SWT 的易访问性(Accessibility)最近由于项目的需要，研究了一下SWT的Accessibility。关于Accessibility，这是一个很难缠的search，给残疾人用的东东，正常人基本上不会用到，网上文章少之又少。可以查阅到的一篇来自于IBM developerWorks的文章：
使用 Eclipse 创建易访问的应用程序：介绍易访问性是一个总括的术语，它包括生成使具有各种残疾的人易用的产品所涉及的所有东西和人。美国已经立法，不符合Accessibility规范的软件不能够在政府部门销售。在美国，创建易访问的应用程序的主要商业（对比人道主义）驱动力是 Rehabilitation Act 1998年的修正法案，称为 Section 508。Section 508 要求联邦机构使他们的信息技术对带有残疾的人易于访问。
Eclipse拥有一个包含 API：org.eclipse.swt.accessibility 的易访问性包。Eclipse 3.0 易访问性特征是基于MSAA 1.3 程序设计模型所提供的功能。您可以将 Eclipse 中的 Accessible 对象联系到每个控件上，并且org.eclipse.swt.accessibility 接口中的方法集对应 MSAA 1.3 IAccessible 界面中的消息集。
org.eclipse.swt.accessibility 的接口：
Interface Summary
AccessibleControlListener Classes that implement this interface provide methods that deal with the events that are generated when an accessibility client sends a message to a control.
AccessibleListener Classes that implement this interface provide methods that deal with the events that are generated when an accessibility client sends a message to a control.
AccessibleTextListener Classes that implement this interface provide methods that deal with the events that are generated when an accessibility client sends a message to a control.
SWT 自身包含的控件中只有寥寥几个用到了Accessibility，JFace里也不多。看了所有的Accessibility相关代码，只能总结一部分规律：
一般的复杂控件是没有必要定义Accessibility的。
如果是模拟实现一个比较简单的基本控件，比如Combo，Label，Spinner等，有必要定义Accessibility。
所有的自定义控件都要实现AccessibleControlListener接口。
所有的包含文本框的控件都要实现AccessibleTextListener接口。
设置AccessibleListener的getHelp( )最好是给控件加上Tooltip，因为Wineyes这些屏幕阅读器阅读都是根据Tooltip，无视getHelp( )的设置。
设置AccessibleListener的getName( )，一般来说，可以设置为这个控件相关联的Label的Text或者该控件上的某部分文字，自己斟酌考虑设置。
getKeyboardShortcut( )，考虑控件的快捷操作方式，如果需要的话。
以下是CCombo的Accessibility代码：
void initAccessible() {
AccessibleAdapter accessibleAdapter = new AccessibleAdapter () {
publicvoid getName (AccessibleEvent e) {
String name = null;
Label label = getAssociatedLabel ();
if (label != null) {
name = stripMnemonic (label.getText());
}
e.result = name;
}
publicvoid getKeyboardShortcut(AccessibleEvent e) {
String shortcut = null;
Label label = getAssociatedLabel ();
if (label != null) {
String text = label.getText ();
if (text != null) {
char mnemonic = _findMnemonic (text);
if (mnemonic != '\0') {
shortcut = "Alt+"+mnemonic;
}
}
}
e.result = shortcut;
}
publicvoid getHelp (AccessibleEvent e) {
e.result = getToolTipText ();
}
};
getAccessible ().addAccessibleListener (accessibleAdapter);
text.getAccessible ().addAccessibleListener (accessibleAdapter);
list.getAccessible ().addAccessibleListener (accessibleAdapter);
arrow.getAccessible ().addAccessibleListener (new AccessibleAdapter() {
publicvoid getName (AccessibleEvent e) {
e.result = isDropped () ? SWT.getMessage ("SWT_Close") : SWT.getMessage ("SWT_Open");
}
publicvoid getKeyboardShortcut (AccessibleEvent e) {
e.result = "Alt+Down Arrow";
}
publicvoid getHelp (AccessibleEvent e) {
e.result = getToolTipText ();
}
});
getAccessible().addAccessibleTextListener (new AccessibleTextAdapter() {
publicvoid getCaretOffset (AccessibleTextEvent e) {
e.offset = text.getCaretPosition ();
}
publicvoid getSelectionRange(AccessibleTextEvent e) {
Point sel = text.getSelection();
e.offset = sel.x;
e.length = sel.y - sel.x;
}
});
getAccessible().addAccessibleControlListener (new AccessibleControlAdapter() {
publicvoid getChildAtPoint (AccessibleControlEvent e) {
Point testPoint = toControl (e.x, e.y);
if (getBounds ().contains (testPoint)) {
e.childID = ACC.CHILDID_SELF;
}
}
publicvoid getLocation (AccessibleControlEvent e) {
Rectangle location = getBounds ();
Point pt = toDisplay (location.x, location.y);
e.x = pt.x;
e.y = pt.y;
e.width = location.width;
e.height = location.height;
}
publicvoid getChildCount (AccessibleControlEvent e) {
e.detail = 0;
}
publicvoid getRole (AccessibleControlEvent e) {
e.detail = ACC.ROLE_COMBOBOX;
}
publicvoid getState (AccessibleControlEvent e) {
e.detail = ACC.STATE_NORMAL;
}
publicvoid getValue (AccessibleControlEvent e) {
e.result = getText ();
}
});
text.getAccessible ().addAccessibleControlListener (new AccessibleControlAdapter () {
publicvoid getRole (AccessibleControlEvent e) {
e.detail = text.getEditable () ? ACC.ROLE_TEXT : ACC.ROLE_LABEL;
}
});
arrow.getAccessible ().addAccessibleControlListener (new AccessibleControlAdapter() {
publicvoid getDefaultAction (AccessibleControlEvent e) {
e.result = isDropped () ? SWT.getMessage ("SWT_Close") : SWT.getMessage ("SWT_Open");
}
});
}
在SWT控件中，包含Accessibility功能的控件有：CCombo，CLabel，CTableFolder，StyledText。
posted @
2006-06-19 17:38 三人行，必有我师焉 阅读(1171) |
评论 (4) |
编辑 收藏扩展Eclipse视图弹出菜单（二）上一篇文章我们知道了Eclipse弹出菜单的基本用法。其实Eclipse的弹出菜单可以用来做很多文章，简单一点的根据文件类别，我们可以进行不同的文件操作，比如Ant的build.xml我们可以用来build，Java文件我们可以用JavaEditor打开，这些基于文件类型的操作我们都可以很容易的实现。但是还有一种情况，如果文件类型一样，我们想进行不同的操作，该怎么实现呢？实际上这样的应用很多，比如同样是Java文件，含有main方法的Java文件有Run和Debug的选项，其它的都没有。还有现在的框架都是基于XML文件进行配置的，如果一个项目使用了多个框架，我们怎么根据不同的XML文件进行框架的区分呢？答案就是enablement的test。
<!ELEMENT EMPTY>
<!ATTLIST test
property CDATA #REQUIRED
args CDATA #IMPLIED
value CDATA #IMPLIED>
This element is used to evaluatethe property state of the object in focus. The set of testableproperties can be extended using the propery tester extension point. Thetest expression returns EvaluationResult.NOT_LOADED if teh propertytester doing the actual testing isn't loaded yet.
property - the name of an object's property to test.
args - additional arguments passed to the property tester. Multiple arguments are seperated by commas. Each individual argument is converted into a Java base type using the same rules as defined for the value attribute of the test expression.
value - the expected value of the property. Can be omitted if the property is a boolean property. The test expression is supposed to return EvaluationResult.TRUE if the property matches the value and EvaluationResult.FALSE otherwise. The value attribute is converted into a Java base type using the following rules: the string "true" is converted into Boolean.TRUE
the string "false" is converted into Boolean.FALSE
if the string contains a dot then the interpreter tries to convert the value into a Float object. If this fails the string is treated as a java.lang.String
if the string only consists of numbers then the interpreter converts the value in an Integer object.
in all other cases the string is treated as a java.lang.String
the conversion of the string into a Boolean, Float, or Integer can be suppressed by surrounding the string with single quotes. For example, the attribute value="'true'" is converted into the string "true"
比如我们要让含有main方法的Java文件它的右键弹出菜单包含一个额外的选项“This is main class”，需要编写如下的Plugin.xml：
<plugin>
<extension
point="org.eclipse.ui.popupMenus">
<objectContribution
id="Advanced.PopupMenus"
objectClass="java.lang.Object">
<action id="Advanced.PopupMenus.Action"
label="AdvancedPopupMenus"
style="pulldown"
menubarPath="additions"
class="advancedpopupmenus.popup.actions.AdvancedPopupMenusAction"
enablesFor="+">
</action>
<enablement>
<test property="advancedpopupmenus.popup.visable"/>
</enablement>
</objectContribution>
</extension>
<extension point="org.eclipse.core.expressions.propertyTesters">
<propertyTester
namespace="advancedpopupmenus.popup"
properties="visable"
type="java.lang.Object"
class="advancedpopupmenus.popup.actions.VisablePropertyTester"
id="advancedpopupmenus.popup.propertyTesters.visable">
</propertyTester>
</extension>
</plugin>
我们需要检测在当前情况下是否需要显示这个菜单项，使用扩展点org.eclipse.core.expressions.propertyTesters：
<!ELEMENT propertyTester EMPTY>
<!ATTLIST propertyTester
id CDATA #REQUIRED
type CDATA #REQUIRED
namespace CDATA #REQUIRED
properties CDATA #REQUIRED
class CDATA #REQUIRED>
id - unique identifier for the property tester
type - the type to be extended by this property tester
namespace - a unique id determining the name space the properties are added to
properties - a comma separated list of properties provided by this property tester
class - the name of the class that implements the testing methods. The class must be public and extend org.eclipse.core.expressions.PropertyTester with a public 0-argument constructor.
这里只须注意propertyTester的namespace和properties正好对应test的property。
至于检测的逻辑我们在advancedpopupmenus.popup.actions.VisablePropertyTester中实现，这个类必须继承自org.eclipse.core.expressions.PropertyTester。
package advancedpopupmenus.popup.actions;
import org.eclipse.core.expressions.PropertyTester;
import org.eclipse.jdt.core.IMethod;
import org.eclipse.jdt.core.IType;
import org.eclipse.jdt.core.JavaModelException;
import org.eclipse.jdt.internal.core.CompilationUnit;
public class VisablePropertyTester extends PropertyTester
{
public boolean test( Object receiver, String property, Object[] args,
Object expectedValue )
{
if ( !( receiver instanceof CompilationUnit ) )
return false;
CompilationUnit unit = (CompilationUnit) receiver;
try
{
IType[] types = unit.getTypes( );
if ( types == null )
return false;
for ( int i = 0; i < types.length; i++ )
{
IMethod[] methods = types[i].getMethods( );
if ( methods == null )
return false;
for ( int j = 0; j < methods.length; j++ )
{
if ( methods[j].isMainMethod( ) )
return true;
}
}
}
catch ( JavaModelException e )
{
e.printStackTrace( );
}
return false;
}
}
我们只要判断接受的Java文件中是否含有main方法，如果有，则返回True，没有则返回False。
如果我们是要接受一个Web开发的配置文件，我们可以这样写：
<plugin>
<extension
point="org.eclipse.ui.popupMenus">
<objectContribution
id="Advanced.PopupMenus"
objectClass="org.eclipse.core.resources.IFile"
nameFilter="*.xml">
<action id="Advanced.PopupMenus.Action"
label="This is web xml"
style="pulldown"
menubarPath="additions"
class="advancedpopupmenus.popup.actions.AdvancedPopupMenusAction"
enablesFor="+">
</action>
<enablement>
<test property="advancedpopupmenus.popup.visable"/>
</enablement>
</objectContribution>
</extension>
<extension point="org.eclipse.core.expressions.propertyTesters">
<propertyTester
namespace="advancedpopupmenus.popup"
properties="visable"
type="org.eclipse.core.resources.IFile"
class="advancedpopupmenus.popup.actions.VisablePropertyTester"
id="advancedpopupmenus.popup.propertyTesters.visable">
</propertyTester>
</extension>
</plugin>
注意和上一个例子不同的地方，objectClass，nameFileter和type(在上一个例子中，我们也可以使用objectClass="org.eclipse.core.resources.IFile" nameFilter="*.java")，相应的我们的VisablePropertyTester类也要做一些改动：
package advancedpopupmenus.popup.actions;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import org.eclipse.core.expressions.PropertyTester;
import org.eclipse.core.resources.IFile;
import org.w3c.dom.Document;
import org.w3c.dom.DocumentType;
public class VisablePropertyTester extends PropertyTester
{
public boolean test( Object receiver, String property, Object[] args,
Object expectedValue )
{
if ( !( receiver instanceof IFile ) )
return false;
IFile xml = (IFile) receiver;
try
{
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance( );
DocumentBuilder db = dbf.newDocumentBuilder( );
Document doc = db.parse( xml.getContents( ) );
DocumentType type = doc.getDoctype( );
if(type.getSystemId( ).equalsIgnoreCase( "http://java.sun.com/j2ee/dtds/web-app_2_2.dtd" ))return true;
}
catch ( Exception e )
{
e.printStackTrace( );
}
return false;
}
}
这样根据不同的xml SystemID，我们就能够知道到底这是哪一种框架的配置文件了
