import com.google.gwt.dom.client.HeadingElement; //导入依赖的package包/类
/**
 * Initializes HTMl elements (DIV and Canvas).<br>
 * It sets also some default behaviors (width in percentage) for resizing
 */
public AbstractChart() {
	// creates DIV
	div = Document.get().createDivElement();
	div.setId(id);
	// sets relative position
	div.getStyle().setPosition(Position.RELATIVE);
	// sets default width values
	div.getStyle().setWidth(DEFAULT_PCT_WIDTH, Unit.PCT);
	div.getStyle().setHeight(100, Unit.PCT);
	// checks if canvas is supported
	if (isCanvasSupported) {
		// creates a canvas and add to DIV
		canvas = Document.get().createCanvasElement();
		div.appendChild(canvas);
	} else {
		// creates a header element
		HeadingElement h = Document.get().createHElement(3);
		// to show the error message
		// because canvas is not supported
		h.setInnerText(CANVAS_NOT_SUPPORTED_MESSAGE);
		div.appendChild(h);
		// resets canvas
		canvas = null;
	}
	// sets DIV as element of the widget
	setElement(div);
	// injects Chart.js java script source
	Injector.ensureInjected();
	// creates plugins container
	plugins = new Plugins(this);
	// creates global options
	options = new GlobalOptions(createGlobalOptions(getType().name()));
}
 

import com.google.gwt.dom.client.HeadingElement; //导入依赖的package包/类
public static HeadingElement createHeading(int n, String value) {
    HeadingElement h = Document.get().createHElement(n);
    h.setInnerHTML(value);
    return h;
}
 

import com.google.gwt.dom.client.HeadingElement; //导入依赖的package包/类
private void updatePreview () {
	pnlPreview.getElement().removeAllChildren();

	Document d = Document.get();
	HeadingElement title = d.createHElement(1);

	title.setInnerHTML(PostHelper.makeHeading(txtTitle.getValue()));
	pnlPreview.getElement().appendChild(title);

	User user = SessionController.get().user();

	DivElement elDate = d.createDivElement();
	if (post != null) {
		if (post.published == null) {
			elDate.setInnerSafeHtml(PostSummaryCell.Templates.INSTANCE
					.notPublished(DateTimeHelper.ago(post.created)));
		} else {
			elDate.setInnerSafeHtml(PostSummaryCell.Templates.INSTANCE
					.publishedDate(DateTimeHelper.ago(post.published)));
		}
	} else {
		elDate.setInnerSafeHtml(PostSummaryCell.Templates.INSTANCE
				.notPublished(DateTimeHelper.ago(new Date())));
	}

	pnlPreview.getElement().appendChild(elDate);

	DivElement elAuthor = d.createDivElement();
	if (PropertyController.get()
			.booleanProperty(PropertyHelper.POST_SHOW_AUTHOR, false)) {
		elAuthor.setInnerSafeHtml(PostSummaryCell.Templates.INSTANCE.author(
				UriUtils.fromString(
						(post != null ? post.author.avatar : user.avatar)
								+ "?s=" + UserHelper.AVATAR_HEADER_SIZE
								+ "&default=retro"),
				UserHelper.handle((post != null ? post.author : user))));
	}

	pnlPreview.getElement().appendChild(elAuthor);

	tagList.getList().clear();
	List<String> tags = TagHelper.convertToTagList(txtTags.getValue());
	if (tags != null) {
		for (String tag : tags) {
			tagList.getList().add(new Tag().name(tag));
		}
	}

	DivElement summary = d.createDivElement();
	summary.setInnerHTML(markup(txtSummary));
	pnlPreview.getElement().appendChild(summary);

	DivElement content = d.createDivElement();
	content.setInnerHTML(markup(txtContent));
	pnlPreview.getElement().appendChild(content);
}