希望有人可以帮助解决这个问题，我有 apex 代码在 Visualforce 页面上生成一个选择列表，这工作正常并且 value 被保存，我遇到的问题是当返回编辑页面时selected value 默认为列表中的第一个 value 而它应该默认为选中的 value。

音频页面

<apex:page standardController="Service__c" extensions="ServiceParameterExtension,ServiceBroadbandController">

    <style type="text/css">
        .commentSize { width: 90%}
    </style>


    <apex:sectionheader title="{!$ObjectType.Service__c.label} Edit" subtitle="{!IF(ISNULL(Service__c.Name), 'New Service',Service__c.Name)}"
    />
    <apex:pagemessages id="editPageMessage"></apex:pagemessages>
       <apex:form rendered="{!contains(Service__c.Type__c, 'Change')}">
            <apex:pageblock mode="edit" title="{!$ObjectType.Service__c.label} Edit">
                <apex:pageBlockButtons >
                    <apex:commandButton value="Save" action="{!Save}" />
                    <apex:commandButton value="Cancel" action="{!Cancel}" />
                </apex:pageBlockButtons>
                <apex:outputPanel >
                    <apex:pageBlockSection title="Information" showheader="true" columns="2" id="InformationChange">
                        <apex:inputField value="{!Service__c.Product__c}" />
                        <apex:inputField value="{!Service__c.Status__c}" />
                        <apex:inputField value="{!Service__c.Type__c}" />
                        <apex:inputField value="{!Service__c.Associated_MSA__c}" />
                        <apex:selectList value="{!changetypeselected}" label="Change Type" size="1">
                            <apex:selectOptions value="{!items}"/>
                        </apex:selectList>
                        <apex:inputField value="{!Service__c.C_I_Number__c}" label="OMS Order No." />
                        <apex:outputField value="{!Service__c.RecordTypeId}"/>
                        <apex:inputField value="{!Service__c.Ordered_Circuit_ID__c}" label="Openreach Ref." />
                        <apex:inputField value="{!Service__c.Product_Variant__c}" />
                        <apex:inputField value="{!Service__c.New_Account__c}" />
                        <apex:inputField value="{!Service__c.Static_IP__c}" label="Static IP Address required?"/>
                        <apex:inputField value="{!Service__c.Static_IP_2__c}" label="Static IP Address" />
                        <apex:inputField value="{!Service__c.Cancellation_Reason__c}" />
                        <apex:inputField value="{!Service__c.L2S__c}" />                        
                        <apex:inputField value="{!Service__c.Openreach_Cablelink__c}" />                        
                        <apex:inputField value="{!Service__c.eir_NGQ__c}" />
                        <apex:inputField value="{!Service__c.OMS_VIM_Circuit_ID__c}" label="OMS Circuit Ref." />
                        <apex:inputField value="{!Service__c.Completion_Date__c}" />                                              
                    </apex:pageBlockSection>
                    <apex:pageBlockSection title="Order Details" showHeader="true" columns="2" id="OrderDetailsChange">
                        <apex:inputField value="{!Service__c.Quantity__c}" />
                        <apex:inputField value="{!Service__c.Account_Number__c}" />
                        <apex:outputLabel value=""/>
                        <apex:inputField value="{!Service__c.Existing_IPVPN_Circuit_ID__c}"/>
                    </apex:pageBlockSection>
                    <apex:pageBlockSection title="Comments" showheader="true" columns="1" id="CommentsChange">
                        <apex:inputField value="{!Service__c.Comments__c}" styleClass="commentSize"/>
                    </apex:pageBlockSection>
                    <apex:pageBlockSection title="Contracting Part Details" showHeader="true" columns="2" id="ContractingPartDetailsChange">
                        <apex:inputField value="{!Service__c.Site_Contact_Name__c}" required="true"/>
                        <apex:inputField value="{!Service__c.Welcome_Pack_Email_new__c}" />
                        <apex:inputField value="{!Service__c.Site_Contact_Phone_No_2__c}" />
                        <apex:inputField value="{!Service__c.Welcome_Pack_Email_2_new__c}" />
                        <apex:inputField value="{!Service__c.Site_Address__c}" style="width: 60%;"/>
                        <apex:inputField value="{!Service__c.Welcome_Pack_Email_3_new__c}" />
                    </apex:pageBlockSection>
                    <apex:pageBlockSection title="Admin Area" showheader="true" columns="2" id="AdminAreaChange">
                        <apex:outputLabel value=""/>
                        <apex:inputField value="{!Service__c.Approved__c}"/>
                    </apex:pageBlockSection>
                    <apex:pageBlockSection title="System Information" showHeader="true" columns="1" id="SystemInformationChange">
                        <apex:outputField value="{!Service__c.RecordTypeId}"/>
                    </apex:pageBlockSection>
                </apex:outputPanel>
            </apex:pageblock>
        </apex:form>
</apex:page>

Apex 控制器

public with sharing class ServiceBroadbandController {
    public String changetypeselected;
    Service__c thisRecord;
    public ServiceBroadbandController(ApexPages.standardController controller) {
        thisRecord = (Service__c)controller.getRecord();
        thisRecord.Static_IP__c = 'No';
    }
    public PageReference Save(){
        if (validations()) {
            thisRecord.Change_Type__c = changetypeselected;
            Database.UpsertResult saveResult = Database.upsert(thisRecord, false);
            if(saveResult.isSuccess()){
                PageReference savePage = new PageReference('/' + thisRecord.id);
                savePage.setRedirect(true);
                return savePage;
            }else{
                for(Database.Error err : saveResult.getErrors()){
                    ApexPages.addMessage(new ApexPages.Message(ApexPages.Severity.ERROR, err.getMessage()));                
                }              
            }  
        }         
        return null;    
    }
    public List<SelectOption> getItems(){
        List<SelectOption> options = new List<SelectOption>();
        options.add(new SelectOption('','--None--'));
        options.add(new SelectOption('Add_static_IP','Add Static IP'));
        options.add(new SelectOption('Remove_static_IP','Remove Static IP'));
        options.add(new SelectOption('Change_SLA','Change SLA'));
        options.add(new SelectOption('Change_Bandwidth','Change Bandwidth'));
        return options;
    }
    public String getchangetypeselected(){
        return changetypeselected;
    }
    public void setchangetypeselected(String changetypeselected){
        this.changetypeselected=changetypeselected;
    }


}