GWT 中的本机 Javascript 方法

我的 GWT Java 类之一中有一个本机 Javascript 方法，但我在从本机 Javascript 代码调用我的 Java 方法时遇到问题。我试着跟随this http://code.google.com/webtoolkit/doc/1.6/DevGuideCodingBasics.html#DevGuideJavaScriptNativeInterface尽我所能，但我无法让它发挥作用。我编译它并在 Firefox 中运行它，错误控制台显示“错误：this.lc 不是一个函数”。我尝试将所有方法更改为public，但这似乎没有什么区别。我究竟做错了什么？

package com.proprintsgear.design_lab.client;
...
public class ValueBox extends HorizontalPanel {
...
private void fireChange() {
    ...
}

private void increaseValue() {
    ...
}

private native void addNativeMouseWheelListener(String id) /*-{
    function mouseOverHandler(e) {
        $wnd.addEventListener("DOMMouseScroll", scrollWheelMove, false);
    }

    function mouseOutHandler(e) {
        $wnd.removeEventListener("DOMMouseScroll", scrollWheelMove, false);
    }

    function scrollWheelMove(e) {
        if ($wnd.event || $wnd.Event) {
            if (!e) e = $wnd.event;
            if (e.wheelDelta <= 0 || e.detail > 0 ) {
                $wnd.alert("DOWN");
            } else {
                [email protected] /cdn-cgi/l/email-protection_lab.client.ValueBox::increaseValue()();
            }
            [email protected] /cdn-cgi/l/email-protection_lab.client.ValueBox::fireChange()();
        }
    }

    var box=$doc.getElementById(id);
    box.addEventListener("mouseout",mouseOutHandler,false);
    box.addEventListener("mouseover",mouseOverHandler,false);
}-*/;

在我过去完成的所有代码中，我从未使用“this”来标识我的类，我已经将类传入了。

例如：改变这个：

private native void addNativeMouseWheelListener(String id) /*-{
    function mouseOverHandler(e) {
        $wnd.addEventListener("DOMMouseScroll", scrollWheelMove, false);
    }

    function mouseOutHandler(e) {
        $wnd.removeEventListener("DOMMouseScroll", scrollWheelMove, false);
    }

    function scrollWheelMove(e) {
        if ($wnd.event || $wnd.Event) {
                if (!e) e = $wnd.event;
                if (e.wheelDelta <= 0 || e.detail > 0 ) {
                        $wnd.alert("DOWN");
                } else {
                        [email protected] /cdn-cgi/l/email-protection_lab.client.ValueBox::increaseValue()();
                }
                [email protected] /cdn-cgi/l/email-protection_lab.client.ValueBox::fireChange()();
        }
    }

    var box=$doc.getElementById(id);
    box.addEventListener("mouseout",mouseOutHandler,false);
    box.addEventListener("mouseover",mouseOverHandler,false);
}-*/;

To this:

private native void addNativeMouseWheelListener(ValueBox instance, String id) /*-{
    function mouseOverHandler(e) {
        $wnd.addEventListener("DOMMouseScroll", scrollWheelMove, false);
    }

    function mouseOutHandler(e) {
        $wnd.removeEventListener("DOMMouseScroll", scrollWheelMove, false);
    }

    function scrollWheelMove(e) {
        if ($wnd.event || $wnd.Event) {
                if (!e) e = $wnd.event;
                if (e.wheelDelta <= 0 || e.detail > 0 ) {
                        $wnd.alert("DOWN");
                } else {
                        [email protected] /cdn-cgi/l/email-protection_lab.client.ValueBox::increaseValue()();
                }
                [email protected] /cdn-cgi/l/email-protection_lab.client.ValueBox::fireChange()();
        }
    }

    var box=$doc.getElementById(id);
    box.addEventListener("mouseout",mouseOutHandler,false);
    box.addEventListener("mouseover",mouseOverHandler,false);
}-*/;