SWT 的易訪問性(Accessibility)最近由于項目的需要，研究了一下SWT的Accessibility。關(guān)于Accessibility，這是一個很難纏的search，給殘疾人用的東東，正常人基本上不會用到，網(wǎng)上文章少之又少。可以查閱到的一篇來自于IBM developerWorks的文章：
使用 Eclipse 創(chuàng)建易訪問的應(yīng)用程序：介紹易訪問性是一個總括的術(shù)語，它包括生成使具有各種殘疾的人易用的產(chǎn)品所涉及的所有東西和人。美國已經(jīng)立法，不符合Accessibility規(guī)范的軟件不能夠在政府部門銷售。在美國，創(chuàng)建易訪問的應(yīng)用程序的主要商業(yè)（對比人道主義）驅(qū)動力是 Rehabilitation Act 1998年的修正法案，稱為 Section 508。Section 508 要求聯(lián)邦機構(gòu)使他們的信息技術(shù)對帶有殘疾的人易于訪問。
Eclipse擁有一個包含 API：org.eclipse.swt.accessibility 的易訪問性包。Eclipse 3.0 易訪問性特征是基于MSAA 1.3 程序設(shè)計模型所提供的功能。您可以將 Eclipse 中的 Accessible 對象聯(lián)系到每個控件上，并且org.eclipse.swt.accessibility 接口中的方法集對應(yīng) 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幾個用到了Accessibility，JFace里也不多。看了所有的Accessibility相關(guān)代碼，只能總結(jié)一部分規(guī)律：
一般的復(fù)雜控件是沒有必要定義Accessibility的。
如果是模擬實現(xiàn)一個比較簡單的基本控件，比如Combo，Label，Spinner等，有必要定義Accessibility。
所有的自定義控件都要實現(xiàn)AccessibleControlListener接口。
所有的包含文本框的控件都要實現(xiàn)AccessibleTextListener接口。
設(shè)置AccessibleListener的getHelp( )最好是給控件加上Tooltip，因為Wineyes這些屏幕閱讀器閱讀都是根據(jù)Tooltip，無視getHelp( )的設(shè)置。
設(shè)置AccessibleListener的getName( )，一般來說，可以設(shè)置為這個控件相關(guān)聯(lián)的Label的Text或者該控件上的某部分文字，自己斟酌考慮設(shè)置。
getKeyboardShortcut( )，考慮控件的快捷操作方式，如果需要的話。
以下是CCombo的Accessibility代碼：
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?guī)熝?閱讀(1171) |
評論 (4) |
編輯 收藏擴展Eclipse視圖彈出菜單（二）上一篇文章我們知道了Eclipse彈出菜單的基本用法。其實Eclipse的彈出菜單可以用來做很多文章，簡單一點的根據(jù)文件類別，我們可以進行不同的文件操作，比如Ant的build.xml我們可以用來build，Java文件我們可以用JavaEditor打開，這些基于文件類型的操作我們都可以很容易的實現(xiàn)。但是還有一種情況，如果文件類型一樣，我們想進行不同的操作，該怎么實現(xiàn)呢？實際上這樣的應(yīng)用很多，比如同樣是Java文件，含有main方法的Java文件有Run和Debug的選項，其它的都沒有。還有現(xiàn)在的框架都是基于XML文件進行配置的，如果一個項目使用了多個框架，我們怎么根據(jù)不同的XML文件進行框架的區(qū)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"
比如我們要讓含有main方法的Java文件它的右鍵彈出菜單包含一個額外的選項“This is main class”，需要編寫如下的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>
我們需要檢測在當(dāng)前情況下是否需要顯示這個菜單項，使用擴展點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.
這里只須注意propertyTester的namespace和properties正好對應(yīng)test的property。
至于檢測的邏輯我們在advancedpopupmenus.popup.actions.VisablePropertyTester中實現(xiàn)，這個類必須繼承自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;
}
}
我們只要判斷接受的Java文件中是否含有main方法，如果有，則返回True，沒有則返回False。
如果我們是要接受一個Web開發(fā)的配置文件，我們可以這樣寫：
<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>
注意和上一個例子不同的地方，objectClass，nameFileter和type(在上一個例子中，我們也可以使用objectClass="org.eclipse.core.resources.IFile" nameFilter="*.java")，相應(yīng)的我們的VisablePropertyTester類也要做一些改動：
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;
}
}
這樣根據(jù)不同的xml SystemID，我們就能夠知道到底這是哪一種框架的配置文件了
