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...link a TFilterComboBox with a TShellListView?
Autor: serge gubenko
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Tip Rating (11):  
     




{
  Question:

  Does anybody know how to make a component just like the
  FilerComboBox but instead of applying the filter to the
  TFilterComboBox doing it to the ShellListView?
}

{
  Answer:

  Looks like you've got two ways to make it work. First is by using standard
  events of the TShellListView and TFilterComboBox controls. Assign the
  OnAddFolder event to the shell listview and check up the file name, which is
  coming as a PathName property of the AFolder parameter. Also, you need to
  refresh the list each time the the value of the filter combobox was changed.
  You could do it in the combobox's OnChange event. Below is an example:
}

// Refresh the ShellListView when the filter changes
procedure TForm1.ShellListView1AddFolder(Sender: TObject;
  AFolder: TShellFolder; var CanAdd: Boolean);
var
  
XFilterExt, XExt: string;
begin
  if 
FilterComboBox1.Mask <> '*.*' then
  begin
    
XFilterExt := ExtractFileExt(FilterComboBox1.Mask);
    XExt := ExtractFileExt(AFolder.PathName);
    // Only accept filter and folders
    
if (CompareText(XExt, XFilterExt) = 0) or AFolder.IsFolder then
      
CanAdd := True
    else
      
CanAdd := False;
  end;
end;

// Refresh the ShellListView when the filter changes
procedure TForm1.FilterComboBox1Change(Sender: TObject);
begin
  
ShellListView1.Refresh;
end;

//

{
  Second approach is to create your own TShellListView and TFilterComboBox
  descendants. There you could implement the needed functionality. Override
  list's OwnerDataFetch method in order to filter the undesired items. You
  also need to add a ShellListView property to the filter combobox. Give a try
  to the code listed below. It's a unit with components I was talking about,
  they seemed to work fine for me :)
}

unit MyShCtrl;
{$WARN UNIT_PLATFORM OFF}

interface

uses
  
Windows, Messages, SysUtils, Graphics, Classes, Controls, Forms,
  Dialogs, ComCtrls, StdCtrls, FileCtrl, ShellCtrls;

type
  
TMyShellListView = class(TShellListView)
  protected
    
FMask: string;

    function OwnerDataFetch(Item: TListItem; Request: TItemRequest): Boolean; override;
    procedure SetMask(AValue: string);

  published
    property 
Mask: string read FMask write SetMask;
  end;

  TMyFilterComboBox = class(TFilterComboBox)
  protected
    
FShellListView: TMyShellListView;
    procedure Notification(AComponent: TComponent; Operation: TOperation); override;
    procedure Change; override;
    procedure SetShellListView(AValue: TMyShellListView);
  published
    property 
ShellListView: TMyShellListView read FShellListView write SetShellListView;
  end;

procedure Register;

  {============================================}

implementation

procedure Register
;
begin
  
RegisterComponents('My Components', [TMyShellListView,
    TMyFilterComboBox]);
end;

{============================================}

function TMyShellListView.OwnerDataFetch(Item: TListItem;
  Request: TItemRequest): Boolean;
var
  
XFolder: TShellFolder;
  XExt, XFltExt: string;
begin
  if 
(Length(FMask) > 0) and (FMask <> '*.*') then
  begin
    
XFolder := Folders[Item.Index];
    if Assigned(XFolder) and not XFolder.IsFolder then
    begin
      
XExt := ExtractFileExt(XFolder.PathName);
      XFltExt := ExtractFileExt(FMask);
      if CompareText(XExt, XFltExt) <> 0 then
      begin
        
Result := False;
        Exit;
      end;
    end;
  end;
  Result := inherited OwnerDataFetch(Item, Request);
end;

procedure TMyShellListView.SetMask(AValue: string);
begin
  if 
FMask <> AValue then
  begin
    
FMask := AValue;
    Invalidate;
  end;
end;

{============================================}

procedure TMyFilterComboBox.Notification(AComponent: TComponent; Operation: TOperation);
begin
  inherited 
Notification(AComponent, Operation);
  if (Operation = opRemove) and (AComponent = FShellListView) then FShellListView := nil;
end;

procedure TMyFilterComboBox.Change;
begin
  inherited 
Change;
  if Assigned(FShellListView) then FShellListView.Mask := Mask
end;

procedure TMyFilterComboBox.SetShellListView(AValue: TMyShellListView);
begin
  if 
AValue <> FShellListView then
  begin
    
FShellListView := AValue;
    if Assigned(AValue) then AValue.FreeNotification(Self);
  end;
end;

end.

 

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