如何将控制台迁移到 swing 应用程序

Question

我有一个基本的计算程序，我已经开始构建一个 GUI，我有一个 window。我的问题是，如何将这两件事联系在一起？我听说我应该先制作 GUI，但这让我更加困惑。

我想知道如何将我的后端连接到前端 (GUI)

public class Calc_functions {

    //declaring subtraction feild
    public int Sub (int num1, int num2) {
        //returns the value num1 subtract num2
        return num1 - num2;
    }

    //declaring addition field
    public int Add (int fnum, int snum) {
        //returns the value num1 add num2
        return fnum + snum;
    }

    //declaring division field
    public int Div (int fnum, int snum) {
        //returns the value num1 divided by num2
        return fnum / snum;
    }

    //declaring multiplication field
    public int Mult (int fnum, int snum) {
        //returns the value num1 multiplied by num2
        return fnum * snum;
    }

}

import java.util.Scanner;

public class calc_main {

    public static void main(String[] args) {
        // calls for the Calc_functions class
        Calc_functions math = new Calc_functions ();
        //waits for user imputs and then store it as a variable
        Scanner numbers = new Scanner(System.in);
        //prints out too interface
        System.out.println("Calulator : Enter two numbers and choose a mathmatic symbol + - x /");
        System.out.println("_____________________");
        //prints out too interface
        System.out.print("First number:");
        int num1 = numbers.nextInt();
        //prints out too interface
        System.out.print("Second number:");
        int num2= numbers.nextInt();
        //prints out too interface
        System.out.print("Enter symbol +  -  x  / of the calculation you would like to perform :");
        String operation= numbers.next();

        // if the user has inputted +, it will carry out the addition of the two variables the user has unputted.
        if (operation.equals("+"))
            System.out.println(math.Add(num1, num2));
        // if the user has inputted -, it will carry out the addition of the two variables the user has unputted.
        else if (operation.equals("-"))
            System.out.println(math.Sub(num1, num2));
        // if the user has inputted x, it will carry out the addition of the two variables the user has unputted.
        else if (operation.equals("x"))
            System.out.println(math.Mult(num1, num2));
        // if the user has inputted /, it will carry out the addition of the two variables the user has unputted.
        else if (operation.equals("/"))
            System.out.println(math.Div(num1, num2));
        else
            System.out.println("The operation is not valid.");

        numbers.close();
        System.exit(0);
    }

}

import javax.swing.*;

// some code used from docs.oracle.com
public class Calc_gui {

    private static void GUI(){
        JFrame createshowGUI = new JFrame("Calc_gui");
        createshowGUI.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        //Add the ubiquitous "Hello World" label.
        JLabel label = new JLabel("calcgui");
        createshowGUI.getContentPane().add(label);

        //Display the window.
        createshowGUI.pack();
        createshowGUI.setVisible(true);
    }

    public static void main(String[] args) {
        //Schedule a job for the event-dispatching thread:
        //creating and showing this application's GUI.
        javax.swing.SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                GUI();
            }
        });
    }

}

Answer 1

对于这样一个简单的任务，您不需要 "backend" 和 "frontend"。 对于此用例，调用您的计算和 gui 组件的相应操作方法就足够了。操作方法意味着您添加例如ActionListener 到 JButton 然后执行相应的命令，例如执行加法。

然后你可以将4个case需要执行的代码提取到监听器中，例如（伪代码，没编译！）：

void actionPerformed(ActionEvent e)
{    //listener for add-button
    int num1 = Integer.parse(textfield1.getText());
    int num2 = Interger.parse(textfield2.getText());
    textField3.setText(String.valueOf( math.add(num1, num2) ) );
}

...然后通过 addActionListener 将它们连接到按钮。

上面的代码从两个文本字段中获取两个值，并尝试将它们转换为 int 值。然后它调用你的计算方法。有多种方法可以将侦听器添加到多个按钮并检测按下了哪个按钮（通过比较事件源与组件），因此您不需要复制所有 "get and set values form textfields" 代码。

这是基本原则。对于更复杂的应用程序或较长的运行操作，这可能不是应该的方式，因为在 ActionListener 中执行它们意味着它们会阻止 EDT，并且不会处理任何 GUI 事件。

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