让JTextPane快速加载大文本

最新推荐文章于 2020-10-28 23:23:49 发布

原创最新推荐文章于 2020-10-28 23:23:49 发布 · 1k 阅读

0 ·

CC 4.0 BY-SA版权

文章标签：

#string #class #exception #performance #import #null

Java 专栏收录该内容

13 篇文章

订阅专栏

本文介绍了一种优化JTextPane加载大型文本效率的方法，通过自定义ViewFactory和调整布局策略，显著提升了用户体验。

项目中一直有个头疼的问题，就是JTextPane和JEditorPane加载大文本的时候，会非常慢，如果文本中没有一个换行符，那基本上就是没响应了。无意中看到一个网站的优化方法，发现非常好，他的是对JEditorPane的，我改成JTextPane，测试效果非常好。

import javax.swing.text.View; import javax.swing.text.BoxView; import javax.swing.text.Element; import javax.swing.text.FlowView; import javax.swing.text.IconView; import javax.swing.text.LabelView; import javax.swing.text.ViewFactory; import javax.swing.text.AttributeSet; import javax.swing.text.ComponentView; import javax.swing.text.ParagraphView; import javax.swing.text.StyleConstants; import javax.swing.text.StyledEditorKit; import javax.swing.text.AbstractDocument; class SimpleEditorKit extends StyledEditorKit { private static ViewFactory factory = new SimpleStyledViewFactory(); public ViewFactory getViewFactory(){ return factory; } private static class SimpleStyledViewFactory implements ViewFactory { public View create( Element elem ) { String kind = elem.getName(); if( kind == null ){ return new LabelView( elem ); } else if( kind.equals( AbstractDocument.ContentElementName ) ){ return new LabelView( elem ); } else if( kind.equals( AbstractDocument.ParagraphElementName ) ){ return new SimpleParagraphView( elem );/*new ParagraphView( elem );*/ } else if( kind.equals( AbstractDocument.SectionElementName ) ){ return new SimpleBoxView( elem );/*new BoxView( elem, View.Y_AXIS );*/ } else if( kind.equals( StyleConstants.ComponentElementName ) ){ return new ComponentView( elem ); } else if( kind.equals( StyleConstants.IconElementName ) ){ return new IconView( elem ); } return new LabelView( elem ); } } } class SimpleParagraphView extends ParagraphView { public static final int MAX_VIEW_SIZE = 100; public SimpleParagraphView( Element elem ) { super( elem ); strategy = new SimpleParagraphView.SimpleFlowStrategy(); } public int getResizeWeight( int axis ){ return 0; } public static class SimpleFlowStrategy extends FlowStrategy { protected View createView( FlowView fv, int startOffset, int spanLeft, int rowIndex ) { View res = super.createView( fv, startOffset, spanLeft, rowIndex ); if( res.getEndOffset() - res.getStartOffset() > MAX_VIEW_SIZE ) { //System.err.println( "startOffset:" + startOffset + " spanLeft:" + spanLeft + " rowIndex:" + rowIndex + " startOffset:" + res.getStartOffset() + " endOffset:" + res.getEndOffset() ); res = res.createFragment( startOffset, startOffset + MAX_VIEW_SIZE ); } return res; } } } class SimpleBoxView extends BoxView { public SimpleBoxView( Element elem ){ super( elem, View.Y_AXIS ); } protected void layout( int width, int height ) { //StackTraceElement[] ste = new Throwable().getStackTrace(); System.err.println( "----------------------------" ); for( int i = 0; i < ste.length; i ++ ){ String name = ste[i].getClassName(); System.err.println( "[" + ste[i].getClassName() + "] [" + ste[i].getMethodName() + "] [" + ste[i].getLineNumber() + "]" ); } //long start = System.currentTimeMillis(); if( width < Integer.MAX_VALUE ){ super.layout( width, height ); } //If the width of component is larger than screen's //start = System.currentTimeMillis() - start; //System.err.println( "w:" + width + " h:" + height + " time:" + start ); } }

import java.awt.BorderLayout; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import javax.swing.JFrame; import javax.swing.JButton; import javax.swing.JToolBar; import javax.swing.JTextPane; import javax.swing.JScrollPane; import javax.swing.SwingUtilities; //http://java-sl.com/JEditorPanePerformance.html public class TestLargeString extends JFrame implements ActionListener { private static final boolean OPTIMIZED = true; private String testText; private final JScrollPane scrollPane; private final JTextPane textPane; private final JButton setTextButton; private final JButton clearButton; public TestLargeString() { super( "Performance test" ); JToolBar toolBar = new JToolBar(); //////////////////////////////////////////////////////////////////////// textPane = new JTextPane(); if( OPTIMIZED ){ textPane.setEditorKit( new SimpleEditorKit() ); textPane.getDocument().putProperty( "i18n", Boolean.TRUE ); } this.getContentPane().add( scrollPane = new JScrollPane( textPane ) ); //////////////////////////////////////////////////////////////////////// setTextButton = new JButton( "Set text" ); setTextButton.addActionListener( this ); toolBar.add( setTextButton ); //////////////////////////////////////////////////////////////////////// clearButton = new JButton( "Clear" ); clearButton.addActionListener( this ); toolBar.add( clearButton ); //////////////////////////////////////////////////////////////////////// this.getContentPane().add( toolBar, BorderLayout.NORTH ); this.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE ); this.setBounds( 0, 0, 600, 600 ); this.setLocationRelativeTo( null ); this.setVisible( true ); } public final String getTestText() { if( testText == null ) { String string = "It's a long long long long long long long long long long" + " long long long long long long long long long long long long long long long long long long long long long long long long" + " long long long long long long long long long long long long long long long long long long long long long long long long" + " long long long long long long long long long long long long long long long long long long long long long long long long" + " long long long long long long long long long long long long long long long long long long long long long long long long" + " long long long long long long long long long long long long long long long long long long long long long long long long" + " long long long long long long long long long long long long long long long long long long long long long long long long" + " long long long long long long long long long long long long long long long long long long long long long long long long" + " long long long long long long long long long long long long long long long long long long long long long long long long" + " long long long long long long long long long long long long long long long long long long long long long long long long" + " long long long long long long long long long long long long long long long long long long long long long long long long" + " long long long long long long long long long long long long long long long long long long long long long long long long" + " long long long long long long long long long long long long long long long long long long long long long long long long" + " long long long long long long long long long long long long long long long long long long long long long long long long" + " long long long long long long long long long long long long long long long long long long long long long long long long" + " long long long long long long long long long long long long long long long long long long long long long long long long" + " long long long long long text"; StringBuffer sb = new StringBuffer(); for( int i = 0; i < 200; i ++ ){ sb.append( string ); } System.err.println( "Text length=" + sb.length() ); testText = sb.toString(); } return testText; } public void actionPerformed( ActionEvent e ) { Object source = e.getSource(); if( source == setTextButton ) { long start = System.currentTimeMillis(); if( OPTIMIZED ) { final int oldPolicy = scrollPane.getVerticalScrollBarPolicy(); scrollPane.setVerticalScrollBarPolicy( JScrollPane.VERTICAL_SCROLLBAR_ALWAYS ); SwingUtilities.invokeLater( new Runnable(){ public void run(){ textPane.setText( getTestText() ); scrollPane.setVerticalScrollBarPolicy( oldPolicy ); } } ); } else { //Because it is in event thread now textPane.setText( getTestText() ); } start = System.currentTimeMillis() - start; System.err.println( "setText time:" + start ); } else if( source == clearButton ) { textPane.setText( "" ); } } public static void main( String[] args ) throws Exception { System.setErr( new java.io.PrintStream( new java.io.FileOutputStream( "log.log" ) ) ); new TestLargeString(); } }

注意，JDK 1.4因为有段落不能超过Short.MAX_VALUE的bug，所以，需要改改代码才能运行。