If check box true it only shows only rows particuler other should be hide on vf page

Question

<apex:form id="formId">
    <script>
    function HideMsg(istrue)
    {
        var checkval = document.getElementById("msg")
        if(istrue.checked)

        {   
            var checkval = document.getElementById("msg").style.display='block';
        }
        else
        {
            var checkval = document.getElementById("msg").style.display='none';
        }
    }
    </script>
    <apex:pagemessages />
    <apex:pageBlock id="pageblockId">
        <apex:pageBlockSection Id="pageblocksectionId"> 
            <apex:inputFile value="{!csvFileBody}"  filename="{!csvAsString}"/>
            <apex:commandButton value="Import Project" action="{!importCSVFile}"/>
        </apex:pageBlockSection>
        <apex:pageBlock >
            <apex:pageBlockSection title="Project List" columns="1" >
                <apex:pageBlockTable value="{!Project2}" var="a" border="1">
                    <apex:column value="{!a.Name}"/>
                    <apex:column >
                           <!--<apex:pageBlockTable value="{!a.Project_Tasks__r}" var="c">
                            <apex:column value="{!c.Name}"/>
                            </apex:pageBlockTable>-->
                        <div>
                            <apex:inputCheckbox id="checkbox" onchange="HideMsg(this); "/>
                        </div>
                        <div class="showp" style="display: none" id="msg">
                            <apex:repeat value="{!a.Project_Tasks__r}" var="c">
                                <apex:outputText value="{!c.Name}">
                                </apex:outputText>
                            </apex:repeat>
                        </div>
                    </apex:column>
                    <apex:column value="{!a.Developer_Name__c}"/>
                    <apex:column value="{!a.Client_Name__c}"/>
                    <apex:column value="{!a.Date__c}"/>
                    <apex:column value="{!a.Start_Date__c}"/>
                    <apex:column value="{!a.End_Date__c}"/>
                    <apex:column value="{!a.Error_at_Project__c}"/>                        
                </apex:pageBlockTable>
            </apex:pageBlockSection>
        </apex:pageBlock>
    </apex:pageBlock>
</apex:form>

Answer 1

You need to assign a particular id on show/hide section and pass the same id reference on some attribute of checkbox so that system show/hide section.

here is example

<apex:page controller="testController">
<apex:form id="formId">
    <script>
    function HideMsg(checkbox)
    {
        console.log(checkbox.title);
        var title = checkbox.title;
       if(checkbox.checked)

        {   
            var checkval = document.getElementById(title).style.display='block';
        }
        else
        {
            var checkval = document.getElementById(title).style.display='none';
        }
    }
    </script>
    <apex:pagemessages />
    <apex:pageBlock id="pageblockId">
        <apex:pageBlockSection Id="pageblocksectionId"> 

        </apex:pageBlockSection>
        <apex:pageBlock >
            <apex:pageBlockSection title="Project List" columns="1" >
                <apex:pageBlockTable value="{!Project2}" var="a" border="1">

                    <apex:column value="{!a.Name}"/>
                    <apex:column >
                           <!--<apex:pageBlockTable value="{!a.Project_Tasks__r}" var="c">
                            <apex:column value="{!c.Name}"/>
                            </apex:pageBlockTable>-->
                        <div>
                            <apex:inputCheckbox id="checkbox" title="{!a.Name+'-'+a.Id}" onchange="HideMsg(this); "/>
                        </div>
                        <div class="showp" style="display: none" id="{!a.Name+'-'+a.Id}">
                            <apex:repeat value="{!a.contacts}" var="c">
                                <apex:outputText value="{!c.Name}">
                                </apex:outputText>
                            </apex:repeat>
                        </div>
                    </apex:column>

                </apex:pageBlockTable>
            </apex:pageBlockSection>
        </apex:pageBlock>
    </apex:pageBlock>
</apex:form>
    </apex:page>

public class testController {

    public List<Account> getProject2(){
        return [Select Id,Name,(SELECT Id,Name FROM Contacts) FROM Account];
    } 
}