13.6 (Tip Calculator Modification) The Tip Calculator app from Section 12.5 does

Q: 13.6 (Tip Calculator Modification) The Tip Calculator app from Section 12.5 does

Please see code as below Reimplemented this app to use property listeners to perform the calculations whenever the user modifies the bill amount amountTextField.valueProperty().addListener( new ChangeListener() { @Override public void changed(ObservableValue

ID: 3710382 • Letter: 1

Question

13.6 (Tip Calculator Modification) The Tip Calculator app from Section 12.5 does not need a Button to perform its calculations. Reimplement this app to use property listeners to perform the calculations whenever the user modifies the bill amount or changes the custom tip percentage. Also use a property binding to update the Label that displays the tip percentage.

Starting code:

// Fig. 12.19: TipCalculator.java
// Main application class that loads and displays the Tip Calculator's GUI.
import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.stage.Stage;

public class TipCalculator extends Application {
@Override
public void start(Stage stage) throws Exception {
Parent root =
FXMLLoader.load(getClass().getResource("TipCalculator.fxml"));

Scene scene = new Scene(root); // attach scene graph to scene
stage.setTitle("Tip Calculator"); // displayed in window's title bar
stage.setScene(scene); // attach scene to stage
stage.show(); // display the stage
}

public static void main(String[] args) {
// create a TipCalculator object and call its start method
launch(args);
}
}

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////

// TipCalculatorController.java
// Controller that handles calculateButton and tipPercentageSlider events
import java.math.BigDecimal;
import java.math.RoundingMode;
import java.text.NumberFormat;
import javafx.beans.value.ChangeListener;
import javafx.beans.value.ObservableValue;
import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.scene.control.Label;
import javafx.scene.control.Slider;
import javafx.scene.control.TextField;

public class TipCalculatorController {
// formatters for currency and percentages
private static final NumberFormat currency =
NumberFormat.getCurrencyInstance();
private static final NumberFormat percent =
NumberFormat.getPercentInstance();

private BigDecimal tipPercentage = new BigDecimal(0.15); // 15% default

// GUI controls defined in FXML and used by the controller's code
@FXML
private TextField amountTextField;

@FXML
private Label tipPercentageLabel;

@FXML
private Slider tipPercentageSlider;

@FXML
private TextField tipTextField;

@FXML
private TextField totalTextField;

// calculates and displays the tip and total amounts
@FXML
private void calculateButtonPressed(ActionEvent event) {
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();
}
}

// called by FXMLLoader to initialize the controller
public void initialize() {
// 0-4 rounds down, 5-9 rounds up
currency.setRoundingMode(RoundingMode.HALF_UP);

// listener for changes to tipPercentageSlider's value
tipPercentageSlider.valueProperty().addListener(
new ChangeListener<Number>() {
@Override
public void changed(ObservableValue<? extends Number> ov,
Number oldValue, Number newValue) {
tipPercentage =
BigDecimal.valueOf(newValue.intValue() / 100.0);
tipPercentageLabel.setText(percent.format(tipPercentage));
}
}
);
}
}

////

<?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?>

Explanation / Answer

Please see code as below

Reimplemented this app to use property listeners to perform the calculations whenever the user modifies the bill amount

amountTextField.valueProperty().addListener(
new ChangeListener<Number>() {
@Override
public void changed(ObservableValue<? extends Number> ov,
Number oldValue, Number newValue) {
amountField= BigDecimal.valueOf(newValue.intValue());

try {
BigDecimal amount = new BigDecimal(amountField);
BigDecimal tip = amount.multiply(tipPercentage);
BigDecimal total = amount.add(tip);

}
}
);

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13.6 (Tip Calculator Modification) The Tip Calculator app from Section 12.5 does

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13.6 (Tip Calculator Modification) The Tip Calculator app from Section 12.5 does

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