当 TextArea 有很多行时，JScrollPane 在 Nimbus L&F 中不显示缩略图

Question

我在 Netbeans 8.1（Java 版本 1.8.0_65）中编写了一个简单的程序，它获取已发现文件的列表并将它们写入 jTextArea。这工作正常，除非有很多行写入 jTextArea（即超过 500 行左右），滚动条中的拇指消失。我看到了这个描述的确切问题。

这似乎是一个带有 Nimbus L&F 的 known issue，人们对此有 posted 解决方法，如上文 post 中所述，他们说要解决此问题只需添加该行：

UIManager.getLookAndFeelDefaults().put("ScrollBar.minimumThumbSize", new Dimension(30, 30));

我遇到的问题是我应该把这行代码放在哪里？我已经尝试在创建 jScrollPanel 之前将它添加到 initComponents（如下面的代码所示）。在检查 Nimbus 是否可用时，我也在 if 语句之后尝试过它：

for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
            if ("Nimbus".equals(info.getName())) {
                javax.swing.UIManager.setLookAndFeel(info.getClassName());
                break;
            }
        }

我显然只是在试图将它贴在不同的地方而不理解我在做什么，毫不奇怪，这是行不通的。

谁能帮我确定这个解决方法代码行应该放在哪里？

我的代码：

    public class ViewFiles extends javax.swing.JFrame {

    /**
     * Creates new form ViewFiles
     */
    public ViewFiles() {
        initComponents();

    }

    public ViewFiles(ArrayList<DiscoveredFile> files){
        initComponents();
        discoveredFiles = files;
        displayFiles();
    }

    /**
     * This method is called from within the constructor to initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is always
     * regenerated by the Form Editor.
     */
    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">                          
    private void initComponents() {

        javax.swing.UIManager.getLookAndFeelDefaults().put("Scrollbar.minimumThumbSize", new Dimension(30,30));
        jScrollPane1 = new javax.swing.JScrollPane();
        viewFilesTextArea = new javax.swing.JTextArea();
        viewFilesCloseButton = new javax.swing.JButton();

        setDefaultCloseOperation(javax.swing.WindowConstants.DISPOSE_ON_CLOSE);

        viewFilesTextArea.setColumns(20);
        viewFilesTextArea.setRows(5);
        jScrollPane1.setViewportView(viewFilesTextArea);

        viewFilesCloseButton.setText("Close");

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addContainerGap()
                .addComponent(jScrollPane1, javax.swing.GroupLayout.DEFAULT_SIZE, 656, Short.MAX_VALUE)
                .addContainerGap())
            .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
                .addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                .addComponent(viewFilesCloseButton)
                .addGap(29, 29, 29))
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addContainerGap()
                .addComponent(jScrollPane1, javax.swing.GroupLayout.DEFAULT_SIZE, 277, Short.MAX_VALUE)
                .addGap(18, 18, 18)
                .addComponent(viewFilesCloseButton)
                .addContainerGap())
        );

        pack();
    }// </editor-fold>                        

    /**
     * @param args the command line arguments
     */
    public static void main(String args[]) {
        /* Set the Nimbus look and feel */
        //<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
        /* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
         * For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html 
         */
        try {
            for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
                if ("Nimbus".equals(info.getName())) {
                    javax.swing.UIManager.setLookAndFeel(info.getClassName());
                    break;
                }
            }

        } catch (ClassNotFoundException ex) {
            java.util.logging.Logger.getLogger(ViewFiles.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(ViewFiles.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(ViewFiles.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(ViewFiles.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        }
        //</editor-fold>

        /* Create and display the form */
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new ViewFiles().setVisible(true);
            }
        });
    }

    // Variables declaration - do not modify                     
    private javax.swing.JScrollPane jScrollPane1;
    private javax.swing.JButton viewFilesCloseButton;
    private javax.swing.JTextArea viewFilesTextArea;
    // End of variables declaration                   
    private ArrayList<DiscoveredFile> discoveredFiles;

    public void displayFiles() {
        for (DiscoveredFile file : discoveredFiles){
            viewFilesTextArea.append(file.getFullPath() + "\n");
        }    
    }
}

Answer 1

这是另一种方法：

UIDefaults def = new UIDefaults();
def.put("ScrollBar.minimumThumbSize", new Dimension(30, 30));
jScrollPane1 = new JScrollPane();
jScrollPane1.getVerticalScrollBar().putClientProperty("Nimbus.Overrides", def);

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

public class ViewFiles2 extends JFrame {
  private JScrollPane jScrollPane1;
  private JButton viewFilesCloseButton;
  private JTextArea viewFilesTextArea;
  public ViewFiles2() {
    initComponents();
    displayFiles();
  }
  private void initComponents() {
      //NG?: UIManager.getLookAndFeelDefaults().put("ScrollBar.minimumThumbSize", new Dimension(30, 30));
      //OK?: UIManager.getDefaults().put("ScrollBar.minimumThumbSize", new Dimension(30, 30));

    jScrollPane1 = new JScrollPane();

    UIDefaults def = new UIDefaults();
    def.put("ScrollBar.minimumThumbSize", new Dimension(30, 30));
    jScrollPane1.getVerticalScrollBar().putClientProperty("Nimbus.Overrides", def);

    viewFilesTextArea = new JTextArea(20, 5);
    viewFilesCloseButton = new JButton("Close");
    jScrollPane1.setViewportView(viewFilesTextArea);

    GroupLayout layout = new GroupLayout(getContentPane());
    getContentPane().setLayout(layout);
    layout.setHorizontalGroup(
      layout.createParallelGroup(GroupLayout.Alignment.LEADING)
      .addGroup(layout.createSequentialGroup()
                .addContainerGap()
                .addComponent(jScrollPane1, GroupLayout.DEFAULT_SIZE, 656, Short.MAX_VALUE)
                .addContainerGap())
      .addGroup(GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
                .addContainerGap(GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                .addComponent(viewFilesCloseButton)
                .addGap(29, 29, 29))
    );
    layout.setVerticalGroup(
      layout.createParallelGroup(GroupLayout.Alignment.LEADING)
      .addGroup(layout.createSequentialGroup()
                .addContainerGap()
                .addComponent(jScrollPane1, GroupLayout.DEFAULT_SIZE, 277, Short.MAX_VALUE)
                .addGap(18, 18, 18)
                .addComponent(viewFilesCloseButton)
                .addContainerGap())
    );

    setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE);
    pack();
  }
  public void displayFiles() {
    viewFilesTextArea.setText(String.join("\n", Collections.nCopies(500, "aaaaaaaaaaaaa")));
  }
  public static void main(String[] args) {
    try {
      for (UIManager.LookAndFeelInfo info : UIManager.getInstalledLookAndFeels()) {
        if ("Nimbus".equals(info.getName())) {
          UIManager.setLookAndFeel(info.getClassName());
          break;
        }
      }
    } catch (Exception ex) {
      ex.printStackTrace();
    }
    //OK?: UIManager.getLookAndFeelDefaults().put("ScrollBar.minimumThumbSize", new Dimension(30, 30));
    //NG?: UIManager.getDefaults().put("ScrollBar.minimumThumbSize", new Dimension(30, 30));

    EventQueue.invokeLater(() -> {
      new ViewFiles2().setVisible(true);
    });
  }
}

当 TextArea 有很多行时，JScrollPane 在 Nimbus L&F 中不显示缩略图

JScrollPane doesn't show thumb in Nimbus L&F when TextArea has many lines

java

swing

textarea

scrollpane

nimbus