一般目标:从javascript调用一些非静态java方法
描述: 在Java Applet代码中查找DOM上的gwt小部件并将其称为java方法(非静态)
JSObject win = JSObject.getWindow(this);
JSObject doc = (JSObject) win.getMember("document");
JSObject gwtWidget = (JSObject) doc.call("getElementsByName", widgetName);
//todo: have possibility to call `exported` java method over here, smth like:
//Object[] params = new Object[1];
//params[0] = widgetName;
//Object result = gwtWidget.call("exportedJavaMethod", params);
//todo: or just call global ($wnd) static JSNI bridge method:
//Object result = win.call("exportedJavaMethod", params);
//
问题是:我可以通过widget的id找到而不是widget,但是它的DivElement没有任何导出的实例化方法。
我的widget类是Exportable(gwt-export):
@Export(value="somewidget")
public class SomeWidget extends SimplePanel implements ..., Exportable {
private final String id = "id_some_widget_" + count++;
private static int count = 0;
public SomeWidget () {
getElement().setAttribute("name", id);
getElement().setId(id);
}
...
public static Element getInstanceById(String elementId) {
Element someWidget= DOM.getElementById(elementId);
return someWidget;
}
public String getSomeInstancedData() {
return "useful_inner_data" + this.id;
}
所以,例如,我想找到添加到DOM的具体小部件,并在javascript中调用非静态方法getSomeInstancedData()
。它有可能吗?
假设smth像:
var someWidget = document.getElementById(widgetId);
alert(someWidget.getSomeInstancedData());
//or:
var someWidgetExported = com.mypackage.widgets.somewidget.getInstanceById(listenerId);
alert(someWidgetExported.getSomeInstancedData());
在Base模块中,我写道:
ExporterUtil.exportAll();
有一个View(ViewWithSomeWidget.ui.xml)包含这个小部件:
... base:Form base:SomeWidget ui:field="someWidget" ... ... /base:SomeWidget ...
当SomeWidget没有实现Exportable时,项目运行良好,但我无法调用找到的widget的DIV元素的非静态方法。
到时候,为了解决问题,SomeWidget实现了Exportable,但是由于使用延迟绑定的ClassCastException,progect没有显示具有SomeWidget的View:
ClassCastException: com.mypackage.widgets.SomeWidgetExporterImpl cannot be cast to com.mypackage.widgets.SomeWidget
那么,可能还有其他方法可以找到widget的javascript对象并调用它的导出java方法吗?无论如何,任何想法都非常感激。
答案 0 :(得分:11)
您可以声明一个javascript函数,它将触发非静态方法。
例如:
package com.example;
public class Layout extends VLayout() {
private String nonStaticVar = "nonStaticVar";
public Layout() {
declareMethod(this);
}
//Method which declares non-static method in javascript
public native void declareMethod(Layout layout) /*-{
var layout = layout;
$wnd.doSomething = function(someString) {
layout.@com.example.Layout::doSomething(Ljava/lang/String;)(someString);
}
}-*/;
//Non static method which is being called
public String doSomething(String someString) {
//Do something, e.g. set var in this instantiated class, or output stuff
this.nonStaticVar = someString;
Window.alert(someString);
}
}
现在,打电话 doSomething的( “BLA”); 从javascript将调用您的非静态方法。
答案 1 :(得分:4)
你可以在div元素上定义一个自己的jsmethod,它可以调用一个widget-method
@Export(value="somewidget")
public class SomeWidget extends SimplePanel implements ..., Exportable {
private final String id = "id_some_widget_" + count++;
private static int count = 0;
public SomeWidget () {
getElement().setAttribute("name", id);
getElement().setId(id);
attachInstanceHook(getElement());
}
...
public String getSomeInstancedData() {
return "useful_inner_data" + this.id;
}
private native void attachInstanceHook(Element element) /*-{
var elem = element;
var widget = this;
elem.getWidgetData = function () {
widget.@your.package.name.SomeWidget::getSomeInstancedData()();
};
}-*/;
你的js-code应该是这样的:
var someWidget = document.getElementById(widgetId); //the id of the div element
alert(someWidget.getWidgetData());
答案 2 :(得分:1)
而不是尝试通过其DOM元素获取窗口小部件,首先将其Java实例注入全局范围并引用它:
public class SomeWidget extends SimplePanel implements ..., Exportable {
//...
public SomeWidget () {
getElement().setAttribute("name", id);
getElement().setId(id);
attachToGlobalScope(id, this);
}
private native void attachToGlobalScope(String id, SomeWidget instance) /*-{
$wnd.shared[id] = instance;
}-*/;
//...
}
比以后更新Applet API层中的相应提取:
JSObject win = JSObject.getWindow(this);
JSObject shared = (JSObject) win.getMember("shared");
Widget widgetRef = (Widget) shared.getMember(widgetId);
免责声明:这个有点弯曲的解决方案继承了JavaScript全局范围变量,这被认为是一般的不良做法,但这里作为唯一的共同范围,因此被滥用于对象存储。