Error messages not getting removed on reloading the page,when I've overridden the view with a visualforce page

Question

I have overridden the standard view of Account object with a visualforce page,& using a custom button that is used to send email to Account,using a custom field,Email__c.The error appears if we've not filled the Email__c field & try to send email.On reload of page showing the error,I want the message to be removed.But the page appears again with the error message.What can I do?

My code is as follows:

    public with sharing class sendEmailToAccount {
    ApexPages.StandardController controller;

    public sendEmailToAccount(ApexPages.StandardController controller) {
        this.controller = controller;


    }


    public PageReference sendEmailToAccount() {
        Messaging.SingleEmailMessage message = new Messaging.SingleEmailMessage();


        List<Account> lstaccount = [select id,Test_Email_Field__c,Name,AccountNumber from Account where id = :ApexPages.currentPage().getParameters().get('id')];

        if(lstaccount[0].Test_Email_Field__c==null)
        {

            ApexPages.addMessage(new ApexPages.Message(ApexPages.Severity.ERROR,'Cannot Send email when Email field is empty.'));
             return null;


        }

        if(lstaccount[0].Test_Email_Field__c!=null)
        {
            String accName=String.valueOf(lstaccount[0].Name);
            String accNumber=String.valueOf(lstaccount[0].AccountNumber);
            String accOwner=String.valueOf(lstaccount[0].Name);
            String toAddress=String.valueOf(lstaccount[0].Test_Email_Field__c);
            EmailTemplate et=[select Id, subject,body,HtmlValue from EmailTemplate where id='00X28000000R3VZ'];


            String subjectTemplate= et.subject;
            String contentTemplate=et.body;
            String htmlcontent=et.HtmlValue;
            String filteredcontent=contentTemplate.replace('{!Account.Name}',accName);
            String filteredcontent1=filteredcontent.replace('{!Account.Id}',accOwner);
            String filteredcontent2=filteredcontent1.replace('{!Account.AccountNumber}',accNumber); 


            message.ToAddresses=new String[]{toAddress};
            message.subject=subjectTemplate;
            message.PlainTextBody=filteredcontent2;
            message.HtmlBody=htmlcontent;

             ApexPages.addMessage(new ApexPages.Message(ApexPages.Severity.Confirm,'Email sent successfully !'));
            Messaging.sendEmail(new Messaging.SingleEmailMessage[] { message });

             return null;


        }


        return controller.view();

    }

}

---

VF Page

    <apex:page standardController="Account" extensions="sendEmailToAccount" action="{!sendEmailToAccount}">
    <apex:pageMessages id="messages" />
   <apex:detail relatedList="true"/>
   </apex:page>

---

JavaScript Code:

if(confirm("Are you sure You want to send Email?"))
 {
  window.open('/apex/SendEmailToAccount?id={!Account.Id}','_self');
}

---

Answer 1

The VisualForce page you have created to override the Account view is calling the sendEmailToAccount() method every time the page loads because of the action="{! sendEmailToAccount}" line within your <apex:page > parameters which is why you see this error every time you re-load the page.

If you are wanting to have the page display a warning message every time the account is viewed then you may wish to create some form of verifyEmailDetails() method which is called upon page load which verifies the required fields and pops up a warning message if needed, you could then create a separate sendEmailToAccount() method which then re-verifies and then sends the email to make sure that the account is still / now valid if edits have been made.

Alternatively to having your validation upon viewing the account you may be better off sticking with the standard salesforce view and having your confirm / validations in a separate page upon the click of the Send Email to Account Holder button.