Java Reference
In-Depth Information
Creating the
Scene
To display the GUI, you must attach it to a
Scene
, then attach the
Scene
to the
Stage
that's
passed into method
start
. Line 17 creates a
Scene
, passing
root
(the scene graph's root
node) as an argument to the constructor. By default, the
Scene
's size is determined by the
size of the scene graph's root node. Overloaded versions of the
Scene
constructor allow you
to specify the
Scene
's size and fill (a color, gradient or image), which appears in the
Scene
's
background. Line 18 uses
Scene
method
setTitle
to specify the text that appears in the
Stage
window's title bar. Line 19 places
Stage
method
setScene
to place the
Scene
onto
the
Stage
. Finally, line 20 calls
Stage
method
show
to display the
Stage
window.
Figures 25.18-25.21 present the
TipCalculatorController
class that responds to user
interactions with the app's
Button
and
Slider
. Replace the code that NetBeans generated
in
TipCalculatorController.java
with the code in Figs. 25.18-25.21.
Class
TipCalculatorController
's
import
Statements
Figure 25.18 shows class
TipCalculatorController
's
import
statements.
1
// TipCalculatorController.jav
2
// Controller that handles calculateButton and tipPercentageSlider events
3
import
java.math.BigDecimal;
4
import
java.math.RoundingMode;
5
import
java.text.NumberFormat;
6
import
javafx.beans.value.ChangeListener;
7
import
javafx.beans.value.ObservableValue;
8
import
javafx.event.ActionEvent;
9
import
javafx.fxml.FXML;
10
import
javafx.scene.control.Label;
11
import
javafx.scene.control.Slider;
12
import
javafx.scene.control.TextField;
13
Fig. 25.18
|
TipCalculatorController
's
import
declarations.
Lines 3-12
import
the classes and interfaces used by class
TipCalculatorController
:
•Cl ss
BigDecimal
of package
java.math
(line 3) is used to perform precise mon-
etary calculations. The
RoundingMode
enum
of package
java.math
(line 4) is used
to specify how
BigDecimal
values are rounded during calculations or when for-
matting floating-point numbers as
String
s.
•Cl ss
NumberFormat
of package
java.text
(line 5) provides numeric formatting
capabilities, such as locale-specific currency and percentage formats. For example,
in the U.S. locale, the monetary value 34.56 is formatted as $34.95 and the per-
centage 15 is formatted as 15%. Class
NumberFormat
determines the locale of the
system on which your app runs, then formats currency amounts and percentages
accordingly.
•
You implement interface
ChangeListener
of package
javafx.beans.value
(line
6) to respond to the user moving the
Slider
's thumb. This interface's
changed
