The code is crashing while removing column from AdvancedDataGrid.

[santusapi]

Hello All,
I am facing problem while removing the columns from
AdvancedDataGri d. It is crashing at one point and i am unable to
resolve it.

The code i'm using to remove the columns is like this.

               public function clearPlot():void
               {
                       cols = cols.slice(0, 0);

                       this.columns = cols;
                       this.validateNow();
               }

The class is extending AdvancedDataGri d and the variable "cols" is an
Array type. And also i have tried many variations, but none of
them solved the problem. So i'm giving the variations also.

[1]

               public function clearPlot():void
               {
                       cols = cols.slice(0, 0);
                       cols.push(new AdvancedDataGridColumn(""));

                       this.columns = cols;
                       this.validateNow();
               }

[2]

             public function clearPlot():void
               {
                       cols = new Array();
                       cols.push(new AdvancedDataGridColumn("dummy"));

                       this.columns = cols;
                       this.validateNow();
               }

[3]

             public function clearPlot():void
               {
                       cols = new Array();

                       this.columns = cols;
                       this.validateNow();
               }

[4]

             public function clearPlot():void
               {
                       this.columns = null;
                       this.validateNow();
               }

[5]

             public function clearPlot():void
               {
                       cols = null;
                       cols = new Array();

                       this.columns = cols;
                       this.validateNow();
               }

The error is like this:

TypeError: Error #1009: Cannot access a property or method of a null
object reference.
at mx.controls::Ad vancedDataGridB aseEx/http://www.adobe.com/2006/flex/
mx/internal::getHe aderInfo()[C:\work\flex\dm v_automation\pr ojects
\datavisualisat ion\src\mx\cont rols\AdvancedDa taGridBaseEx.as :2366]
at mx.controls::Ad vancedDataGrid/http://www.adobe.com/2006/flex/mx/
internal::getHe aderInfo()[C:\work\flex\dm v_automation\pr ojects
\datavisualisat ion\src\mx\cont rols\AdvancedDa taGrid.as:2147]
at mx.controls::Ad vancedDataGrid/getFieldSortInf o()[C:\work\flex
\dmv_automation \projects\datav isualisation\sr c\mx\controls
\AdvancedDataGr id.as:6840]
at
mx.controls.adv ancedDataGridCl asses::Advanced DataGridHeaderR enderer/
getFieldSortInf o()[C:\work\flex\dm v_automation\pr ojects
\datavisualisat ion\src\mx\cont rols\advancedDa taGridClasses
\AdvancedDataGr idHeaderRendere r.as:757]
at
mx.controls.adv ancedDataGridCl asses::Advanced DataGridHeaderR enderer/
updateDisplayLi st()[C:\work\flex\dm v_automation\pr ojects
\datavisualisat ion\src\mx\cont rols\advancedDa taGridClasses
\AdvancedDataGr idHeaderRendere r.as:560]
at mx.core::UIComp onent/validateDisplay List()[C:\autobuild
\3.3.0\framewor ks\projects\fra mework\src\mx\c ore\UIComponent .as:6351]
at mx.managers::La youtManager/validateDisplay List()[C:\autobuild
\3.3.0\framewor ks\projects\fra mework\src\mx\m anagers\LayoutM anager.as:
622]
at mx.managers::La youtManager/doPhasedInstant iation()[C:\autobuild
\3.3.0\framewor ks\projects\fra mework\src\mx\m anagers\LayoutM anager.as:
695]
at Function/http://adobe.com/AS3/2006/builtin::apply( )
at mx.core::UIComp onent/callLaterDispat cher2()[C:\autobuild
\3.3.0\framewor ks\projects\fra mework\src\mx\c ore\UIComponent .as:8628]
at mx.core::UIComp onent/callLaterDispat cher()[C:\autobuild
\3.3.0\framewor ks\projects\fra mework\src\mx\c ore\UIComponent .as:8568]


And i'm giving the stack trace also. It is:
mx.controls::Ad vancedDataGridB aseEx/http://www.adobe.com/2006/flex/mx/
internal::getHe aderInfo
mx.controls::Ad vancedDataGrid/http://www.adobe.com/2006/flex/mx/
internal::getHe aderInfo
mx.controls::Ad vancedDataGrid/getFieldSortInf o
mx.controls.adv ancedDataGridCl asses::Advanced DataGridHeaderR enderer/
getFieldSortInf o
mx.controls.adv ancedDataGridCl asses::Advanced DataGridHeaderR enderer/
updateDisplayLi st
mx.core::UIComp onent/validateDisplay List
mx.managers::La youtManager/validateDisplay List
mx.managers::La youtManager/doPhasedInstant iation
Function/http://adobe.com/AS3/2006/builtin::apply [no source]
mx.core::UIComp onent/callLaterDispat cher2
mx.core::UIComp onent/callLaterDispat cher


Please help me in solving this.