java - 整数验证问题并显示用户输入了无效数据

Question

这是我作为家庭作业的一部分正在处理的 Java 程序。我不想为我完成工作，但我被卡住了。我对 Java 还很陌生，使用的是 NetBeans IDE 7.0.1。

尝试验证用户输入时，我在处理某些异常时遇到了困难。该程序将根据用户输入记录慈善捐赠。但是，我没有成功验证捐赠金额文本字段输入。如果用户输入文本而不是数字，我希望他们被通知他们的输入无效，并且我希望异常处理来处理错误并在用户修复他们的输入后继续。非常感谢任何帮助。

这是我的代码:

package donorgui;


import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.*;
import java.io.*;
import java.awt.*;

public class DonorGUI extends JFrame
{

// Components
private JPanel panel;
private JTextArea results;
private JButton entryButton;
private JButton exitButton;
private JButton clearButton;
private JTextField donorField;
private JTextField charityField;
private JTextField pledgeField;

//create variables
String[] donorName = new String[20];
String[] charityName = new String[20];
double[] donationAmt = new double[20];
int i = 0;


// Constants for the window size
private final int WINDOW_WIDTH = 750;
private final int WINDOW_HEIGHT = 510;

//Constructor
public DonorGUI(){

    // Set the title.
    setTitle("Donor");

    // Specify what happens when the close button is clicked.
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    // Build the panel that contains the other components.
    buildPanel();

    // Add the panel to the content pane.
    add(panel);

    // Size and display the window.
    setSize(WINDOW_WIDTH, WINDOW_HEIGHT);
    setVisible(true);
}

//The buildPanel method creates a panel containing other components.
private void buildPanel(){

    // Create labels to display instructions.
    JLabel message1 = new JLabel("Name of the Donor:");
    JLabel message2 = new JLabel("Name of the Charity:");
    JLabel message3 = new JLabel("Amount of the Pledge:");

    //instantiate the results area
    results = new JTextArea(25,60);

    // Create text fields to receive user input
    donorField = new JTextField(10);
    charityField = new JTextField(10);
    pledgeField = new JTextField(10);


    //create the user buttons to cause action
    entryButton = new JButton("Enter Donation.");
    entryButton.addActionListener(new EntryButtonListener());
    exitButton = new JButton("EXIT");
    exitButton.addActionListener(new ExitButtonListener());
    clearButton = new JButton ("Clear Fields");
    clearButton.addActionListener(new ClearButtonListener());


    // Create a panel.
    panel = new JPanel();

    //set the LayoutManager
    panel.setLayout(new FlowLayout());

    // Add the labels, text fields, and button to the panel.
    panel.add(message1);
    panel.add(donorField);
    panel.add(message2);
    panel.add(charityField);
    panel.add(message3);
    panel.add(pledgeField);
    panel.add(results);
    panel.add(entryButton);
    panel.add(exitButton);
    panel.add(clearButton);

}
private class EntryButtonListener implements ActionListener {

    public void actionPerformed(ActionEvent e) {

        donorName[i] = donorField.getText();
        charityName[i] = charityField.getText();
        donationAmt[i] = Double.parseDouble(pledgeField.getText());
        results.append(donorName[i]+" "+charityName[i]+" "+donationAmt[i]+"\n ");
        i++;
    } 
}
public boolean donationAmt(String amount) {
    int i = 0;
    try {
        i = Integer.parseInt (amount);
        return true;
    }
    catch (NumberFormatException e) {
        JOptionPane.showMessageDialog(null, "Invalid Input.  Please enter a dollar amount");
        return false;
    }


}
private class ClearButtonListener implements ActionListener {
    @Override
    public void actionPerformed (ActionEvent e) {
        donorField.setText("");
        charityField.setText("");
        pledgeField.setText("");
        }
}
private class ExitButtonListener implements ActionListener {

    public void actionPerformed(ActionEvent e) {
        System.exit(0);
    }
}

/* Application method */
public static void main(String[] args){

    DonorGUI rpc = new DonorGUI();
}

}

这是我修改后的代码。经过一些用户输入测试后，当我使用 100.00、40.00 等而不是整个美元金额(例如 100、40 等)时，出现异常。
有什么想法吗？

package donorgui;


import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.*;
import java.io.*;
import java.awt.*;

public class DonorGUI extends JFrame
{
// Components
private JPanel panel;
private JTextArea results;
private JButton entryButton;
private JButton exitButton;
private JButton clearButton;
private JTextField donorField;
private JTextField charityField;
private JTextField pledgeField;

//create variables
String[] donorName = new String[20];
String[] charityName = new String[20];
double[] donationAmt = new double[20];
int i = 0;


// Constants for the window size
private final int WINDOW_WIDTH = 750;
private final int WINDOW_HEIGHT = 550;

//Constructor
public DonorGUI(){

    // Set the title.
    setTitle("Donor");

    // Specify what happens when the close button is clicked.
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    // Build the panel that contains the other components.
    buildPanel();

    // Add the panel to the content pane.
    add(panel);

    // Size and display the window.
    setSize(WINDOW_WIDTH, WINDOW_HEIGHT);
    setVisible(true);
}

//The buildPanel method creates a panel containing other components.
private void buildPanel(){

    // Create labels to display instructions.
    JLabel message1 = new JLabel("Name of the Donor:");
    JLabel message2 = new JLabel("Name of the Charity:");
    JLabel message3 = new JLabel("Amount of the Pledge:");

    //instantiate the results area
    results = new JTextArea(25,60);


    // Create text fields to receive user input
    donorField = new JTextField(10);
    charityField = new JTextField(10);
    pledgeField = new JTextField(10);


    //create the user buttons to cause action
    entryButton = new JButton("Enter Donation.");
    entryButton.addActionListener(new EntryButtonListener());
    exitButton = new JButton("EXIT");
    exitButton.addActionListener(new ExitButtonListener());
    clearButton = new JButton ("Clear Fields");
    clearButton.addActionListener(new ClearButtonListener());


    // Create a panel.
    panel = new JPanel();

    //set the LayoutManager
    panel.setLayout(new FlowLayout());

    // Add the labels, text fields, and button to the panel.
    panel.add(message1);
    panel.add(donorField);
    panel.add(message2);
    panel.add(charityField);
    panel.add(message3);
    panel.add(pledgeField);
    panel.add(results);
    panel.add(entryButton);
    panel.add(exitButton);
    panel.add(clearButton);

}
private class EntryButtonListener implements ActionListener {

    public void actionPerformed(ActionEvent e) {

        donorName[i] = donorField.getText();
        charityName[i] = charityField.getText();
                if (donationAmt(pledgeField.getText())) {
                    donationAmt[i] = Double.parseDouble(pledgeField.getText());
                }
        results.append(donorName[i]+" "+charityName[i]+" "+donationAmt[i]+"\n ");
        i++;
    } 
}

public boolean donationAmt(String amount) {
   if(amount==null || amount=="" || amount.length()<1){  //checking for empty field
        JOptionPane.showMessageDialog(null, "Please enter a dollar amount");
        return false;
    }

    for(int i = 0; i < amount.length(); i++){  //verifying dollar amount entered as number
            if (!Character.isDigit(amount.charAt(i))){ 
                JOptionPane.showMessageDialog(null, "Invalid input.  Please enter a dollar amount");
                return false;
            } 
    }
    return true;

}



private class ClearButtonListener implements ActionListener {
    @Override
    public void actionPerformed (ActionEvent e) {
        donorField.setText("");
        charityField.setText("");
        pledgeField.setText("");
        }
}
private class ExitButtonListener implements ActionListener {

    public void actionPerformed(ActionEvent e) {
        System.exit(0);
    }
}

/* Application method */
public static void main(String[] args){

    DonorGUI rpc = new DonorGUI();
}

}

Answer 1

您可以使用 InputVerifier , 讨论 here .