Question

好吧，在addActionListener（this）语句之前我没有问题。我不知道将按钮链接到要在文本字段中输入的各自字符串的位置

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

public class GUI extends JFrame implements ActionListener {

    private JButton one, two, three, four, five, six, seven, eight, nine, zero, point, cancel;

    private JTextField t;

    private JFrame frame;

    private String number = "";



    public GUI() {

        //creating button objects

        JButton one = new JButton("1");

        JButton two = new JButton("2");

        JButton three = new JButton("3");

        JButton four = new JButton("4");

        JButton five = new JButton("5");

        JButton six = new JButton("6");

        JButton seven = new JButton("7");

        JButton eight = new JButton("8");

        JButton nine = new JButton("9");

        JButton zero = new JButton("0");

        JButton point = new JButton(".");

        JButton cancel = new JButton("cancel");

        //call addActionListener() method

        one.addActionListener(this);

        two.addActionListener(this);

        three.addActionListener(this);

        four.addActionListener(this);

        five.addActionListener(this);

        six.addActionListener(this);

        seven.addActionListener(this);

        eight.addActionListener(this);

        nine.addActionListener(this);

        //point.addActionListener(this);

        //cancel.addActionListener(this);

        //create jframe object

        JFrame frame = new JFrame("Vendor");

        //create text field

        JTextField t = new JTextField();

        frame.setSize(400, 400);

        setVisible(true);

        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); //remove this after creating other modules

        //creating panel object

        JPanel panel = new JPanel();

        GridLayout grid = new GridLayout(0, 3);

        panel.setLayout(grid);

        panel.setComponentOrientation(ComponentOrientation.LEFT_TO_RIGHT);

        //setting text field to the top of the frame

        add(t, BorderLayout.NORTH);

        //adding buttons to panel

        panel.add(one);

        panel.add(two);

        panel.add(three);

        panel.add(four);

        panel.add(five);

        panel.add(six);

        panel.add(seven);

        panel.add(eight);

        panel.add(nine);

        panel.add(zero);

        panel.add(point);

        panel.add(cancel);

        //adding panel to frame

        add(panel);

    }

    public void actionPerformed(ActionEvent e) {


        if (e.getSource() == one) {

            t.setText(t.getText().concat("1"));

        }

        if (e.getSource() == two) {

            t.setText(t.getText().concat("2"));

        }

        if (e.getSource() == three) {

            t.setText(t.getText().concat("3"));

        }

        if (e.getSource() == four) {

            t.setText(t.getText().concat("4"));

        }

        if (e.getSource() == five) {

            t.setText(t.getText().concat("5"));

        }

        if (e.getSource() == six) {

            t.setText(t.getText().concat("6"));

        }

        if (e.getSource() == seven) {

            t.setText(t.getText().concat("7"));

        }

        if (e.getSource() == eight) {

            t.setText(t.getText().concat("8"));

        }

        if (e.getSource() == nine) {

            t.setText(t.getText().concat("9"));

        }

        if (e.getSource() == zero) {

            t.setText(t.getText().concat("0"));

        }

        /*if(e.getSource() == point) {

     t.setText(t.getText().concat("."));

  }*/
    }

    public static void main(String[] args) {

        GUI object = new GUI();

    }
}

Answer 1

您在构造函数中本地声明了按钮，从而覆盖了您的成员变量。您的成员变量一，二，三......将始终为null。您可以像这样编写构造函数：

public GUI() {

    //creating button objects

    one = new JButton("1");

    two = new JButton("2");
    .
    .
    .

如何将按钮链接到动作侦听器和文本字段？

1 个答案: