Java
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JavaFX
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/
Change Listener
➟
➟
Last update: 17-11-2021
Change Listener
p 344 Some JavaFX controls can generate events (like Slider's value).
Scene Builder Controls:
- 4 Labels (Amount, 15%, Tip, Total)
- 4 TextFields
- 1 Slider
- 1 Button
Inspector: fx:id
- amountTextField
- tipPercentageLabel
- tipPercentageSlider
- tipTextField
- totalTextField
ControllerClass ... com.minte9.javafx.change_listener.CalculateApp
Add Listener
p 535 App class with button action method and slider listener.
/**
* CalculateApp class ...
*
* Set button action and slider listener.
* FXMLLoader calls initialize() to intialize the Controller.
*/
package com.minte9.javafx.change_listener;
import java.math.BigDecimal;
import java.math.RoundingMode;
import java.text.NumberFormat;
import javafx.fxml.FXML;
import javafx.scene.control.Label;
import javafx.scene.control.Slider;
import javafx.scene.control.TextField;
public class CalculateApp {
private NumberFormat CURRENCY = NumberFormat.getCurrencyInstance();
private NumberFormat PERCENT = NumberFormat.getPercentInstance();
private BigDecimal tipPercentage = new BigDecimal(0.15);
@FXML private TextField amountTextField;
@FXML private Label tipPercentageLabel;
@FXML private Slider tipPercentageSlider;
@FXML private TextField tipTextField;
@FXML private TextField totalTextField;
public static void main(String[] args) {
CalculateGui.main(args);
}
@FXML void calculateButtonPressed() {
try {
BigDecimal amount = new BigDecimal(amountTextField.getText());
BigDecimal tip = amount.multiply(tipPercentage);
BigDecimal total = amount.add(tip);
tipTextField.setText(CURRENCY.format(tip));
totalTextField.setText(CURRENCY.format(total));
} catch (NumberFormatException ex) {
amountTextField.setText("Enter amount");
amountTextField.selectAll();
amountTextField.requestFocus();
}
}
@FXML void initialize() {
CURRENCY.setRoundingMode(RoundingMode.HALF_UP);
tipPercentageSlider.valueProperty().addListener( // Look Here
(o, v, newValue) -> {
tipPercentage = BigDecimal.valueOf(
newValue.intValue() / 100.0
);
tipPercentageLabel.setText(PERCENT.format(tipPercentage));
}
);
}
}
Load fxml
Gui class loads tipcalculator.fxml file.
/**
* CalculateGui launcher which loads the fxml file
*/
package com.minte9.javafx.change_listener;
import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.stage.Stage;
public class CalculateGui extends Application {
public static void main(String[] args) {
launch(args);
}
@Override public void start(Stage stage) throws Exception {
Parent root =
FXMLLoader.load(getClass().getResource("tipcalculator.fxml"));
stage.setTitle("Button Event FXML");
stage.setScene(new Scene(root));
stage.show();
}
}
Fxml file
Fxml file generated by Scene Builder.
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.geometry.Insets?>
<?import javafx.scene.control.Button?>
<?import javafx.scene.control.Label?>
<?import javafx.scene.control.Slider?>
<?import javafx.scene.control.TextField?>
<?import javafx.scene.layout.ColumnConstraints?>
<?import javafx.scene.layout.GridPane?>
<?import javafx.scene.layout.RowConstraints?>
<?import javafx.scene.text.Font?>
<GridPane maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="200.0" prefWidth="300.0" xmlns="http://javafx.com/javafx/17" xmlns:fx="http://javafx.com/fxml/1" fx:controller="com.minte9.javafx.change_listener.CalculateApp">
<columnConstraints>
<ColumnConstraints hgrow="SOMETIMES" maxWidth="294.0" minWidth="10.0" prefWidth="78.0" />
<ColumnConstraints hgrow="SOMETIMES" maxWidth="421.0" minWidth="10.0" prefWidth="202.0" />
</columnConstraints>
<rowConstraints>
<RowConstraints minHeight="10.0" prefHeight="30.0" vgrow="SOMETIMES" />
<RowConstraints minHeight="10.0" prefHeight="30.0" vgrow="SOMETIMES" />
<RowConstraints minHeight="10.0" prefHeight="30.0" vgrow="SOMETIMES" />
<RowConstraints minHeight="10.0" prefHeight="30.0" vgrow="SOMETIMES" />
<RowConstraints minHeight="10.0" prefHeight="30.0" vgrow="SOMETIMES" />
</rowConstraints>
<children>
<Label text="Amout" GridPane.halignment="RIGHT" GridPane.valignment="CENTER">
<font>
<Font size="15.0" />
</font>
<GridPane.margin>
<Insets right="10.0" />
</GridPane.margin>
</Label>
<TextField fx:id="amountTextField" minWidth="-Infinity" GridPane.columnIndex="1">
<GridPane.margin>
<Insets right="20.0" />
</GridPane.margin>
</TextField>
<TextField fx:id="tipTextField" editable="false" focusTraversable="false" GridPane.columnIndex="1" GridPane.rowIndex="2">
<GridPane.margin>
<Insets right="20.0" />
</GridPane.margin>
</TextField>
<TextField fx:id="totalTextField" editable="false" focusTraversable="false" GridPane.columnIndex="1" GridPane.rowIndex="3">
<GridPane.margin>
<Insets right="20.0" />
</GridPane.margin>
</TextField>
<Slider fx:id="tipPercentageSlider" blockIncrement="5.0" max="30.0" min="15.0" GridPane.columnIndex="1" GridPane.rowIndex="1">
<GridPane.margin>
<Insets right="20.0" />
</GridPane.margin>
</Slider>
<Button mnemonicParsing="false" onAction="#calculateButtonPressed" prefHeight="29.0" prefWidth="184.0" text="Calculate" GridPane.columnIndex="1" GridPane.rowIndex="4">
<font>
<Font size="15.0" />
</font>
</Button>
<Label fx:id="tipPercentageLabel" text="15%" GridPane.halignment="RIGHT" GridPane.rowIndex="1">
<GridPane.margin>
<Insets right="10.0" />
</GridPane.margin>
</Label>
<Label text="Tip" GridPane.halignment="RIGHT" GridPane.rowIndex="2">
<GridPane.margin>
<Insets right="10.0" />
</GridPane.margin>
</Label>
<Label text="Total" GridPane.halignment="RIGHT" GridPane.rowIndex="3">
<GridPane.margin>
<Insets right="10.0" />
</GridPane.margin>
</Label>
</children>
<padding>
<Insets bottom="10.0" left="10.0" right="10.0" top="10.0" />
</padding>
</GridPane>
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