Question

47

Native Javascript method in GWT

rated 0 times [ 49] [ 2] / answers: 1 / hits: 34143 / 15 Years ago, thu, june 11, 2009, 12:00:00

I have a native Javascript method in one of my GWT Java classes, but I'm having trouble calling my Java methods from the native Javascript code. I tried to follow this as closely as I could, but I can't get it to work. I compiled it and ran it in Firefox, and the error console said Error: this.lc is not a function. I tried changing all the methods to public, but that didn't seem to make a difference. What am I doing wrong?

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]_lab.client.ValueBox::increaseValue()();

            }

            [email protected]_lab.client.ValueBox::fireChange()();

        }

    }



    var box=$doc.getElementById(id);

    box.addEventListener(mouseout,mouseOutHandler,false);

    box.addEventListener(mouseover,mouseOverHandler,false);

}-*/;

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forrestn

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answered 15 Years ago cody · Accepted Answer

In all the code I've done in the past, I've never used 'this' to identify my class, I have passed the class in.

Eg: Change this:

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]_lab.client.ValueBox::increaseValue()();

                }

                [email protected]_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]_lab.client.ValueBox::increaseValue()();

                }

                [email protected]_lab.client.ValueBox::fireChange()();

        }

    }



    var box=$doc.getElementById(id);

    box.addEventListener(mouseout,mouseOutHandler,false);

    box.addEventListener(mouseover,mouseOverHandler,false);

}-*/;