GWT CellTable and ListBoxes Integrated Identifiers

Question

I follow the Goolge example on how to add ListBoxes / SelectionCells to a CellTable, but I cannot figure out how to change the behavior, so the mapping is not done with the displayed string value.

The elements displayed by @SelectionCell are not unique (i.e. there may be two elements with the same name), so I need to use other fields associated with the object to find out which one is selected

for (IrrigationProgramDTO program: programOptions) categoryNames.add(program.getName()); SelectionCell categoryCell = new SelectionCell(categoryNames); Column<IrrigationGapDTO, String> categoryColumn = new Column<IrrigationGapDTO, String> (categoryCell) { @Override public String getValue(IrrigationGapDTO object) { if (object.getProgramSelected()!=null) return object.getProgramSelected().getName(); else return ""; } }; categoryColumn.setFieldUpdater(new FieldUpdater<IrrigationGapDTO, String>() { public void update(int index, IrrigationGapDTO object, String value) { for (IrrigationProgramDTO program: programOptions) { //not valid as there could be more than 1 program with the same name if (program.getName().equals(value)) { object.setProgramSelected(program); break; } } } 

Answer 1

Here is my new implementation of solution # 3 (note that you must add FieldUpdater to the column for it to work):

 import java.util.Arrays; import java.util.List; import com.google.gwt.cell.client.AbstractEditableCell; import com.google.gwt.cell.client.Cell; import com.google.gwt.cell.client.ValueUpdater; import com.google.gwt.core.client.GWT; import com.google.gwt.dom.client.BrowserEvents; import com.google.gwt.dom.client.Element; import com.google.gwt.dom.client.NativeEvent; import com.google.gwt.dom.client.SelectElement; import com.google.gwt.safehtml.client.SafeHtmlTemplates; import com.google.gwt.safehtml.client.SafeHtmlTemplates.Template; import com.google.gwt.safehtml.shared.SafeHtml; import com.google.gwt.safehtml.shared.SafeHtmlBuilder; /** * A {@link Cell} used to render a drop-down list. * * @author Gaspard van Koningsveld */ public class ItemSelectionCell<C> extends AbstractEditableCell<C, C> { interface Template extends SafeHtmlTemplates { @Template("<select tabindex=\"-1\" style=\"width:100%\">") SafeHtml beginSelect(); @Template("<option value=\"{0}\">{1}</option>") SafeHtml deselected(int hash, String option); @Template("<option value=\"{0}\" selected=\"selected\">{1}</option>") SafeHtml selected(int hash, String option); @Template("</select>") SafeHtml endSelect(); } private static Template template; private List<C> items; public ItemSelectionCell(C itemsArray[]) { this(Arrays.asList(itemsArray)); } public ItemSelectionCell(List<C> items) { super(BrowserEvents.CHANGE); if (template == null) { template = GWT.create(Template.class); } this.items = items; } @Override public void onBrowserEvent(Context context, Element parent, C value, NativeEvent event, ValueUpdater<C> valueUpdater) { super.onBrowserEvent(context, parent, value, event, valueUpdater); if (BrowserEvents.CHANGE.equals(event.getType())) { SelectElement select = parent.getFirstChild().cast(); int newIndex = select.getSelectedIndex(); valueUpdater.update(items.get(newIndex)); } } @Override public void render(Context context, C value, SafeHtmlBuilder sb) { sb.append(template.beginSelect()); for (int i = 0; i < items.size(); i++) { C item = items.get(i); if (item.equals(value)) { sb.append(template.selected(i, getItemDisplayString(item))); } else { sb.append(template.deselected(i, getItemDisplayString(item))); } } sb.append(template.endSelect()); } public String getItemDisplayString(C item) { return item.toString(); } public List<C> getItems() { return items; } public void setItems(List<C> items) { this.items = items; } @Override public boolean isEditing(Context context, Element parent, C value) { return false; } } 

Answer 2

3 possible solutions:

1. Dirty workaround :

Instead of getName() return getName() + with some unique identifier:

 public String getValue(IrrigationGapDTO object) { if (object.getProgramSelected()!=null) return object.getProgramSelected().getName()+"_"+object.getUniqueIdentiufier(); else return ""; } 

then in FieldUpdater you can divide by the symbol "_" and process duplicates

2. Use a unique identifier instead of getName() : Just create / assign a unique identifier to your programs and use it instead of a name.

3. Use IrrigationProgramDTO instead of String :

Instead of String you can use the IrrigationProgramDTO class in the column definition. However, you may have to use a custom SelectionCell, which instead of String uses the IrrigationProgramDTO type instead of the data type.

 Column<IrrigationGapDTO, IrrigationProgramDTO> categoryColumn = new Column<IrrigationGapDTO, IrrigationProgramDTO> (categoryCell) { @Override public IrrigationProgramDTO (IrrigationGapDTO object) { if (object.getProgramSelected()!=null) return object.getProgramSelected(); else return null; } }; categoryColumn.setFieldUpdater(new FieldUpdater<IrrigationGapDTO, IrrigationProgramDTO>() { public void update(int index, IrrigationGapDTO object, IrrigationProgramDTO value) { object.setProgramSelected(program); } } 

Answer 3

Here is my implementation of solution # 3 @ Ümit:

 public static abstract class EditSelectColumn<E, S> { Map<String, S> selectionMap = new HashMap<String, S>(); EditColumn<E> column; protected final String relationshipFieldName; public EditSelectColumn(String relationshipFieldName) { this.relationshipFieldName = relationshipFieldName; for (S option : getOptions()) { assert getOptionString(option) != null : "Option string cannot be null, please check your database"; selectionMap.put(getOptionString(option), option); } SelectionCell cell = new SelectionCell(new ArrayList<String>(selectionMap.keySet())); column = new EditColumn<E>(cell) { @Override public String getValue(E object) { if (getOption(object) == null) return ""; return getOptionString(getOption(object)); } @Override public void setValue(E object, String value) { setOption(object, selectionMap.get(value)); } }; } public EditColumn<E> getColumn() { return column; } public abstract List<S> getOptions(); public abstract String getOptionString(S option); public abstract S getOption(E object); public abstract void setOption(E object, S value); }