Disabling commandButton in VisualForce Page

Question

EDIT:

<apex:commandButton value="Save" rerender="IdPanel" 
disabled="{!AND(SelectedText == null && SelectedText == '')}" />
    <apex:outputPanel id="IdPanel">
      <apex:repeat var="TheID" value="{!CurrentList}"> 
    <apex:outputText value="{!TheID}" />;
      </apex:repeat>
  </apex:outputPanel> 

How can I enable/disable commandButton based on the user have selected?

Here I'm checking to see if the User have selectedText and if the SelectedText is null or empty I want the commandButton to be disabled but the below code does disable the button but but never enable even though I have value in the SelectedText

<apex:commandButton value="Save" rerender="IdPanel" 
disabled="{!AND(SelectedText == null && SelectedText == '')}" />

Answer 1

Without knowing much about your code, the following works assuming you have something like...

public String selectedText {
  get;
  set;
}

... In your controller.

See below:

<apex:form>
    <apex:actionFunction name="myActFunct" reRender="myPanel" />
    <apex:inputText value="{!selectedText}" onkeyup="myActFunct();" />
    <apex:outputPanel id="myPanel">
        <apex:commandButton value="Save" rerender="IdPanel" disabled="{!AND(SelectedText == null || SelectedText == '')}" />
    </apex:outputPanel>
</apex:form>

Basically you've got your inputText which, onkeyup, calls the ActionFunction which then rerenders the panel and then can check whether or not SelectedText is empty or not.

I've tested this and it should meet your requirements.

Good luck!

Answer 2

Its quite simple to achieve this. You just need to capture the keyup action and rerender the section containing the CommandButton. Use ActionSupport to capture the events as shown below.

Also added an actionStatus so that you know that the re-rendering is happening.

  <apex:pageBlock id="someblock">
        <apex:inputText value="{!SelectedText}">
            <apex:actionSupport event="onkeyup" reRender="commandButtonPanel" status="status"/>
        </apex:inputText>

        <apex:outputPanel id="commandButtonPanel">
            <apex:commandButton action="{!enable}" disabled="{!SelectedText==null}" value="Submit"/>
        </apex:outputPanel>

        <apex:actionStatus startText="Re-evalutaing..."  stopText="Idle" id="status"/>
    </apex:pageBlock>