My error in the visual force page is not displaying

Question

On the visual force page I have a method that is being called by clicking on the command link as follows

<apex:actionRegion>
                    <apex:input type="date" value="{!recurringTaskLPP.endDate}">
                    </apex:input>
                    <apex:commandLink action="{!calculateEndDate}" value="Calculate End Date"
                                      reRender="RecurringDatesSection">
                    </apex:commandLink>
                </apex:actionRegion>

After clicking the command link I have the following method being called on in the controller

 public void calculateEndDate() {
   PageReference pageError = this.checkForErrors();
    if (recurringTaskLPP.getFrequency() == FREQUENCY_TYPE_DAILY) {
        this.calculateEndDateForDailyView();
    }
    if (recurringTaskLPP.getFrequency() == FREQUENCY_TYPE_WEEKLY) {
        this.calculateEndDateForWeeklyView();
    }
    if (recurringTaskLPP.getFrequency() == FREQUENCY_TYPE_MONTHLY) {
        this.calculateEndDateForMonthlyView();
    }
}

public PageReference checkForErrors(){
    if (recurringTaskLPP.recurringAmount == null || recurringTaskLPP.startDate == null || recurringTaskLPP.numberOfLppDetails == null) {
        ApexPages.Message recurringTaskErrorMessage = new ApexPages.Message(ApexPages.Severity.WARNING, 'Amount field and Start Date and Lpp Details Count should not be left empty!');
        ApexPages.addMessage(recurringTaskErrorMessage);
    }
    return null;
}

But the error message never displays and it gives an error that you are trying to De-reference the null object. Can some one please help me in understanding why the error is not displayed and how cna it be resolved.

Answer 1

few points. As you are getting attempt to de-reference null object error. So I suggest you to put your code in try catch block

try {
  // code here
}
catch(exception ex)
{

        ApexPages.addMessage(new ApexPages.Message(ApexPages.Severity.WARNING, ex.getmessage()););
}

And then in the VF page use apex:pageMessages and rerender it to display error message properly.

<apex:pageMessages id="msg"/>