在GWT中,在任何主机页面标签上添加一个事件处理程序 [英] In GWT, adding an event handler on any of the host page tags
问题描述
我想为任何标签添加一个MouseOver事件处理程序。比方说,我想为传统HTML页面中的每个锚点页面添加事件处理程序。
继 GWT指南中,我能够使用他们的JSNI方法建议在修正小错误(缺少括号和类型)。
但是,我想使用ArrayList中收集的元素并将它们全部绑定到事件处理程序。我该怎么做?
我写的代码如下:
private native void putElementLinkIDsInList(BodyElement elt,ArrayList list)/ * - {
var links = elt.getElementsByTagName(a);
for(var i = 0; i< links.length; i ++){
var link = links.item(i);
link.id =(uid-a-+ i);
list。@ java.util.ArrayList :: add(Ljava / lang / Object;)(link.id);
}
} - * /;
/ **
*找到所有锚点标记,并且如果网站外的任何点将其重定向到
*阻止页面。
* /
private void rewriteLinksIterative(){
ArrayList links = new ArrayList();
putElementLinkIDsInList(Document.get()。getBody(),links);
for(int i = 0; i< links.size(); i ++){
Element elt = DOM.getElementById((String)links.get(i));
rewriteLink(elt,www.example.com);
}
}
/ **
*阻止所有与网站名称不符的网站访问
*
* @param元素
*锚点链接元素
* @param sitename
*要检查的网站名称。例如www.example.com
* /
private void rewriteLink(Element element,String sitename){
String href = DOM.getElementProperty(element,href);
if(null == href){
return;
}
//我们希望重新编写超出此网站的绝对网址
if(href.startsWith(http://)
&&!href.startsWith(http://+ sitename +/)){
DOM.setElementProperty(element,href,http://+ sitename
+/Blocked.html);
$ div $解析方案
你可能要使用 Document.getElementsByTagName(a)
,它返回一个 NodeList
包含这些元素,它们可以转换为 AnchorElement
s来暴露标签的 href
属性。
试试这段代码:
NodeList< Element> elems = Document.get()。getElementsByTagName(a);
for(int i = 0; i< elems.getLength(); i ++){
Element elem = elems.getItem(i);
AnchorElement a = AnchorElement.as(elem);
if(!a.getHref()。startsWith(http://yoursite.com)){
a.setHref(http://yoursite.com/blockedpage);
$ / code $ / pre
要添加一个事件处理函数, 元素
在锚点
中使用 wrap()
for(int i = 0; i< elems。 getLength(); i ++){
Element elem = elems.get(i);
Anchor a = Anchor.wrap(elem);
a.addClickHandler(new ClickHandler(){
@Override
public void onClick(ClickEvent event){
Window.alert(yay!);
}
});
$ / code>
(如果处理程序总是执行相同的操作,那么您需要只实例化一个 ClickHandler
,并将其添加到每个元素,而不是为每个元素创建一个处理程序)
I want to add a MouseOver event handler for any tag. Let say just for the example, that I want to add the event handler for every anchor page in a legacy HTML page.
Following the GWT guide, I was able to use their a JSNI method suggested to retrieve all anchor tags after correcting small errors (missing parenthesis and types).
However, I want to use the elements collected in the ArrayList and bind all of them to an event handler. How can I do that?
The code I wrote is listed below:
private native void putElementLinkIDsInList(BodyElement elt, ArrayList list) /*-{
var links = elt.getElementsByTagName("a");
for (var i = 0; i < links.length; i++ ) {
var link = links.item(i);
link.id = ("uid-a-" + i);
list.@java.util.ArrayList::add(Ljava/lang/Object;) (link.id);
}
}-*/;
/**
* Find all anchor tags and if any point outside the site, redirect them to a
* "blocked" page.
*/
private void rewriteLinksIterative() {
ArrayList links = new ArrayList();
putElementLinkIDsInList(Document.get().getBody(), links);
for (int i = 0; i < links.size(); i++) {
Element elt = DOM.getElementById((String) links.get(i));
rewriteLink(elt, "www.example.com");
}
}
/**
* Block all accesses out of the website that don't match 'sitename'
*
* @param element
* An anchor link element
* @param sitename
* name of the website to check. e.g. "www.example.com"
*/
private void rewriteLink(Element element, String sitename) {
String href = DOM.getElementProperty(element, "href");
if (null == href) {
return;
}
// We want to re-write absolute URLs that go outside of this site
if (href.startsWith("http://")
&& !href.startsWith("http://" + sitename + "/")) {
DOM.setElementProperty(element, "href", "http://" + sitename
+ "/Blocked.html");
}
}
解决方案 You'll probably want to use Document.getElementsByTagName("a")
, which returns a NodeList
containing the elements, which can be cast to AnchorElement
s exposing the tag's href
attribute.
Try this code:
NodeList<Element> elems = Document.get().getElementsByTagName("a");
for (int i = 0; i < elems.getLength(); i++) {
Element elem = elems.getItem(i);
AnchorElement a = AnchorElement.as(elem);
if (!a.getHref().startsWith("http://yoursite.com")) {
a.setHref("http://yoursite.com/blockedpage");
}
}
To add an event handler, you can instead wrap the Element
in an Anchor
using wrap()
for (int i = 0; i < elems.getLength(); i++) {
Element elem = elems.get(i);
Anchor a = Anchor.wrap(elem);
a.addClickHandler(new ClickHandler() {
@Override
public void onClick(ClickEvent event) {
Window.alert("yay!");
}
});
}
(If the handler will always do the same thing, you'll want to only instantiate one ClickHandler
and add it to each element instead of creating a handler for each element)
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