此外，如果视觉化树状结构的变更强制更新复合场景图形，也会呼叫事件处理常式方法。

In addition, if changes to the visual tree force updates to the composition scene graph, your event handler method is also called.

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下列图形显示了此场景。

The following graphic shows this scenario.

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在该特殊场景的图形视图中，有两个项目比较醒目。

Within the Graph view for this particular scenario, two items stick out.

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