Oracle Magazine - November/December 2010

tion to handle the width and height values for the fan-shaped layout:

else { // arrangementStyle == FAN_
ARRANGEMENT
preferredWidth = Math.sqrt(
Math.pow(lastNodeWidth, 2) +
Math.pow(lastNodeHeight, 2)) 2;
preferredHeight = preferredWidth;

}

And be sure to also change the ELSE for the arrangementStyle == HORIZONTAL_ ARRANGEMENT statement to an ELSE IF for proper syntax.

Step 2: Override the doLayout() function.

The doLayout() function contains the rules for how nodes should be laid out. For the example projects, the overridden doLayout() function iterates over the managed nodes and affects their sizes and positions.

override function doLayout():Void { if (preferredDirty) { }

When the JavaFX runtime calls the doLayout() function, it first determines if the arrangement of a layout manager’s nodes should be re-evaluated by checking the value of the preferredDirty variable. When preferredDirty is set to true, doLayout() calls the calcPreferredSize() helper function to calculate the width and the height based on the arrangement style, size, and number of cards to be arranged, as well as the offset value.

The calcPreferredSize() function returns these values for the card stack in question and then resets the preferredDirty variable to false, so that when the processing control returns back to the calling function (in this case, doLayout()), the returned values will be handled by the appropriate IF statement in the function. In other words, the playing card will be positioned properly within its designated arrangement (horizontal, vertical, or fan-shaped).

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if (arrangementStyle == VERTICAL_
ARRANGEMENT) {
for (node in getManaged(content)) {
layoutNode(node, 0,
indexof node verticalOffset,
getNodePrefWidth(node),
getNodePrefHeight(node));

}
}
else if (arrangementStyle ==
HORIZONTAL_ARRANGEMENT) {
for (node in getManaged(content)) {
layoutNode(node,
indexof node horizontalOffset,
0,
getNodePrefWidth(node),
}
else if (arrangementStyle ==
FAN_ARRANGEMENT) {
def startAngle = (sizeof
getManaged(content)) -0.5 fanAngle;
for (node in getManaged(content)) {
def rot = Rotate.rotate(
startAngle + (indexof node
fanAngle), 0,
node.layoutBounds.height);
delete node.transforms;
insert rot into node.transforms;
var ph = getNodePrefHeight(node);
var pw = getNodePrefWidth(node);
layoutNode(node, ph, pw, pw, pw);
}
}
}

getNodePrefHeight(node)); }

Within the overridden doLayout() func-
tion are several convenience functions (from
Container) for managing nodes:
documentation ( download.oracle.com/
docs/cd/E17802_01/javafx/javafx/1.3/
docs/api) for complete details.
getNodePref Width() •;—determines the pre-
ferred width of a node.
getNodePrefHeight() •;—determines the pre-
ferred height of a node.

CONCLUSION

JavaFX includes several built-in layout managers, but occasionally they don’t meet the requirements of an application. When this happens, consider creating your own, following the steps detailed in this article. 

James L. Weaver has been a developer for more than 25 years. Since 2000 he has specialized in Java, object-oriented, and Web-based technologies. He is the author of Pro JavaFX Platform: Script, Desktop and Mobile RIA with Java Technology (Apress, 2009) and JavaFX Script: Dynamic Java Scripting for Rich Internet/Client-Side Applications (Apress, 2007).