GWT CellTable and ListBoxes complex identifiers - gwt

Question

I'm following Goolge's example on how to add ListBoxes/SelectionCells to a CellTable, but I can't figure how to change the behaviour so the matching is done not with the string value displayed.
The items I display #SelectionCell are not unique (i.e there can be 2 elements with the same name), so I need to use other fields associated with the object to know which one was 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 a 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() + some unique identifier:
public String getValue(IrrigationGapDTO object) {
if (object.getProgramSelected()!=null)
return object.getProgramSelected().getName()+"_"+object.getUniqueIdentiufier();
else
return "";
}
then in the FieldUpdater you can split on the "_" character and deal with duplicates
2. Use a unique id instead of getName():
Just generate/assign a unique id to your programms and use it instead of name.
3. Use IrrigationProgramDTO type instead of String:
Instead of String you can use IrrigationProgramDTO class in the Column definition. However you probably have to use a user-defined SelectionCell which takes IrrigationProgramDTO type instead of String as 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 of #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);
}