未写入java JFrame

Question

我的JFrame正在打开一个空白窗口
我试图创建calcView类的实例，以便打开并写入JFrame窗口，但它没有正常工作。 基本上，我必须使用MVC方法来开发一个只使用乘法运算的计算器，所以这里显示了3个单独的类：

CalcView

import javax.swing.*;
import java.math.BigInteger;
import java.awt.*;
public class CalcView extends JFrame{
      private static final String INITIAL_VALUE = "1";

    private JTextField m_totalTf = new JTextField(10);
    private JTextField m_userInputTf = new JTextField(10);
    private JButton m_multiplyBtn = new JButton("Multiply");
    private JButton m_clearBtn = new JButton("Clear");

    private BigInteger m_total; // The total current value state.

   public void CalcGUI() {
         JFrame window = new CalcView();
        window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
         window.setTitle("Performs Simple Multiplications");
         window.setVisible(true);
        m_total = new BigInteger(INITIAL_VALUE);
        m_totalTf.setText(INITIAL_VALUE);
        m_totalTf.setEditable(false);

        JPanel content = new JPanel();
        content.setLayout(new FlowLayout());
        content.add(new JLabel("Input"));
        content.add(m_userInputTf);
        content.add(m_multiplyBtn);
        content.add(new JLabel("Total"));
        content.add(m_totalTf);
        content.add(m_clearBtn);

        this.setContentPane(content);
        this.pack();
   
    }
    public void throwExcept(){
        JOptionPane.showMessageDialog(CalcView.this, "Bad Number");
    }
}

CalcModel

import java.awt.event.*;
public class CalcModel{
    public static final String INITIAL_VALUE = "1";
    
    public float multiply(){
        float i = 0;
        return i;
    }
}

钙控制器

import javax.swing.*;

public class CalcController {
    public static void main(String[] args) {
    CalcView v = new CalcView();
    v.CalcGUI();
    }
  
    public void listener() {
        m_clearBtn.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                m_total = new BigInteger(INITIAL_VALUE);
                m_totalTf.setText(INITIAL_VALUE);
            }
        });
        m_multiplyBtn.addActionListener(new ActionListener() {

            public void actionPerformed(ActionEvent e) {
                try {
                    CalcModel m = new CalcModel();
                    m.multiply(e);
                } catch (NumberFormatException nex) {
                   CalcView v = new CalcView();
                   v.throwExcept();
                }
            }
        });
    }
}

此外，如何在类之间传递事件处理程序

Answer 1

原因是将内容面板添加到错误的JFrame。 在这行代码中，您创建了一个新的JFrame

JFrame window = new CalcView();

但是在这些代码行中，您将内容JPanel添加到CalcView类中，而不是它自己

this.setContentPane(content);
this.pack();

有两个选项可以使其可见，第一个选项是不扩展JFrame，并将内容JPanel添加到窗口JFrame。第二个选项是ExtendJFrame，不创建新的窗口JFrame

第一个选项显示在下面的代码中

import javax.swing.*;
import java.math.BigInteger;
import java.awt.*;
public class CalcView{
    private static final String INITIAL_VALUE = "1";

    private JTextField m_totalTf = new JTextField(10);
    private JTextField m_userInputTf = new JTextField(10);
    private JButton m_multiplyBtn = new JButton("Multiply");
    private JButton m_clearBtn = new JButton("Clear");

    private BigInteger m_total; // The total current value state.

    JFrame window = new JFrame();

    public void CalcGUI() {
        window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        window.setTitle("Performs Simple Multiplications");
        window.setVisible(true);
        m_total = new BigInteger(INITIAL_VALUE);
        m_totalTf.setText(INITIAL_VALUE);
        m_totalTf.setEditable(false);

        JPanel content = new JPanel();
        content.setLayout(new FlowLayout());
        content.add(new JLabel("Input"));
        content.add(m_userInputTf);
        content.add(m_multiplyBtn);
        content.add(new JLabel("Total"));
        content.add(m_totalTf);
        content.add(m_clearBtn);

        window.setContentPane(content);
        window.pack();
    }

    public void throwExcept(){
        JOptionPane.showMessageDialog(window, "Bad Number");
    }
}

第二个选项显示在下面的代码中

import javax.swing.*;
import java.math.BigInteger;
import java.awt.*;
public class CalcView extends JFrame{
    private static final String INITIAL_VALUE = "1";

    private JTextField m_totalTf = new JTextField(10);
    private JTextField m_userInputTf = new JTextField(10);
    private JButton m_multiplyBtn = new JButton("Multiply");
    private JButton m_clearBtn = new JButton("Clear");

    private BigInteger m_total; // The total current value state.

    public void CalcGUI() {
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        this.setTitle("Performs Simple Multiplications");
        this.setVisible(true);
        m_total = new BigInteger(INITIAL_VALUE);
        m_totalTf.setText(INITIAL_VALUE);
        m_totalTf.setEditable(false);

        JPanel content = new JPanel();
        content.setLayout(new FlowLayout());
        content.add(new JLabel("Input"));
        content.add(m_userInputTf);
        content.add(m_multiplyBtn);
        content.add(new JLabel("Total"));
        content.add(m_totalTf);
        content.add(m_clearBtn);

        this.setContentPane(content);
        this.pack();

    }
    public void throwExcept(){
        JOptionPane.showMessageDialog(CalcView.this, "Bad Number");
    }
}

此外，您可以使用构造函数在类之间传递事件处理程序，或者只创建一个setter函数。您可以在这里https://www.javatpoint.com/java-constructor阅读有关构造函数的更多信息