Question

我已经讨论了一段时间了，我变得更加困惑。我想完成一些事情：

向JTextField添加2个标签1.第一个要求他们输入电子邮件。第二个表示已经为他们输入了@ address.com。

我很困惑如何传递String变量，也许我应该只有一个方法？

import javax.swing.*;
import java.awt.*;

public class Email {

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

        //get user input
        JPanel panel = new JPanel();  //create new JPanel

        JTextField field1 = new JTextField(20);  //create a field for email and show 20 characters
        panel.add(field1);

        JTextField field2 = new JTextField(6); //create a field for grade and show to 6 characters
        panel.add(field2);

        int iValue = JOptionPane.showConfirmDialog (
        null,
        panel,
        "Please enter students email adress and test grade",
        JOptionPane.OK_OPTION); //create button in panel

        if (iValue == JOptionPane.OK_OPTION) {

            //capture email address as String
            String sEmail = field1.getText() + "@address.com"; 

            //capture numerical grade input and convert it to a float    
            float fGrade = Float.parseFloat(field2.getText());
        }
    } //end main


    public void convertGrades(float fGrade) {

        /***"shortcut if" grade conversion***********
        String sLetterGrade =    (fGrade >= 97) ? "A+" :
        (fGrade >= 94) ? "A" :
        (fGrade >= 90) ? "A-" :
        (fGrade >= 87) ? "B+" : 
        (fGrade >= 84) ? "B" :
        (fGrade >= 80) ? "B-" :
        (fGrade >= 77) ? "C+" :
        (fGrade >= 74) ? "C" :
        (fGrade >= 70) ? "C-" :
        (fGrade >= 67) ? "D+" :
        (fGrade >= 64) ? "D" :
        (fGrade >= 60) ? "D-" : "F";
        *************************************************************************/


        //experimental grade conversion
        // Determine letter grade
        String sAlphaGrade =    (fGrade >= 90) ? "A" :
        (fGrade >= 80) ? "B" :
        (fGrade >= 70) ? "C" :
        (fGrade >= 60) ? "D" : "F";
        //determine + or -
        if (fGrade >= 60) {
            float fGradeModifier = (fGrade % 10); 
            String sAlphaModifier = (fGradeModifier >= 7) ? "+" :
            (fGradeModifier >= 4)? "" : "-";

            //concatenate letter grade and modifier
            String sLetterGrade = sAlphaGrade + sAlphaModifier;

        } // end if


        String sResults =    getInput.sEmail  + "\n" +
        sMessage + "\n" +
        "your test score is: " + fGrade + "\n" + 
        "your letter grade is: " + sLetterGrade;


        JOptionPane.showMessageDialog(null, sOutput,"Email and Grade",
        JOptionPane.INFORMATION_MESSAGE);

    } //end convertGrades
} //end class Email

Answer 1

您的代码在声明和访问变量的位置存在一些问题。 sMessage和sOutput永远不会在任何地方声明或赋值。此外，当您在sEmail中声明convertGrades时，尝试访问main方法中的sLetterGrade，并尝试在if阻止之外访问sEmail被宣布进入。

如果您想在convertGrades方法中使用sLetterGrade，则需要在调用时将其传递给方法。 if必须在convertGrades块之外声明，以便稍后使用。此外，您实际上从未通过main方法调用JTextField，因此不会执行任何代码。

要标记import javax.swing.*; import java.awt.*; public class Email { public static void main(String[] args) { //main method //get user input JPanel panel = new JPanel(); //create new JPanel Box field1Box = Box.createHorizontalBox(); // Box to hold field1 and its labels field1Box.add(new JLabel("Enter email: ")); // JLabels can be added directly; we don't need to keep a reference JTextField field1 = new JTextField(20); //create a field for email and show 20 characters field1Box.add(field1); field1Box.add(new JLabel("@address.com")); panel.add(field1Box); // Adds the Box containing field1 and the two labels to panel JTextField field2 = new JTextField(6); //create a field for grade and show to 6 characters panel.add(field2); int iValue = JOptionPane.showConfirmDialog ( null, panel, "Please enter student's email adress and test grade", JOptionPane.OK_OPTION); //create button in panel if (iValue == JOptionPane.OK_OPTION) { //capture email address as String String sEmail = field1.getText() + "@address.com"; //capture numerical grade input and convert it to a float float fGrade = Float.parseFloat(field2.getText()); //call convertGrades to display the results convertGrades(fGrade, sEmail); } } //end main // convertGrades must be static to be called from main public static void convertGrades(float fGrade, String sEmail) { /***"shortcut if" grade conversion*********** String sLetterGrade = (fGrade >= 97) ? "A+" : (fGrade >= 94) ? "A" : (fGrade >= 90) ? "A-" : (fGrade >= 87) ? "B+" : (fGrade >= 84) ? "B" : (fGrade >= 80) ? "B-" : (fGrade >= 77) ? "C+" : (fGrade >= 74) ? "C" : (fGrade >= 70) ? "C-" : (fGrade >= 67) ? "D+" : (fGrade >= 64) ? "D" : (fGrade >= 60) ? "D-" : "F"; *************************************************************************/ //experimental grade conversion // Determine letter grade String sAlphaGrade = (fGrade >= 90) ? "A" : (fGrade >= 80) ? "B" : (fGrade >= 70) ? "C" : (fGrade >= 60) ? "D" : "F"; String sLetterGrade; // This needs to be visible outside of the if //determine + or - if (fGrade >= 60) { float fGradeModifier = (fGrade % 10); String sAlphaModifier = (fGradeModifier >= 7) ? "+" : (fGradeModifier >= 4)? "" : "-"; //concatenate letter grade and modifier sLetterGrade = sAlphaGrade + sAlphaModifier; } // end if else { // sLetterGrade still needs to get a value sLetterGrade = sAlphaGrade; } String sResults = sEmail + "\n" + // sMessage has been commented out so the program will compile and run // Uncomment it if you declare it and give it a value somewhere. // sMessage + "\n" + "your test score is: " + fGrade + "\n" + "your letter grade is: " + sLetterGrade; // Assuming sOutput was meant to mean sResults JOptionPane.showMessageDialog(null, sResults,"Email and Grade", JOptionPane.INFORMATION_MESSAGE); } //end convertGrades } //end class Email，我建议将所有标签和字段放在Box中。这将确保他们都以正确的顺序在一起。

以下是您编辑的代码，其中包含所有这些更改：

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需要帮助传递变量和标记JPanel

1 个答案: