下拉选择的 onChange 中未触发 API 调用

Question

我在父页面中定义了下拉列表，在那里我想添加其他行为，使得只要选择从下拉列表中的选项时，会拨打一个呼叫以确定标志的值（isTall）然后使用此标志来确定是否显示附加文本。

ParentPage.java

private Person person;
private PropertyModel<CertapayContact> personModel = new PropertyModel<>( this, "person" );

// sub-component that sets the disclaimer text and the optional text I want to add
final Panel somePanel = new SomePanel( "SomePanel", personModel );
somePanel.setOutputMarkupId( true );
somePanel.setOutputMarkupPlaceholderTag( true );

// retrieve list of people

// Recipient Drop down
recipientDropDownChoice = new DropDownChoice<Person>( "Recipient", personModel, people
contacts, new PersonRenderer<Person>( personMap ))
    {
        @Override
        ...
    };

recipientDropDownChoice.getInternalComponent().add( new AjaxFormComponentUpdatingBehavior( "onchange" )
    {
        @Override
        protected void onUpdate( AjaxRequestTarget ajaxRequestTarget )
        {

            // re-render the page to show other selection-dependent text
            ajaxRequestTarget.addComponent( somePanel );
            ajaxRequestTarget.addChildren( somePanel, Component.class );
        }

    } );

add(somePanel);
add(recipientDropDownChoice);

SomePanel.java

public SomePanel( String id, IModel<Person> personModel )
{
    Person person = personModel.getObject();
    boolean isTall = apiCallToCheckIfTall( person );

    tallLabel = isTall ? new Label( "height", "Tall" ) : new Label( "height", "Short" );

    add(tallLabel);
}

在调试过程中，API 调用仅在页面首次加载时进行一次。在下拉列表中进行选择时，不会触发调用。我不太清楚为什么。

Answer 1

SomePanel 的构造函数只执行一次。

您必须更改 SomePanel 始终显示最新数据的代码：

public SomePanel( String id, IModel<Person> personModel)
{
  tallLabel = new Label( "height", new LoadableDetachableModel() {
    pubic String getObject() {
      Person person = personModel.getObject();
      boolean isTall = apiCallToCheckIfTall( person );
  
      return isTall ? "Tall" : "Short";
    }
  });

  add(tallLabel);
}

Answer 2

您的活动名称有误，应该是

new AjaxFormComponentUpdatingBehavior( "change" )