GWT UiBinder CSS styling

Question

I declare some colors for the border of a VerticalLayout panel, like in:

<ui:style>
    .onMouseOverBorderColor {border-color: red; border-style: outset}
    .onMouseOutBorderColor {border-color: black; border-style: outset}
</ui:style>

Then i want to change the color of the panel's border according to the position of the mouse, and i add to the constructor of my widget the following:

    clickable.addMouseOverHandler(new MouseOverHandler() {

        @Override
        public void onMouseOver(MouseOverEvent event) {
            GWT.log("mouse over");
            border.setStyleName("onMouseOverBorderColor");
        }

    });
    clickable.addMouseOutHandler(new MouseOutHandler() {

        @Override
        public void onMouseOut(MouseOutEvent event) {
            GWT.log("mouse out");
            border.setStyleName("onMouseOutBorderColor");
        }

    });

But ... nothing happens! What i do wrong?

Code after suggestion (does not work):

<ui:UiBinder xmlns:ui="urn:ui:com.google.gwt.uibinder"
    xmlns:g="urn:import:com.google.gwt.user.client.ui">

    <ui:style>
        .fontStyleTitle {font-weight: bold }        
        .border {border-color: black; border-style: outset}
    .border:hover {border-color: red; border-style: outset}
    </ui:style>

    <g:FocusPanel ui:field="clickable">
            <g:VerticalPanel ui:field="border" borderWidth="1" styleName="style.border">
                <g:Image ui:field="myImage"/>
                <g:Label ui:field="myTitle" horizontalAlignment="ALIGN_CENTER" styleName="{style.fontStyleTitle}"/>
            </g:VerticalPanel>          
    </g:FocusPanel>

</ui:UiBinder> 

and the java class:

public UiWidget(String path, String theTitle) {
        initWidget(uiBinder.createAndBindUi(this));
        GWT.log(URL_PREFIX+path);
        myImage.setUrl(URL_PREFIX+path);
        myTitle.setText(theTitle);
        myImage.setSize(IMG_WIDTH, IMG_HEIGHT);
        /*
        clickable.addMouseOverHandler(new MouseOverHandler() {

            @Override
            public void onMouseOver(MouseOverEvent event) {
                GWT.log("mouse over");
            }

        });
        clickable.addMouseOutHandler(new MouseOutHandler() {

            @Override
            public void onMouseOut(MouseOutEvent event) {
                GWT.log("mouse out");
            }
*/
}

Answer 1

By default all the styles declared in a UiBinder are obfuscated.

It means your style 'onMouseOverBorderColor' will propably become something like 'GLX0QCICAR'.

But when in your JAVA code you do:

border.setStyleName("onMouseOverBorderColor");

your border element will really have the style 'onMouseOverBorderColor'.

So 2 solutions:

Use external to not obfuscate style names:

<ui:style>
    @external onMouseOverBorderColor onMouseOutBorderColor;
    .onMouseOverBorderColor {border-color: red; border-style: outset}
    .onMouseOutBorderColor {border-color: black; border-style: outset}
</ui:style>

Use the obfuscated style in your JAVA code:

<ui:style type="your.package.name.UiWidget.MyStyle">
    .onMouseOverBorderColor {border-color: red; border-style: outset}
    .onMouseOutBorderColor {border-color: black; border-style: outset}
</ui:style>

public class UiWidget {
    ...
    public interface MyStyle extends CssResource {
        String onMouseOverBorderColor();
        String onMouseOutBorderColor();
    }

    @UiField
    protected MyStyle style;

    public UiWidget(String path, String theTitle) {
        ...
        clickable.addMouseOverHandler(new MouseOverHandler() {
            @Override
            public void onMouseOver(MouseOverEvent event) {
                border.setStyleName(style.onMouseOverBorderColor);
            }
        });
        ...
    }
}