最近由于項(xiàng)目的需要，研究了一下SWT的Accessibility。關(guān)于Accessibility，這是一個(gè)很難纏的search，給殘疾人用的東東，正常人基本上不會(huì)用到，網(wǎng)上文章少之又少。可以查閱到的一篇來(lái)自于IBM developerWorks的文章：使用 Eclipse 創(chuàng)建易訪(fǎng)問(wèn)的應(yīng)用程序：介紹
易訪(fǎng)問(wèn)性是一個(gè)總括的術(shù)語(yǔ)，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(guó)已經(jīng)立法，不符合Accessibility規(guī)范的軟件不能夠在政府部門(mén)銷(xiāo)售。在美國(guó)，創(chuàng)建易訪(fǎng)問(wèn)的應(yīng)用程序的主要商業(yè)（對(duì)比人道主義）驅(qū)動(dòng)力是 Rehabilitation Act 1998 年的修正法案，稱(chēng)為 Section 508。Section 508 要求聯(lián)邦機(jī)構(gòu)使他們的信息技術(shù)對(duì)帶有殘疾的人易于訪(fǎng)問(wèn)。
Eclipse 擁有一個(gè)包含 API：org.eclipse.swt.accessibility 的易訪(fǎng)問(wèn)性包。Eclipse 3.0 易訪(fǎng)問(wèn)性特征是基于 MSAA 1.3 程序設(shè)計(jì)模型所提供的功能。您可以將 Eclipse 中的 Accessible 對(duì)象聯(lián)系到每個(gè)控件上，并且 org.eclipse.swt.accessibility 接口中的方法集對(duì)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(gè)用到了Accessibility，JFace里也不多?？戳怂械腁ccessibility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(méi)有必要定義Accessibility的。
- 如果是模擬實(shí)現(xiàn)一個(gè)比較簡(jiǎn)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(shí)現(xiàn)AccessibleControlListener接口。
- 所有的包含文本框的控件都要實(shí)現(xiàn)AccessibleTextListener接口。
- 設(shè)置AccessibleListener的getHelp( )最好是給控件加上Tooltip，因?yàn)閃ineyes這些屏幕閱讀器閱讀都是根據(jù)Tooltip，無(wú)視getHelp( )的設(shè)置。
- 設(shè)置AccessibleListener的getName( )，一般來(lái)說(shuō)，可以設(shè)置為這個(gè)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(huà)。
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。