gistfile1.java

/**
 * Copyright 2014 Richard Wallis.
 * All rights reserved.
 */
package com.wallissoftware.wave.client.widgets;

import com.google.gwt.user.client.ui.HTMLPanel;
import com.google.gwt.user.client.ui.IsWidget;
import com.google.gwt.user.client.ui.SimplePanel;
import com.google.gwt.user.client.ui.Widget;

/**
 * Panel that wraps a GWT simple panel to be replaced by the widgetToAttach. This will make sure that the DIV element
 * is being replaced rather than having the widget inserted in it.
 * <p/>
 * The result of this will be to have a better, cleaner, dom.
 */
public class ReplacePanel extends SimplePanel {
    static class WrongParentTypeException extends RuntimeException {
        public WrongParentTypeException(final String message) {
            super(message);
        }
    }

    private IsWidget widget;

    @Override
    public Widget asWidget() {
        return widget != null ? widget.asWidget() : super.asWidget();
    }

    @Override
    public Widget getWidget() {
        return widget != null ? widget.asWidget() : super.getWidget();
    }

    @Override
    public void setWidget(final IsWidget widget) {
        setWidget(widget.asWidget());
    }

    @Override
    public void setWidget(final Widget widgetToAttach) {
        final Widget parentAsWidget = asWidget().getParent();
        if (!(parentAsWidget instanceof HTMLPanel)) {
            throw new WrongParentTypeException("The parent of ReplacePanel must be of type HTMLPanel");
        }

        final HTMLPanel parent = (HTMLPanel) parentAsWidget;

        parent.addAndReplaceElement(widgetToAttach, asWidget().getElement());

        widget = widgetToAttach;
    }
}