JAVAFX BASICS - Introduction to Java Programming: Comprehensive Version - page 554

(a) (b)

F IGURE 14.16

The nodes fill in the rows in the FlowPane one after another.

The program creates a FlowPane (line 13) and sets its padding property with an Insets
object (line 14). An Insets object specifies the size of the border of a pane. The constructor
Insets(11, 12, 13, 14) creates an Insets with the border sizes for top (11), right (12),
bottom (13), and left (14) in pixels, as shown in Figure 14.17. You can also use the constructor
Insets(value) to create an Insets with the same value for all four sides. The hGap and
vGap properties are in lines 15-16 to specify the horizontal gap and vertical gap between two
nodes in the pane, as shown in Figure 14.17.

hGap Top side

Pane

vGap

Right side

Left side

Bottom side

F IGURE 14.17

You can specify hGap and vGap between the nodes in a FlowLPane .

Each FlowPane contains an object of ObservableList for holding the nodes. This list
can be obtained using the getChildren() method (line 19). To add a node into a FlowPane
is to add it to this list using the add(node) or addAll(node1, node2, ...) method.
You can also remove a node from the list using the remove(node) method or use the
removeAll() method to remove all nodes from the pane. The program adds the labels and
text fields into the pane (lines 19-24). Invoking tfMi.setPrefColumnCount(1) sets the
preferred column count to 1 for the MI text field (line 22). The program declares an explicit
reference tfMi for a TextField object for MI. The explicit reference is necessary, because
we need to reference the object directly to set its prefColumnCount property.
The program adds the pane to the scene (line 27), sets the scene in the stage (line 29),
and displays the stage (line 30). Note that if you resize the window, the nodes are auto-
matically rearranged to fit in the pane. In Figure 14.16a, the first row has three nodes, but in
Figure 14.16b, the first row has four nodes, because the width has been increased.
Suppose you wish to add the object tfMi to a pane ten times; will ten text fields appear in
the pane? No, a node such as a text field can be added to only one pane and once. Adding a
node to a pane multiple times or to different panes will cause a runtime error.

Note
A node can be placed only in one pane. Therefore, the relationship between a
pane and a node is the composition denoted by a filled diamond, as shown in
Figure 14.3b.