深入解析ExpandableComposite.addExpansionListener()方法及其应用

在Java开发中，特别是基于Eclipse平台的应用程序，org.eclipse.ui.forms.widgets.ExpandableComposite是一个非常有用的组件，用于创建可折叠和展开的复合控件。本文将重点介绍其addExpansionListener()方法的具体用法及其实现细节。

ExpandableComposite.addExpansionListener方法概述

addExpansionListener()方法允许开发者为ExpandableComposite组件添加一个监听器，在组件的扩展状态发生变化时触发相应的事件处理逻辑。这使得应用程序能够动态响应用户交互，例如调整布局或更新界面内容。

代码示例与应用场景

以下是一些具体的代码示例，展示了如何在不同场景下使用addExpansionListener()方法：

private void manage(ExpandableComposite section) {
  if (section == null)
    throw new NullPointerException();
  if (fSections.add(section)) {
    section.addExpansionListener(fListener);
    makeScrollableCompositeAware(section);
  }
}

此代码片段来自org.eclipse.jdt.ui项目，展示了如何管理ExpandableComposite实例并为其添加扩展监听器。

private ExpandableComposite createExpandibleComposite(Composite parent, int style, String label, int hspan, int fill) {
  ExpandableComposite ex = SWTFactory.createExpandibleComposite(parent, style, label, hspan, fill);
  ex.addExpansionListener(new ExpansionAdapter() {
    public void expansionStateChanged(ExpansionEvent e) {
      ScrollPain sp = getParentScrollPane((ExpandableComposite) e.getSource());
      if (sp != null) {
        sp.reflow(true);
      }
    }
  });
  return ex;
}

这段代码来自org.eclipse.jdt.debug.ui项目，演示了创建带有自定义样式和监听器的ExpandableComposite。

@Override
protected void createContents(Composite parent) {
  final Composite p = parent;
  expandable = new ExpandableComposite(parent, SWT.NONE,
      ExpandableComposite.TREE_NODE | ExpandableComposite.TWISTIE);
  super.createContents(expandable);
  createClearButton(group);
  expandable.setClient(group);
  expandable.addExpansionListener(new ExpansionAdapter() {
    @Override
    public void expansionStateChanged(ExpansionEvent e) {
      p.layout();
      adjustSize(e.getState());
    }
  });
}

这个例子来自org.eclipse.compare项目，说明了如何在创建复合控件时设置监听器以响应扩展状态的变化。

protected ExpandableComposite createStyleSection(Composite parent, String label, int nColumns) {
  ExpandableComposite excomposite = new ExpandableComposite(parent, SWT.NONE, ExpandableComposite.TWISTIE | ExpandableComposite.CLIENT_INDENT);
  excomposite.setText(label);
  excomposite.setExpanded(false);
  excomposite.setFont(JFaceResources.getFontRegistry().getBold(JFaceResources.DIALOG_FONT));
  excomposite.setLayoutData(new GridData(GridData.FILL, GridData.FILL, true, false, nColumns, 1));
  excomposite.addExpansionListener(new ExpansionAdapter() {
    @Override
    public void expansionStateChanged(ExpansionEvent e) {
      expandedStateChanged((ExpandableComposite) e.getSource());
    }
  });
  fExpandedComposites.add(excomposite);
  makeScrollableCompositeAware(excomposite);
  return excomposite;
}

此代码片段来自org.eclipse.xtext.ui项目，展示了如何创建带标签的ExpandableComposite并为其添加监听器。

private Composite createExpansibleComposite(Composite parent, String title) {
  ExpandableComposite ecomp = SWTFactory.createExpandibleComposite(parent, title, 1, GridData.FILL_HORIZONTAL);
  ecomp.addExpansionListener(new ExpansionAdapter() {
    @Override
    public void expansionStateChanged(ExpansionEvent e) {
      Object obj = e.getSource();
      handleExpand(getScrollingParent(obj));
    }
  });
  ecomp.setFont(JFaceResources.getFontRegistry().getBold(JFaceResources.DIALOG_FONT));
  fExpComps.add(ecomp);
  Composite client = SWTFactory.createComposite(ecomp, 2, 1, GridData.FILL_BOTH);
  ecomp.setClient(client);
  return client;
}

最后一个示例来自org.eclipse.pde.api.tools.ui项目，演示了如何创建带有默认网格布局的ExpandableComposite并添加监听器。