In a GWT web app, I am using a DataGrid to manage elements from a database. I represent a list of elements as rows, the columns being editable fields of their characteristics (id, name, description). I am mostly using the EditTextCell class.
I now want to create a custom cell, for a column that has to represent a list of "tags" that can be attached to every element. From this cell, tags could be added, using a + button (that makes a drop-down menu appear or something), and deleted. Each tag should be a kind of button, or interactive widget (I later want to display pop-up with info, trigger actions, etc).
Actually, it would not be so different from the "tags" bar on the Stack Overflow website...
So I have been looking for a solution:
I thought this would be easy to do. I imagined just putting a FlowPanel in the cell, adding/removing Buttons/Widgets dynamically. But it turns out that in GWT Widgets and Cells and very different objects apparently..
I read making use of the AbstractCell class to create a custom cell allows to do anything, but its working is very low level and obscure to me.
I saw that CompositeCell allows to combine various cell widgets into one cell, but I have not found if it is possible to do it dynamically, or if the widgets are going to be the same for all lines throughout a column. I mostly saw examples about, for instance, how to put two Buttons in every cell of a single column.
What is the easiest way to implement what I need?
EDIT:
So, after some tests, I am going for Andrei's suggestion and going "low-level", creating a custom cell extending AbstractCell<>. I could create an appropriate "render" function, that generates a list of html "button", and also attaches Javascript calls to my Java functions when triggering a Javascript event (onclick, onmouseover, onmouseout...).
It is working pretty well. For instance, by clicking the "+" button at the end a tag list, it calls a MenuBar widget that presents the list of tags that can be added.
But I am struggling to find a way to update the underlying data when adding a tag.
To sum up:
I have a CustomData class that represents the data I want to display in each line of the table. It also contains the list of tags as a Set.
ModelTable (extends DataGrid) is my table.
CustomCell (extends AbstractCell) can renders the list of tags as several buttons on a line.
A click on a "+" button in a cell makes a AddTagMenu popup drop down, from which I can click on the tag to add.
How do I update the content of the cell?
I tried playing around with onBrowserEvent, onEnterKeyDown, bus events... with no success. At best I can indeed add a tag element to the underlying object, but the table is not updated.
It's not possible to meet your requirements without going really "low-level", as you call it.
It's relatively easy to create a cell that would render tags exactly as you want them. Plus icon is also easy, if this is the only action on the cell. However, it is very difficult to make every tag within a cell an interactive widget, because the DataGrid will not let you attach handlers to HTML rendered within a cell. You will need to supply your own IDs to these widgets, and then attach handlers to them in your code. The problem, however, is that when the DataGrid refreshes/re-renders, your handlers will most likely be lost. So you will have to attach them again to every tag in every cell on every change in the DataGrid.
A much simpler approach is to create a composite widget that represents a "row", and then add these "rows" to a FlowPanel. You can easily make it look like a table with CSS, and supply your own widget that looks like a table header. You will need to recreate some of the functionality of the DataGrid, e.g. sorting when clicked on "column" header - if you need this functionality, of course.
As you have already noted, using CompositeCell could be a way to get what you want.
The idea is to create a cell for every tag and then (during rendering) decide which one should be shown (rendered). Finally combine all those cells into one by creating a CompositeCell.
The main disadvantage of this solution is that you need to know all possible tags before you create a DataGrid.
So, if you have a fixed list of possible tags or can get a list of all existing tags and this list is reasonably small, here is a solution.
First, we need to know which tag is represented by a column so I extended a Column class to keep information about a tag. Please, note that TagColumn uses ButtonCell and also handles update when the button is clicked:
public class TagColumn extends Column<DataType, String> {
private TagEnum tag;
public TagColumn(TagEnum tag) {
super(new ButtonCell());
this.tag = tag;
setFieldUpdater(new FieldUpdater<DataType, String>() {
#Override
public void update(int index, DataType object, String value) {
Window.alert("Tag " + getTag().getName() + " clicked");
}
});
}
public TagEnum getTag() {
return tag;
}
#Override
public String getValue(DataType object) {
return tag.getName();
}
}
Then create a cell for each tag (I have hard-coded all tags in a TagEnum):
List<HasCell<DataType, ?>> tagColumns = new ArrayList<HasCell<DataType, ?>>();
for(TagEnum tag : TagEnum.values())
tagColumns.add(new TagColumn(tag));
Now, the most important part: decide either to show the tag or not - overwrite render method of the CompositeCell:
CompositeCell<DataType> tagsCell = new CompositeCell<DataType>(tagColumns) {
#Override
protected <X> void render(Context context, DataType value, SafeHtmlBuilder sb, HasCell<DataType, X> hasCell) {
if(value.getTagList().contains(((TagColumn) hasCell).getTag()))
super.render(context, value, sb, hasCell);
else
sb.appendHtmlConstant("<span></span>");
}
};
This is important to always render any element (for example empty span when the tag should not be shown). Otherwise the CompositeCell's implemantation will get confused when accessing sibling elements.
Finally, full, working example code:
private DataGrid<DataType> getGrid() {
DataGrid<DataType> grid = new DataGrid<DataType>();
List<HasCell<DataType, ?>> tagColumns = new ArrayList<HasCell<DataType, ?>>();
for(TagEnum tag : TagEnum.values())
tagColumns.add(new TagColumn(tag));
CompositeCell<DataType> tagsCell = new CompositeCell<DataType>(tagColumns) {
#Override
protected <X> void render(Context context, DataType value, SafeHtmlBuilder sb, HasCell<DataType, X> hasCell) {
if(value.getTagList().contains(((TagColumn) hasCell).getTag()))
super.render(context, value, sb, hasCell);
else
sb.appendHtmlConstant("<span></span>");
}
};
Column<DataType, DataType> tagsColumn = new Column<DataType, DataType>(tagsCell) {
#Override
public DataType getValue(DataType object) {
return object;
}
};
grid.addColumn(tagsColumn, "Tags");
grid.setRowData(Arrays.asList(
new DataType(Arrays.asList(TagEnum.gwt)),
new DataType(Arrays.asList(TagEnum.table, TagEnum.datagrid)),
new DataType(Arrays.asList(TagEnum.datagrid, TagEnum.widget, TagEnum.customCell)),
new DataType(Arrays.asList(TagEnum.gwt, TagEnum.table, TagEnum.widget, TagEnum.customCell)),
new DataType(Arrays.asList(TagEnum.gwt, TagEnum.customCell)),
new DataType(Arrays.asList(TagEnum.gwt, TagEnum.table, TagEnum.datagrid, TagEnum.widget, TagEnum.customCell))
)
);
return grid;
}
public class TagColumn extends Column<DataType, String> {
private TagEnum tag;
public TagColumn(TagEnum tag) {
super(new ButtonCell());
this.tag = tag;
setFieldUpdater(new FieldUpdater<DataType, String>() {
#Override
public void update(int index, DataType object, String value) {
Window.alert("Tag " + getTag().getName() + " clicked");
}
});
}
public TagEnum getTag() {
return tag;
}
#Override
public String getValue(DataType object) {
return tag.getName();
}
}
public class DataType {
List<TagEnum> tagList;
public DataType(List<TagEnum> tagList) {
this.tagList = tagList;
}
public List<TagEnum> getTagList() {
return tagList;
}
}
public enum TagEnum {
gwt ("gwt"),
table ("table"),
datagrid ("datagrid"),
widget ("widget"),
customCell ("custom-cell");
private String name;
private TagEnum(String name) {
this.name = name;
}
public String getName() {
return name;
}
}
I have a problem with validation on form actually sub-form.
In my website I have some kind of table and "Add row" button (BlockingAjaxSubmitLink).
When I try add let say 2 rows, I get validation error (because row in this table has Required=True parameter) and I can't add another row. I tried use simple AjaxLink but it doesn't have reference to form in onClick method and when I complete some rows and click "Add row" this data get lost.
I want to enable validation only after "save" button click.
Any idea how to deal with this problem?
I do something like you want using an AjaxLink.
My AjaxLink:
private AjaxLink addNewRow = new AjaxLink("addNewRow") {
#Override
public void onClick(AjaxRequestTarget target) {
MyEntityObject newTableRowObject = new MyEntityObject(irrelevantParameter);
entityObjectTableService.createNewRowInDB(newTableRowObject );
target.add(listViewContainer);
}
};
In this code the listViewContainer is a WebMarkupContainer which contains a ListView holding the table rows.
When i click this AjaxLink a new object representing a row in my table is added to the database and then the container containing the ListView is being refreshed refreshing the ListView and the new empty object is being fetched from the DB and shown as a new row in my table at the end.
Depending on your structure maybe you are looking after disabling validation using setDefaultFormProcessing(true); - http://ci.apache.org/projects/wicket/apidocs/6.x/org/apache/wicket/markup/html/form/AbstractSubmitLink.html#setDefaultFormProcessing%28boolean%29
For now I write some kind of hack
First I set
addKnowledgeLink.setDefaultFormProcessing(false);
and next
BlockingAjaxSubmitLink<Object> addKnowledgeLink = new BlockingAjaxSubmitLink<Object>(
"link_knowledge_add") {
#Override
protected void onSubmit(AjaxRequestTarget target, Form<?> form) {
ChangeDataForm.this.process(this);
/* some code */
target.add(form.get(MY_CONTAINER_ID));
}
(...)
and my hack...
//HACK
public void process(IFormSubmitter object){
if (!isEnabledInHierarchy() || !isVisibleInHierarchy())
{
return;
}
// run validation
validate();
/*if (hasError())
{
// mark all children as invalid
markFormComponentsInvalid();
// let subclass handle error
callOnError(object);
}
else
{*/
// mark all children as valid
markFormComponentsValid();
// before updating, call the interception method for clients
beforeUpdateFormComponentModels();
// Update model using form data
updateFormComponentModels();
// validate model objects after input values have been bound
onValidateModelObjects();
if (hasError())
{
callOnError(object);
return;
}
// Form has no error
delegateSubmit(object);
//}
}
and I ovveride one method
#Override
protected void onError(){
super.onError();
this.updateFormComponentModels();
}
I know it is ugly solution but I couldn't figure out anything better..
And I couldn't shutdown feedback messages
Im populating a table using ListView component in wicket.The last column of my table is button. So for each row I'll have a button in the last column.What I'm trying to implement is onlick of the button I need to delete the appropriate row. So for this I need to get the current index of the list on click of button. How to achieve/get this ?
I would extend Ajax button and pass the row reference (item) in the constructor...then you can do anything you want..by overriding the onSubmit method
Example:
private class SpecialButton extends AjaxButton {
final Item<Object> rowItem;
public SpecialButton(final String id, final Item<Object> rowItem) {
super(id);
this.rowItem = rowItem;
}
#Override
protected void onSubmit(final AjaxRequestTarget target, final Form<?> form) {
// here you cand do everything you want with the item and the model object of the item.(row)
Object object = rowItem.getModelObject();
}
}
You should replace Object from Item<Object> with your reapeater model. After creating this private class you can reuse it for every row in your repeater.
If you want to delete that row you just have to remove the model from the list used to generate the repeater and refresh the repeater container(Wicket does not allow you to refresh the repeater by adding it to the target...instead you have to add the repeater continer.)
Have a look at the repeaters Wicket Examples page to understand how to use ListView and other repeaters:
http://www.wicket-library.com/wicket-examples/repeater/
You can get the current index of the list from item.getIndex()
protected void populateItem(final ListItem<T> item) {
int index = item.getIndex();
...
Look here for inspirations on how to do it properly (without index):
Wicket ListView not refreshing
I have a bunch of TextBox-es generated dynamically. At the step of creation I'm assigning the ID property for them.
e.g.
id = ...
Button b = new Button();
b.setText("add textbox");
b.addClickHandler(new Clickhandler() {
Textbox tb = new TextBox();
tb.getElement().setId(Integer.toString(id));
tb.setText("some text");
}
id += 1;
I need to access them later by their IDs, but I cannot do it.
I tried to use the DOM object in order to get a widget, but it produces an exception:
String id = "some id";
Element el = DOM.getElementById(id);
String value = el.getAttribute("value"); - this line produces an exception.
I've also tried to use el.getInnerText, el.getNodeValue - no luck. I have see in the chrome debugger - the textboxes don't have the 'value' property.
you can get the widget associated to an element this way:
public static IsWidget getWidget(com.google.gwt.dom.client.Element element) {
EventListener listener = DOM
.getEventListener((com.google.gwt.dom.client.Element) element);
// No listener attached to the element, so no widget exist for this
// element
if (listener == null) {
return null;
}
if (listener instanceof Widget) {
// GWT uses the widget as event listener
return (Widget) listener;
}
return null;
}
Since you are constructing your textboxes in gwt java code, why not put them into a map and access them later?
One thing to keep in mind is the difference between an attribute and a property in HTML/DOM. In your example, "value" is a property. You could try Element#getPropertyString. It used to be that attributes and properties were used interchangeably, but in modern browsers that's no longer the case.
GWT's CellBrowser is a great way of presenting dynamic data.
However when the browser contains more rows than some (seemingly) arbitrary maximum, it offers a "Show More" label that the user can click to fetch the unseen rows.
How can I disable this behavior, and force it to always show every row?
There are several ways of getting rid of the "Show More" (which you can combine):
In your TreeViewModel, in your NodeInfo's setDisplay or in the DataProvider your give to the DefaultNodeInfo, in onRangeChange: overwrite the display's visible range to the size of your data.
Extend CellBrowser and override its createPager method to return null. It won't change the list's page size though, but you can set it to some very high value there too.
The below CellBrowser removes the "Show More" text plus loads all available elements without paging.
public class ShowAllElementsCellBrowser extends CellBrowser {
public ShowAllElementsCellBrowser(TreeViewModel viewModel, CellBrowser.Resources resources) {
super(viewModel, null, resources);
}
#Override
protected <C> Widget createPager(HasData<C> display) {
PageSizePager pager = new PageSizePager(Integer.MAX_VALUE);
// removes the text "Show More" during loading
display.setRowCount(0);
// increase the visible range so that no one ever needs to page
display.setVisibleRange(0, Integer.MAX_VALUE);
pager.setDisplay(display);
return pager;
}
}
I found a valid and simple solution in setting page size to the CellBrowser's builder.
Hope this will help.
CellBrowser.Builder<AClass> cellBuilder = new CellBrowser.Builder<AClass>(myModel, null);
cellBuilder.pageSize(Integer.MAX_VALUE);
cellBrowser = cellBuilder.build();
The easiest way to do this is by using the:
cellTree.setDefaultNodeSize(Integer.MAX_VALUE);
method on your Cell Tree. You must do this before you begin expanding the tree.
My workaround is to navigate through elements of treeview dom to get "show more" element with
public static List<Element> findElements(Element element) {
ArrayList<Element> result = new ArrayList<Element>();
findShowMore(result, element); return result; }
private static void findShowMore(ArrayList res, Element element) {
String c;
if (element == null) { return; }
if (element.getInnerText().equals("Show more")) { res.add(element);
}
for (int i = 0; i < DOM.getChildCount(element); i++) { Element
child = DOM.getChild(element, i); findShowMore(res, child); } }
and than use:
if (show) { element.getStyle().clearDisplay(); } else {
element.getStyle().setDisplay(Display.NONE); }