5 replies to this topic

[user22]

Hello Boki,

trying to use NextDbGrid with a LookupColumn - from this moment i have lot's of AV's, not only when running the program, also every time i stop the program and in the IDE too.
One of the errors i have found here: when i close the program the error occurs in NxDBColumns.pas in procedure "TLookupDataLink.ActiveChanged", where it checks if DataSet is active, but DataSet is nil ...

I use latest version of Next Suite and D7 pro.

thanks,
Helmut

[rond]

I noticed the same here as well.
I had a NextDbGrid ( v5111, Unicode ) with two columns using DbLookupColumns in a frame.

I got an access violation as soon as the destructor tried to free the frame.
Clearing the datasources for the lookup-columns didn't help either.
I did manage to contain the error within a try/except in the destructor.

[Boki (Berg)]

Hello,

I will check this. It is strange, since I didn't change anything in here.

Please sorry for this problem

Best regards

[rond]

Hello,

I will check this. It is strange, since I didn't change anything in here.

Please sorry for this problem

Best regards

I've stumbled upon a solution/fix.
By closing and freeing the table associated to the ListDataSource for the LookupColumn the access violation is gone.
I did this in the destructor for the frame I had the grid in.

[Boki (Berg)]

I've stumbled upon a solution/fix.
By closing and freeing the table associated to the ListDataSource for the LookupColumn the access violation is gone.
I did this in the destructor for the frame I had the grid in.

Hello Rond,

Can you please send me a sample code that you do, to I integrate it into grid.

Best regards

[rond]

Hello Rond,

Can you please send me a sample code that you do, to I integrate it into grid.

Best regards

I didn't modify any of your controls.
I only changed the order in which I destroy/close the list-source in my frame, which looks a bit like this :

CODE

  TfrShiftProducts = class(TFrame)
private
    FProductSelectionItems: TAdoQuery;
public
    Constructor Create(AOwner : TComponent); override;
    Destructor  Destroy; override;
end;
...

constructor TfrShiftProducts.Create(AOwner: TComponent);
begin
  inherited;
  FProductDataSource     := TDataSource.Create(Nil);
  FProductSelectionItems := TAdoQuery.Create(Nil);
  FProductSelectionItems.LockType := ltReadOnly;
  FProductSelectionItems.ConnectionString := datMsSql.ConnectionString;
  FProductSelectionItems.SQL.Clear;
  // I build query for listbox here (the actual query is a bit more complex, but this is the basic idea :
  FProductSelectionItems.SQL.Add("SELECT PrCode, PrNaam FROM OEE_PR");
  //
  // and linked the list to the column like this :
  FProductDataSource.DataSet    := FProductSelectionItems;
  colProductDescriptions.ListDataSource := FProductDataSource;
  colProductDescriptions.KeyFieldName  := 'PrCode';
  colProductDescriptions.ListFieldName   := 'PrNaam';
  // the grid uses a query as a datasource, which contains a field named 'PrCode'
end;


destructor TfrShiftProducts.Destroy;
begin
try
  // this is the bit I have which appears to have solved the issue for me :
  if (Nil <> FProductSelectionItems) then
  begin
    if FProductSelectionItems.Active then
    begin
      FProductSelectionItems.Close;
    end;
    FreeAndNil(FProductSelectionItems);
  end;
  // ---
  if FProducts.Active then
    FProducts.Close;
  if Assigned(FProductDataSource) then
  begin
    grdShiftProducts.DataSource := Nil;
    // this bit appeared to cause the exception somewhere in the component :
    colProductDescriptions.ListDataSource := Nil;
    FreeAndNil(FProductDataSource);
    // ---
  end;
except
  on E : Exception do // at first I simply caught the exception
  begin
    Fc.SystemEventLogger.Exception(E);
  end;
end;
  inherited;
end;

...