Module javafx.graphics
Package javafx.scene

Class Parent

  • All Implemented Interfaces:
    Styleable, EventTarget
    Direct Known Subclasses:
    Group, Region, WebView
    public abstract 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

    • Constructor Detail

      • Parent

        protected Parent()
        Constructs a new Parent.

    • Method Detail

      • 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 showning (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

      • lookup

        public Node lookup​(String selector)
        Description copied from class: Node
        Finds this Node, or the first sub-node, based on the given CSS selector. If this node is a Parent, then this function will traverse down into the branch until it finds a match. If more than one sub-node matches the specified selector, this function returns the first of them.

        For example, if a Node is given the id of "myId", then the lookup method can be used to find this node as follows: scene.lookup("#myId");.

        Overrides:
        lookup in class Node
        Parameters:
        selector - The css selector of the node to find
        Returns:
        The first node, starting from this Node, which matches the CSS selector, null if none is found.

      • setNeedsLayout

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

      • isNeedsLayout

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

      • 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 layout 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.

      • prefWidth

        public double prefWidth​(double height)
        Description copied from class: Node
        Returns the node's preferred width for use in layout calculations. If the node is resizable, its parent should treat this value as the node's ideal width within its range. If the node is not resizable, just returns its layoutBounds width, which should be treated as the rigid width of the node.

        Layout code which calls this method should first check the content-bias of the node. If the node has a vertical content-bias, then callers should pass in a height value that the preferred width should be based on. If the node has either a horizontal or null content-bias, then the caller should pass in -1.

        Node subclasses with a vertical content-bias should honor the height parameter whether -1 or a positive value. All other subclasses may ignore the height parameter (which will likely be -1).

        Overrides:
        prefWidth in class Node
        Parameters:
        height - the height that should be used if preferred width depends on it
        Returns:
        the preferred width that the node should be resized to during layout The result will never be NaN, nor will it ever be negative.
        See Also:
        Node.isResizable(), Node.getContentBias(), Node.autosize()

      • prefHeight

        public double prefHeight​(double width)
        Description copied from class: Node
        Returns the node's preferred height for use in layout calculations. If the node is resizable, its parent should treat this value as the node's ideal height within its range. If the node is not resizable, just returns its layoutBounds height, which should be treated as the rigid height of the node.

        Layout code which calls this method should first check the content-bias of the node. If the node has a horizontal content-bias, then callers should pass in a width value that the preferred height should be based on. If the node has either a vertical or null content-bias, then the caller should pass in -1.

        Node subclasses with a horizontal content-bias should honor the height parameter whether -1 or a positive value. All other subclasses may ignore the height parameter (which will likely be -1).

        Overrides:
        prefHeight in class Node
        Parameters:
        width - the width that should be used if preferred height depends on it
        Returns:
        the preferred height that the node should be resized to during layout The result will never be NaN, nor will it ever be negative.
        See Also:
        Node.getContentBias(), Node.autosize()

      • minWidth

        public double minWidth​(double height)
        Description copied from class: Node
        Returns the node's minimum width for use in layout calculations. If the node is resizable, its parent should not resize its width any smaller than this value. If the node is not resizable, returns its layoutBounds width.

        Layout code which calls this method should first check the content-bias of the node. If the node has a vertical content-bias, then callers should pass in a height value that the minimum width should be based on. If the node has either a horizontal or null content-bias, then the caller should pass in -1.

        Node subclasses with a vertical content-bias should honor the height parameter whether -1 or a positive value. All other subclasses may ignore the height parameter (which will likely be -1).

        If Node's Node.maxWidth(double) is lower than this number, minWidth takes precedence. This means the Node should never be resized below minWidth.

        Overrides:
        minWidth in class Node
        Parameters:
        height - the height that should be used if minimum width depends on it
        Returns:
        the minimum width that the node should be resized to during layout. The result will never be NaN, nor will it ever be negative.
        See Also:
        Node.isResizable(), Node.getContentBias()

      • minHeight

        public double minHeight​(double width)
        Description copied from class: Node
        Returns the node's minimum height for use in layout calculations. If the node is resizable, its parent should not resize its height any smaller than this value. If the node is not resizable, returns its layoutBounds height.

        Layout code which calls this method should first check the content-bias of the node. If the node has a horizontal content-bias, then callers should pass in a width value that the minimum height should be based on. If the node has either a vertical or null content-bias, then the caller should pass in -1.

        Node subclasses with a horizontal content-bias should honor the width parameter whether -1 or a positive value. All other subclasses may ignore the width parameter (which will likely be -1).

        If Node's Node.maxHeight(double) is lower than this number, minHeight takes precedence. This means the Node should never be resized below minHeight.

        Overrides:
        minHeight in class Node
        Parameters:
        width - the width that should be used if minimum height depends on it
        Returns:
        the minimum height that the node should be resized to during layout The result will never be NaN, nor will it ever be negative.
        See Also:
        Node.isResizable(), Node.getContentBias()

      • computePrefWidth

        protected double computePrefWidth​(double height)
        Calculates the preferred width of this Parent. The default implementation calculates this width as the width of the area occupied by its managed children when they are positioned at their current positions at their preferred widths.
        Parameters:
        height - the height that should be used if preferred width depends on it
        Returns:
        the calculated preferred width

      • computePrefHeight

        protected double computePrefHeight​(double width)
        Calculates the preferred height of this Parent. The default implementation calculates this height as the height of the area occupied by its managed children when they are positioned at their current positions at their preferred heights.
        Parameters:
        width - the width that should be used if preferred height depends on it
        Returns:
        the calculated preferred height

      • computeMinWidth

        protected double computeMinWidth​(double height)
        Calculates the minimum width of this Parent. The default implementation simply returns the pref width.
        Parameters:
        height - the height that should be used if min width depends on it
        Returns:
        the calculated min width
        Since:
        JavaFX 2.1

      • computeMinHeight

        protected double computeMinHeight​(double width)
        Calculates the min height of this Parent. The default implementation simply returns the pref height;
        Parameters:
        width - the width that should be used if min height depends on it
        Returns:
        the calculated min height
        Since:
        JavaFX 2.1

      • 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 during the layout pass to layout the children in this Parent. By default it will only set the size of managed, resizable content to their preferred sizes and does not do any node positioning.

        Subclasses should override this function to layout content as needed.

      • 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.

      • queryAccessibleAttribute

        public Object queryAccessibleAttribute​(AccessibleAttribute attribute,
                                       Object... parameters)
        This method is called by the assistive technology to request the value for an attribute.

        This method is commonly overridden by subclasses to implement attributes that are required for a specific role.
        If a particular attribute is not handled, the superclass implementation must be called.

        Overrides:
        queryAccessibleAttribute in class Node
        Parameters:
        attribute - the requested attribute
        parameters - optional list of parameters
        Returns:
        the value for the requested attribute
        See Also:
        AccessibleAttribute