不要使用 height, 这样就可以了
<mx:TabNavigator
resizeToContent="true" id="tabPurchase" width="100%" change="tab_changeHandler(event)" creationComplete="tab_creationCompleteHandler(event)">
<mx:Canvas label="淘宝订单" width="100%" height="100%">
<taobao:TaobaoOrderList/>
</mx:Canvas>
<mx:Canvas label="自拍" width="100%" height="100%">
<taobao:TaobaoCounterfeitList/>
</mx:Canvas>
</mx:TabNavigator>