JScrollPane不适用于我的JPanel [英] JScrollPane doesn't work for my JPanel

问题描述

首先，我必须说我已经检查了这些问题并且没有找到我的答案：

first of all I must say that I have checked these questions and didn't find my answer :

1 ， 2 ， 3 ，4 ， 5 ， 6 ， 7

以及其他许多问题喜欢这样

and many other questions like so

我也检查了这些教程和示例：

also I have checked these tutorials and examples:

1 ， 9 ， 10 ， 11

和许多其他网站。但我无法解决我的问题。

and many other sites. but I couldn't fix my problem.

和
这是我的代码的简单类型：

and this is the simple kind of my code:

public class Question extends JFrame {
public Question() {
    Dimension d = Toolkit.getDefaultToolkit().getScreenSize();
    setLayout(new BorderLayout());
    setSize(d.width, d.height);
    setResizable(false);
    setDefaultCloseOperation(EXIT_ON_CLOSE);

    JPanel panel = new JPanel();
    panel.setPreferredSize(new Dimension(d.width, d.height));
    panel.setBorder(BorderFactory.createLineBorder(Color.red));
    panel.setLayout(new BoxLayout(panel, 1));
    for (int i = 0; i < 100; i++) {
        panel.add(new JButton("kjdh"));
    }
    JScrollPane scrollPane = new JScrollPane(panel);
    scrollPane.setPreferredSize(new Dimension(500, 500));
    getContentPane().add(scrollPane);
    getContentPane().add(panel);
    setVisible(true);

}

public static void main(String[] args) {
    new Question();
} 
}

但 JScrollPane 没有出现。我测试过很多东西。我已经改变了将面板和 scrollPane 添加到我的框架但它不起作用。任何人都可以帮助我吗？

but the JScrollPane doesn't appear. I have tested many things. I have changed the way adding panel and scrollPane to my frame but it didn't work. can any one help me plz?

推荐答案

1. 不要在面板上设置首选大小。请参阅我是否应避免在Java Swing中使用setPreferred / Maximum / MinimumSize方法？出于原因。


2. 仅将 滚动窗格添加到内容窗格。
   
   

1. Don't set a preferred size on the panel. See Should I avoid the use of setPreferred/Maximum/MinimumSize methods in Java Swing? for the reasons why.
2. Add only the scroll pane to the content pane.

1. 使用默认布局（ BorderLayout ）的内容窗格将默认将组件放入 CENTER 约束（如果没有提供）， CENTER 区域只能接受单个组件。


2. 除此之外该面板已经添加到滚动窗格中，它已经显示在其中，并且只能出现在一个容器中。

1. A content pane using the default layout (BorderLayout) will default to putting the component in the CENTER constraint if none is supplied, and the CENTER area can only accept a single component.
2. Besides that, the panel has already been added to the scroll pane, it will already appear inside it, and can only appear in a single container.

不要扩展框架，只使用一个实例。

不要 setSize ，但 setExtendedState 。

应在EDT上构建和更新GUI。

更好的关闭操作是 DISPOSE_ON_CLOSE 。

Don't extend frame, just use an instance of one.

Don't setSize, but setExtendedState.

GUIs should be constructed and updated on the EDT.

A better close operation is DISPOSE_ON_CLOSE.

---

---

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

public class Question {

    public Question() {
        JFrame f = new JFrame();
        f.setLayout(new BorderLayout());
        f.setResizable(false);
        f.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);

        JPanel panel = new JPanel();
        panel.setBorder(BorderFactory.createLineBorder(Color.red));
        panel.setLayout(new BoxLayout(panel, 1));
        for (int i = 0; i < 100; i++) {
            panel.add(new JButton("kjdh"));
        }
        JScrollPane scrollPane = new JScrollPane(panel);
        f.getContentPane().add(scrollPane);
        f.pack();
        f.setExtendedState(JFrame.MAXIMIZED_BOTH);
        f.setVisible(true);
    }

    public static void main(String[] args) {
        Runnable r = new Runnable() {
            @Override
            public void run() {
                new Question();
            }
        };
        SwingUtilities.invokeLater(r);
    }
}

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