Question

我是初学程序员，我为学校班级写了这篇文章。但不知怎的，即使我在displaypay（）下的JOptionPane.showMessageDialog也行不通！我希望会弹出一个消息框，但是在我输入每天的小时数之后，没有任何反应！它甚至没有跳过这部分，整个程序只是暂停！我感到很困惑！相反，如果我使用System.out.println（），它可以正常工作。

另外我不想为displaypay（）做System.out.println，我必须使用showMessageDialog。

 package payroll.program;

 import java.util.Scanner;
 import javax.swing.JOptionPane; //imports

 class Employee
{
int hourlypay;
int totalhours = 0;
String name; //variables

void getname()
{
    Scanner scan = new Scanner(System.in);

    System.out.println("What is this employee's name?");
    name = scan.next(); //gets name
}

void calculatepay()
{
    int[] hours = new int[5]; //creates array for hours

    Scanner scan = new Scanner(System.in);

    System.out.println("How much is " + name + " paid per hour?");
    hourlypay = scan.nextInt(); //gets hourly pay

    for (int i = 0; i < 5; i++)
    {
        System.out.println("How many hours did " + name + " work on day " + (i + 1) + "?");
        hours[i] = scan.nextInt(); //gets hour on each day

        totalhours = totalhours + hours[i]; //adds hours up
    }
}
void displaypay()
{
    JOptionPane.showMessageDialog(null, "You have to pay " + " $" + totalhours * hourlypay + " to " + name + "!"); //displays total pay
}
 }

 public class PayrollProgram {

    public static void main(String[] args) {

    int numberofemployees; //variable for # of employees

    System.out.println("Welcome to the Payroll Program!"); //welcomes user

    Scanner scan = new Scanner(System.in);
    System.out.println("How many employees do you have?");
    numberofemployees = scan.nextInt(); //gets input for # of employees

    Employee[] ArrayofEmployees = new Employee[numberofemployees]; //creates array of employees with the same size as the number of employees

    for (int i = 0; i < numberofemployees; i++)
    {
        ArrayofEmployees[i] = new Employee(); //creates an Employee for each space in the array
    }

    for (int i = 0; i < numberofemployees; i++)
    {
        ArrayofEmployees[i].getname();
        ArrayofEmployees[i].calculatepay();
        ArrayofEmployees[i].displaypay(); //runs functions in class Employee for each employee
    }
}

}

这是我的程序，而JOptionPane.showMessageDialog不起作用。

请帮忙！

Answer 1

当您尝试显示swing组件时，您需要从事件调度线程执行此操作。否则，您将无法获得可靠的结果。因此，在这种情况下，在调用SwingUtilities.invokeLater：

的调用中将所有代码包装在main中

public static void main(String[] args) {
    javax.swing.SwingUtilities.invokeLater(new Runnable() {
        public void run() {
            int numberofemployees; //variable for # of employees

            System.out.println("Welcome to the Payroll Program!"); //welcomes user

            Scanner scan = new Scanner(System.in);
            System.out.println("How many employees do you have?");
            numberofemployees = scan.nextInt(); //gets input for # of employees

            Employee[] ArrayofEmployees = new Employee[numberofemployees]; //creates array of employees with the same size as the number of employees

            for (int i = 0; i < numberofemployees; i++) {
                ArrayofEmployees[i] = new Employee(); //creates an Employee for each space in the array
            }

            for (int i = 0; i < numberofemployees; i++) {
                ArrayofEmployees[i].getname();
                ArrayofEmployees[i].calculatepay();
                ArrayofEmployees[i].displaypay(); //runs functions in class Employee for each employee
            }
        }
    });
}

可以在此处找到更多信息：The Event Dispatch Thread。

特别注意，如果您无法从事件调度程序线程运行Swing组件，它会发生什么：

忽略此规则的程序可能在大多数情况下正常运行，但会遇到难以重现的不可预测的错误。

为什么我的JOptionPane.showMessageDialog不起作用？

1 个答案: