我在我的一个项目中有以下问题,花了我一段时间来弄清楚什么导致问题,我可以用我附加的这个简单的代码重现它。JScrollBar + JTextPane与HTML不正确滚动到最大值
我动态添加内容有一个HTMLEditorKit JTextPane中。我将autoscroll设置为关闭状态,因为我想手动控制它(当用户向上滚动,停止以及触发事件再次激活时)。
现在的问题是,当我将JScrollBar的值设置为最大值时,在将内容插入到HTMLDocument中之后,这是一个不同的时刻。当我手动再次触发setValue时,它会滚动到正确的最大值。
看来的JScrollBar不知道如何正确maximumValue只是增加了HTMLDocument的后右侧,只是一个(延迟)时间之后。
使用
caret.setUpdatePolicy(DefaultCaret.ALWAYS_UPDATE);
是不是一个解决方案,因为它也不能正常工作。它也不会滚动到最大值,在下面留下一个视图像素,这是我不想要的。
以下是完整的代码再生的问题。如果你点击右边的按钮(添加&滚动条),它会在主体中插入一个DIV元素。当到达最后一条可见行时,它不会正确滚动到最后一个最大值,最后一行是隐藏的。但是当你手动点击左键来触发第二个scrollToEnd()时,它会正确滚动到最大值。
代码:
/*
* To change this license header, choose License Headers in Project Properties.
* To change this template file, choose Tools | Templates
* and open the template in the editor.
*/
package javaapplication26;
import java.io.IOException;
import java.math.BigInteger;
import java.security.SecureRandom;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.swing.text.BadLocationException;
import javax.swing.text.DefaultCaret;
import javax.swing.text.Element;
import javax.swing.text.html.HTMLDocument;
import javax.swing.text.html.HTMLEditorKit;
public class NewJFrame extends javax.swing.JFrame {
/**
* Creates new form NewJFrame
*/
public NewJFrame() {
initComponents();
this.setSize(500, 200);
this.setLocationRelativeTo(null);
this.jTextPane1.setEditorKit(new HTMLEditorKit());
this.jTextPane1.setContentType("text/html");
this.jTextPane1.setText("<html><body><div id=\"GLOBALDIV\"></div></body></html>");
this.jScrollPane1.setHorizontalScrollBarPolicy(javax.swing.ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);
this.jScrollPane1.setVerticalScrollBarPolicy(javax.swing.ScrollPaneConstants.VERTICAL_SCROLLBAR_AS_NEEDED);
DefaultCaret caret = (DefaultCaret) this.jTextPane1.getCaret();
caret.setUpdatePolicy(DefaultCaret.NEVER_UPDATE);
this.jScrollPane1.setAutoscrolls(false);
this.jTextPane1.setAutoscrolls(false);
}
private void scrollToEnd() {
this.jScrollPane1.getVerticalScrollBar().setValue(this.jScrollPane1.getVerticalScrollBar().getMaximum());
//this.jTextPane1.setCaretPosition(this.jTextPane1.getDocument().getLength());
}
/**
* 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() {
jPanel1 = new javax.swing.JPanel();
jScrollPane1 = new javax.swing.JScrollPane();
jTextPane1 = new javax.swing.JTextPane();
jPanel2 = new javax.swing.JPanel();
jButton1 = new javax.swing.JButton();
jButton2 = new javax.swing.JButton();
setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
jPanel1.setLayout(new java.awt.BorderLayout());
jScrollPane1.setViewportView(jTextPane1);
jPanel1.add(jScrollPane1, java.awt.BorderLayout.CENTER);
getContentPane().add(jPanel1, java.awt.BorderLayout.CENTER);
jButton1.setText("Scroll to end");
jButton1.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
jButton1ActionPerformed(evt);
}
});
jPanel2.add(jButton1);
jButton2.setText("Add & scroll");
jButton2.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
jButton2ActionPerformed(evt);
}
});
jPanel2.add(jButton2);
getContentPane().add(jPanel2, java.awt.BorderLayout.PAGE_END);
pack();
}// </editor-fold>
private void jButton2ActionPerformed(java.awt.event.ActionEvent evt) {
try {
HTMLDocument doc = (HTMLDocument) this.jTextPane1.getDocument();
HTMLEditorKit editorKit = (HTMLEditorKit) this.jTextPane1.getEditorKit();
SecureRandom random = new SecureRandom();
String htmlCode = "<div style=\"background-color: #FFFF22; height: 12px; font-size: 12;\">"+new BigInteger(64, random).toString(64)+"</div>";
//editorKit.insertHTML(doc, doc.getLength(), htmlCode, 0, 0, null);
Element element = doc.getElement("GLOBALDIV");
if (element != null) {
doc.insertBeforeEnd(element, htmlCode);
}
this.scrollToEnd();
} catch (BadLocationException ex) {
Logger.getLogger(NewJFrame.class.getName()).log(Level.SEVERE, null, ex);
} catch (IOException ex) {
Logger.getLogger(NewJFrame.class.getName()).log(Level.SEVERE, null, ex);
}
}
private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {
this.scrollToEnd();
}
/**
* @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(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (InstantiationException ex) {
java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (IllegalAccessException ex) {
java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (javax.swing.UnsupportedLookAndFeelException ex) {
java.util.logging.Logger.getLogger(NewJFrame.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 NewJFrame().setVisible(true);
}
});
}
// Variables declaration - do not modify
private javax.swing.JButton jButton1;
private javax.swing.JButton jButton2;
private javax.swing.JPanel jPanel1;
private javax.swing.JPanel jPanel2;
private javax.swing.JScrollPane jScrollPane1;
private javax.swing.JTextPane jTextPane1;
// End of variables declaration
}
此代码更换工作,虽然,但留下一个小缺口,也无法正常滚动到最大值:
this.jTextPane1.setCaretPosition(0);
this.jTextPane1.setCaretPosition(this.jTextPane1.getDocument().getLength());
非常感谢您!这似乎解决了这个问题!这是做这种事的正确方法吗?如果我将大量内容动态添加到窗格,例如每秒几行,会怎么样?不会“吹”整个事情,为每个scrollToEnd()创建一个新的Runnable? –
这是否正确取决于确切的用例。这是正确的,即更新模型的顺序,然后是视图正常工作。由于它从视图更新中分离了模型更新,因此可能会出现这种情况无法正常工作的罕见用例,例如,当模型的几个冲突更新没有以正确的顺序更新GUI时。然而,这是不太可能的,因为执行runnable的EDT事件按照它们生成的顺序排序到事件队列中。 –
至于较高的负载,如每秒几行,这应该仍然没问题。实例化Runnable并不昂贵,因为它不会创建新线程。 EDT线程调用Runnables的run()方法,因此不会创建新的线程。最终每个'invokeLater'都有一个新对象,但这是可以接受的(每个Swing事件都有相同的问题)。 如果可能的话,将几个模型更新合并到一个'scrollToEnd()'更新中当然会有所帮助,但这取决于创建文档更改的逻辑。 –