如何禁用 JButton

Question

我希望在所有字段都有输入之前禁用我的 JButton。

package Grade;

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

public class GradeGUI extends JFrame {
    private  JLabel quizL,exerL,partL,partLL,examL,finalSL,totalIL,totalL,blankL,blankL2,blankL3,blankL4,blankL5,blankL6,blankL7,blankL8;
    private  JTextField quizTF,exerTF,examTF,partTF,quizTF1,exerTF1,examTF1,total1,total2,total3,total4,totalF,letterTF;
    private  JButton calculateB,exitB;
    private  CalculateButtonHandler cbHandler;
   private  ExitButtonHandler exitHandler;



    public GradeGUI(){
        blankL8=new JLabel("");
        blankL7=new JLabel("");
        blankL6=new JLabel("");
        blankL5=new JLabel("");
        blankL4=new JLabel("");
        blankL3=new JLabel("");
        blankL2=new JLabel("");
        blankL=new JLabel("");
        partLL=new JLabel("");
        quizL=new JLabel("Quiz: ");
        exerL=new JLabel("Exercise: ");
        partL=new JLabel("Participation: ");
        examL=new JLabel("Exams: ");
        finalSL=new JLabel("Final Score");
        totalIL=new JLabel("Total # of Items");
        totalL=new JLabel("Final Score");

        letterTF=new JTextField(25);
        quizTF=new JTextField(25);
        exerTF=new JTextField(25);
        examTF=new JTextField(25);
        partTF=new JTextField(25);
        quizTF1=new JTextField(25);
        exerTF1=new JTextField(25);
        examTF1=new JTextField(25);
        total1=new JTextField(25);
        total2=new JTextField(25);
        total3=new JTextField(25);
        total4=new JTextField(25);
        totalF=new JTextField(25);

        total1.setEditable(false);
        total2.setEditable(false);
        total3.setEditable(false);
        total4.setEditable(false);
        totalF.setEditable(false);
        letterTF.setEditable(false);

        calculateB=new JButton("Calculate");
        exitB=new JButton("Exit");

        calculateB=new JButton("Calculate");
        cbHandler= new CalculateButtonHandler();
        calculateB.addActionListener(cbHandler);

        exitB=new JButton("Exit");
        exitHandler= new ExitButtonHandler();
        exitB.addActionListener(exitHandler);

         setTitle("Grade Calculator");

        Container p = getContentPane();
        p.setLayout(new GridLayout(6,5));

        p.add(blankL);
        p.add(finalSL);
        p.add(totalIL);
        p.add(totalL);
        p.add(blankL4);
        p.add(quizL);
        p.add(quizTF);
        p.add(quizTF1);
        p.add(total1); 
        p.add(blankL5);
        p.add(exerL);
        p.add(exerTF);
        p.add(exerTF1);
        p.add(total2);
        p.add(blankL6);
        p.add(partL);
        p.add(partTF);

        p.add(blankL2);
        p.add(total3);
        p.add(blankL7);
        p.add(examL);
        p.add(examTF);
        p.add(examTF1);
        p.add(total4);
        p.add(blankL8);
        p.add(blankL3);
        p.add(calculateB);
        p.add(exitB);
        p.add(totalF);
        p.add(letterTF);

        setSize(500,400);

        setVisible(true);
        setDefaultCloseOperation(EXIT_ON_CLOSE);


    }

    private class CalculateButtonHandler implements ActionListener{
    public void actionPerformed(ActionEvent e){

       try{ 
        double quiz,exam,exer,part,quizT,examT,exerT;
        double total11,total22,total33,total44,totalFf;
        double quizTT,examTT,partTT,exerTT;

        quiz=Integer.parseInt(quizTF.getText());
        exam=Integer.parseInt(examTF.getText());
        exer=Integer.parseInt(exerTF.getText());
        part=Integer.parseInt(partTF.getText());

        quizT=Integer.parseInt(quizTF1.getText());
        examT=Integer.parseInt(examTF1.getText());
        exerT=Integer.parseInt(exerTF1.getText());


        quizTT=((quiz/quizT)*100)*0.20;
        examTT=((exam/examT)*100)*0.30;
        partTT=part*0.10;
        exerTT=((exer/exerT)*100)*0.40;

        total1.setText(""+quizTT);
        total2.setText(""+examTT);
        total3.setText(""+partTT);
        total4.setText(""+exerTT);

        total11=Double.parseDouble(total1.getText());
        total22=Double.parseDouble(total2.getText());
        total33=Double.parseDouble(total3.getText());
        total44=Double.parseDouble(total4.getText());






        totalFf=total11+total22+total33+total44;
        totalF.setText(""+totalFf);

        if(totalFf>=95){

            letterTF.setText("A");
        }else if(totalFf>=90){

            letterTF.setText("B");
        }else if(totalFf>=85){

            letterTF.setText("C");
        }else if(totalFf>=80){

            letterTF.setText("D");
        }else if(totalFf>=75){

            letterTF.setText("E");
        }else{
            letterTF.setText("F");
        }
         }catch(Exception s){
             JOptionPane.showMessageDialog(null,"Please Try Again!!","ERROR",JOptionPane.ERROR_MESSAGE);
    }


    }
}

    private class ExitButtonHandler implements ActionListener{
        public void actionPerformed(ActionEvent e){

            System.exit(0);
        }
    }

    public static void main(String[]args){

        GradeGUI a=new GradeGUI();
    }
}

Answer 1

使用 JTextField class 的 addCaretListener 方法，您可以检查每个文本字段中的更改。当在文本字段中输入字符时，插入符号的位置会发生变化，并且会触发 javax.swing.event.CaretEvent ，您可以使用它来检查每个文本字段是否为空；基于此，您可以将按钮设置为启用或禁用。例如：

quizTF.addCaretListener(new CaretListener() {
    public void caretUpdate(CaretEvent ev) {
        calculateB.setEnabled(!quizTF.getText().isEmpty() && !exerTF.getText().isEmpty() && ...);
    }
});

// code here

就个人而言，我会将所有 JTextField 对象放在 ArrayList 或类似的东西中，这样您就可以遍历它们并对其执行操作，并且编写这么多代码不会乏味。

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