Dynamically and Programatically Uncheck a CheckboxCell - gwt

Question

I have a Datagrid with a CheckboxCell column. There will be some rows that cannot be checked, and the way I would like to implement this would be to handle the "checked" event and cancel it if some criteria is met. Here is the code I have tried:
Column<Job, Boolean> selectColumn = new Column<Job, Boolean>(new CheckboxCell()) {
#Override
public Boolean getValue(Job job) {
// do I uncheck the cell here?
return JobDataGrid.this.jobSelection.isSelected(job);
}
#Override
public void onBrowserEvent(Cell.Context context, Element elem, Job object, NativeEvent event)
{
super.onBrowserEvent(context, elem, object, event);
String eventType = event.getType();
if ("change".equals(eventType)) {
// do I uncheck the cell here?
}
}
};
How do I handle the event and set the checkbox to be unchecked?

Answer 1

If you want to prevent the change in a checkbox, you can simply cancel the native event inside your onBrowserEvent method:
event.preventDefault();
Note that if you don't update your object when a checkbox is clicked, you can always refresh() your DataGrid and the checkbox will be displayed in its original state.

Answer 2

If you want to make a check box uncheckable, from the UX perspective it is better be disabled.
You can create a custom check box cell where you can control every aspect of rendering of the element including disabled state:
public class UncheckableCheckboxCell extends CheckboxCell {
interface Template extends SafeHtmlTemplates {
#Template("<input type=\"checkbox\" tabindex=\"-1\" checked/>")
SafeHtml INPUT_CHECKED();
#Template("<input type=\"checkbox\" tabindex=\"-1\"/>")
SafeHtml INPUT_UNCHECKED();
#Template("<input type=\"checkbox\" tabindex=\"-1\" disabled=\"disabled\"/>")
SafeHtml INPUT_UNCHECKED_DISABLED();
}
private static UncheckableCheckboxCell.Template template = GWT.create(UncheckableCheckboxCell.Template.class);
public UncheckableCheckboxCell(boolean dependsOnSelection, boolean handlesSelection) {
super(dependsOnSelection, handlesSelection);
}
#Override
public void render(Context context, Boolean value, SafeHtmlBuilder sb) {
// Get the view data.
Object key = context.getKey();
Boolean viewData = getViewData(key);
if (viewData != null && viewData.equals(value)) {
clearViewData(key);
viewData = null;
}
if (value != null && ((viewData != null) ? viewData : value)) {
sb.append(template.INPUT_CHECKED());
} else if (value == null) {
//use null value as an indicator of unchecked and disable state
sb.append(template.INPUT_UNCHECKED_DISABLED());
} else {
sb.append(template.INPUT_UNCHECKED());
}
}
}
Then inside your getValue() method you can return null when you want the check box to be unchecked/disabled:
#Override
public Boolean getValue(Job job) {
// is my job checkable?
if (job.checkable()) {
//return null explicitly so my custom cell knows it should be rendered as disabled
return null;
} else {
return JobDataGrid.this.jobSelection.isSelected(job);
}
}