如何在自定义MXML标记中填充必需参数？

Question

这是班级:

package fnc {
    import mx.containers.Canvas;

    public class Deck extends Canvas {

        protected var _chipCount:int;

        public function Deck(chipCount:int) {
            /* Associate some chips with this deck */
            _chipCount = chipCount;
        }

        public function get chipCount():int {
            return _chipCount;
        }
    }
}

这是MXML:

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute" xmlns:ns1="fnc.*">
    <ns1:Deck horizontalCenter="0" verticalCenter="0">
    </ns1:Deck>
</mx:Application>

运行此应用程序会收到此错误:

ArgumentError:错误#1063:fnc :: Deck()上的参数计数不匹配.预期1,在mx.core上获得0.在mx.core :: Container/createComponentFromDescriptor()[C:\ autobuild\3.2.0\frameworks\projects\framework\src\mx\core\Container.as:3579]: :Container/createComponentsFromDescriptors()[C:\ autobuild\3.2.0\frameworks\projects\framework\src\mx\core\Container.as:3493] at mx.core :: Container/createChildren()[C:\ autobuild mx.core上的\ 3.2.0\frameworks\projects\framework\src\mx\core\Container.as:2589] :: UIComponent/initialize()[C:\ autobuild\3.2.0\frameworks\projects\framework\src\mx\core\UIComponent.as:5370]在mx.core :: Container/initialize()[C:\ autobuild\3.2.0\frameworks\projects\framework\src\mx\core\Container.as:2526 ]在mx.core :: Application/initialize()[C:\ autobuild\3.2.0\frameworks\projects\framework\src\mx\core\Application.as:846]在Practice/initialize()[C:\文档和设置\ LocalService\My Documents\Flex Builder 3\Practice\src\Practice.mxml:0]在mx.managers :: SystemManager/http://www.adobe.com/2006/flex/mx/internal :: childAdded()[C:\ autobuild\3.2.0\frameworks\projects\framework\src\mx\managers\SystemManager.as:2009]在mx.managers :: SystemManager/initializeTopLevelWindow()[C:\ autobuild\3.2.0\frameworks\projects\framework\src\mx\managers\SystemManager.as:3234]在mx.managers :: SystemManager/http://www.adobe.com/2006/flex/mx/internal::docFrameHandler()[C :\autobuild\3.2.0\frameworks\projects\framework\src\mx\managers\SystemManager.as:3064] at mx.managers :: SystemManager/docFrameListener()[C:\ autobuild\3.2.0\frameworks\projects\framework\src\mx\managers\SystemManager.as :2916]

chipCount="0"像这样添加到MXML:

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute" xmlns:ns1="fnc.*">
    <ns1:Deck chipCount="0" horizontalCenter="0" verticalCenter="0">
    </ns1:Deck>
</mx:Application>

获取此编译错误:

严重性和描述路径资源位置创建时间Id属性'chipCount'是只读的.Practice/src Practice.mxml第3行1242656555328 26

如何指定初始芯片数量？

Answer 1

在MXML中声明参数时,您无法将参数传递给元素的构造函数.你需要一个空的构造函数,然后有一个名为ChipCount的属性.您的代码也必须更新以处理ChipCount未设置(或设置为0).

我的建议是将Deck更改为:

public class Deck extends Canvas {

    protected var _chipCount:int;

    public function Deck() {
        _chipCount = 0; // Default ChipCount and wait for it to be set.
    }

    public function get chipCount():int {
        return _chipCount;
    }

    public function set chipCount(value:int):int {
        // Add logic here to validate ChipCount before setting.
        _chipCount = value;

    }
}