JScrollPane 不起作用/显示滚动条

Posted 2023-02-23

【中文标题】JScrollPane 不起作用/显示滚动条

【英文标题】：JScrollPane doesn't work/show scroll Bars

【发布时间】：2014-12-14 02:00:12

【问题描述】：

我有一个JFrame，它包含一个JPanel，它包含一个JScrollPane，它包含另一个JPanel，有两个组件（JPanels）。 出于某种原因，当我使用 WindowBuilder 的预览选项查看框架时，JScrollPane 显示 horizo​​ntal 滚动条，但是当我编译并运行应用程序时，它没有。 这是它的样子：

来自预览选项：

编译时：

这是我的代码：

package home;

import java.awt.EventQueue;

import javax.swing.JFrame;

import java.awt.SystemColor;

import javax.swing.JPanel;
import javax.swing.SpringLayout;
import javax.swing.UIManager;

import net.miginfocom.swing.MigLayout;

import javax.swing.JLabel;
import javax.swing.SwingConstants;

import java.awt.Component;
import java.awt.BorderLayout;
import java.awt.Frame;

import com.jgoodies.forms.layout.FormLayout;
import com.jgoodies.forms.layout.ColumnSpec;
import com.jgoodies.forms.layout.RowSpec;
import com.jgoodies.forms.factories.FormFactory;

import javax.swing.GroupLayout;
import javax.swing.GroupLayout.Alignment;
import javax.swing.JButton;
import javax.swing.LayoutStyle.ComponentPlacement;
import javax.swing.UnsupportedLookAndFeelException;

import java.awt.Font;

import javax.swing.BoxLayout;

import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.awt.Color;
import java.awt.Dimension;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;

import javax.swing.ImageIcon;
import javax.swing.JScrollPane;
import javax.swing.border.EtchedBorder;
import javax.swing.border.LineBorder;
import javax.swing.ScrollPaneConstants;

public class AtmManeger implements Serializable  

    private JFrame frmAtmManeger;
    public int NumOfOpenAtmMachines = 0;
    private final AtmManeger frame = this;
    private ArrayList<ATMmachine> ATMs = new ArrayList<ATMmachine>();//Array list of all the ATM machines that were opened
    private AtmAccountDataBase atmDataBase = new AtmAccountDataBase();
    private JLabel contLabel = null;
    /**
     * Launch the application.
     */
    public static void main(String[] args) 

        EventQueue.invokeLater(new Runnable() 
            public void run() 
                try 
                    AtmManeger window = new AtmManeger();
                    window.frmAtmManeger.setVisible(true);
                 catch (Exception e) 
                    e.printStackTrace();
                
            
        );

    

    /**
     * Create the application.
     */
    public AtmManeger getFrame() 
        return this.frame;
    
    public AtmManeger() 
        initialize();
    

    /**
     * Initialize the contents of the frame.
     */
    private void initialize() 
        try 
            UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
         catch (ClassNotFoundException e1) 
            // TODO Auto-generated catch block
            e1.printStackTrace();
         catch (InstantiationException e1) 
            // TODO Auto-generated catch block
            e1.printStackTrace();
         catch (IllegalAccessException e1) 
            // TODO Auto-generated catch block
            e1.printStackTrace();
         catch (UnsupportedLookAndFeelException e1) 
            // TODO Auto-generated catch block
            e1.printStackTrace();
        
        frmAtmManeger = new JFrame();
        frmAtmManeger.setMinimumSize(new Dimension(615, 420));
        frmAtmManeger.getContentPane().setBackground(SystemColor.activeCaption);
        JPanel mainPanel = new JPanel();
        mainPanel.setPreferredSize(new Dimension(10, 10));
        frmAtmManeger.setContentPane(mainPanel);
        JScrollPane scrollPane = new JScrollPane();
        mainPanel.add(scrollPane, BorderLayout.CENTER);
        JPanel subPanel = new JPanel();
        subPanel.setSize(new Dimension(1190, 350));
        subPanel.setBackground(SystemColor.activeCaption);
        subPanel.setPreferredSize(new Dimension(1190, 350));
        scrollPane.setViewportView(subPanel);
        subPanel.setLayout(new MigLayout("", "[50.00%,grow][50.00%,grow]", "[grow]"));
        JPanel panel = new JPanel();
        subPanel.add(panel,"cell 0 0,grow");
        panel.setBorder(null);
        panel.setBackground(SystemColor.textHighlight);

        panel.setLayout(new MigLayout("", "[100.00%,grow]", "[71px][13.54%][10.09%][41px][][grow]"));

        JPanel panel_1 = new JPanel();
        subPanel.add(panel_1, "cell 1 0,grow");
        frmAtmManeger.setTitle("ATM Maneger");
        frmAtmManeger.setBounds(700, 400, 609, 420);
        frmAtmManeger.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    

我制作了另一个与这个非常相似的应用程序，只是那个固有的JFrame。我找不到这段代码和上面的代码有什么区别。代码：

package home;

import java.awt.BorderLayout;
import java.awt.EventQueue;

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.border.EmptyBorder;
import javax.swing.JScrollPane;

import java.awt.Color;
import java.awt.FlowLayout;

import net.miginfocom.swing.MigLayout;

import java.awt.Dimension;
import javax.swing.JLabel;
import javax.swing.JButton;

public class test02 extends JFrame 

    private JPanel contentPane;

    /**
     * Launch the application.
     */
    public static void main(String[] args) 
        EventQueue.invokeLater(new Runnable() 
            public void run() 
                try 
                    test02 frame = new test02();
                    frame.setVisible(true);
                 catch (Exception e) 
                    e.printStackTrace();
                
            
        );
    

    /**
     * Create the frame.
     */
    public test02() 
        try 
            UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
         catch (Exception e) 
            // Handle exception
        
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setBounds(100, 100, 432, 300);
        contentPane = new JPanel();
        contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
        contentPane.setLayout(new BorderLayout(0, 0));
        setContentPane(contentPane);

        JScrollPane scrollPane = new JScrollPane();
        contentPane.add(scrollPane, BorderLayout.CENTER);

        JPanel panel = new JPanel();
        panel.setPreferredSize(new Dimension(800, 220));
        panel.setBackground(Color.RED);
        scrollPane.setViewportView(panel);
        panel.setLayout(new MigLayout("", "[50.00%,grow][50.00%,grow]", "[grow]"));

        JPanel panel_1 = new JPanel();
        panel.add(panel_1, "cell 0 0,grow");
        panel_1.setLayout(new MigLayout("", "[][][][][][][]", "[][][][][][]"));

        JLabel lblNewLabel = new JLabel("New label");
        panel_1.add(lblNewLabel, "cell 2 1");

        JButton btnNewButton_1 = new JButton("New button");
        panel_1.add(btnNewButton_1, "cell 3 3");

        JButton btnNewButton = new JButton("New button");
        panel_1.add(btnNewButton, "cell 2 5");

        JLabel lblNewLabel_1 = new JLabel("New label");
        panel_1.add(lblNewLabel_1, "cell 6 5");

        JPanel panel_2 = new JPanel();
        panel.add(panel_2, "cell 1 0,grow");
    

所以这可能只是一个愚蠢的错误，但它是什么？

【问题讨论】：

我不使用MigLayout，但如果您愿意放弃它，我会发布答案。

【参考方案1】：

我没有看到您更改滚动条策略。 由于没有溢出，如果不更改该设置，您将不会看到滚动条出现。

尝试：

scrollbar.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);

【讨论】：

我的问题是水平滚动条。但无论如何，它仍然不起作用。但是感谢您的帮助:)

所以即使使用 setHorizo​​nalScrollBarPolicy 也无法修复它？

【参考方案2】：

我已经编写了一个程序来根据要求显示面板。

代码：

private void createUI() 
        JFrame frame = new JFrame();
        JPanel panel = new JPanel(new FlowLayout(FlowLayout.LEFT));
        JScrollPane pane = new JScrollPane();

        JPanel leftPnl = new JPanel(new BorderLayout());
        JPanel rightPnl = new JPanel(new BorderLayout());

        leftPnl.add(new JLabel("Left"), BorderLayout.CENTER);
        leftPnl.setBorder(new LineBorder(Color.black, 5));
        leftPnl.setPreferredSize(new Dimension(400, 400));
        rightPnl.add(new JLabel("Right"), BorderLayout.CENTER);
        rightPnl.setBorder(new LineBorder(Color.black, 5));
        rightPnl.setPreferredSize(new Dimension(400, 400));

        panel.add(leftPnl);
        panel.add(rightPnl);
        panel.add(pane);

        frame.setPreferredSize(new Dimension(400, 400));
        frame.setTitle("ScrollPane Example");
        frame.add(new JScrollPane(panel));
        frame.setVisible(true);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    

【讨论】：

实际上我遇到了问题..当我通过将ScrollPane 放在面板上并将其添加到框架中来做同样的事情时，即使我的滚动条也不可见。但是在我编写的示例中，我将滚动窗格直接添加到框架中，而不是将其添加到面板中。

我尝试直接在 JFrame 中添加 scrollPane，它可以工作，但是窗口构建器没有显示框架。我不明白为什么相同的代码在 test02 类中工作，而不是在这个类中......