Java Reference
In-Depth Information
The initial stage is created by the JavaFX runtime, and passed to you via the
start()
method, as described in the
previous paragraph. The
Stage
class has a set of properties and methods. Some of these properties and methods, as
shown in the following code snippet from the listing, are as follows.
•
A scene that contains the graphical nodes in the UI
•
A title that appears in the title bar of the window (when deployed on the desktop)
Stage
•
The visibility of the
stage.setScene(scene);
stage.setTitle("Hello Earthrise");
stage.show();
A
Scene
is the top container in the JavaFX scene graph. A
Scene
holds the graphical elements that are displayed
on the
Stage
. Every element in a
Scene
is a graphical node, which is any class that extends
javafx.scene.Node
. The
scene graph is a hierarchical representation of the
Scene
. Elements in the scene graph may contain child elements,
and all of them are instances of the
Node
class.
The
Scene
class contains a number of properties, such as its width and height. A
Scene
also has a property named
root
that holds the graphical elements that are displayed in the
Scene
, in this case a
Group
instance that contains an
ImageView
instance (which displays an image) and a
Group
instance. Nested within the latter
Group
is a
Text
instance
(which is a graphical element, usually called a graphical node, or simply node).
Notice that the
root
property of the
Scene
contains an instance of the
Group
class. The
root
property may
contain an instance of any subclass of
javafx.scene.Node
, and typically contains one capable of holding its own set
of
Node
instances. Take a look at the JavaFX API documentation that we showed you how to access in the “Use the
Official Specifications” section earlier and check out the
Node
class to see the properties and methods available to any
graphical node. Also, take a look at the
ImageView
class in the
javafx.scene.image
package and the
Group
class in the
javafx.scene
package. In both cases, they inherit from the
Node
class.
■
We can't emphasize enough the importance of having the JavaFX api documentation handy while reading this
book. as classes, variables, and functions are mentioned, it's a good idea to look at the documentation to get more
information. in addition, this habit helps you become more familiar with what is available to you in the api.
Tip
Displaying Images
As shown in the following code, displaying an image entails using an
ImageView
instance in conjunction with an
Image
instance.
Image image = new Image ("
http://projavafx.com/images/earthrise.jpg
"
);
ImageView imageView = new ImageView(image);
The
Image
instance identifies the image resource and loads it from the URL assigned to its URL variable. Both of
these classes are located in the
javafx.scene.image
package.
Displaying Text
In the example, we created a Text Node as follows:
Text textRef = new Text(message);
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