CheckboxCell, MultiSelectionModel unwantonly reset DataGrid's data

Question

Using GWT 2.4...

I am building upon a complex Composite dual view/edit mode implementation that is backed GWT's DataGrid and MultiSelectionModel. My goal is for a user to be able to click a checkbox in each row that they'd like to post updates for.

Here's a screenshot from a semi-functional interface:

Note the selected (highlighted) rows.

Now the problem is that when I type something in any of the cells (e.g., the first row's $ cell under the $/Mw 1 composite cell header), then click that row's checkbox (or any other row's checkbox for that matter) to select or de-select, the value gets reset to the original value when the screen's data was first requested. Not desired behavior by any stretch!

Let's take a look at my custom implementation for the grid. (Excuse the length).

public abstract class ToggleableGrid<T extends Identifiable<?>> extends Composite {

private static final int CHKBOX_COLUMN_WIDTH = App.INSTANCE.checkboxColumnWidth();
private static final DisplayMode DEFAULT_MODE = DisplayMode.VIEW;


private ProvidesKey<T> keyProvider;

private DataGrid<T> grid;

private MultiSelectionModel<T> selectionModel;

private ListDataProvider<T> dataProvider;
private int tabIndex = 0;


public ToggleableGrid() {
    final DataGridConfiguration config = new DefaultDataGridConfiguration();
    initGrid(config);
}

public ToggleableGrid(DataGridConfiguration config) {
    initGrid(config);
}

private void initGrid(DataGridConfiguration config) {
    keyProvider = new ProvidesKey<T>() {
        @Override
        public Object getKey(T item) {
            return item == null ? null : item.getId();
        }
    };
    grid = new DataGrid<T>(config.getPageSize(), config.getResources(), keyProvider);
    // Set the message to display when the table is empty.
    grid.setEmptyTableWidget(new Label(UiMessages.INSTANCE.no_results()));
    initWidget(grid);
    setVisible(true);
}

public void setInput(List<T> content) {
    setInput(content, DEFAULT_MODE);
}

public void setInput(List<T> content, DisplayMode mode) {
    resetTableColumns();
    if (isInEditMode(mode)) {
        // Add a selection model so we can select cells
        selectionModel = new MultiSelectionModel<T>(keyProvider);
        grid.setSelectionModel(selectionModel, DefaultSelectionEventManager.<T> createCheckboxManager(0));
        addRowSelector();
    }
    dataProvider = new ListDataProvider<T>(content);
    final ListHandler<T> sortHandler = new ListHandler<T>(dataProvider.getList());
    grid.addColumnSortHandler(sortHandler);
    initializeStructure(constructMetadata(), sortHandler, mode);
    dataProvider.addDataDisplay(grid);
}

// see https://stackoverflow.com/questions/3772480/remove-all-columns-from-a-celltable
// concrete classes are forced to maintain a handle on all columns added
private void resetTableColumns() {
    for (final Column<T, ?> column: allColumns()) {
        grid.removeColumn(column);
    }
    allColumns().clear();
}

protected boolean isInEditMode(DisplayMode currentDisplayMode) {
    boolean result = false;
    if (currentDisplayMode.equals(DisplayMode.EDIT)) {
        result = true;
    }
    return result;
}

protected abstract Set<Column<T, ?>> allColumns();

protected abstract TableMetadata constructMetadata();

protected abstract void initializeStructure(TableMetadata metadata, ListHandler<T> sortHandler, DisplayMode mode);

protected void setColumnHorizontalAlignment(Column<T, ?> column, HorizontalAlignmentConstant alignment) {
    column.setHorizontalAlignment(alignment);
}

// TODO figure out how to add a checkbox to column header that provides select/de-select all capability

// see https://stackoverflow.com/questions/6174689/gwt-celltable-programmatically-select-checkboxcell
protected void addRowSelector() {
    final Column<T, Boolean> rowSelectColumn = new Column<T, Boolean>(new CheckboxCell(true, false)) {

        @Override
        public Boolean getValue(T value) {
            Boolean result;
            // check for null value and return null;
            if(value == null || value.getId() == null) {
                result = null;
            } else {  // get value from the selection model
                result = selectionModel.isSelected(value);
            }
            return result;
        }

    };

    addColumn(rowSelectColumn, UiMessages.INSTANCE.select());
    setColumnWidth(rowSelectColumn, CHKBOX_COLUMN_WIDTH, Unit.PX);
    setColumnHorizontalAlignment(rowSelectColumn, HasHorizontalAlignment.ALIGN_CENTER);
}

protected void setColumnWidth(Column<T, ?> column, int width, Unit unit) {
    grid.setColumnWidth(column, width, unit);
}

protected void addColumn(Column<T, ?> column, String columnHeaderName) {
    addColumn(column, columnHeaderName, HasHorizontalAlignment.ALIGN_RIGHT);
}

protected void addColumn(Column<T, ?> column, String columnHeaderName, HorizontalAlignmentConstant alignment) {
    final SafeHtmlBuilder sb = new SafeHtmlBuilder();
    final String divStart = "<div align=\""+ alignment.getTextAlignString() + "\" class=\"" +UiResources.INSTANCE.style().word_wrap() + "\">";
    sb.appendHtmlConstant(divStart).appendEscaped(columnHeaderName).appendHtmlConstant("</div>");
    final SafeHtml header = sb.toSafeHtml();
    grid.addColumn(column, header);
    allColumns().add(column);
}

protected CompositeCell<T> generateCompositeCell(final List<HasCell<T, ?>> hasCells) {
    final CompositeCell<T> compositeCell = new CompositeCell<T>(hasCells) {

        @Override
        public void render(Context context, T value, SafeHtmlBuilder sb) {
            sb.appendHtmlConstant("<table><tbody><tr>");
            super.render(context, value, sb);
            sb.appendHtmlConstant("</tr></tbody></table>");
        }

        @Override
        protected Element getContainerElement(Element parent) {
            // Return the first TR element in the table.
            return parent.getFirstChildElement().getFirstChildElement().getFirstChildElement();
        }

        @Override
        protected <X> void render(Context context, T value,
                SafeHtmlBuilder sb, HasCell<T, X> hasCell) {
            final Cell<X> cell = hasCell.getCell();
            sb.appendHtmlConstant("<td>");
            cell.render(context, hasCell.getValue(value), sb);
            sb.appendHtmlConstant("</td>");
        }
    };
    return compositeCell;
}

// FIXME not working quite the way we'd expect, index incremented within column for each row, not each row by column
protected int nextTabIndex() {
    tabIndex++;
    return tabIndex;
}

protected AbstractCellTable<T> getGrid() {
    return grid;
}

/**
 * Gets the selected (row(s) of) data from grid (used in edit mode)
 * @return the selected data (as per selection model)
 */
public List<T> getSelectedData() {
    final List<T> data = new ArrayList<T>();
    data.addAll(selectionModel.getSelectedSet());
    return data;
}

/**
 * Gets all (row(s) of) data in grid (used in edit mode)
 * @return all data as list
 */
public List<T> getAllData() {
    return dataProvider.getList();
}

/**
 * Clears the currently selected (row(s) of) data (used in edit mode)
 */
public void clearSelectedData() {
    selectionModel.clear();
    grid.redraw();
}

}

So, the interesting methods to stare at above (I think) are setInput, generateCompositeCell and addRowSelector.

We initialize the grid with List data and set a display mode in setInput. It's here as well that the selection model is initialized. It uses GWT's DefaultSelectionEventManager createCheckboxManager().

I've been trying to grok the event model, but it eludes me. I've visited the following sources online, but have come up short on avenues to solving this problem.

-- https://groups.google.com/forum/?fromgroups#!topic/google-web-toolkit/k5sfURxDaVg AbstractInputCell's getConsumedEventsImpl adds focus, blur and keydown, so this (I believe) is not a track I need to explore

-- GWT CellTable programmatically select CheckBoxCell The various ways you can instantiate a CheckBoxCell got me curious, and I've tried many constructor argument permutations, but the one I settled on (true, false) is (I believe) the right one

Agreeing here and now (before being reprimanded) that there's perhaps some unnecessary complexity in my implementation, but I am looking for guidance nonetheless. Thanks!

Update

If it helps here's an impl of the aforementioned ToggleableGrid. If anything it gives you more detail on what goes into each CompositeCell. For details on AbstractValidatableColumn and ValidatableInputCell, see: In search of a GWT validation example... where art thou?.

public class EnergyOfferGrid extends ToggleableGrid<EnergyOfferDTO> {

public EnergyOfferGrid() {
    super();
}

public EnergyOfferGrid(DataGridConfiguration config) {
    super(config);
}

private static final int MAX_NUMBER_OF_MW_PRICE_POINTS = App.INSTANCE.maxNoOfMwPricePoints();

private Set<Column<EnergyOfferDTO, ?>> columns = new HashSet<Column<EnergyOfferDTO, ?>>();

@Override
protected Set<Column<EnergyOfferDTO, ?>> allColumns() {
    return columns;
}

@Override
protected TableMetadata constructMetadata() {
    final TableMetadata metadata = new TableMetadata();

    // TODO Consider a predefined set of ReferenceData to be held in a common package

    // Use Slope
    metadata.addColumnMetadata(UiMessages.INSTANCE.use_slope(), new String[] {UiMessages.INSTANCE.yes(), UiMessages.INSTANCE.no()}, new String[] {"true", "false"});

    return metadata;
}

@Override
protected void initializeStructure(TableMetadata metadata, ListHandler<EnergyOfferDTO> sortHandler, DisplayMode currentDisplayMode) {
    addHourColumn(sortHandler);
    addUseSlopeColumn(metadata, sortHandler, currentDisplayMode);
    for (int i = 0; i < MAX_NUMBER_OF_MW_PRICE_POINTS; i++) {  // zero-based indexing
        addPriceMwColumn(i, currentDisplayMode);
    }
}

protected void addHourColumn(ListHandler<EnergyOfferDTO> sortHandler) {
    final Column<EnergyOfferDTO, String> hourColumn = new Column<EnergyOfferDTO, String>(new TextCell()) {

        @Override
        public String getValue(EnergyOfferDTO energyOffer) {
            String result = "";
            if (energyOffer.getId() != null) {
                final String isoDateTime = energyOffer.getId().getOperatingHour();
                if (isoDateTime != null && !isoDateTime.isEmpty()) {
                    final Date dateTime = CSTimeUtil.isoToDate(isoDateTime);
                    if (dateTime != null) {
                        result = CSTimeUtil.dateToHour(dateTime);
                    }
                }
            }
            return result;
        }

    };
    hourColumn.setSortable(true);
    sortHandler.setComparator(hourColumn, new Comparator<EnergyOfferDTO>() {
        @Override
        public int compare(EnergyOfferDTO eo1, EnergyOfferDTO eo2) {
            final String date1 = eo1.getId() != null ? eo1.getId().getOperatingHour() : "";
            final String date2 = eo2.getId() != null ? eo2.getId().getOperatingHour() : "";
            return date1.compareTo(date2);
        }
    });

    // We know that the data is sorted by hour by default.
    getGrid(). getColumnSortList().push(hourColumn);

    addColumn(hourColumn, UiMessages.INSTANCE.hour());
    setColumnWidth(hourColumn, 45, Unit.PX);
    setColumnHorizontalAlignment(hourColumn, HasHorizontalAlignment.ALIGN_RIGHT);
}


protected void addUseSlopeColumn(TableMetadata metadata, ListHandler<EnergyOfferDTO> sortHandler, DisplayMode currentDisplayMode) {
    final ReferenceData refData = metadata.allColumnMetadata().get(UiMessages.INSTANCE.use_slope());
    Column<EnergyOfferDTO, String> useSlopeColumn;
    Cell<String> cell;
    if (isInEditMode(currentDisplayMode)) {
        cell = new ReferenceDataBackedSelectionCell(refData);
    } else {
        cell = new TextCell();
    }
    useSlopeColumn = new Column<EnergyOfferDTO, String>(cell) {

        @Override
        public String getValue(EnergyOfferDTO energyOffer) {
            return refData.getDisplayValueForSubmitValue(Boolean.toString(energyOffer.isSlopeUsed()));
        }

    };

    useSlopeColumn.setSortable(true);
    sortHandler.setComparator(useSlopeColumn, new Comparator<EnergyOfferDTO>() {
        @Override
        public int compare(EnergyOfferDTO eo1, EnergyOfferDTO eo2) {
            final String slopeUsed1 = String.valueOf(eo1.isSlopeUsed());
            final String slopeUsed2 = String.valueOf(eo1.isSlopeUsed());
            return slopeUsed1.compareTo(slopeUsed2);
        }
    });

    addColumn(useSlopeColumn, UiMessages.INSTANCE.use_slope());
    setColumnWidth(useSlopeColumn, 75, Unit.PX);
    setColumnHorizontalAlignment(useSlopeColumn, HasHorizontalAlignment.ALIGN_RIGHT);
}

protected void addPriceMwColumn(final int colIndex, DisplayMode currentDisplayMode) {

    // Construct a composite cell for energy offers that includes a pair of text inputs
    final List<HasCell<EnergyOfferDTO, ?>> columns = new ArrayList<
            HasCell<EnergyOfferDTO, ?>>();

    // this DTO is passed along so that price and mw values for new entries are kept together
    final OfferPriceMwPair newOfferPriceMwPair = new OfferPriceMwPair();

    // Price
    final Column<EnergyOfferDTO, String> priceColumn = generatePriceColumn(colIndex, newOfferPriceMwPair, currentDisplayMode);
    columns.add(priceColumn);

    // MW
    final Column<EnergyOfferDTO, String> mwColumn = generateMwColumn(colIndex, newOfferPriceMwPair, currentDisplayMode);
    columns.add(mwColumn);

    // Composite
    final CompositeCell<EnergyOfferDTO> priceMwColumnInnards = generateCompositeCell(columns);

    final IdentityColumn<EnergyOfferDTO> priceMwColumn = new IdentityColumn<EnergyOfferDTO>(priceMwColumnInnards);

    final StringBuilder colHeader = new StringBuilder();
    colHeader.append(UiMessages.INSTANCE.price_mw_header()).append(" ").append(String.valueOf(colIndex + 1));

    addColumn(priceMwColumn, colHeader.toString());
    setColumnWidth(priceMwColumn, 7, Unit.EM);
    setColumnHorizontalAlignment(priceMwColumn, HasHorizontalAlignment.ALIGN_RIGHT);
}

protected Column<EnergyOfferDTO, String> generatePriceColumn(final int colIndex, final OfferPriceMwPair newOfferPriceMwPair, DisplayMode currentDisplayMode) {
    Column<EnergyOfferDTO, String> priceColumn;

    if (isInEditMode(currentDisplayMode)) {
        priceColumn = new BigDecimalValidatableColumn<EnergyOfferDTO, OfferPriceMwPair>(nextTabIndex(), getGrid()) {

            @Override
            public String getValue(EnergyOfferDTO energyOffer) {
                return obtainPriceValue(colIndex, energyOffer, false);
            }

            @Override
            public void doUpdate(int index, EnergyOfferDTO energyOffer, String value) {
                if (value != null && !value.isEmpty()) {
                    // number format exceptions should be caught and handled by event bus's handle method
                    final double valueAsDouble = NumberFormat.getDecimalFormat().parse(value);

                    final BigDecimal price = BigDecimal.valueOf(valueAsDouble);
                    final List<OfferPriceMwPair> offerPriceCurve = energyOffer.getCurve();
                    final OfferPriceMwPair offerPriceMwPair = offerPriceCurve.get(colIndex);
                    if (offerPriceMwPair == null) {  // we have a new price value
                        newOfferPriceMwPair.setPrice(price);
                        offerPriceCurve.add(newOfferPriceMwPair);
                    } else {
                        offerPriceMwPair.setPrice(price);
                    }

                }
            }

            @Override
            protected String getPropertyName() {
                return "price";
            }

            @Override
            protected Class<OfferPriceMwPair> getPropertyOwner() {
                return OfferPriceMwPair.class;
            }

        };
    } else {
        priceColumn = new Column<EnergyOfferDTO, String>(new TextCell()) {

            @Override
            public String getValue(EnergyOfferDTO energyOffer) {
                final String result = obtainPriceValue(colIndex, energyOffer, true);
                return result;
            }
        };
    }
    return priceColumn;
}

private String obtainPriceValue(final int colIndex, EnergyOfferDTO energyOffer, boolean withCurrency) {
    String result = "";
    if (energyOffer != null) {
        final List<OfferPriceMwPair> offerPriceCurve = energyOffer.getCurve();
        final int numberOfPairs = offerPriceCurve.size();
        if (colIndex < numberOfPairs) {
            final OfferPriceMwPair offerPriceMwPair = offerPriceCurve.get(colIndex);
            if (offerPriceMwPair != null) {
                final BigDecimal price = offerPriceMwPair.getPrice();
                if (price != null) {
                    final double value = price.doubleValue();
                    if (withCurrency) {
                        result = NumberFormat.getCurrencyFormat().format(value);
                    } else {
                        result = NumberFormat.getDecimalFormat().format(value);
                    }
                }

            }
        }
    }
    return result;
}

protected Column<EnergyOfferDTO, String> generateMwColumn(final int colIndex, final OfferPriceMwPair newOfferPriceMwPair, DisplayMode currentDisplayMode) {
    Column<EnergyOfferDTO, String> mwColumn;

    if (isInEditMode(currentDisplayMode)) {
        mwColumn = new BigDecimalValidatableColumn<EnergyOfferDTO, PriceMwPair>(nextTabIndex(), getGrid()) {

            @Override
            public String getValue(EnergyOfferDTO energyOffer) {
                return obtainMwValue(colIndex, energyOffer);
            }

            @Override
            public void doUpdate(int index, EnergyOfferDTO energyOffer, String value) {
                if (value != null && !value.isEmpty()) {
                    // number format exceptions should be caught and handled by event bus's handle method
                    final double valueAsDouble = NumberFormat.getDecimalFormat().parse(value);

                    final BigDecimal mw = BigDecimal.valueOf(valueAsDouble);
                    final List<OfferPriceMwPair> offerPriceCurve = energyOffer.getCurve();
                    final OfferPriceMwPair offerPriceMwPair = offerPriceCurve.get(colIndex);
                    if (offerPriceMwPair == null) {  // we have a new price value
                        newOfferPriceMwPair.setMw(mw);
                        offerPriceCurve.add(newOfferPriceMwPair);
                    } else {
                        offerPriceMwPair.setMw(mw);
                    }

                }
            }

            @Override
            protected String getPropertyName() {
                return "mw";
            }

            @Override
            protected Class<PriceMwPair> getPropertyOwner() {
                return PriceMwPair.class;
            }

        };
    } else {
        mwColumn = new Column<EnergyOfferDTO, String>(new TextCell()) {

            @Override
            public String getValue(EnergyOfferDTO energyOffer) {
                final String result = obtainMwValue(colIndex, energyOffer);
                return result;
            }
        };
    }
    return mwColumn;
}

private String obtainMwValue(final int colIndex, EnergyOfferDTO energyOffer) {
    String result = "";
    if (energyOffer != null) {
        final List<OfferPriceMwPair> offerPriceCurve = energyOffer.getCurve();
        final int numberOfPairs = offerPriceCurve.size();
        if (colIndex < numberOfPairs) {
            final PriceMwPair offerPriceMwPair = offerPriceCurve.get(colIndex);
            if (offerPriceMwPair != null) {
                final BigDecimal mw = offerPriceMwPair.getMw();
                if (mw != null) {
                    result = NumberFormat.getDecimalFormat().format(mw);
                }
            }
        }
    }
    return result;
}

} 

Answer 1

All that custom work w.r.t. WrapperCell and CompositeValidatableColumn was unnecessary.

It turns out that there's a way you should not construct CompositeCells. See http://code.google.com/p/google-web-toolkit/issues/detail?id=5714. My CompositeCells were not receiving events. So, I changed the way I construct them in ToggleableGrid.

protected CompositeCell<T> generateCompositeCell(final List<HasCell<T, String>> hasCells) {
    final CompositeCell<T> compositeCell = new CompositeCell<T>(hasCells) {

        // to not run afoul of http://code.google.com/p/google-web-toolkit/issues/detail?id=5714
        @Override
        public void render(Context context, T value, SafeHtmlBuilder sb) {
            sb.appendHtmlConstant("<div style=\"display: inline\">");
            super.render(context, value, sb);
            sb.appendHtmlConstant("</div>");
        }

        @Override
        protected Element getContainerElement(Element parent) {
            // Return the first element in the DIV.
            return parent.getFirstChildElement();
        }

    };

    return compositeCell;
}

After that change and incorporating my other validation-oriented classes: ValidatableFieldUpdater, AbstractValidatableColumn (and derivatives), ValidatableInputField and ConversionResult, life couldn't be more grand!