Class WTreeNode

Direct Known Subclasses:

public class WTreeNode extends WCompositeWidget
A single node in a tree.

A tree list is constructed by combining several tree node objects in a tree hierarchy, by passing the parent tree node as the last argument in the child node constructor, or by using addChildNode(), to add a child to its parent.

Each tree node has a label, and optionally a label icon pair. The icon pair offers the capability to show a different icon depending on the state of the node (expanded or collapsed). When the node has any children, a child count may be displayed next to the label using setChildCountPolicy().

Expanding a tree node it will collapse all its children, so that a user may collapse/expand a node as a short-cut to collapsing all children.

The treenode provides several policies to communicate the current contents of the tree to the client (if possible):

  • ContentLoading.Eager: the entire tree is transmitted to the client, and all tree navigation requires no further communication.
  • ContentLoading::Lazy: only the minimum is transmitted to the client. When expanding a node for the first time, only then it is transmitted to the client, and this may thus have some latency.
  • ContentLoading.NextLevel: all leafs of visible children are transmitted, but not their children. This provides a good trade-off between bandwith use and interactivity, since expanding any tree node will happen instantly, and at the same time trigger some communication in the back-ground to load the next level of invisible nodes.

The default policy is ContentLoading::Lazy. Another load policy may be specified using setLoadPolicy() on the root node and before adding any children. The load policy is inherited by all children in the tree.

There are a few scenarios where it makes sense to specialize the WTreeNode class. One scenario is create a tree that is populated dynamically while browsing. For this purpose you should reimplement the populate() method, whose default implementation does nothing. This method is called when 'loading' the node. The exact moment for loading a treenode depends on the LoadPolicy.

A second scenario that is if you want to customize the look of the tree label (see getLabelArea()) or if you want to modify or augment the event collapse/expand event handling (see doExpand() and doCollapse()).

See WTree for a usage example.

See Also:
  • Constructor Details

  • Method Details

    • remove

      public void remove()
      remove in class WCompositeWidget
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    • getTree

      public WTree getTree()
      Returns the tree.

      By default if this node has no parent the result will be 0.

    • getLabel

      public WText getLabel()
      Returns the label.
    • getLabelIcon

      public WIconPair getLabelIcon()
      Returns the label icon.
    • setLabelIcon

      public void setLabelIcon(WIconPair labelIcon)
      Sets the label icon.
    • insertChildNode

      public void insertChildNode(int index, WTreeNode node)
      Inserts a child node.

      Inserts the node node at index index.

    • addChildNode

      public WTreeNode addChildNode(WTreeNode node)
      Adds a child node.

      Equivalent to:

       insertChildNode(childNodes().size(), std::move(node));

      See Also:
    • removeChildNode

      public WTreeNode removeChildNode(WTreeNode node)
      Removes a child node.
    • getChildNodes

      public List<WTreeNode> getChildNodes()
      Returns the list of children.
    • getDisplayedChildCount

      public int getDisplayedChildCount()
      Returns the number of children that should be displayed.

      This is used to display the count in the count label. The default implementation simply returns getChildNodes().size().

    • setChildCountPolicy

      public void setChildCountPolicy(ChildCountPolicy policy)
      Configures how and when the child count should be displayed.

      By default, no child count indication is disabled (this is the behaviour since 2.1.1). Use this method to enable child count indications.

      The child count policy is inherited by all children in the tree.

    • getChildCountPolicy

      public ChildCountPolicy getChildCountPolicy()
      Returns the child count policy.

      See Also:
    • setLoadPolicy

      public void setLoadPolicy(ContentLoading loadPolicy)
      Sets the load policy for this tree.

      This may only be set on the root of a tree, and before adding any children.

    • isExpanded

      public boolean isExpanded()
      Returns whether this node is expanded.
    • setSelectable

      public void setSelectable(boolean selectable)
      Allows this node to be selected.

      By default, all nodes may be selected.

      setSelectable in class WCompositeWidget
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    • isSelectable

      public boolean isSelectable()
      Returns if this node may be selected.

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    • getParentNode

      public WTreeNode getParentNode()
      Returns the parent node.

      See Also:
    • setNodeVisible

      public void setNodeVisible(boolean visible)
      Sets the visibility of the node itself.

      If false, then the node itself is not displayed, but only its children. This is typically used to hide the root node of a tree.

    • setChildrenDecorated

      public void setChildrenDecorated(boolean decorated)
      Sets whether this node's children are decorated.

      By default, node's children have expand/collapse and other lines to display their linkage and offspring.

      By setting decorated to false, you can hide the decorations for the node's children.

    • setInteractive

      public void setInteractive(boolean interactive)
      Sets whether this node is interactive.

      Interactive nodes can be clicked upon and will populate a list of children when clicked. By disabling the interactivity, a node will not react to a click event.

    • expand

      public void expand()
      Expands this node.

      Besides the actual expansion of the node, this may also trigger the loading and population of the node children, or of the children's children.

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    • collapse

      public void collapse()
      Collapses this node.

      See Also:
    • expanded

      public EventSignal1<WMouseEvent> expanded()
      Signal emitted when the node is expanded by the user.

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    • collapsed

      public EventSignal1<WMouseEvent> collapsed()
      Signal emitted when the node is collapsed by the user.

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    • selected

      public Signal1<Boolean> selected()
      Signal that is emitted when the node is added or removed from the selection

      See Also:
    • getLabelArea

      protected WContainerWidget getLabelArea()
      Accesses the container widget that holds the label area.

      Use this to customize how the label should look like.

    • populate

      protected void populate()
      Populates the node dynamically on loading.

      Reimplement this method if you want to populate the widget dynamically, as the tree is being browsed and therefore loaded. This is only usefull with LazyLoading or NextLevelLoading strategies.

    • isPopulated

      protected boolean isPopulated()
      Returns whether this node has already been populated.

      See Also:
    • isExpandable

      protected boolean isExpandable()
      Returns whether this node can be expanded.

      The default implementation populates the node if necessary, and then checks if there are any child nodes.

      You may wish to reimplement this method if you reimplement populate(), and you have a quick default for determining whether a node may be expanded (which does not require populating the node).

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    • renderSelected

      protected void renderSelected(boolean isSelected)
      Renders the node to be selected.

      The default implementation changes the style class of the getLabelArea() to "selected".

    • descendantRemoved

      protected void descendantRemoved(WTreeNode node)
      Reacts to the removal of a descendant node.

      Reimplement this method if you wish to react on the removal of a descendant node. The default implementation simply propagates the event to the parent.

    • descendantAdded

      protected void descendantAdded(WTreeNode node)
      Reacts to the addition of a descendant node.

      Reimplement this method if you wish to react on the addition of a descendant node. The default implementation simply propagates the event to the parent.

    • doExpand

      protected void doExpand()
      The actual expand.

      This method, which is implemented as a stateless slot, performs the actual expansion of the node.

      You may want to reimplement this function (and undoDoExpand()) if you wish to do additional things on node expansion.

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    • doCollapse

      protected void doCollapse()
      The actual collapse.

      This method, which is implemented as a stateless slot, performs the actual collapse of the node.

      You may want to reimplement this function (and undoDoCollapse()) if you wish to do additional things on node expansion.

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    • undoDoExpand

      protected void undoDoExpand()
      Undo method for doCollapse() stateless implementation.

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    • undoDoCollapse

      protected void undoDoCollapse()
      Undo method for doCollapse() stateless implementation.

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    • getExpandIcon

      protected WIconPair getExpandIcon()
      Accesses the icon pair that allows expansion of the tree node.
    • getImpl

      protected WTemplate getImpl()