Joptionpane 不处理 switch-case

Question

我的 switch-case 选项和 joptionpane 有问题。选择四个选项之一后，程序结束。它不显示选择。它应该显示 choice/selection.

  import javax.swing.JOptionPane; // JOptionPane call

  public class OnlineStore 
  {
     // public static void main(String[] args) // main program
      public void display_menu() // Not the main program but the main menu.
      {
          String main_selection;
          int mSelect;

          main_selection = JOptionPane.showInputDialog("Welcome!\n\n1. Add T-                Shirt Order\n2. Edit T-Shirt Order\n3. View Current Order\n4. Checkout\n\nPlease   enter your choice: ");
    mSelect = Integer.parseInt(main_selection);

      }

      public OnlineStore() // Switch-case program
      {
          display_menu(); // Call display menu.
          switch (mSelect)
          {
              case 1:
                  JOptionPane.showMessageDialog(null, "Option 1");
                  break;
              case 2:
                  JOptionPane.showMessageDialog(null, "Option 2");
                  break;
              case 3:
                  JOptionPane.showMessageDialog(null, "Option 3");
                  break;
              case 4:  // Deliberately not including a default selection.
                  JOptionPane.showMessageDialog(null, "Option 4");
                  break;  
           } 

      } 

      public static void main(String[] args) // main program
      {
          new OnlineStore(); // Call out the program.
      }
  }

当我使用扫描仪时，结果正常。

Answer 1

目前，没有扫描仪，没有整数设置为 mselect - 所以如果您要定义这样的一个，则您的开关选择大小写 default：

switch(mSelect){
.
.
.
default: JOptionPane.showMessageDialog(null, "ERROR");
}

另一种解决方案是将默认值设置为 mSelect，如

int mSelect = 1;

Answer 2

在 class 而非方法内声明 mSelect 变量。

public class OnlineStore {
int mSelect;
// public static void main(String[] args) // main program

public void display_menu() // Not the main program but the main menu.
{
    String main_selection;

    main_selection = JOptionPane.showInputDialog("Welcome!\n\n1. Add T-                Shirt Order\n2. Edit T-Shirt Order\n3. View Current Order\n4. Checkout\n\nPlease   enter your choice: ");
    mSelect = Integer.parseInt(main_selection);

}

public OnlineStore() // Switch-case program
{
    display_menu(); // Call display menu.
    switch (mSelect) {
        case 1:
            JOptionPane.showMessageDialog(null, "Option 1");
            break;
        case 2:
            JOptionPane.showMessageDialog(null, "Option 2");
            break;
        case 3:
            JOptionPane.showMessageDialog(null, "Option 3");
            break;
        case 4:  // Deliberately not including a default selection.
            JOptionPane.showMessageDialog(null, "Option 4");
            break;
    }

}

public static void main(String[] args) // main program
{
    new OnlineStore(); // Call out the program.
}}

Answer 3

主要问题是 display_menu 中发生的事情与您在 OnlineStore 中处理的事情之间没有上下文关系。

相反，为什么不选择 display_menu return value/option 并将其包含在 switch 语句中，例如

public class OnlineStore {

    // public static void main(String[] args) // main program

    public int display_menu() // Not the main program but the main menu.
    {
        String main_selection;

        main_selection = JOptionPane.showInputDialog("Welcome!\n\n1. Add T-                Shirt Order\n2. Edit T-Shirt Order\n3. View Current Order\n4. Checkout\n\nPlease   enter your choice: ");
        return Integer.parseInt(main_selection);

    }

    public OnlineStore() // Switch-case program
    {
        switch (display_menu()) {
            case 1:
                JOptionPane.showMessageDialog(null, "Option 1");
                break;
            case 2:
                JOptionPane.showMessageDialog(null, "Option 2");
                break;
            case 3:
                JOptionPane.showMessageDialog(null, "Option 3");
                break;
            case 4:  // Deliberately not including a default selection.
                JOptionPane.showMessageDialog(null, "Option 4");
                break;
        }

    }

    public static void main(String[] args) // main program
    {
        new OnlineStore(); // Call out the program.
    }
}

循环菜单

public class OnlineStore {

    // public static void main(String[] args) // main program

    public int display_menu() // Not the main program but the main menu.
    {
        String main_selection;

        main_selection = JOptionPane.showInputDialog("Welcome!\n\n1. Add T-                Shirt Order\n2. Edit T-Shirt Order\n3. View Current Order\n4. Checkout\n\nPlease   enter your choice: ");
        return Integer.parseInt(main_selection);

    }

    public OnlineStore() // Switch-case program
    {
        boolean exit = false;
        do {
            switch (display_menu()) {
                case 1:
                    JOptionPane.showMessageDialog(null, "Option 1");
                    break;
                case 2:
                    JOptionPane.showMessageDialog(null, "Option 2");
                    break;
                case 3:
                    JOptionPane.showMessageDialog(null, "Option 3");
                    break;
                case 4:  // Deliberately not including a default selection.
                    JOptionPane.showMessageDialog(null, "Option 4");
                    break;
            }
        } while (!exit);
    }

    public static void main(String[] args) // main program
    {
        new OnlineStore(); // Call out the program.
    }
}

Joptionpane 不处理 switch-case

Joptionpane does not process switch-case

java

swing

joptionpane

switch-statement

循环菜单