FLEX不能用addchild sprite()的原因

Flex Application里的addChild()
February 15th, 2008
在Flex Application里，是不能直接用addChild添加Sprite，MovieClip等来自flash.display包里的类的。譬如以下代码就会报错：

private function init():void {    var sp:Sprite = new Sprite();    addChild(sp);}
private function init():void {    var sp:Sprite = new Sprite();    addChild(sp);}TypeError: Error #1034: 强制转换类型失败:无法将 flash.display::Sprite@156b7b1 转换为 mx.core.IUIComponent。

这是因为Application的addChild方法并非完全继承自DisplayObjectContainer，

Application→LayoutContainer→Container→UIComponent→FlexSprite→Sprite

→DisplayObjectContainer

而是在Container那里被重写了：

public override function addChild(child:displayObject):displayObject
public  override   function  addChild(child:displayObject):DisplayObject虽然参数child的类型是DisplayObject，但是它必须实现IUIComponent接口（所有Flex组件都实现了这一接口），才能添加。

如果要在Application里添加Sprite，可以先把它装进一个UIComponent，然后再添加这个UIComponent：

import mx.core.UIComponent;private function init():void {    var sp:Sprite = new Sprite();    var uc:UIComponent = new UIComponent();    uc.addChild(sp);    addChild(uc);}
import mx.core.UIComponent;private function init():void {    var sp:Sprite = new Sprite();    var uc:UIComponent = new UIComponent();    uc.addChild(sp);    addChild(uc);}


posted by mybeky at 12:34 am & filed under flex |




One comment to “Flex Application里的addChild()”


再贴一下Container中重写addChild的部分源码
    override public function addChild(child:DisplayObject):DisplayObject
    {
        return addChildAt(child, numChildren);
}
    override public function addChildAt(child:DisplayObject,
                                        index:int):DisplayObject
    {
        var formerParent:DisplayObjectContainer = child.parent;
        if (formerParent && !(formerParent is Loader))
            formerParent.removeChild(child);
           
        addingChild(child);

        // Add the child to either this container or its contentPane.
        // The player will dispatch an "added" event from the child
        // after it has been added, so all "added" handlers execute here.
        if (contentPane)
            contentPane.addChildAt(child, index);
        else
            $addChildAt(child, _firstChildIndex + index);

        childAdded(child);

        if ((child is UIComponent) && UIComponent(child).isDocument)
            BindingManager.setEnabled(child, true);

        // Execute bindings to initialize new children and to refresh
        // existing children.
        if (child is IDeferredInstantiationUIComponent)
            IDeferredInstantiationUIComponent(child).executeBindings(true);

        return child;
    }

    override public function addChild(child:DisplayObject):DisplayObject
    {
        return addChildAt(child, numChildren);
        // Throw an RTE if child is not an IUIComponent.
        // 在这里将添加过来的displayobject强制转换成了IUIComponent
        //错语的原因也应该是这里，
        var uiChild:IUIComponent = IUIComponent(child);

        // Set the child's virtual parent, nestLevel, document, etc.
        super.addingChild(child);

       
        invalidateSize();
        invalidateDisplayList();

        if (!contentPane)
        {
            // If this is the first content child, then any chrome
            // that already exists is positioned in front of it.
            // If other content children already existed, then set the
            // depth of this object to be just behind the existing
            // content children.
            if (_numChildren == 0)
                _firstChildIndex = super.numChildren;

            // Increment the number of content children.
            _numChildren++;
        }

        if (contentPane && !autoLayout)
        {
            forceLayout = true;
            // weak reference
            UIComponentGlobals.layoutManager.addEventListener(
                FlexEvent.UPDATE_COMPLETE, layoutCompleteHandler, false, 0, true);
        }
    }