Class Parent

java.lang.Object
javafx.scene.Node
javafx.scene.Parent
All Implemented Interfaces:
Styleable, EventTarget
Direct Known Subclasses:
Group, Region, WebView
public abstract non-sealed class Parent extends Node
The base class for all nodes that have children in the scene graph.

This class handles all hierarchical scene graph operations, including adding/removing child nodes, marking branches dirty for layout and rendering, picking, bounds calculations, and executing the layout pass on each pulse.

There are two direct concrete Parent subclasses

  • Group effects and transforms to be applied to a collection of child nodes.
  • Region class for nodes that can be styled with CSS and layout children.
Since:
JavaFX 2.0

  • Property Details

  • Constructor Details

    • Parent

      protected Parent()
      Constructs a new Parent.

  • Method Details

    • getChildren

      protected ObservableList<Node> getChildren()
      Gets the list of children of this Parent.

      See the class documentation for Node for scene graph structure restrictions on setting a Parent's children list. If these restrictions are violated by a change to the list of children, the change is ignored and the previous value of the children list is restored. An IllegalArgumentException is thrown in this case.

      If this Parent node is attached to a Scene attached to a Window, that is, showing (Window.isShowing()), then its list of children must only be modified on the JavaFX Application Thread. An IllegalStateException is thrown if this restriction is violated.

      Note to subclasses: if you override this method, you must return from your implementation the result of calling this super method. The actual list instance returned from any getChildren() implementation must be the list owned and managed by this Parent. The only typical purpose for overriding this method is to promote the method to be public.

      Returns:
      the list of children of this Parent.

    • getChildrenUnmodifiable

      public ObservableList<Node> getChildrenUnmodifiable()
      Gets the list of children of this Parent as a read-only list.
      Returns:
      read-only access to this parent's children ObservableList

    • getManagedChildren

      protected <E extends Node> List<E> getManagedChildren()
      Gets the list of all managed children of this Parent.
      Type Parameters:
      E - the type of the children nodes
      Returns:
      list of all managed children in this parent

    • setNeedsLayout

      protected final void setNeedsLayout(boolean value)
      Sets the value of the needsLayout property.
      Property description:
      Indicates that this Node and its subnodes requires a layout pass on the next pulse.
      Parameters:
      value - the value for the needsLayout property
      See Also:

    • isNeedsLayout

      public final boolean isNeedsLayout()
      Gets the value of the needsLayout property.
      Property description:
      Indicates that this Node and its subnodes requires a layout pass on the next pulse.
      Returns:
      the value of the needsLayout property
      See Also:

    • needsLayoutProperty

      public final ReadOnlyBooleanProperty needsLayoutProperty()
      Indicates that this Node and its subnodes requires a layout pass on the next pulse.
      Returns:
      the needsLayout property
      See Also:

    • requestLayout

      public void requestLayout()
      Requests a layout pass to be performed before the next scene is rendered. This is batched up asynchronously to happen once per "pulse", or frame of animation.

      If this parent is either a scene root or unmanaged, then it will be added directly to the scene's dirty layout list, otherwise requestParentLayout will be invoked.

      Since:
      JavaFX 8.0

    • requestParentLayout

      protected final void requestParentLayout()
      Requests a layout pass of the parent to be performed before the next scene is rendered. This is batched up asynchronously to happen once per "pulse", or frame of animation.

      This may be used when the current parent have changed it's min/max/preferred width/height, but doesn't know yet if the change will lead to it's actual size change. This will be determined when it's parent recomputes the layout with the new hints.

    • computePrefWidth

      protected double computePrefWidth(double height)
      Computes the preferred width for the specified height.

      An overriding implementation should be consistent with the layout policy implemented by layoutChildren(). If pixel snapping is used, corresponding measurement and layout calculations must use the same snapped values.

      Implementation Note:
      The default implementation computes the horizontal span containing the parent's origin and all managed children. It uses each child's current layout position and preferred width, constrained by the child's minimum and maximum widths. The height parameter is ignored.
      Parameters:
      height - the height on which to base the preferred width, or -1 if no height is specified
      Returns:
      the computed preferred width
      See Also:

    • computePrefHeight

      protected double computePrefHeight(double width)
      Computes the preferred height for the specified width.

      An overriding implementation should be consistent with the layout policy implemented by layoutChildren(). If pixel snapping is used, corresponding measurement and layout calculations must use the same snapped values.

      Implementation Note:
      The default implementation computes the vertical span containing the parent's origin and all managed children. It uses each child's current layout position and preferred height, constrained by the child's minimum and maximum heights. The width parameter is ignored.
      Parameters:
      width - the width on which to base the preferred height, or -1 if no width is specified
      Returns:
      the computed preferred height
      See Also:

    • computeMinWidth

      protected double computeMinWidth(double height)
      Computes the minimum width for the specified height.

      An overriding implementation should be consistent with the layout policy implemented by layoutChildren(). If pixel snapping is used, corresponding measurement and layout calculations must use the same snapped values.

      Implementation Note:
      The default implementation returns prefWidth(height).
      Parameters:
      height - the height on which to base the minimum width, or -1 if no height is specified
      Returns:
      the computed minimum width
      Since:
      JavaFX 2.1
      See Also:

    • computeMinHeight

      protected double computeMinHeight(double width)
      Computes the minimum height for the specified width.

      An overriding implementation should be consistent with the layout policy implemented by layoutChildren(). If pixel snapping is used, corresponding measurement and layout calculations must use the same snapped values.

      Implementation Note:
      The default implementation returns prefHeight(width).
      Parameters:
      width - the width on which to base the minimum height, or -1 if no width is specified
      Returns:
      the computed minimum height
      Since:
      JavaFX 2.1
      See Also:

    • getBaselineOffset

      public double getBaselineOffset()
      Calculates the baseline offset based on the first managed child. If there is no such child, returns Node.getBaselineOffset().
      Overrides:
      getBaselineOffset in class Node
      Returns:
      baseline offset

    • layout

      public final void layout()
      Executes a top-down layout pass on the scene graph under this parent. Calling this method while the Parent is doing layout is a no-op.

    • layoutChildren

      protected void layoutChildren()
      Invoked by layout() during a layout pass to position and resize the managed children.

      Subclasses should override this method to implement their layout policy. When pixel snapping is used, this parent owns the snapping policy for the positions and sizes it allocates to its children. The snapped allocations made here must be consistent with the corresponding minimum-size and preferred-size calculations.

      Implementation Requirements:
      The default implementation invokes Node.autosize() on each managed, resizable child and leaves all child positions unchanged.
      See Also:

    • getStylesheets

      public final ObservableList<String> getStylesheets()
      Gets an observable list of string URLs linking to the stylesheets to use with this Parent's contents. See Scene.getStylesheets() for details.

      For additional information about using CSS with the scene graph, see the CSS Reference Guide.

      Returns:
      the list of stylesheets to use with this Parent
      Since:
      JavaFX 2.1

    • updateBounds

      protected void updateBounds()
      Updates the bounds of this Parent and its children.