ActionScript:这怎么会失败？

Question

这段代码抛出一个错误:

    if (modalMessage != null && contains(modalMessage))
    {
        removeChild(modalMessage); // the error is here
        modalMessage = null;            
    }

错误是:

[Fault] exception, information=ArgumentError: Error #2025: The supplied DisplayObject must be a child of the caller.

这怎么可能？我正在事先检查它是否是一个 child 。

Answer 1

如果主题是调用者的后代，

contains() 将返回 true。对于间接后代、 child 的 child 等，这也会返回 true。

Determines whether the specified display object is a child of the DisplayObjectContainer instance or the instance itself. The search includes the entire display list including this DisplayObjectContainer instance. Grandchildren, great-grandchildren, and so on each return true.

http://help.adobe.com/en_US/FlashPlatform/reference/actionscript/3/flash/display/DisplayObjectContainer.html#contains%28%29

你可以检查父级:

if(modalMessage && modalMessage.parent && modalMessage.parent == this)

或者，对于更通用的处置解决方案:

if(modalMessage) {
    if(modalMessage.parent) DisplayObjectContainer(modalMessage.parent).removeChild(modalMessage);
    modalMessage = null;
}