T
- The type of the value
property within TreeItem.public class TreeItem<T> extends Object implements EventTarget
The model allows registration of listeners which will be notified as the
number of items changes, their position or if the values themselves change.
Note however that a TreeItem is not a Node, and therefore no visual
events will be fired on the TreeItem. To get these events, it is necessary to
add relevant observers to the TreeCell instances (via a custom cell factory -
see the Cell
class documentation for more details).
In the simplest case, TreeItem instances may be created in memory as such:
TreeItem<String> root = new TreeItem<String>("Root Node");
root.setExpanded(true);
root.getChildren().addAll(
new TreeItem<String>("Item 1"),
new TreeItem<String>("Item 2"),
new TreeItem<String>("Item 3")
);
TreeView<String> treeView = new TreeView<String>(root);
This approach works well for simple tree structures, or when the data is not
excessive (so that it can easily fit in memory). In situations where the size
of the tree structure is unknown (and therefore potentially huge), there is
the option of creating TreeItem instances on-demand in a memory-efficient way.
To demonstrate this, the code below creates a file system browser:
private TreeView buildFileSystemBrowser() {
TreeItem<File> root = createNode(new File("/"));
return new TreeView<File>(root);
}
// This method creates a TreeItem to represent the given File. It does this
// by overriding the TreeItem.getChildren() and TreeItem.isLeaf() methods
// anonymously, but this could be better abstracted by creating a
// 'FileTreeItem' subclass of TreeItem. However, this is left as an exercise
// for the reader.
private TreeItem<File> createNode(final File f) {
return new TreeItem<File>(f) {
// We cache whether the File is a leaf or not. A File is a leaf if
// it is not a directory and does not have any files contained within
// it. We cache this as isLeaf() is called often, and doing the
// actual check on File is expensive.
private boolean isLeaf;
// We do the children and leaf testing only once, and then set these
// booleans to false so that we do not check again during this
// run. A more complete implementation may need to handle more
// dynamic file system situations (such as where a folder has files
// added after the TreeView is shown). Again, this is left as an
// exercise for the reader.
private boolean isFirstTimeChildren = true;
private boolean isFirstTimeLeaf = true;
@Override public ObservableList<TreeItem<File>> getChildren() {
if (isFirstTimeChildren) {
isFirstTimeChildren = false;
// First getChildren() call, so we actually go off and
// determine the children of the File contained in this TreeItem.
super.getChildren().setAll(buildChildren(this));
}
return super.getChildren();
}
@Override public boolean isLeaf() {
if (isFirstTimeLeaf) {
isFirstTimeLeaf = false;
File f = (File) getValue();
isLeaf = f.isFile();
}
return isLeaf;
}
private ObservableList<TreeItem<File>> buildChildren(TreeItem<File> TreeItem) {
File f = TreeItem.getValue();
if (f != null && f.isDirectory()) {
File[] files = f.listFiles();
if (files != null) {
ObservableList<TreeItem<File>> children = FXCollections.observableArrayList();
for (File childFile : files) {
children.add(createNode(childFile));
}
return children;
}
}
return FXCollections.emptyObservableList();
}
};
}
TreeItem Events
TreeItem supports the same event bubbling concept as elsewhere in the
scenegraph. This means that it is not necessary to listen for events on all
TreeItems (and this is certainly not encouraged!). A better, and far more low
cost solution is to instead attach event listeners to the TreeView
root
item. As long as there is a path between
where the event occurs and the root TreeItem, the event will be bubbled to the
root item.
It is important to note however that a TreeItem is not a
Node, which means that only the event types defined in TreeItem will be
delivered. To listen to general events (for example mouse interactions), it is
necessary to add the necessary listeners to the cells
contained
within the TreeView (by providing a cell factory
).
The TreeItem class defines a number of events, with a defined hierarchy. These are shown below (follow the links to learn more about each event type):
TreeItem.treeNotificationEvent()
TreeItem.valueChangedEvent()
TreeItem.graphicChangedEvent()
TreeItem.treeItemCountChangeEvent()
The indentation shown above signifies the relationship between event types.
For example, all TreeItem event types have
treeNotificationEvent()
as their
parent event type, and the branch
expand
/
collapse
event types are both
treeNotificationEvent()
. For
performance reasons, it is encouraged to listen
to only the events you need to listen to. This means that it is encouraged
that it is better to listen to, for example,
TreeItem.valueChangedEvent()
,
rather than TreeItem.treeNotificationEvent()
.
Type | Property and Description |
---|---|
BooleanProperty |
expanded
The expanded state of this TreeItem.
|
ObjectProperty<Node> |
graphic
The node that is generally shown to the left of the value property.
|
ReadOnlyBooleanProperty |
leaf
Represents the TreeItem leaf property, which is true if the TreeItem has no children.
|
ReadOnlyObjectProperty<TreeItem<T>> |
parent
A property that represents the parent of this TreeItem.
|
ObjectProperty<T> |
value
A property representing the application-specific data contained within
this TreeItem.
|
Modifier and Type | Class and Description |
---|---|
static class |
TreeItem.TreeModificationEvent<T>
An
Event that contains relevant information for all forms of
TreeItem modifications. |
Constructor and Description |
---|
TreeItem()
Creates an empty TreeItem.
|
TreeItem(T value)
Creates a TreeItem with the value property set to the provided object.
|
TreeItem(T value,
Node graphic)
Creates a TreeItem with the value property set to the provided object, and
the graphic set to the provided Node.
|
Modifier and Type | Method and Description |
---|---|
<E extends Event> |
addEventHandler(EventType<E> eventType,
EventHandler<E> eventHandler)
Registers an event handler to this TreeItem.
|
static <T> EventType<TreeItem.TreeModificationEvent<T>> |
branchCollapsedEvent()
An EventType used when the TreeItem receives a modification to its
expanded property, such that the TreeItem is now in the collapsed state.
|
static <T> EventType<TreeItem.TreeModificationEvent<T>> |
branchExpandedEvent()
An EventType used when the TreeItem receives a modification to its
expanded property, such that the TreeItem is now in the expanded state.
|
EventDispatchChain |
buildEventDispatchChain(EventDispatchChain tail)
Construct an event dispatch chain for this target.
|
static <T> EventType<TreeItem.TreeModificationEvent<T>> |
childrenModificationEvent()
An EventType used when the TreeItem receives a direct modification to its
children list.
|
static <T> EventType<TreeItem.TreeModificationEvent<T>> |
expandedItemCountChangeEvent()
The general EventType used when the TreeItem receives a modification that
results in the number of children being visible changes.
|
BooleanProperty |
expandedProperty()
The expanded state of this TreeItem.
|
ObservableList<TreeItem<T>> |
getChildren()
The children of this TreeItem.
|
Node |
getGraphic()
Returns the node that is generally shown to the left of the value property.
|
TreeItem<T> |
getParent()
The parent of this TreeItem.
|
T |
getValue()
Returns the application-specific data represented by this TreeItem.
|
static <T> EventType<TreeItem.TreeModificationEvent<T>> |
graphicChangedEvent()
An EventType used when the TreeItem receives a modification to its
graphic property.
|
ObjectProperty<Node> |
graphicProperty()
The node that is generally shown to the left of the value property.
|
boolean |
isExpanded()
Returns the expanded state of this TreeItem.
|
boolean |
isLeaf()
A TreeItem is a leaf if it has no children.
|
ReadOnlyBooleanProperty |
leafProperty()
Represents the TreeItem leaf property, which is true if the TreeItem has no children.
|
TreeItem<T> |
nextSibling()
Returns the next sibling of the TreeItem.
|
TreeItem<T> |
nextSibling(TreeItem<T> afterNode)
Returns the next sibling after the given node.
|
ReadOnlyObjectProperty<TreeItem<T>> |
parentProperty()
A property that represents the parent of this TreeItem.
|
TreeItem<T> |
previousSibling()
Returns the previous sibling of the TreeItem.
|
TreeItem<T> |
previousSibling(TreeItem<T> beforeNode)
Returns the previous sibling after the given node.
|
<E extends Event> |
removeEventHandler(EventType<E> eventType,
EventHandler<E> eventHandler)
Unregisters a previously registered event handler from this TreeItem.
|
void |
setExpanded(boolean value)
Sets the expanded state of this TreeItem.
|
void |
setGraphic(Node value)
Sets the node that is generally shown to the left of the value property.
|
void |
setValue(T value)
Sets the application-specific data represented by this TreeItem.
|
String |
toString()
Returns a string representation of this
TreeItem object. |
static <T> EventType<TreeItem.TreeModificationEvent<T>> |
treeNotificationEvent()
The base EventType used to indicate that an event has occurred within a
TreeItem.
|
static <T> EventType<TreeItem.TreeModificationEvent<T>> |
valueChangedEvent()
An EventType used when the TreeItem receives a modification to its
value property.
|
ObjectProperty<T> |
valueProperty()
A property representing the application-specific data contained within
this TreeItem.
|
public final ObjectProperty<T> valueProperty
public final ObjectProperty<Node> graphicProperty
getGraphic()
,
setGraphic(Node)
public final BooleanProperty expandedProperty
isExpanded()
,
setExpanded(boolean)
public final ReadOnlyBooleanProperty leafProperty
isLeaf()
public final ReadOnlyObjectProperty<TreeItem<T>> parentProperty
getParent()
public TreeItem()
public TreeItem(T value)
value
- The object to be stored as the value of this TreeItem.public TreeItem(T value, Node graphic)
value
- The object to be stored as the value of this TreeItem.graphic
- The Node to show in the TreeView next to this TreeItem.public static <T> EventType<TreeItem.TreeModificationEvent<T>> treeNotificationEvent()
T
- The type of the value contained within the TreeItem.public static <T> EventType<TreeItem.TreeModificationEvent<T>> expandedItemCountChangeEvent()
branchExpandedEvent()
,
branchCollapsedEvent()
and childrenModificationEvent()
for the three sub-types).T
- The type of the value contained within the TreeItem.public static <T> EventType<TreeItem.TreeModificationEvent<T>> branchExpandedEvent()
T
- The type of the value contained within the TreeItem.public static <T> EventType<TreeItem.TreeModificationEvent<T>> branchCollapsedEvent()
T
- The type of the value contained within the TreeItem.public static <T> EventType<TreeItem.TreeModificationEvent<T>> childrenModificationEvent()
T
- The type of the value contained within the TreeItem.public static <T> EventType<TreeItem.TreeModificationEvent<T>> valueChangedEvent()
T
- The type of the value contained within the TreeItem.public static <T> EventType<TreeItem.TreeModificationEvent<T>> graphicChangedEvent()
T
- The type of the value contained within the TreeItem.public final void setValue(T value)
public final T getValue()
public final ObjectProperty<T> valueProperty()
public final void setGraphic(Node value)
value
- The graphic node that will be displayed to the user.public final Node getGraphic()
public final ObjectProperty<Node> graphicProperty()
getGraphic()
,
setGraphic(Node)
public final void setExpanded(boolean value)
value
- If this TreeItem has children, calling setExpanded with
true
will result in the children becoming visible.
Calling setExpanded with false
will hide any children
belonging to the TreeItem.public final boolean isExpanded()
public final BooleanProperty expandedProperty()
isExpanded()
,
setExpanded(boolean)
public boolean isLeaf()
public final ReadOnlyBooleanProperty leafProperty()
isLeaf()
public final TreeItem<T> getParent()
public final ReadOnlyObjectProperty<TreeItem<T>> parentProperty()
getParent()
public ObservableList<TreeItem<T>> getChildren()
public TreeItem<T> previousSibling()
public TreeItem<T> previousSibling(TreeItem<T> beforeNode)
beforeNode
- The TreeItem for which the previous sibling is being
sought.public TreeItem<T> nextSibling()
public TreeItem<T> nextSibling(TreeItem<T> afterNode)
afterNode
- The TreeItem for which the next sibling is being
sought.public String toString()
TreeItem
object.public EventDispatchChain buildEventDispatchChain(EventDispatchChain tail)
EventTarget
. This event target is
not automatically added to the chain, so if it wants to process events,
it needs to add an EventDispatcher
for itself to the chain.
In the case the event target is part of some hierarchy, the chain for it is usually built from event dispatchers collected from the root of the hierarchy to the event target.
The event dispatch chain is constructed by modifications to the provided initial event dispatch chain. The returned chain should have the initial chain at its end so the dispatchers should be prepended to the initial chain.
The caller shouldn't assume that the initial chain remains unchanged nor that the returned value will reference a different chain.
buildEventDispatchChain
in interface EventTarget
tail
- the initial chain to build frompublic <E extends Event> void addEventHandler(EventType<E> eventType, EventHandler<E> eventHandler)
Cell
class documentation for more details).eventType
- the type of the events to receive by the handlereventHandler
- the handler to registerNullPointerException
- if the event type or handler is nullpublic <E extends Event> void removeEventHandler(EventType<E> eventType, EventHandler<E> eventHandler)
eventType
- the event type from which to unregistereventHandler
- the handler to unregisterNullPointerException
- if the event type or handler is nullCopyright (c) 2008, 2015, Oracle and/or its affiliates. All rights reserved.