您如何指定要使工具栏中的元素居中？

Question

For some reason, JavaFX's ToolBar only proposes two options for items alignment: LEFT_TO_RIGHT and RIGHT_TO_LEFT .

And funnily enough, if this is RIGHT_TO_LEFT you have to specify your items in reverse order so that they show up naturally...

However I don't see any option for aligning elements in the center . How do you achieve that? Or must I use something else than a toolbar?

---

edit: here is the current code... Unfortunately this doesn't work :(

FXML:

<BorderPane xmlns="http://javafx.com/javafx/8" xmlns:fx="http://javafx.com/fxml/1"
    fx:controller="com.github.fge.grappa.debugger.csvtrace.tabs.linechart.LineChartTabDisplay">
    <top>
        <ToolBar fx:id="toolbar">
            <HBox fx:id="hbox" alignment="CENTER">
                <Region fx:id="leftSpacer"/>
                <Button text="Refresh"/>
                <ProgressBar visible="false"/>
                <Label text="Layout testing"/>
                <Region fx:id="rightSpacer"/>
            </HBox>
        </ToolBar>
    </top>
</BorderPane>

the class:

public class LineChartTabDisplay
    extends JavafxDisplay<LineChartTabPresenter>
{

    public Region leftSpacer;
    public Region rightSpacer;
    public ToolBar toolbar;
    public HBox hbox;

    @Override
    public void init()
    {
        HBox.setHgrow(leftSpacer, Priority.SOMETIMES);
        leftSpacer.setMinWidth(Region.USE_PREF_SIZE);
        HBox.setHgrow(rightSpacer, Priority.SOMETIMES);
        rightSpacer.setMinWidth(Region.USE_PREF_SIZE);
    }
}

But this is what it gives:

Answer 1

FOUND.

In fact, the code is pretty "simple". Kind of, since this really should be in the ToolBar for starters, but here goes...

The FXML is now as follows:

<BorderPane xmlns="http://javafx.com/javafx/8" xmlns:fx="http://javafx.com/fxml/1"
    fx:controller="com.github.fge.grappa.debugger.csvtrace.tabs.linechart.LineChartTabDisplay">
    <top>
        <ToolBar fx:id="toolbar">
            <HBox fx:id="hbox" alignment="CENTER" spacing="5.0">
                <Button text="Refresh"/>
                <Label text="Layout testing"/>
            </HBox>
        </ToolBar>
    </top>
</BorderPane>

And the code is simply:

public class LineChartTabDisplay
    extends JavafxDisplay<LineChartTabPresenter>
{
    @FXML
    protected ToolBar toolbar;

    @FXML
    protected HBox hbox;

    @Override
    public void init()
    {
        hbox.minWidthProperty().bind(toolbar.widthProperty());
    }
}

Answer 2

Well there is this little hack to produce a dynamic spacer:

final Region spacer = new Region();
HBox.setHgrow(spacer, Priority.SOMETIMES);
spacer.setMinWidth(Region.USE_PREF_SIZE);

If you put one as first item and another one as last item on the ToolBar your items inbetween should be centered.

Answer 3

Just keep an eye on the width of the Toolbar and apply the new value to the HBox. This is necessary in order to monitor the size of the Stage

toolbar.widthProperty().addListener((obs, oldVal, newVal) -> {  
    hbox.setPrefWidth(newVal.doubleValue());
});