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 flextable that gets populated with data from a database.
I want to get the ROW number of the clicked row.
So far I figured out only how to get the value of a particular cell in a particular row. You have to know the position and hard code it which isn't practical.
String test =flexTable.getFlexCellFormatter().getElement(2, 2).getInnerHTML();
System.out.println(test);
How can I create a ClickHandler to get the selected row?
//flexTable is a FlexTable object. Add a ClickHandler to it.
flexTable.addClickHandler(new ClickHandler() {
public void onClick(ClickEvent event) {
//gets the index of the cell you clicked on
int cellIndex = flexTable.getCellForEvent(event).getCellIndex();
//gets the index of the row you clicked on
int rowIndex = flexTable.getCellForEvent(event).getRowIndex();
//print statements below will verify
System.out.println("cellIndex "+cellIndex);
System.out.println("rowIndex "+rowIndex);
//gets the value of the selected cell
String test =flexTable.getFlexCellFormatter().getElement(rowIndex,cellIndex ).getInnerHTML();
System.out.println(test);
}
});
The FlexTable supports row spans and column spans, allowing you to layout data in a variety of ways. I think you should use CellTable or a DataGrid or for that matter even a CellList if only single column data is being displayed. To these widgets you can add a selectionhandler to which you can achieve your goal. Refer this it has some pre coded examples.
I am new at GWT, and I have been trying to get the value of a EditTextCell which is inside a cellTable, So I was wondering what is the best way to accomplish this?
Thanks
When you've got an EditTextCell in a CellTable, I assume you mean that you have an entire column like that:
Column<RowObject, String> editTextCellColumn = new Column<RowObject, String>( new EditTextCell() ){
#Override
public String getValue(RowObject object) {
// return the value that is supposed to be displayed in the EditTextCell
}
};
If that is the case, you can simply add a fieldupdater to the column. The FieldUpdater is triggered every time the user successfully edits the text cell.
editTextCellColumn.setFieldUpdater( new FieldUpdater<RowObject, String>(){
public void update(int index, final RowObject object, final String value) {
// 'value' is the new value the user entered in the EditTextCell.
// 'object' is the object that contains the old row information.
// 'index' is the current row index of 'object'
// Code for performing whatever you want to do with the new value goes here.
}
};
When I select a row in a CellTable which contains several columns, the whole row gets colored in yellow. It does not depend on which area of the row I click (which column of the row).
What I try to do is to keep the selected row colored in yellow as long as no other row of this very table is selected. At the moment, as soon as I click somewhere else in the browser, the row gets back its original color.
I tried to use a selection model, but this changed nothing. Do you have any advise or is this simply not possible, since the focus is managed by the browser? The behavior is the same in the Google showcase for the CellTable...
The selection model actually does what you want to do: it paints a row blue and the row does not change color if you click elsewhere in the page. (Only when another row is selected)
There are 2 selection models:
One that lets you select only one row, and another one that lets you select multiple rows.
MultiSelectionModel<Row> selectionModel = new MultiSelectionModel<Row>();
table.setSelectionModel(selectionModel);
SingleSelectionModel<Row> selectionModel = new SingleSelectionModel<Row>();
table.setSelectionModel(selectionModel);
The solution of user905374 did actually work. I mentioned in my first post that I already tried the solution with a selectionModel and that it did not work. This was partially true. It does work, but only if the table does NOT contain a CheckboxCell.
Following a working and the not working example. I think this might be a bug, but I am not sure if I miss something.
final CellTable<LicenceDto> licenseTable = new CellTable<LicenceDto>();
final SingleSelectionModel<LicenceDto> selectionModel = new SingleSelectionModel<LicenceDto>();
licenseTable.setSelectionModel(selectionModel);
//--- If I add this column, the selection does work.
Column<LicenceDto, String> workingColumn = new Column<LicenceDto, String>(new TextCell()) {
#Override
public String getValue(LicenceDto object) {
return "Works";
}
};
workingColumn.setFieldUpdater(new FieldUpdater<LicenceDto, String>() {
#Override
public void update(int index, LicenceDto object, String value) {
;
}
});
licenseTable.addColumn(workingColumn);
//--- If I add this column, the selection does NOT work anymore.
Column<LicenceDto, Boolean> notWorkingColumn = new Column<LicenceDto, Boolean>(new CheckboxCell(true, true)) {
#Override
public Boolean getValue(LicenceDto object) {
return object.getEnabled();
}
};
notWorkingColumn.setFieldUpdater(new FieldUpdater<LicenceDto, Boolean>() {
#Override
public void update(int index, LicenceDto object, Boolean value) {
presenter.enableLicense(object, value);
}
});
licenseTable.addColumn(notWorkingColumn);
You can even combine multiple cells and add them to the table (e.g. LinkActionCell etc). As long as there is no CheckboxCell, the blue selection with the SingleSelectionModel does work like a charm. Does anyone see what I do wrong with this CheckboxCell or is there a bug?
UPDATE
It was simply a usage error of me. The problem was that I set handlesSelection to true (second parameter of the CheckboxCell constructor) even thought I don't handle anything. Setting it to false solves the problem.
Bottomline: Use a selection model (e.g. SingleSelectionModel) and do not set the handlesSelection parameter to true of the CheckboxCell constructor to true, if you don't handle the selection by yourself.
You should observe the Showcase demo again. This time use the checkbox on the left most column i.e the first column. On selection the row turns blue indicating the row selection is made. This is when you have SelectionModel set up. Click on the page anywhere outside the CellTable/DataGrid the selection is not changed.
Now, instead of choosing the row via checkbox from first column, you click on a row in any other column. The row turns yellow. Click on the page anywhere outside the CellTable/DataGrid the focus/yellow is lost.
"colored in yellow" indicates row is under focus and being edited and not selected.
Note - you can force row selection by using click events per cell.
Try something like this:
CellTable table;
YourDataObject object = new YourDataObject(...);
SingleSelectionModel<YourDataObject> selectionModel =
new SingleSelectionModel<YourDataObject>();
table.setSelectionModel(selectionModel);
...
table.setSelected(object, true);
Use MultiSelectionModel if you wish more than one line to be highlighted.
Store the selected row's index. When user selects row, change row's style to some "selected-style" appropriate for your case (defined in your css file) and remove selected style from the previously selected row. Also don't forget to update selected row's index.
If you provide some code from the original version I help you out with some code with pleasure.
I started using the CellTable widget. I need an editable text cell so I tried TextInputCell but to my dismay, I can't find the "value change handler".
How can I get notified when the cell content changes?
You don't need change handlers for cells. You set a FieldUpdater on your column. It has update() method which fires when value of a cell in this column changes. For example:
myEditableColumn.setFieldUpdater(new FieldUpdater<T, String>() {
#Override
public void update(int index, T object, String value) {
// do something when value changes
}
});