencha.gxt.core.client.util.Margins;
import com.sencha.gxt.data.shared.LabelProvider;
import com.sencha.gxt.data.shared.ListStore;
import com.sencha.gxt.data.shared.ModelKeyProvider;
import com.sencha.gxt.test.client.combo_multi_checkselect2.Data;
import com.sencha.gxt.widget.core.client.button.TextButton;
import com.sencha.gxt.widget.core.client.container.BorderLayoutContainer;
import com.sencha.gxt.widget.core.client.container.BorderLayoutContainer.BorderLayoutData;
import com.sencha.gxt.widget.core.client.container.SimpleContainer;
import com.sencha.gxt.widget.core.client.container.VerticalLayoutContainer;
import com.sencha.gxt.widget.core.client.container.VerticalLayoutContainer.VerticalLayoutData;
import com.sencha.gxt.widget.core.client.container.Viewport;
import com.sencha.gxt.widget.core.client.event.SelectEvent;
import com.sencha.gxt.widget.core.client.event.SelectEvent.SelectHandler;
import com.sencha.gxt.widget.core.client.info.Info;

public class MultiSelectComboTest4 implements EntryPoint {

  @Override
  public void onModuleLoad() {
    List<Data> values = new ArrayList<Data>();
    values.add(new Data("0", "1"));
    //values.add(new Data("5", "102"));
    //values.add(new Data("7", "234"));
    
    List<Data> selectionValues = new ArrayList<Data>();    
    selectionValues.add(new Data("0", "1"));
    selectionValues.add(new Data("1", "2"));
    selectionValues.add(new Data("2", "3"));
    selectionValues.add(new Data("3", "4"));
    selectionValues.add(new Data("4", "101"));
    selectionValues.add(new Data("5", "102"));
    selectionValues.add(new Data("6", "103"));
    selectionValues.add(new Data("7", "234"));
    selectionValues.add(new Data("8", "235"));
    selectionValues.add(new Data("9", "236"));
    
    for (int i = 1000; i < 1500; i++) {
      selectionValues.add(new Data(i + "", "Item: " + i));
    }
    
    ListStore<Data> listStore = new ListStore<Data>(new ModelKeyProvider<Data>() {
      @Override
      public String getKey(Data item) {
        return item.getId().toString();
      }
    });
    listStore.addAll(selectionValues);

    LabelProvider<Data> labelProvider = new LabelProvider<Data>() {
      @Override
      public String getLabel(Data item) {
        return item.getName();
      }
    };

    final MultiSelectComboBox<Data> combo = new MultiSelectComboBox<Data>(listStore, labelProvider);
    combo.setValue(values);
   
    final TextButton button = new TextButton("Get Values");
    button.addSelectHandler(new SelectHandler() {
      @Override
      public void onSelect(SelectEvent event) {
        List<Data> values = combo.getValue();
        Info.display("", "values=" + values.size() + " values=" + values);
      }
    });

    VerticalLayoutContainer vlc = new VerticalLayoutContainer();
    vlc.getElement().getStyle().setProperty("border", "1px solid green");
    vlc.add(combo, new VerticalLayoutData(1, 50, new Margins(10)));
    vlc.add(button, new VerticalLayoutData(1, -1, new Margins(10)));

    BorderLayoutData layoutData = new BorderLayoutData(100);

    BorderLayoutContainer blc = new BorderLayoutContainer();
    blc.setNorthWidget(new SimpleContainer(), layoutData);
    blc.setEastWidget(new SimpleContainer(), layoutData);
    blc.setWestWidget(new SimpleContainer(), layoutData);
    blc.setWidget(vlc);

    Viewport vp = new Viewport();
    vp.add(blc);

    RootPanel.get().add(vp);
  }

}

Hello, dear Brandon. Please, help me with your MultiSelectComboBox. How can I attach SelectionHandler, or order Handler to handle Selection Events to this MultiSelectComboBox ? I need to handle selection events, but all handlers i tryed with this component had no effect. Can you explain in some words possibilityes of selection handling in MultiSelectComboBox ?