VAADIN23 COMBOBOX.SETVALUE失败，转换错误

Question

我正在使用VAADIN23使用粘合剂在Combobox中显示时区的列表：

ComboBox<ZoneId> timezoneField = new ComboBox<>();
timezoneField.setItemLabelGenerator(zoneId -> zoneId.getId());
timezoneField.setItems(Timezones.getZones());
binder.forField(timezoneField)
                .bind("timezone");
final var registration = new Registration(member, organisation);
binder.setBean(registration);

上面的代码似乎正常工作，直到我尝试设置默认值：

        UI.getCurrent().getPage().retrieveExtendedClientDetails(extendedClientDetails ->
            {
                int timezoneOffest = extendedClientDetails.getRawTimezoneOffset();
                var possibleZones = Conversions.timezonesFromOffset(timezoneOffest);
                if (possibleZones.size() != 0)
                {
                    // this line throws
                    this.timezoneField.setValue((ZoneId) possibleZones.get(0));
                }

            });

FossibleZones返回ZoneID列表，但在调试器中它们显示为ZonereGion的列表。 我认为这是可以的，因为区域是一种ZoneDID。 当调用setValue时，我会做铸件，以防万一。

因此，当我致电时：

this.timezoneField.setValue((ZoneId) possibleZones.get(0));

抛出以下错误：

 com.vaadin.flow.data.binder.BindingException: An exception has been thrown inside binding logic for the field element [suppress-template-warning='', _inputElementValue='', _clientSideFilter='false', selectedItem='null', invalid='false', pageSize='50', itemValuePath='key', itemIdPath='key', value='1']
    at com.vaadin.flow.data.binder.Binder$BindingImpl.execute(Binder.java:1542) ~[flow-data-23.0.4.jar:23.0.4]
    at com.vaadin.flow.data.binder.Binder$BindingImpl.doConversion(Binder.java:1286) ~[flow-data-23.0.4.jar:23.0.4]
    at com.vaadin.flow.data.binder.Binder$BindingImpl.doValidation(Binder.java:1306) ~[flow-data-23.0.4.jar:23.0.4]
    at com.vaadin.flow.data.binder.Binder$BindingImpl.validate(Binder.java:1247) ~[flow-data-23.0.4.jar:23.0.4]
    at com.vaadin.flow.data.binder.Binder.lambda$doWriteIfValid$3(Binder.java:2245) ~

...

    at com.vaadin.flow.data.binder.Binder.doWriteIfValid(Binder.java:2246) ~[flow-data-23.0.4.jar:23.0.4]

....
com.vaadin.flow.component.internal.AbstractFieldSupport.setValue(AbstractFieldSupport.java:135) ~[flow-server-23.0.4.jar:23.0.4]
    at com.vaadin.flow.component.AbstractField.setValue(AbstractField.java:181) ~[flow-server-23.0.4.jar:23.0.4]
    at com.vaadin.flow.component.combobox.ComboBox.setValue(ComboBox.java:396) ~[vaadin-combo-box-flow-23.0.5.jar:?]
    at dev.onepub.ui.views.noauth.RegistrationView.lambda$4(RegistrationView.java:171) ~[classes/:?]

...

caused by:

Caused by: java.lang.ClassCastException: Cannot cast java.time.ZoneRegion to java.lang.String
    at java.lang.Class.cast(Class.java:3889) ~[?:?]
    at com.vaadin.flow.data.converter.Converter.lambda$from$957be2b0$1(Converter.java:104) ~[flow-data-23.0.4.jar:23.0.4]
    at com.vaadin.flow.data.binder.Result.of(Result.java:90) ~[flow-data-23.0.4.jar:23.0.4]
    at com.vaadin.flow.data.converter.Converter.lambda$from$b652e465$1(Converter.java:104) ~[flow-data-23.0.4.jar:23.0.4]
    at com.vaadin.flow.data.converter.Converter$1.convertToModel(Converter.java:130) ~[flow-data-23.0.4.jar:23.0.4]
    at com.vaadin.flow.data.converter.Converter$2.lambda$convertToModel$6b579330$1(Converter.java:165) ~[flow-data-23.0.4.jar:23.0.4]
    at com.vaadin.flow.data.binder.SimpleResult.flatMap(SimpleResult.java:65) ~[flow-data-23.0.4.jar:23.0.4]
    at com.vaadin.flow.data.binder.ValidationResultWrap.flatMap(ValidationResultWrap.java:67) ~[flow-data-23.0.4.jar:23.0.4]
    at com.vaadin.flow.data.converter.Converter$2.convertToModel(Converter.java:165) ~[flow-data-23.0.4.jar:23.0.4]
    at com.vaadin.flow.data.binder.Binder$BindingImpl.lambda$doConversion$0(Binder.java:1288) ~[flow-data-23.0.4.jar:23.0.4]

我注意到转换在抱怨将划分转换为字符串。

鉴于Combobox是类型ZoneID，并且具有ItemLabelgenerator，我不知道为什么可以生成此错误？

Answer 1

因此，答案是创建一个转换器。
对于我为什么使用与组合框相同的类型，SetValue需要转换器需要转换器，这仍然是没有意义的。

在这里记录是转换器：

package dev.onepub.fields.converters;

import java.time.ZoneId;

import com.vaadin.flow.data.binder.Result;
import com.vaadin.flow.data.binder.ValueContext;
import com.vaadin.flow.data.converter.Converter;

public class ZoneIdToStringConverter implements Converter<ZoneId, String>
{
    private static final long serialVersionUID = 1L;

    @Override
    public Result<String> convertToModel(ZoneId fieldValue, ValueContext context)
    {

        // Converting to the field type should always succeed,
        // so there is no support for returning an error Result.
        if (fieldValue == null)
        {
            return Result.ok(ZoneId.systemDefault().getId());
        }
        return Result.ok(fieldValue.getId());
    }

    @Override
    public ZoneId convertToPresentation(String zoneId, ValueContext context)
    {
        // Produces a converted value or an error

        // ok is a static helper method that creates a Result
        if (zoneId == null)
            return ZoneId.systemDefault();
        else
            return ZoneId.of(zoneId);

    }

}

并称呼它

ComboBox<ZoneId> timezoneField = new ComboBox<>();
timezoneField.setItemLabelGenerator(zoneId -> zoneId.getId());
timezoneField.setItems(Timezones.getZones());
binder.forField(timezoneField)
    .withConverter(new ZoneIdToStringConverter())
    .bind("timezone");
final var registration = new Registration(member, organisation);
binder.setBean(registration);