Script Tool Multivalue Check Boxes Not Updating

EvanMyers1

I have been trying to figure out why the Multivalue boxes in my tool don't respond with the "Select All" and "Unselect All" buttons.  They also don't stay unchecked (they are default checked) when I click other buttons.

Here is my validation code (the commented out part at the bottom was my attempt but I get errors):

 

import arcpy
import os


class ToolValidator(object):
    """Class for validating a tool's parameter values and controlling
    the behavior of the tool's dialog."""
    def __init__(self):
        """Setup arcpy and the list of tool parameters."""
        self.params = arcpy.GetParameterInfo()

    def initializeParameters(self):
        """Refine the properties of a tool's parameters.  This method is
        called when the tool is opened."""
        return

    def updateParameters(self):
        """Modify the values and properties of parameters before internal
        validation is performed.  This method is called whenever a parameter
        has been changed."""

        if self.params[1].value:
            if self.params[1].valueAsText.find(";") > -1:
                fclist = self.params[1].valueAsText.split(";")
                layerList = []
                for each in fclist:
                    # source = arcpy.Describe(each).catalogPath
                    # desc = arcpy.Describe(each)
                    # layersource = desc.catalogPath
                    layerList.append(each)
                print layerList
            else:
                layerList = []
                # desc = arcpy.Describe(self.params[0].value)
                # layersource = desc.catalogPath
                # layerList.append(layersource)
                layerList = [self.params[1].valueAsText]
                print layerList
            fieldlist = []
            for each in layerList:
                #fieldnames = [f.name for f in arcpy.Describe(each).fields]
                fieldnames = arcpy.Describe(each).fields
                for fields in fieldnames:
                    if fields not in fieldlist:
                        #fieldlist.append(fields)
                        fieldlist.append(fields.baseName.upper())
            self.params[2].value = fieldlist
            print fieldlist
            # if self.params[1].hasBeenValidated:
            #     for checked in self.params[2].valueAsText.split(';'):
            #         if checked not in self.params[2].filter.list:
            #             self.params[2].value = self.params[2].filter.list[2]

        return

    def updateMessages(self):
        """Modify the messages created by internal validation for each tool
        parameter.  This method is called after internal validation."""
        return

 

Any help would be appreciated.  Thank you!

EvanMyers1

Thank you for providing a piece of your code, but this did not work for me.  

I need to use feature layers inside arcmap for my tool to work properly.  I cannot use a file path.  There are only two issues that prevent my script from working and it comes down to the Validator.

1.  If the layers are in a group it will not work at all.  E.g. "IOError: "'New Group Layer\wControlValve'" does not exist".  On line 42, arcpy.Describe(each).fields, isn't working.

2.  If I ungroup my layers, the field list populates, but now none of the boxes will stay unchecked, making my tool useless.

Right now, the way I have my code works to an extent, it is my lack of understanding why the boxes wont stay unchecked.