T
- The type of the item contained within the Cell.public class Cell<T> extends Labeled
ListView
,
TreeView
, and TableView
.
A Cell is a Labeled
Control
, and is used to render a single
"row" inside a ListView, TreeView or TableView. Cells are also used for each
individual 'cell' inside a TableView (i.e. each row/column intersection). See
the JavaDoc for each control separately for more detail.
Every Cell is associated with a single data item (represented by the
item
property). The Cell is responsible for
rendering that item and, where appropriate, for editing the item. An item
within a Cell may be represented by text or some other control such as a
CheckBox
, ChoiceBox
or any other Node
such as a
HBox
, GridPane
, or even a Rectangle
.
Because TreeView, ListView, TableView and other such controls can potentially be used for displaying incredibly large amounts of data, it is not feasible to create an actual Cell for every single item in the control. We represent extremely large data sets using only very few Cells. Each Cell is "recycled", or reused. This is what we mean when we say that these controls are virtualized.
Since Cell is a Control, it is essentially a "model". Its Skin is responsible for defining the look and layout, while the Behavior is responsible for handling all input events and using that information to modify the Control state. Also, the Cell is styled from CSS just like any other Control. However, it is not necessary to implement a Skin for most uses of a Cell. This is because a cell factory can be set - this is detailed more shortly.
Because by far the most common use case for cells is to show text to a user,
this use case is specially optimized for within Cell. This is done by Cell
extending from Labeled
. This means that subclasses of Cell need only
set the text
property, rather than create a separate
Label
and set that within the Cell. However, for situations where
something more than just plain text is called for, it is possible to place
any Node
in the Cell graphic
property.
Despite the term, a graphic can be any Node, and will be fully interactive.
For example, a ListCell might be configured with a Button
as its
graphic. The Button text could then be bound to the cells
item
property. In this way, whenever the item in the
Cell changes, the Button text is automatically updated.
Cell sets focusTraversable to false.
Cell Factories
The default representation of the Cell item
is up to the various
virtualized container's skins to render. For example, the ListView by default
will convert the item to a String and call Labeled.setText(java.lang.String)
with this value. If you want to specialize the Cell used for the
ListView (for example), then you must provide an implementation of the
cellFactory
callback function defined
on the ListView. Similar API exists on most controls that use Cells (for example,
TreeView
,
TableView
,
TableColumn
and
ListView
.
The cell factory is called by the platform whenever it determines that a new cell needs to be created. For example, perhaps your ListView has 10 million items. Creating all 10 million cells would be prohibitively expensive. So instead the ListView skin implementation might only create just enough cells to fit the visual space. If the ListView is resized to be larger, the system will determine that it needs to create some additional cells. In this case it will call the cellFactory callback function (if one is provided) to create the Cell implementation that should be used. If no cell factory is provided, the built-in default implementation will be used.
The implementation of the cell factory is then responsible not just for creating a Cell instance, but also configuring that Cell such that it reacts to changes in its state. For example, if I were to create a custom Cell which formatted Numbers such that they would appear as currency types, I might do so like this:
public class MoneyFormatCell extends ListCell<Number> { public MoneyFormatCell() { } @Override protected void updateItem(Number item, boolean empty) { // calling super here is very important - don't skip this! super.updateItem(item, empty); // format the number as if it were a monetary value using the // formatting relevant to the current locale. This would format // 43.68 as "$43.68", and -23.67 as "-$23.67" setText(item == null ? "" : NumberFormat.getCurrencyInstance().format(item)); // change the text fill based on whether it is positive (green) // or negative (red). If the cell is selected, the text will // always be white (so that it can be read against the blue // background), and if the value is zero, we'll make it black. if (item != null) { double value = item.doubleValue(); setTextFill(isSelected() ? Color.WHITE : value == 0 ? Color.BLACK : value < 0 ? Color.RED : Color.GREEN); } } }This class could then be used inside a ListView as such:
ObservableList<Number> money = ...; final ListView<Number> listView = new ListView<Number>(money); listView.setCellFactory(new Callback<ListView<Number>, ListCell<Number>>() { @Override public ListCell<Number> call(ListView<Number> list) { return new MoneyFormatCell(); } });In this example an anonymous inner class is created, that simply returns instances of MoneyFormatCell whenever it is called. The MoneyFormatCell class extends
ListCell
, overriding the
updateItem
method. This method
is called whenever the item in the cell changes, for example when the user
scrolls the ListView or the content of the underlying data model changes
(and the cell is reused to represent some different item in the ListView).
Because of this, there is no need to manage bindings - simply react to the
change in items when this method occurs. In the example above, whenever the
item changes, we update the cell text property, and also modify the text fill
to ensure that we get the correct visuals. In addition, if the cell is "empty"
(meaning it is used to fill out space in the ListView but doesn't have any
data associated with it), then we just use the empty String.
Note that there are additional methods prefixed with 'update' that may be of interest, so be sure to read the API documentation for Cell, and subclasses of Cell, closely.
Of course, we can also use the binding API rather than overriding the 'update' methods. Shown below is a very trivial example of how this could be achieved.
public class BoundLabelCell extends ListCell<String> { public TextFieldCell() { textProperty().bind(itemProperty()); } }
Changing the Cell's Colors
This should be extraordinarily simple in JavaFX. Each Cell can be styled directly from CSS. So for example, if you wanted to change the default background of every cell in a ListView to be WHITE you could do the following CSS:
.list-cell { -fx-padding: 3 3 3 3; -fx-background-color: white; }If you wanted to set the color of selected ListView cells to be blue, you could add this to your CSS file:
.list-cell:selected { -fx-background-color: blue; }Most Cell implementations extend from
IndexedCell
rather than Cell.
IndexedCell adds two other pseudoclass states: "odd" and "even". Using this
you can get alternate row striping by doing something like this in your CSS
file:
.list-cell:odd { -fx-background-color: grey; }Each of these examples require no code changes. Simply update your CSS file to alter the colors. You can also use the "hover" and other pseudoclasses in CSS the same as with other controls.
Another approach to the first example above (formatting a list of numbers) would
be to use style classes. Suppose you had an ObservableList
of Numbers
to display in a ListView and wanted to color all of the negative values red
and all positive or 0 values black.
One way to achieve this is with a custom cellFactory which changes the
styleClass of the Cell based on whether the value is negative or positive. This
is as simple as adding code to test if the number in the cell is negative,
and adding a "negative" styleClass. If the number is not negative, the "negative"
string should be removed. This approach allows for the colors to be defined
from CSS, allowing for simple customization. The CSS file would then include
something like the following:
.list-cell { -fx-text-fill: black; } .list-cell .negative { -fx-text-fill: red; }
Type | Property and Description |
---|---|
BooleanProperty |
editable
A property representing whether this cell is allowed to be put into an
editing state.
|
ReadOnlyBooleanProperty |
editing
Property representing whether this cell is currently in its editing state.
|
ReadOnlyBooleanProperty |
empty
A property used to represent whether the cell has any contents.
|
ObjectProperty<T> |
item
The data value associated with this Cell.
|
ReadOnlyBooleanProperty |
selected
Indicates whether or not this cell has been selected.
|
alignment, contentDisplay, ellipsisString, font, graphic, graphicTextGap, labelPadding, mnemonicParsing, textAlignment, textFill, textOverrun, text, underline, wrapText
contextMenu, height, maxHeight, maxWidth, minHeight, minWidth, prefHeight, prefWidth, skinClassName, skin, tooltip, width
needsLayout
blendMode, boundsInLocal, boundsInParent, cacheHint, cache, clip, cursor, depthTest, disabled, disable, effect, eventDispatcher, focused, focusTraversable, hover, id, inputMethodRequests, layoutBounds, layoutX, layoutY, localToParentTransform, localToSceneTransform, managed, mouseTransparent, onContextMenuRequested, onDragDetected, onDragDone, onDragDropped, onDragEntered, onDragExited, onDragOver, onInputMethodTextChanged, onKeyPressed, onKeyReleased, onKeyTyped, onMouseClicked, onMouseDragEntered, onMouseDragExited, onMouseDragged, onMouseDragOver, onMouseDragReleased, onMouseEntered, onMouseExited, onMouseMoved, onMousePressed, onMouseReleased, onRotate, onRotationFinished, onRotationStarted, onScrollFinished, onScroll, onScrollStarted, onSwipeDown, onSwipeLeft, onSwipeRight, onSwipeUp, onTouchMoved, onTouchPressed, onTouchReleased, onTouchStationary, onZoomFinished, onZoom, onZoomStarted, opacity, parent, pickOnBounds, pressed, rotate, rotationAxis, scaleX, scaleY, scaleZ, scene, style, translateX, translateY, translateZ, visible
USE_COMPUTED_SIZE, USE_PREF_SIZE
Constructor and Description |
---|
Cell()
Creates a default Cell with the default style class of 'cell'.
|
Modifier and Type | Method and Description |
---|---|
void |
cancelEdit()
Call this function to transition from an editing state into a non-editing
state, without saving any user input.
|
void |
commitEdit(T newValue)
Call this function to transition from an editing state into a non-editing
state, and in the process saving any user input.
|
BooleanProperty |
editableProperty()
A property representing whether this cell is allowed to be put into an
editing state.
|
ReadOnlyBooleanProperty |
editingProperty()
Property representing whether this cell is currently in its editing state.
|
ReadOnlyBooleanProperty |
emptyProperty()
A property used to represent whether the cell has any contents.
|
T |
getItem()
Returns the data value associated with this Cell.
|
boolean |
isEditable()
Returns whether this cell is allowed to be put into an editing state.
|
boolean |
isEditing()
Represents whether the cell is currently in its editing state or not.
|
boolean |
isEmpty()
Returns a boolean representing whether the cell is considered to be empty
or not.
|
boolean |
isSelected()
Returns whether this cell is currently selected or not.
|
ObjectProperty<T> |
itemProperty()
The data value associated with this Cell.
|
ReadOnlyBooleanProperty |
selectedProperty()
Indicates whether or not this cell has been selected.
|
void |
setEditable(boolean value)
Allows for certain cells to not be able to be edited.
|
void |
setItem(T value)
Sets the item to the given value - should not be called directly as the
item is managed by the virtualized control.
|
void |
startEdit()
Call this function to transition from a non-editing state into an editing
state, if the cell is editable.
|
protected void |
updateItem(T item,
boolean empty)
Updates the item associated with this Cell.
|
void |
updateSelected(boolean selected)
Updates whether this cell is in a selected state or not.
|
alignmentProperty, contentDisplayProperty, ellipsisStringProperty, fontProperty, getAlignment, getContentBias, getContentDisplay, getEllipsisString, getFont, getGraphic, getGraphicTextGap, getLabelPadding, getText, getTextAlignment, getTextFill, getTextOverrun, graphicProperty, graphicTextGapProperty, isMnemonicParsing, isUnderline, isWrapText, labelPaddingProperty, mnemonicParsingProperty, setAlignment, setContentDisplay, setEllipsisString, setFont, setGraphic, setGraphicTextGap, setMnemonicParsing, setText, setTextAlignment, setTextFill, setTextOverrun, setUnderline, setWrapText, textAlignmentProperty, textFillProperty, textOverrunProperty, textProperty, underlineProperty, wrapTextProperty
computeMaxHeight, computeMaxWidth, computeMinHeight, computeMinWidth, computePrefHeight, computePrefWidth, contextMenuProperty, getBaselineOffset, getContextMenu, getHeight, getMaxHeight, getMaxWidth, getMinHeight, getMinWidth, getPrefHeight, getPrefWidth, getSkin, getTooltip, getUserAgentStylesheet, getWidth, heightProperty, intersects, isResizable, layoutChildren, maxHeight, maxHeightProperty, maxWidth, maxWidthProperty, minHeight, minHeightProperty, minWidth, minWidthProperty, prefHeight, prefHeightProperty, prefWidth, prefWidthProperty, resize, setContextMenu, setHeight, setMaxHeight, setMaxSize, setMaxWidth, setMinHeight, setMinSize, setMinWidth, setPrefHeight, setPrefSize, setPrefWidth, setSkin, setSkinClassName, setTooltip, setWidth, skinClassNameProperty, skinProperty, tooltipProperty, widthProperty
getChildren, getChildrenUnmodifiable, getManagedChildren, getStylesheets, isNeedsLayout, layout, lookup, needsLayoutProperty, requestLayout, setNeedsLayout
addEventFilter, addEventHandler, autosize, blendModeProperty, boundsInLocalProperty, boundsInParentProperty, buildEventDispatchChain, cacheHintProperty, cacheProperty, clipProperty, contains, contains, cursorProperty, depthTestProperty, disabledProperty, disableProperty, effectProperty, eventDispatcherProperty, fireEvent, focusedProperty, focusTraversableProperty, getBlendMode, getBoundsInLocal, getBoundsInParent, getCacheHint, getClip, getCursor, getDepthTest, getEffect, getEventDispatcher, getId, getInputMethodRequests, getLayoutBounds, getLayoutX, getLayoutY, getLocalToParentTransform, getLocalToSceneTransform, getOnContextMenuRequested, getOnDragDetected, getOnDragDone, getOnDragDropped, getOnDragEntered, getOnDragExited, getOnDragOver, getOnInputMethodTextChanged, getOnKeyPressed, getOnKeyReleased, getOnKeyTyped, getOnMouseClicked, getOnMouseDragEntered, getOnMouseDragExited, getOnMouseDragged, getOnMouseDragOver, getOnMouseDragReleased, getOnMouseEntered, getOnMouseExited, getOnMouseMoved, getOnMousePressed, getOnMouseReleased, getOnRotate, getOnRotationFinished, getOnRotationStarted, getOnScroll, getOnScrollFinished, getOnScrollStarted, getOnSwipeDown, getOnSwipeLeft, getOnSwipeRight, getOnSwipeUp, getOnTouchMoved, getOnTouchPressed, getOnTouchReleased, getOnTouchStationary, getOnZoom, getOnZoomFinished, getOnZoomStarted, getOpacity, getParent, getProperties, getRotate, getRotationAxis, getScaleX, getScaleY, getScaleZ, getScene, getStyle, getStyleClass, getTransforms, getTranslateX, getTranslateY, getTranslateZ, getUserData, hasProperties, hoverProperty, idProperty, inputMethodRequestsProperty, intersects, isCache, isDisable, isDisabled, isFocused, isFocusTraversable, isHover, isManaged, isMouseTransparent, isPickOnBounds, isPressed, isVisible, layoutBoundsProperty, layoutXProperty, layoutYProperty, localToParent, localToParent, localToParent, localToParentTransformProperty, localToScene, localToScene, localToScene, localToSceneTransformProperty, lookupAll, managedProperty, mouseTransparentProperty, onContextMenuRequestedProperty, onDragDetectedProperty, onDragDoneProperty, onDragDroppedProperty, onDragEnteredProperty, onDragExitedProperty, onDragOverProperty, onInputMethodTextChangedProperty, onKeyPressedProperty, onKeyReleasedProperty, onKeyTypedProperty, onMouseClickedProperty, onMouseDragEnteredProperty, onMouseDragExitedProperty, onMouseDraggedProperty, onMouseDragOverProperty, onMouseDragReleasedProperty, onMouseEnteredProperty, onMouseExitedProperty, onMouseMovedProperty, onMousePressedProperty, onMouseReleasedProperty, onRotateProperty, onRotationFinishedProperty, onRotationStartedProperty, onScrollFinishedProperty, onScrollProperty, onScrollStartedProperty, onSwipeDownProperty, onSwipeLeftProperty, onSwipeRightProperty, onSwipeUpProperty, onTouchMovedProperty, onTouchPressedProperty, onTouchReleasedProperty, onTouchStationaryProperty, onZoomFinishedProperty, onZoomProperty, onZoomStartedProperty, opacityProperty, parentProperty, parentToLocal, parentToLocal, parentToLocal, pickOnBoundsProperty, pressedProperty, relocate, removeEventFilter, removeEventHandler, requestFocus, resizeRelocate, rotateProperty, rotationAxisProperty, scaleXProperty, scaleYProperty, scaleZProperty, sceneProperty, sceneToLocal, sceneToLocal, sceneToLocal, setBlendMode, setCache, setCacheHint, setClip, setCursor, setDepthTest, setDisable, setDisabled, setEffect, setEventDispatcher, setEventHandler, setFocused, setFocusTraversable, setHover, setId, setInputMethodRequests, setLayoutX, setLayoutY, setManaged, setMouseTransparent, setOnContextMenuRequested, setOnDragDetected, setOnDragDone, setOnDragDropped, setOnDragEntered, setOnDragExited, setOnDragOver, setOnInputMethodTextChanged, setOnKeyPressed, setOnKeyReleased, setOnKeyTyped, setOnMouseClicked, setOnMouseDragEntered, setOnMouseDragExited, setOnMouseDragged, setOnMouseDragOver, setOnMouseDragReleased, setOnMouseEntered, setOnMouseExited, setOnMouseMoved, setOnMousePressed, setOnMouseReleased, setOnRotate, setOnRotationFinished, setOnRotationStarted, setOnScroll, setOnScrollFinished, setOnScrollStarted, setOnSwipeDown, setOnSwipeLeft, setOnSwipeRight, setOnSwipeUp, setOnTouchMoved, setOnTouchPressed, setOnTouchReleased, setOnTouchStationary, setOnZoom, setOnZoomFinished, setOnZoomStarted, setOpacity, setPickOnBounds, setPressed, setRotate, setRotationAxis, setScaleX, setScaleY, setScaleZ, setStyle, setTranslateX, setTranslateY, setTranslateZ, setUserData, setVisible, snapshot, snapshot, startDragAndDrop, startFullDrag, styleProperty, toBack, toFront, toString, translateXProperty, translateYProperty, translateZProperty, visibleProperty
public final ObjectProperty<T> itemProperty
This value should only be set in subclasses of Cell by the virtualised user interface controls that know how to properly work with the Cell class.
getItem()
,
setItem(T)
public final ReadOnlyBooleanProperty emptyProperty
When a cell is empty, it can be styled differently via the 'empty' CSS pseudo class state. For example, it may not receive any alternate row highlighting, or it may not receive hover background fill when hovered.
isEmpty()
public final ReadOnlyBooleanProperty selectedProperty
isSelected()
public final ReadOnlyBooleanProperty editingProperty
isEditing()
public final BooleanProperty editableProperty
editable
property is also
true.isEditable()
,
setEditable(boolean)
public Cell()
public final ObjectProperty<T> itemProperty()
This value should only be set in subclasses of Cell by the virtualised user interface controls that know how to properly work with the Cell class.
getItem()
,
setItem(T)
public final void setItem(T value)
public final T getItem()
public final ReadOnlyBooleanProperty emptyProperty()
When a cell is empty, it can be styled differently via the 'empty' CSS pseudo class state. For example, it may not receive any alternate row highlighting, or it may not receive hover background fill when hovered.
isEmpty()
public final boolean isEmpty()
public final ReadOnlyBooleanProperty selectedProperty()
isSelected()
public final boolean isSelected()
public final boolean isEditing()
public final ReadOnlyBooleanProperty editingProperty()
isEditing()
public final void setEditable(boolean value)
value
- A boolean representing whether the cell is editable or not.
If true, the cell is editable, and if it is false, the cell can not
be edited.public final boolean isEditable()
public final BooleanProperty editableProperty()
editable
property is also
true.isEditable()
,
setEditable(boolean)
public void startEdit()
public void cancelEdit()
public void commitEdit(T newValue)
newValue
- The value as input by the end user, which should be
persisted in the relevant way given the data source underpinning the
user interface.protected void updateItem(T item, boolean empty)
Updates the item associated with this Cell. This method should only be called by Skin implementations of ListView, TableView, TreeView, or other controls using Cells. It is not intended to be called by application developers.
Because null
is a perfectly valid value in the application
domain, Cell needs some way to distinguish whether or not the cell
actually holds a value. The empty
flag indicates this.
It is an error to supply a non-null item
but a true value for
empty
.
item
- The new item for the cellempty
- whether or not this cell represents data from the list. If it
is empty, then it does not represent any domain data, but is a cell
being used to render an "empty" row.public void updateSelected(boolean selected)
selected
- whether or not to select this cell.Copyright (c) 2008, 2014, Oracle and/or its affiliates. All rights reserved.