GWT：PopupPanel setPopupPositionAndShow() 提供错误的 offsetWidth 和 offsetHeight

Question

我用 GWT 编写了自己的 PopupPanel。我想显示相对于其他小部件的弹出窗口。我对该类的实现如下所示：

public class Popover extends PopupPanel implements PositionCallback {

    private static final Binder binder = GWT.create(Binder.class);
    private UIObject relative;

    interface Binder extends UiBinder<Widget, Popover> {
    }

    public Popover() {
        setWidget(binder.createAndBindUi(this));
        setStylePrimaryName("popover");
    }

    public void show(UIObject relative) {

        this.relative = relative;
        setPopupPositionAndShow(this);

    }

    public void setPosition(int offsetWidth, int offsetHeight) {

        if (relative != null) {

            int left = relative.getAbsoluteLeft();
            int top = relative.getAbsoluteTop();
            int width = relative.getOffsetWidth();
            int height = relative.getOffsetHeight();

            int topCenter = top + height / 2 - offsetHeight / 2;


            if (offsetWidth < left) {
                setPopupPosition(left - offsetWidth, topCenter);
            } else {
                setPopupPosition(left + width, topCenter);

            }
        }
    }

}

问题是 offsetWidth 和 offsetHeight 始终是 10？

我的 Popover.ui.xml 如下所示：

<g:FlowPanel stylePrimaryName="popover">
    <g:FlowPanel stylePrimaryName="arrow" />
    <g:FlowPanel stylePrimaryName="inner">
        <g:Label stylePrimaryName="title" text="New Label" />
        <g:FlowPanel stylePrimaryName="content">
            <g:Label text="Hallo" />
        </g:FlowPanel>
    </g:FlowPanel>
</g:FlowPanel>

Answer 1

为了解决这个问题，我遵循了 PopupPanel 的 setPopupPositionAndShow() 使用的步骤，但我将定位步骤设置为延迟命令。我的代码没有扩展 PopupPanel，因此 popupPanel 变量：

popupPanel.setVisible(false);
popupPanel.show();

// Pausing until the event loop is clear appears to give the browser
// sufficient time to apply CSS styling.  We use the popup's offset
// width and height to calculate the display position, but those
// dimensions are not accurate until styling has been applied.
Scheduler.get().scheduleDeferred(new ScheduledCommand() {
   @Override
   public void execute() {
      yourMethodToSetPositionGoesHere(popupPanel);
      popupPanel.setVisible(true);
   }
});

Answer 2

getOffsetWidth() 和 getOffsetHeight() 仅当 DOM 完全构建并且您要获取其值的容器可见且附加时才有效。

为什么不使用 PopupPanel 的 showRelativeTo() 函数？

popup.showRelativeTo(SomeWidget);