inputverificationdemo.java

java tutorial.sun公司官方出品。java入门书籍。最新版

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package misc;

import java.util.Set;
import java.util.HashSet;

import java.awt.*;
import java.awt.event.*;

import javax.swing.*;
import javax.swing.event.*;
import javax.swing.text.*;

import java.beans.PropertyChangeListener;
import java.beans.PropertyChangeEvent;

import java.text.*;

/**
 * InputVerificationDemo.java requires no other files.
 *
 * Yet another mortgage calculator.
 * However, instead of using a formatted text field,
 * as shown in FormattedTextFieldDemo, this example
 * uses input verification to validate user input.
 */
public class InputVerificationDemo extends JPanel {
    //Default values
    private static double DEFAULT_AMOUNT = 100000;
    private static double DEFAULT_RATE = 7.5; //7.5%
    private static int DEFAULT_PERIOD = 30;
    
    //Labels to identify the text fields
    private JLabel amountLabel;
    private JLabel rateLabel;
    private JLabel numPeriodsLabel;
    private JLabel paymentLabel;
    
    //Strings for the labels
    private static String amountString = "Loan Amount (10,000-10,000,000): ";
    private static String rateString = "APR (>= 0%): ";
    private static String numPeriodsString = "Years (1-40): ";
    private static String paymentString = "Monthly Payment: ";
    
    //Text fields for data entry
    private JTextField amountField;
    private JTextField rateField;
    private JTextField numPeriodsField;
    private JTextField paymentField;
    
    //Formats to format and parse numbers
    private NumberFormat moneyFormat;
    private NumberFormat percentFormat;
    private DecimalFormat decimalFormat;
    private DecimalFormat paymentFormat;
    private MyVerifier verifier = new MyVerifier();
    
    public InputVerificationDemo() {
        super(new BorderLayout());
        setUpFormats();
        double payment = computePayment(DEFAULT_AMOUNT,
                DEFAULT_RATE,
                DEFAULT_PERIOD);
        
        //Create the labels.
        amountLabel = new JLabel(amountString);
        rateLabel = new JLabel(rateString);
        numPeriodsLabel = new JLabel(numPeriodsString);
        paymentLabel = new JLabel(paymentString);
        
        //Create the text fields and set them up.
        amountField = new JTextField(moneyFormat.format(DEFAULT_AMOUNT), 10);
        amountField.setInputVerifier(verifier);
        
        rateField = new JTextField(percentFormat.format(DEFAULT_RATE), 10);
        rateField.setInputVerifier(verifier);
        
        numPeriodsField = new JTextField(decimalFormat.format(DEFAULT_PERIOD), 10);
        numPeriodsField.setInputVerifier(verifier);
        
        paymentField = new JTextField(paymentFormat.format(payment), 10);
        paymentField.setInputVerifier(verifier);
        paymentField.setEditable(false);
        //Remove this component from the focus cycle.
        paymentField.setFocusable(false);
        paymentField.setForeground(Color.red);
        
        //Register an action listener to handle Return.
        amountField.addActionListener(verifier);
        rateField.addActionListener(verifier);
        numPeriodsField.addActionListener(verifier);
        
        //Tell accessibility tools about label/textfield pairs.
        amountLabel.setLabelFor(amountField);
        rateLabel.setLabelFor(rateField);
        numPeriodsLabel.setLabelFor(numPeriodsField);
        paymentLabel.setLabelFor(paymentField);
        
        //Lay out the labels in a panel.
        JPanel labelPane = new JPanel(new GridLayout(0,1));
        labelPane.add(amountLabel);
        labelPane.add(rateLabel);
        labelPane.add(numPeriodsLabel);
        labelPane.add(paymentLabel);
        
        //Layout the text fields in a panel.
        JPanel fieldPane = new JPanel(new GridLayout(0,1));
        fieldPane.add(amountField);
        fieldPane.add(rateField);
        fieldPane.add(numPeriodsField);
        fieldPane.add(paymentField);
        
        //Put the panels in this panel, labels on left,
        //text fields on right.
        setBorder(BorderFactory.createEmptyBorder(20, 20, 20, 20));
        add(labelPane, BorderLayout.CENTER);
        add(fieldPane, BorderLayout.LINE_END);
    }
    
    class MyVerifier extends InputVerifier
            implements ActionListener {
        double MIN_AMOUNT = 10000.0;
        double MAX_AMOUNT = 10000000.0;
        double MIN_RATE = 0.0;
        int MIN_PERIOD = 1;
        int MAX_PERIOD = 40;
        
        public boolean shouldYieldFocus(JComponent input) {
            boolean inputOK = verify(input);
            makeItPretty(input);
            updatePayment();
            
            if (inputOK) {
                return true;
            } else {
                Toolkit.getDefaultToolkit().beep();
                return false;
            }
        }
        
        protected void updatePayment() {
            double amount = DEFAULT_AMOUNT;
            double rate = DEFAULT_RATE;
            int numPeriods = DEFAULT_PERIOD;
            double payment = 0.0;
            
            //Parse the values.
            try {
                amount = moneyFormat.parse(amountField.getText()).
                        doubleValue();
            } catch (ParseException pe) {pe.printStackTrace();}
            try {
                rate = percentFormat.parse(rateField.getText()).
                        doubleValue();
            } catch (ParseException pe) {pe.printStackTrace();}
            try {
                numPeriods = decimalFormat.parse(numPeriodsField.getText()).
                        intValue();
            } catch (ParseException pe) {pe.printStackTrace();}
            
            //Calculate the result and update the GUI.
            payment = computePayment(amount, rate, numPeriods);
            paymentField.setText(paymentFormat.format(payment));
        }
        
        //This method checks input, but should cause no side effects.
        public boolean verify(JComponent input) {
            return checkField(input, false);
        }
        
        protected void makeItPretty(JComponent input) {
            checkField(input, true);
        }
        
        protected boolean checkField(JComponent input, boolean changeIt) {
            if (input == amountField) {
                return checkAmountField(changeIt);
            } else if (input == rateField) {
                return checkRateField(changeIt);
            } else if (input == numPeriodsField) {
                return checkNumPeriodsField(changeIt);
            } else {