如何將 JSpinner 值從 Java class 傳遞給另一個 Java class

Question

我對 Java 的了解很差，尤其是在課程方面。 我有一個 class，它有一個public static JSpinner和SpinnerNumberModel(2, 2, 4, 1) 。 更新 JSpinner 中的值（2、3 或 4）后，按下 JButton（單獨的類）后，必須將其傳遞給同一個 JButton。 但是只傳遞我已經設置為默認值的值，即2。在搜索所有可能的論壇后，我意識到問題可能出在static修飾符上。 但是，如果沒有這個修飾符，就會出現“Non-static field 'JSpinner_name' cannot be referenced from a static context”的錯誤。 JSpinner所在的class的代碼：

public class settingsPanel extends JPanel {
    public static JSpinner playersCount = new JSpinner(new SpinnerNumberModel(2, 2, 4, 1));
    
    public void main(){

        //some code with JSpinner change listener

        add(playersCount);
        saveSettingsButton saveSettingsButton = new saveSettingsButton();
        add(saveSettingsButton);
        saveSettingsButton.main();
    }
}

我需要從 JSpinner 向其傳遞值的 class 代碼：

public class saveSettingsButton extends JButton {
    public void main(){

        //some code

        addActionListener(e -> {
            int errorChecking = 0;
            switch ((int) settingsPanel.playersCount.getValue()) {

                //some code

        });
    }
}

我想將settingsPanel.playersCount.getValue()傳遞給 saveSettingsButton class，但如上所述，僅傳遞預定義值。 我試圖創建一個方法，但仍然無法正常工作（也許我是方法的菜鳥）。 如何在另一個 class 中提供來自 JSpinner 的更新值？

Answer 1

Java 教程通常希望用戶“擴展”用戶界面類以使用它們。 這在理論上很棒，但在實踐中，通常會導致過度殺戮，尤其是對於初學者而言。

這是一個使用您的組件的簡單程序，它允許按鈕從您的微調器中讀取值。

我添加了評論來解釋應用程序的每個組件在做什么以及為什么這樣做。

package com.company;

import javax.swing.*;

public class MyApp {
    // Declare the UI components we plan on using
    // Note: Without "private" or "public" modifiers
    //   they'll default to "package private", which
    //   is a sane default.
    JFrame mainFrame;
    JPanel settingsPanel;
    JButton saveSettingsButton;
    JSpinner playersCount;

    public MyApp() {
        // Initialize our UI components
        mainFrame = new JFrame("My App");
        settingsPanel = new JPanel();
        saveSettingsButton = new JButton("Click Me");
        playersCount = new JSpinner(new SpinnerNumberModel(2, 2, 4, 1));

        // Add any listeners (such a "click" listener)
        saveSettingsButton.addActionListener(e -> {
            int errorChecking = 0;
            // The button can read the spinner because they're both declared within the same scope (same class)
            switch ((int) playersCount.getValue()) {
                default:
                        System.out.println((int)playersCount.getValue());
            };
        });

        // Add UI components to panel
        settingsPanel.add(playersCount);
        settingsPanel.add(saveSettingsButton);

        // Add panel to frame/window
        mainFrame.add(settingsPanel);

        // Show our UI
        mainFrame.pack(); // Automatically set size of frame to fit components
        mainFrame.setLocationRelativeTo(null); // Center frame on primary screen
        mainFrame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE); // Close the app when this window is closed
        mainFrame.setVisible(true);

        // Perform our initial action
        saveSettingsButton.doClick();
    }

    // This is the main entry point into the application when run
    // By default, applications are NOT synchronized onto the UI thread (known as the "Event Dispatch Thread")
    // UIs that aren't synchronized can flicker, crash and have weird behavior
    // SwingUtilities has two functions to synchronize, we'll use "invokeLater()" for this purpose. 
    public static void main(String ... args) {
        SwingUtilities.invokeLater(() -> new MyApp()); // invokeLater(): UI should always be created on EDT!
    }


}