SOQLによる検索結果をエクセル出力するVisualForce画面の作り方(出力対象の選択を標準画面で行うやり方付き)

public class ContactListPageController{

    public List selectedContactList{get;set;}
    public List exportObjectList{get;set;}
    List ssId{get;set;}


    public ContactListPageController(ApexPages.StandardSetController controller) {
    
        //選択したレコードを取得
        ssId = (List)controller.getSelected();

        selectedContactList=[SELECT Id, IsDeleted, Name, Email, Title, Account.Name FROM Contact where Id IN :ssId order by Name ];

        system.debug('★SELECT='+ssId);

        exportObjectList= new List();
        ContactMeisaiInfo cInfo;

        for(Contact oneCont : selectedContactList){
            
            cInfo = new ContactMeisaiInfo();
            cInfo.AccountName =oneCont.Account.Name;
            cInfo.ConactId =oneCont.Id;
            cInfo.ConactName =oneCont.Name;            

            exportObjectList.add(cInfo);

        }
    }

    public PageReference exportAction() {
        
        system.debug('★exportAction');
        
        //return null;
        
        return Page.VFPreviewContact_Export;

    }
   
    public PageReference back() {
        String rtnPage= ApexPages.currentPage().getParameters().get('retURL');
        PageReference cancel = new PageReference(rtnPage);
        return cancel;
    }

    public class ContactMeisaiInfo{
    
        public String ConactId {get;set;}
        public String ConactName {get;set;}
        public String AccountName {get;set;}
        
        public ContactMeisaiInfo(){

        }
    
    }
    
}