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，并且我有一个窗口。我的问题是，我如何将这两件事联系在一起？我听说我应该首先制作GUI，但这让我更加困惑。

我希望能够知道如何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，你将不需要“后端”和“前端”。 对于此用例，只需调用您的计算和贵组件的相应操作方法即可。操作方法意味着您可以添加例如ActionListener到JButton然后执行相应的命令，例如执行加法。

然后，您可以提取需求为4例为听众要执行的代码，例如（伪代码，没有编译！）：

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))); 
} 

...，然后将它们连接通过addActionListener的按钮。

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（通过比较事件的来源与组件），因此您不需要重复所有“获取和设置值为textfields”的代码。

这是基本原理。它可能不是应该为更复杂的应用程序或长时间运行的操作完成的方式，因为在ActionListener中执行它们意味着它们阻止了EDT，并且不会处理GUI事件。