Tapestry onEvent问题

Question

我在更新链接的select组件时遇到了一个问题--我键入的似乎是有效的，但它给了我一个很大的丑陋的错误消息。

Component.tml (相关章节)

<tr>
    <td>
        <h3>Powers:</h3>
    </td>
    <td>
        <t:select t:id="powersSelect" t:model="powersModel"
            t:value="powersItem" t:encoder="itemEncoder"
             t:validate="required" t:blankOption="ALWAYS" t:blankLabel="Choose..." zone="groundsZone" />
    </td>
</tr>
<tr>
    <td>
        <h3>Grounds:</h3>
    </td>
    <td>
        <t:zone t:id="groundsZone" id="groundsZone" visible="false">
            <t:select  t:model="groundsModel"
                t:value="groundsItem" t:encoder="itemEncoder"
                t:validate="required" t:blankOption="ALWAYS" t:blankLabel="Choose..."/>
        </t:zone>
    </td>
</tr>

Component.java (相关章节)

     @InjectComponent
    private Zone groundsZone;

    @Inject
    private SelectModelFactory selectModelFactory;

    @Property
    private SelectModel powersModel, groundsModel;

    @Property
    StandingDataItem powersStandingDataItem, groundsStandingDataItem;

@SetupRender
void setupRender() {
    powersList = service.getList()
    powersModel = selectModelFactory.create(powersList, "displayText");

   //included as I was getting a null pointer without instantiating 
    groundsList = new ArrayList<StandingDataItem>();
    groundsModel = selectModelFactory.create(new ArrayList<StandingDataItem>(), "displayText");
}

@OnEvent(value = EventConstants.VALUE_CHANGED, component = "powersSelect")
    Object updateGrounds(StandingDataItem sdi) {
        powersStandingDataItem=sdi;
        groundsList = service.getList()
        groundsModel = selectModelFactory.create(groundsList, "displayText");
        return groundsZone.getBody();
    }

然而，我一直遇到以下错误，并且一直无法解决。服务方法调用完成，返回预期的列表，两个Select组件都包含预期的信息-但是我得到了一条红色的丑陋的大错误消息，占据了半个屏幕。

TypeError: Cannot call method 'getFormEventManager' of null 
at klass.Tapestry.FieldEventManager.Class.create.initialize (http://localhost:8080/nottsStops/assets/1.0.0-SNAPSHOT/tapestry/tapestry.js:1588:38) 
at new klass (http://localhost:8080/nottsStops/assets/1.0.0-SNAPSHOT/tapestry/scriptaculous_1_9_0/prototype.js:101:23) 
at Element.addMethods.getFieldEventManager (http://localhost:8080/nottsStops/assets/1.0.0-SNAPSHOT/tapestry/tapestry.js:841:23) 
at HTMLSelectElement._methodized [as getFieldEventManager] (http://localhost:8080/nottsStops/assets/1.0.0-SNAPSHOT/tapestry/scriptaculous_1_9_0/prototype.js:438:23) 
at http://localhost:8080/nottsStops/assets/1.0.0-SNAPSHOT/tapestry/tapestry.js:1145:26 
at http://localhost:8080/nottsStops/assets/1.0.0-SNAPSHOT/tapestry/scriptaculous_1_9_0/prototype.js:825:18 
at klass._each (http://localhost:8080/nottsStops/assets/1.0.0-SNAPSHOT/tapestry/scriptaculous_1_9_0/prototype.js:1237:7) 
at klass.each (http://localhost:8080/nottsStops/assets/1.0.0-SNAPSHOT/tapestry/scriptaculous_1_9_0/prototype.js:824:12) 
at T5.extendInitializers.validate (http://localhost:8080/nottsStops/assets/1.0.0-SNAPSHOT/tapestry/tapestry.js:1135:14) 
at http://localhost:8080/nottsStops/assets/1.0.0-SNAPSHOT/tapestry/tapestry.js:268:23
Ajax failure: Status 200 for /nottsStops/stopsentrybuild.powerscomponent.powersselect:change: TypeError: Cannot call method 'getFormEventManager' of null
Communication with the server failed: TypeError: Cannot call method 'getFormEventManager' of null

我使用的是tapestry 5.3.7。该组件是由许多子组件组成的表单的一部分-其他子组件都没有这个问题(可能是因为这是唯一使用链式select的组件)。有没有人能解释一下我做错了什么/为什么我会得到这个错误？

Answer 1

看起来我找到了答案(尽管我必须承认我不理解这种行为)。就在select之前，我在我的tml文件中包含了一个自定义组件。自定义组件包含一个元素，这似乎导致表单在标记之前关闭(更有可能是在tml结构上搞乱了，而不是提前关闭表单，因为没有其他错误)。从我的自定义组件中删除已解决此问题。