我正在构建一个需要用户输入的简单 JFrame GUI。如果用户单击提交按钮，它会检查输入，然后呈现一条 JOptionPane 消息，告诉用户完整填写表单，或者告诉用户表单已提交并关闭程序。问题是，如果用户留下空白字段，则消息对话框将呈现，并且仅在您尝试关闭它时才添加到循环计数，并且不允许用户返回 JFrame 以将输入应用到表单。
import java.io.*;
import java.util.*;
import javax.swing.*;
import javax.swing.JOptionPane;
import java.awt.*;
import java.util.Scanner.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
/**
*
* @author joel.ramsey
*/
public class JRStarPhase5 extends JFrame{
public static void main (String [] args) throws IOException {
JFrame window = new JRStarPhase5();
window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
window.setVisible(true);
}//end main method
private boolean validationError;
private final JTextField fNameInput;
private final JTextField miInput;
private final JTextField lNameInput;
private final JTextField productChoiceInput;
private final JTextField licenseQuantityInput;
private final JTextField streetAddressInput;
private final JTextField cityInput;
private final JTextField stateInput;
private final JTextField zipInput;
private final JTextField phoneInput;
//constructor for JFrame
public JRStarPhase5(){
setTitle("JRStar Star Gaze Order Processing");
setSize (800,800);
Container pane = getContentPane();
GridLayout grid = new GridLayout(0,2);
pane.setLayout(grid);
JLabel fNameLabel = new JLabel ("First name:");
JLabel mi = new JLabel ("Middle initial:");
JLabel lNameLabel = new JLabel ("Last name:");
JLabel productChoice = new JLabel ("Star Gaze version:");
JLabel licenseQuantity = new JLabel ("License quantity:");
JLabel streetAddress = new JLabel ("Street address:");
JLabel city = new JLabel ("City:");
JLabel state = new JLabel ("State abbrev:");
JLabel zip = new JLabel ("Zip code:");
JLabel phone = new JLabel ("Phone Number:");
this.fNameInput = new JTextField(15);
this.miInput = new JTextField (1);
this.lNameInput = new JTextField (15);
this.productChoiceInput = new JTextField (1);
this.licenseQuantityInput = new JTextField (2);
this.streetAddressInput = new JTextField (20);
this.cityInput = new JTextField (20);
this.stateInput = new JTextField (2);
this.zipInput = new JTextField (5);
this.phoneInput = new JTextField (10);
//add as last buttons
JButton submit = new JButton("Submit");
SubmitButtonHandler sbh = new SubmitButtonHandler();
submit.addActionListener(sbh);
JButton clear = new JButton("Clear");
ClearButtonHandler cbh = new ClearButtonHandler();
clear.addActionListener(cbh);
pane.add(fNameLabel);
pane.add(fNameInput);
pane.add(mi);
pane.add(miInput);
pane.add(lNameLabel);
pane.add(lNameInput);
pane.add(productChoice);
pane.add(productChoiceInput);
pane.add(licenseQuantity);
pane.add(licenseQuantityInput);
pane.add(streetAddress);
pane.add(streetAddressInput);
pane.add(city);
pane.add(cityInput);
pane.add(state);
pane.add(stateInput);
pane.add(zip);
pane.add(zipInput);
pane.add(phone);
pane.add(phoneInput);
//add last
pane.add(submit);
pane.add(clear);
}//end constructor
private class SubmitButtonHandler implements ActionListener{
public void actionPerformed(ActionEvent e){
validationError = (fNameInput.getText().equals("")||
miInput.getText().equals("")||
lNameInput.getText().equals("")||
streetAddressInput.getText().equals("")||
cityInput.getText().equals("")||
stateInput.getText().equals("")||
zipInput.getText().equals("")||
phoneInput.getText().equals(""));
for (int n=1; n<3; n++){
if (validationError){
if (n == 3){
System.exit(0);
}
JOptionPane.showMessageDialog(null,"Please complete each field within the order form.");
}
else break;
}
if (validationError = false)
JOptionPane.showMessageDialog(null,"Your order has been submitted!");
System.exit(0);
}
}//end submit
private class ClearButtonHandler implements ActionListener{
public void actionPerformed(ActionEvent e){
fNameInput.setText("");
miInput.setText("");
lNameInput.setText("");
productChoiceInput.setText("");
licenseQuantityInput.setText("");
streetAddressInput.setText("");
cityInput.setText("");
stateInput.setText("");
zipInput.setText("");
phoneInput.setText("");
}
}//end clear
}//end main class
最佳答案
老实说，我不知道您还期望什么(无意冒犯)。
Swing 是一个事件驱动的环境。事件发生，你对其使用react...
循环将在 EDT 的上下文中开始执行，这意味着用户无法实际关闭对话框、更正错误并尝试重新提交。
即使确实如此，循环也不允许有任何机会重新计算 validationError 变量，这意味着它将始终是方法中先前设置的值(让现在假设true)...
for (int n = 1; n < 3; n++) {
if (validationError) {
if (n == 3) {
System.exit(0);
}
JOptionPane.showMessageDialog(null, "Please complete each field within the order form.");
} else {
break;
}
}
if (validationError = false) {
JOptionPane.showMessageDialog(null, "Your order has been submitted!");
}
System.exit(0);
所以基本上你已经陷入了死亡陷阱，根本没有办法逃脱......
让我们采取另一种方法。我们可以创建一个软循环，而不是使用硬循环，例如 for 或 while，这样，每次执行方法并且表单无效时，我们都会更新一个计数器，直到该计数器用完...
// How many times retries has the user used...
private int retries = 0;
/*...*/
public void actionPerformed(ActionEvent e) {
validationError = (fNameInput.getText().equals("")
|| miInput.getText().equals("")
|| lNameInput.getText().equals("")
|| streetAddressInput.getText().equals("")
|| cityInput.getText().equals("")
|| stateInput.getText().equals("")
|| zipInput.getText().equals("")
|| phoneInput.getText().equals(""));
if (validationError) {
retries++;
if (retries < 3) {
JOptionPane.showMessageDialog(this, "Please complete each field within the order form.");
} else {
JOptionPane.showMessageDialog(this, "You've used up all your tries...");
System.exit(0);
}
} else {
JOptionPane.showMessageDialog(this, "Your order has been submitted!");
System.exit(0);
}
}
您可能还想阅读Validating Input来自How to use the focus subsystem教程...
关于java - 使JOptionPane消息对话框渲染后消失，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/18931230/