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我希望能够将用户输入从我的 GUI 传递给我的一个类。但是，输入不会被传递并立即检查 if 语句。如何让程序等待输入并且仅在单击按钮后检查？

主班

public class MainTest {
    public static void main(String[] args) {
        String weaponCategory;
        //Create Java GUI
        GUITest window = new GUITest();

        if(window.getCategory() != "")
        {
            System.out.println("test");
        }
    }

}

GUITest 类

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

public class GUITest implements ActionListener{

    private JFrame frmInventorysystem;
    private JPanel frameBottom;
    private JComboBox equipList;
    private String category = "";
    private JButton confirmBtn, cancelBtn;

    /**
     * Create the application.
     */
    public GUITest() 
    {       
        frmInventorysystem = new JFrame();
        frmInventorysystem.setTitle("InventorySystem");
        frmInventorysystem.setBounds(100, 100, 450, 300);
        frmInventorysystem.getContentPane().setLayout(new BorderLayout(0, 0));

        frmInventorysystem.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        /*JFrame inside another JFrame is not recommended. JPanels are used instead.
        * Creating a flow layout for the bottom frame
        */
        frameBottom = new JPanel();
        frameBottom.setLayout(new FlowLayout());

        //creates comboBox to find out which of the three items player is looking to insert
        String[] weaponCategories = {"Weapon", "Armor", "Mod"};
        equipList = new JComboBox(weaponCategories);
        frmInventorysystem.getContentPane().add(equipList, BorderLayout.NORTH);

        //Converting BorderLayout.south into a flow layout
        frmInventorysystem.getContentPane().add(frameBottom, BorderLayout.SOUTH);

        confirmBtn = new JButton("Confirm");
        confirmBtn.addActionListener(this);

        frameBottom.add(confirmBtn);

        cancelBtn = new JButton("Cancel");
        cancelBtn.addActionListener(this);
        frameBottom.add(cancelBtn);

        frmInventorysystem.setVisible(true);
    }

    public void actionPerformed(ActionEvent e)
    {
        //creates new windows to sort equipment when confirmBtn is clicked
        if(e.getSource() == confirmBtn) 
        {
            if(equipList.getSelectedItem().equals("Weapon"))
            {
                //GUIWeaponCategory weapon = new GUIWeaponCategory();
                category = equipList.getSelectedItem().toString();
            }
        }
        //Exits when cancelBtn is clicked
        if(e.getSource() == cancelBtn)
        {
            System.exit(0);
        }
    }

    public String getCategory()
    {
        return category;
    }

    public void setCategory(String a)
    {
        category = a;
    }
}

GUITest 按预期启动。但是，缺少第一个 println。我该怎么做呢？我缺少哪些概念或代码片段？

EDIT1：添加了更多细节以使程序可重复和完整。

EDIT2：使代码更具可读性以便于理解。

4

1 回答 1

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您的程序需要进行一些更改

  1. extends JFrame如我上面的评论中所述删除，请参阅扩展 JFrame 与在程序中创建它

  2. 将您的程序放在 EDT 上，请参阅此答案的第 3 点以及main有关如何执行此操作的示例的方法。

  3. 你对如何ActionListeners工作感到困惑，他们等到你在程序中执行某些操作（即你按下Confirm按钮）然后做一些事情。程序中的“某事”意味着：打印所选项目并检查它是否是武器，然后执行其他操作。

因此，在这种情况下，您无需返回main以继续您的程序，main仅用于初始化您的应用程序，而不是其他任何东西。你需要在事件中思考，而不是按顺序思考。这是最棘手和最重要的部分。

您需要从控制台应用程序更改您的编程范例，并且do-while一切都以顺序方式发生，而不是当用户对您的应用程序执行某些操作时触发的事件。

例如：

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

public class GUITest implements ActionListener {
    private JFrame frmInventorysystem;
    private JPanel frameBottom;
    private JComboBox equipList;
    private JButton confirmBtn, cancelBtn;

    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> new GUITest()); //Java 8+ if using an earlier version check the point #2 in this answer and modify the code accordingly.
    }

    /**
     * Create the application.
     */
    public GUITest() {
        frmInventorysystem = new JFrame();
        frmInventorysystem.setTitle("InventorySystem");
        frmInventorysystem.setBounds(100, 100, 450, 300);
        frmInventorysystem.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frmInventorysystem.getContentPane().setLayout(new BorderLayout(0, 0));

        /*
         * JFrame inside another JFrame is not recommended. JPanels are used instead
         * Creating a flow layout for the bottom frame
         */
        frameBottom = new JPanel();
        frameBottom.setLayout(new FlowLayout());

        // creates comboBox to find out which of the three items player is looking to
        // insert
        String[] weaponCategories = { "Weapon", "Armor", "Mod" };
        equipList = new JComboBox(weaponCategories);
        frmInventorysystem.getContentPane().add(equipList, BorderLayout.NORTH);

        // Converting BorderLayout.south into a flow layout
        frmInventorysystem.getContentPane().add(frameBottom, BorderLayout.SOUTH);

        confirmBtn = new JButton("Confirm");
        confirmBtn.addActionListener(this);

        frameBottom.add(confirmBtn);

        cancelBtn = new JButton("Cancel");
        cancelBtn.addActionListener(this);
        frameBottom.add(cancelBtn);

        frmInventorysystem.setVisible(true);
    }

    public void actionPerformed(ActionEvent e) {
        // creates new windows to sort equipment when confirmBtn is clicked
        if (e.getSource() == confirmBtn) {
            String category = equipList.getSelectedItem().toString(); //Get the selected category
            doSomething(category); //Pass it as a parameter
        }
        // Exits when cancelBtn is clicked
        if (e.getSource() == cancelBtn) {
            frmInventorysystem.dispose();
        }
    }

    // Do something with the category
    private void doSomething(String selectedEquipment) {
        System.out.println(selectedEquipment);
        if (selectedEquipment.equals("Weapon")) {
            System.out.println("It's a weapon!"); //You can open dialogs or do whatever you need here, not necessarily a print.
        } else {
            System.out.println("Not a weapon");
        }
    }
}

请注意，我删除了继承，我没有返回main并仍在打印所选项目并检查它是否是武器。

我还以更安全的方式退出应用程序。

这是一个示例输出：

Weapon
It's a weapon!
Armor
Not a weapon
于 2019-05-30T16:23:52.187 回答