Package javafx.scene.layout

Class GridPane

java.lang.Object
javafx.scene.Node
javafx.scene.Parent
javafx.scene.layout.Region
javafx.scene.layout.Pane
javafx.scene.layout.GridPane
All Implemented Interfaces:
LayoutMeasurable, LayoutMeasurableMixin, HasBackgroundProperty, HasBlendModeProperty, HasBorderProperty, HasClipProperty, HasEffectProperty, HasHeightProperty, HasLayoutXProperty, HasLayoutYProperty, HasManagedProperty, HasMaxHeightProperty, HasMaxWidthProperty, HasMinHeightProperty, HasMinWidthProperty, HasMouseTransparentProperty, HasOnMouseClickedProperty, HasOpacityProperty, HasPaddingProperty, HasParentProperty, HasPrefHeightProperty, HasPrefWidthProperty, HasSnapToPixelProperty, HasVisibleProperty, HasWidthProperty, Styleable, EventTarget, INode, PreferenceResizableNode
public class GridPane extends Pane
GridPane lays out its children within a flexible grid of rows and columns. If a border and/or padding is set, then its content will be layed out within those insets.

A child may be placed anywhere within the grid and may span multiple rows/columns. Children may freely overlap within rows/columns and their stacking order will be defined by the order of the gridpane's children list (0th node in back, last node in front).

GridPane may be styled with backgrounds and borders using CSS. See Region superclass for details.

Grid Constraints

A child's placement within the grid is defined by it's layout constraints:

ConstraintTypeDescription
columnIndexintegercolumn where child's layout area starts.
rowIndexintegerrow where child's layout area starts.
columnSpanintegerthe number of columns the child's layout area spans horizontally.
rowSpanintegerthe number of rows the child's layout area spans vertically.

If the row/column indices are not explicitly set, then the child will be placed in the first row/column. If row/column spans are not set, they will default to 1. A child's placement constraints can be changed dynamically and the gridpane will update accordingly.

The total number of rows/columns does not need to be specified up front as the gridpane will automatically expand/contract the grid to accommodate the content.

To use the GridPane, an application needs to set the layout constraints on the children and add those children to the gridpane instance. Constraints are set on the children using static setter methods on the GridPane class: 

     GridPane gridpane = new GridPane();

     // Set one constraint at a time...
     // Places the button at the first row and second column
     Button button = new Button();
     GridPane.setRowIndex(button, 0);
     GridPane.setColumnIndex(button, 1);

     // or convenience methods set more than one constraint at once...
     Label label = new Label();
     GridPane.setConstraints(label, 2, 0); // column=2 row=0

     // don't forget to add children to gridpane
     gridpane.getChildren().addAll(button, label);
Applications may also use convenience methods which combine the steps of setting the constraints and adding the children: 

     GridPane gridpane = new GridPane();
     gridpane.add(new Button(), 1, 0); // column=1 row=0
     gridpane.add(new Label(), 2, 0);  // column=2 row=0

Row/Column Sizing

By default, rows and columns will be sized to fit their content; a column will be wide enough to accommodate the widest child, a row tall enough to fit the tallest child.However, if an application needs to explicitly control the size of rows or columns, it may do so by adding RowConstraints and ColumnConstraints objects to specify those metrics. For example, to create a grid with two fixed-width columns: 

     GridPane gridpane = new GridPane();
     gridpane.getColumnConstraints().add(new ColumnConstraints(100)); // column 0 is 100 wide
     gridpane.getColumnConstraints().add(new ColumnConstraints(200)); // column 1 is 200 wide
By default the gridpane will resize rows/columns to their preferred sizes (either computed from content or fixed), even if the gridpane is resized larger than its preferred size. If an application needs a particular row or column to grow if there is extra space, it may set its grow priority on the RowConstraints or ColumnConstraints object. For example: 

     GridPane gridpane = new GridPane();
     ColumnConstraints column1 = new ColumnConstraints(100,100,Double.MAX_VALUE);
     column1.setHgrow(Priority.ALWAYS);
     ColumnConstraints column2 = new ColumnConstraints(100);
     gridpane.getColumnConstraints().addAll(column1, column2); // first column gets any extra width

Note: Nodes spanning multiple rows/columns will be also size to the preferred sizes. The affected rows/columns are resized by the following priority: grow priorities, last row. This is with respect to row/column constraints.

Percentage Sizing

Alternatively, RowConstraints and ColumnConstraints allow the size to be specified as a percentage of gridpane's available space: 

     GridPane gridpane = new GridPane();
     ColumnConstraints column1 = new ColumnConstraints();
     column1.setPercentWidth(50);
     ColumnConstraints column2 = new ColumnConstraints();
     column2.setPercentWidth(50);
     gridpane.getColumnConstraints().addAll(column1, column2); // each get 50% of width
If a percentage value is set on a row/column, then that value takes precedent and the row/column's min, pref, max, and grow constraints will be ignored.

Note that if the sum of the widthPercent (or heightPercent) values total greater than 100, the values will be treated as weights. e.g. if 3 columns are each given a widthPercent of 50, then each will be allocated 1/3 of the gridpane's available width (50/(50+50+50)).

Mixing Size Types

An application may freely mix the size-types of rows/columns (computed from content, fixed, or percentage). The percentage rows/columns will always be allocated space first based on their percentage of the gridpane's available space (size minus insets and gaps). The remaining space will be allocated to rows/columns given their minimum, preferred, and maximum sizes and grow priorities.

Resizable Range

A gridpane's parent will resize the gridpane within the gridpane's resizable range during layout. By default the gridpane computes this range based on its content and row/column constraints as outlined in the table below.

widthheight
minimum left/right insets plus the sum of each column's min width. top/bottom insets plus the sum of each row's min height.
preferred left/right insets plus the sum of each column's pref width. top/bottom insets plus the sum of each row's pref height.
maximum Double.MAX_VALUEDouble.MAX_VALUE

A gridpane's unbounded maximum width and height are an indication to the parent that it may be resized beyond its preferred size to fill whatever space is assigned to it.

GridPane provides properties for setting the size range directly. These properties default to the sentinel value USE_COMPUTED_SIZE, however the application may set them to other values as needed: 

     gridpane.setPrefSize(300, 300);
     // never size the gridpane larger than its preferred size:
     gridpane.setMaxSize(Region.USE_COMPUTED_SIZE, Region.USE_COMPUTED_SIZE);
Applications may restore the computed values by setting these properties back to USE_COMPUTED_SIZE.

GridPane does not clip its content by default, so it is possible that childrens' bounds may extend outside its own bounds if a child's min size prevents it from being fit within it space.

Optional Layout Constraints

An application may set additional constraints on children to customize how the child is sized and positioned within the layout area established by it's row/column indices/spans:

ConstraintTypeDescription
halignmentjavafx.geometry.HPosThe horizontal alignment of the child within its layout area.
valignmentjavafx.geometry.VPosThe vertical alignment of the child within its layout area.
hgrowjavafx.scene.layout.PriorityThe horizontal grow priority of the child.
vgrowjavafx.scene.layout.PriorityThe vertical grow priority of the child.
marginjavafx.geometry.InsetsMargin space around the outside of the child.

By default the alignment of a child within its layout area is defined by the alignment set for the row and column. If an individual alignment constraint is set on a child, that alignment will override the row/column alignment only for that child. Alignment of other children in the same row or column will not be affected.

Grow priorities, on the other hand, can only be applied to entire rows or columns. Therefore, if a grow priority constraint is set on a single child, it will be used to compute the default grow priority of the encompassing row/column. If a grow priority is set directly on a RowConstraint or ColumnConstraint object, it will override the value computed from content.

Since:
JavaFX 2.0

  • Property Details

  • Field Details

    • REMAINING

      public static final int REMAINING
      Sentinel value which may be set on a child's row/column span constraint to indicate that it should span the remaining rows/columns.
      See Also:

  • Constructor Details

    • GridPane

      public GridPane()
      Creates a GridPane layout with hgap/vgap = 0 and TOP_LEFT alignment.

    • GridPane

      public GridPane(double hgap, double vgap)
      Creates a GridPane layout with the given hgap and vgap.
      Parameters:
      hgap - the size of the horizontal gaps between columns
      vgap - the size of the vertical gaps between rows
      Since:
      21

  • Method Details

    • setRowIndex

      public static void setRowIndex(Node child, Integer value)
      Sets the row index for the child when contained by a gridpane so that it will be positioned starting in that row of the gridpane. If a gridpane child has no row index set, it will be positioned in the first row. Setting the value to null will remove the constraint.
      Parameters:
      child - the child node of a gridpane
      value - the row index of the child

    • getRowIndex

      public static Integer getRowIndex(Node child)
      Returns the child's row index constraint if set.
      Parameters:
      child - the child node of a gridpane
      Returns:
      the row index for the child or null if no row index was set

    • setColumnIndex

      public static void setColumnIndex(Node child, Integer value)
      Sets the column index for the child when contained by a gridpane so that it will be positioned starting in that column of the gridpane. If a gridpane child has no column index set, it will be positioned in the first column. Setting the value to null will remove the constraint.
      Parameters:
      child - the child node of a gridpane
      value - the column index of the child

    • getColumnIndex

      public static Integer getColumnIndex(Node child)
      Returns the child's column index constraint if set.
      Parameters:
      child - the child node of a gridpane
      Returns:
      the column index for the child or null if no column index was set

    • setRowSpan

      public static void setRowSpan(Node child, Integer value)
      Sets the row span for the child when contained by a gridpane so that it will span that number of rows vertically. This may be set to REMAINING, which will cause the span to extend across all the remaining rows.

      If a gridpane child has no row span set, it will default to spanning one row. Setting the value to null will remove the constraint.

      Parameters:
      child - the child node of a gridpane
      value - the row span of the child

    • getRowSpan

      public static Integer getRowSpan(Node child)
      Returns the child's row-span constraint if set.
      Parameters:
      child - the child node of a gridpane
      Returns:
      the row span for the child or null if no row span was set

    • setColumnSpan

      public static void setColumnSpan(Node child, Integer value)
      Sets the column span for the child when contained by a gridpane so that it will span that number of columns horizontally. This may be set to REMAINING, which will cause the span to extend across all the remaining columns.

      If a gridpane child has no column span set, it will default to spanning one column. Setting the value to null will remove the constraint.

      Parameters:
      child - the child node of a gridpane
      value - the column span of the child

    • getColumnSpan

      public static Integer getColumnSpan(Node child)
      Returns the child's column-span constraint if set.
      Parameters:
      child - the child node of a gridpane
      Returns:
      the column span for the child or null if no column span was set

    • setMargin

      public static void setMargin(Node child, Insets value)
      Sets the margin for the child when contained by a gridpane. If set, the gridpane will lay it out with the margin space around it. Setting the value to null will remove the constraint.
      Parameters:
      child - the child node of a gridpane
      value - the margin of space around the child

    • getMargin

      public static Insets getMargin(Node child)
      Returns the child's margin constraint if set.
      Parameters:
      child - the child node of a gridpane
      Returns:
      the margin for the child or null if no margin was set

    • setHalignment

      public static void setHalignment(Node child, HPos value)
      Sets the horizontal alignment for the child when contained by a gridpane. If set, will override the gridpane's default horizontal alignment. Setting the value to null will remove the constraint.
      Parameters:
      child - the child node of a gridpane
      value - the hozizontal alignment for the child

    • getHalignment

      public static HPos getHalignment(Node child)
      Returns the child's halignment constraint if set.
      Parameters:
      child - the child node of a gridpane
      Returns:
      the horizontal alignment for the child or null if no alignment was set

    • setValignment

      public static void setValignment(Node child, VPos value)
      Sets the vertical alignment for the child when contained by a gridpane. If set, will override the gridpane's default vertical alignment. Setting the value to null will remove the constraint.
      Parameters:
      child - the child node of a gridpane
      value - the vertical alignment for the child

    • getValignment

      public static VPos getValignment(Node child)
      Returns the child's valignment constraint if set.
      Parameters:
      child - the child node of a gridpane
      Returns:
      the vertical alignment for the child or null if no alignment was set

    • setHgrow

      public static void setHgrow(Node child, Priority value)
      Sets the horizontal grow priority for the child when contained by a gridpane. If set, the gridpane will use the priority to allocate the child additional horizontal space if the gridpane is resized larger than it's preferred width. Setting the value to null will remove the constraint.
      Parameters:
      child - the child of a gridpane
      value - the horizontal grow priority for the child

    • getHgrow

      public static Priority getHgrow(Node child)
      Returns the child's hgrow constraint if set.
      Parameters:
      child - the child node of a gridpane
      Returns:
      the horizontal grow priority for the child or null if no priority was set

    • setVgrow

      public static void setVgrow(Node child, Priority value)
      Sets the vertical grow priority for the child when contained by a gridpane. If set, the gridpane will use the priority to allocate the child additional vertical space if the gridpane is resized larger than it's preferred height. Setting the value to null will remove the constraint.
      Parameters:
      child - the child of a gridpane
      value - the vertical grow priority for the child

    • getVgrow

      public static Priority getVgrow(Node child)
      Returns the child's vgrow constraint if set.
      Parameters:
      child - the child node of a gridpane
      Returns:
      the vertical grow priority for the child or null if no priority was set

    • setFillWidth

      public static void setFillWidth(Node child, Boolean value)
      Sets the horizontal fill policy for the child when contained by a gridpane. If set, the gridpane will use the policy to determine whether node should be expanded to fill the column or resized to its preferred width. Setting the value to null will remove the constraint. If not value is specified for the node nor for the column, the default value is true.
      Parameters:
      child - the child node of a gridpane
      value - the horizontal fill policy or null for unset
      Since:
      JavaFX 8.0

    • isFillWidth

      public static Boolean isFillWidth(Node child)
      Returns the child's horizontal fill policy if set
      Parameters:
      child - the child node of a gridpane
      Returns:
      the horizontal fill policy for the child or null if no policy was set
      Since:
      JavaFX 8.0

    • setFillHeight

      public static void setFillHeight(Node child, Boolean value)
      Sets the vertical fill policy for the child when contained by a gridpane. If set, the gridpane will use the policy to determine whether node should be expanded to fill the row or resized to its preferred height. Setting the value to null will remove the constraint. If not value is specified for the node nor for the row, the default value is true.
      Parameters:
      child - the child node of a gridpane
      value - the vertical fill policy or null for unset
      Since:
      JavaFX 8.0

    • isFillHeight

      public static Boolean isFillHeight(Node child)
      Returns the child's vertical fill policy if set
      Parameters:
      child - the child node of a gridpane
      Returns:
      the vertical fill policy for the child or null if no policy was set
      Since:
      JavaFX 8.0

    • setConstraints

      public static void setConstraints(Node child, int columnIndex, int rowIndex)
      Sets the column,row indeces for the child when contained in a gridpane.
      Parameters:
      child - the child node of a gridpane
      columnIndex - the column index position for the child
      rowIndex - the row index position for the child

    • setConstraints

      public static void setConstraints(Node child, int columnIndex, int rowIndex, int columnspan, int rowspan)
      Sets the column, row, column-span, and row-span value for the child when contained in a gridpane.
      Parameters:
      child - the child node of a gridpane
      columnIndex - the column index position for the child
      rowIndex - the row index position for the child
      columnspan - the number of columns the child should span
      rowspan - the number of rows the child should span

    • setConstraints

      public static void setConstraints(Node child, int columnIndex, int rowIndex, int columnspan, int rowspan, HPos halignment, VPos valignment)
      Sets the grid position, spans, and alignment for the child when contained in a gridpane.
      Parameters:
      child - the child node of a gridpane
      columnIndex - the column index position for the child
      rowIndex - the row index position for the child
      columnspan - the number of columns the child should span
      rowspan - the number of rows the child should span
      halignment - the horizontal alignment of the child
      valignment - the vertical alignment of the child

    • setConstraints

      public static void setConstraints(Node child, int columnIndex, int rowIndex, int columnspan, int rowspan, HPos halignment, VPos valignment, Priority hgrow, Priority vgrow)
      Sets the grid position, spans, and alignment for the child when contained in a gridpane.
      Parameters:
      child - the child node of a gridpane
      columnIndex - the column index position for the child
      rowIndex - the row index position for the child
      columnspan - the number of columns the child should span
      rowspan - the number of rows the child should span
      halignment - the horizontal alignment of the child
      valignment - the vertical alignment of the child
      hgrow - the horizontal grow priority of the child
      vgrow - the vertical grow priority of the child

    • setConstraints

      public static void setConstraints(Node child, int columnIndex, int rowIndex, int columnspan, int rowspan, HPos halignment, VPos valignment, Priority hgrow, Priority vgrow, Insets margin)
      Sets the grid position, spans, alignment, grow priorities, and margin for the child when contained in a gridpane.
      Parameters:
      child - the child node of a gridpane
      columnIndex - the column index position for the child
      rowIndex - the row index position for the child
      columnspan - the number of columns the child should span
      rowspan - the number of rows the child should span
      halignment - the horizontal alignment of the child
      valignment - the vertical alignment of the child
      hgrow - the horizontal grow priority of the child
      vgrow - the vertical grow priority of the child
      margin - the margin of space around the child

    • clearConstraints

      public static void clearConstraints(Node child)
      Removes all gridpane constraints from the child node.
      Parameters:
      child - the child node

    • hgapProperty

      public final DoubleProperty hgapProperty()
      The width of the horizontal gaps between columns.
      Returns:
      the hgap property
      See Also:

    • setHgap

      public final void setHgap(double value)
      Sets the value of the hgap property.
      Property description:
      The width of the horizontal gaps between columns.
      Parameters:
      value - the value for the hgap property
      See Also:

    • getHgap

      public final double getHgap()
      Gets the value of the hgap property.
      Property description:
      The width of the horizontal gaps between columns.
      Returns:
      the value of the hgap property
      See Also:

    • vgapProperty

      public final DoubleProperty vgapProperty()
      The height of the vertical gaps between rows.
      Returns:
      the vgap property
      See Also:

    • setVgap

      public final void setVgap(double value)
      Sets the value of the vgap property.
      Property description:
      The height of the vertical gaps between rows.
      Parameters:
      value - the value for the vgap property
      See Also:

    • getVgap

      public final double getVgap()
      Gets the value of the vgap property.
      Property description:
      The height of the vertical gaps between rows.
      Returns:
      the value of the vgap property
      See Also:

    • alignmentProperty

      public final ObjectProperty<Pos> alignmentProperty()
      The alignment of of the grid within the gridpane's width and height.
      Returns:
      the alignment property
      See Also:

    • setAlignment

      public final void setAlignment(Pos value)
      Sets the value of the alignment property.
      Property description:
      The alignment of of the grid within the gridpane's width and height.
      Parameters:
      value - the value for the alignment property
      See Also:

    • getAlignment

      public final Pos getAlignment()
      Gets the value of the alignment property.
      Property description:
      The alignment of of the grid within the gridpane's width and height.
      Returns:
      the value of the alignment property
      See Also:

    • gridLinesVisibleProperty

      public final Property<Boolean> gridLinesVisibleProperty()
      For debug purposes only: controls whether lines are displayed to show the gridpane's rows and columns. Default is false.
      Returns:
      the gridLinesVisible property
      See Also:

    • setGridLinesVisible

      public final void setGridLinesVisible(boolean value)
      Sets the value of the gridLinesVisible property.
      Property description:
      For debug purposes only: controls whether lines are displayed to show the gridpane's rows and columns. Default is false.
      Parameters:
      value - the value for the gridLinesVisible property
      See Also:

    • isGridLinesVisible

      public final boolean isGridLinesVisible()

    • getRowConstraints

      public final ObservableList<RowConstraints> getRowConstraints()
      Returns list of row constraints. Row constraints can be added to explicitly control individual row sizing and layout behavior. If not set, row sizing and layout behavior is computed based on content. Index in the ObservableList denotes the row number, so the row constraint for the first row is at the position of 0.

    • getColumnConstraints

      public final ObservableList<ColumnConstraints> getColumnConstraints()
      Returns list of column constraints. Column constraints can be added to explicitly control individual column sizing and layout behavior. If not set, column sizing and layout behavior is computed based on content. Index in the ObservableList denotes the column number, so the column constraint for the first column is at the position of 0.

    • add

      public void add(Node child, int columnIndex, int rowIndex)
      Adds a child to the gridpane at the specified column,row position. This convenience method will set the gridpane column and row constraints on the child.
      Parameters:
      child - the node being added to the gridpane
      columnIndex - the column index position for the child within the gridpane, counting from 0
      rowIndex - the row index position for the child within the gridpane, counting from 0

    • add

      public void add(Node child, int columnIndex, int rowIndex, int colspan, int rowspan)
      Adds a child to the gridpane at the specified column,row position and spans. This convenience method will set the gridpane column, row, and span constraints on the child.
      Parameters:
      child - the node being added to the gridpane
      columnIndex - the column index position for the child within the gridpane, counting from 0
      rowIndex - the row index position for the child within the gridpane, counting from 0
      colspan - the number of columns the child's layout area should span
      rowspan - the number of rows the child's layout area should span

    • addRow

      public void addRow(int rowIndex, Node... children)
      Convenience method for placing the specified nodes sequentially in a given row of the gridpane. If the row already contains nodes the specified nodes will be appended to the row. For example, the first node will be positioned at [column,row], the second at [column+1,row], etc. This method will set the appropriate gridpane row/column constraints on the nodes as well as add the nodes to the gridpane's children sequence.
      Parameters:
      rowIndex - the row index position for the children within the gridpane
      children - the nodes to be added as a row in the gridpane

    • addColumn

      public void addColumn(int columnIndex, Node... children)
      Convenience method for placing the specified nodes sequentially in a given column of the gridpane. If the column already contains nodes the specified nodes will be appended to the column. For example, the first node will be positioned at [column, row], the second at [column, row+1], etc. This method will set the appropriate gridpane row/column constraints on the nodes as well as add the nodes to the gridpane's children sequence.
      Parameters:
      columnIndex - the column index position for the children within the gridpane
      children - the nodes to be added as a column in the gridpane

    • computeMinWidth

      protected double computeMinWidth(double height)
      Description copied from class: Region
      Computes the minimum width of this region. Returns the sum of the left and right insets by default. region subclasses should override this method to return an appropriate value based on their content and layout strategy. If the subclass doesn't have a VERTICAL content bias, then the height parameter can be ignored.
      Overrides:
      computeMinWidth in class Region
      Parameters:
      height - the height that should be used if min width depends on it
      Returns:
      the computed minimum width of this region

    • computeMinHeight

      protected double computeMinHeight(double width)
      Description copied from class: Region
      Computes the minimum height of this region. Returns the sum of the top and bottom insets by default. Region subclasses should override this method to return an appropriate value based on their content and layout strategy. If the subclass doesn't have a HORIZONTAL content bias, then the width parameter can be ignored.
      Overrides:
      computeMinHeight in class Region
      Parameters:
      width - the width that should be used if min height depends on it
      Returns:
      the computed minimum height for this region

    • computePrefWidth

      protected double computePrefWidth(double height)
      Description copied from class: Region
      Computes the preferred width of this region for the given height. Region subclasses should override this method to return an appropriate value based on their content and layout strategy. If the subclass doesn't have a VERTICAL content bias, then the height parameter can be ignored.
      Overrides:
      computePrefWidth in class Region
      Parameters:
      height - the height that should be used if preferred width depends on it
      Returns:
      the computed preferred width for this region

    • computePrefHeight

      protected double computePrefHeight(double width)
      Description copied from class: Region
      Computes the preferred height of this region for the given width; Region subclasses should override this method to return an appropriate value based on their content and layout strategy. If the subclass doesn't have a HORIZONTAL content bias, then the width parameter can be ignored.
      Overrides:
      computePrefHeight in class Region
      Parameters:
      width - the width that should be used if preferred height depends on it
      Returns:
      the computed preferred height for this region

    • getContentBias

      public Orientation getContentBias()
      Returns:
      null unless one of its children has a content bias.

    • requestLayout

      public void requestLayout()
      Description copied from class: Parent
      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.

      Overrides:
      requestLayout in class Parent

    • layoutChildren

      protected void layoutChildren()
      Description copied from class: Parent
      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.

      Overrides:
      layoutChildren in class Parent

    • toString

      public String toString()
      Returns a string representation of this GridPane object.
      Overrides:
      toString in class Object
      Returns:
      a string representation of this GridPane object.

    • getRowCount

      public final int getRowCount()
      Returns the number of rows in this GridPane.
      Returns:
      the row count
      Since:
      9

    • getColumnCount

      public final int getColumnCount()
      Returns the number of columns in this GridPane.
      Returns:
      the column count
      Since:
      9