D12 TItemClickEvent undeclared identifier

[Fudley 1]

Trying to reference the events for a TListBox in order to save and restore them. This is so I can make changes to the listbox without triggering the events, then restore the events.

 

However I'm having trouble with FMX.ListBox.TCustomListBox.OnItemClick as Delphi suggests that TItemClickEvent  is an undeclared identifier.

 

Thoughts?

 

 

 

[Olli73 0]

var
  ItemClickEvent: TCustomListBox.TItemClickEvent;

 

[Fudley 1]

Thanks. But still undeclared identifier TCustomListBox.TItemClickEvent

 

 

Edited 14 hours ago by Fudley

[Lajos Juhász 286]

That is only possible if you have not included FMX.ListBox into the uses clause.

[Fudley 1]

In this case, FMX.Listbox is definately in the uses clause

[Dave Nottage 546]

4 hours ago, Fudley said:

In this case, FMX.Listbox is definately in the uses clause

Please post a reproducible example.

[Remy Lebeau 1349]

8 hours ago, Fudley said:

Thanks. But still undeclared identifier TCustomListBox.TItemClickEvent

It should not be undeclared. It is a public sub-type of TCustomListBox.  The following is taken from FMX.ListBox.pas:

  TCustomListBox = class(...)
  ...
  public type
    ...
    TItemClickEvent = procedure(const Sender: TCustomListBox; const Item: TListBoxItem) of object;
    ...
  strict private
    ...
    FOnItemClick: TItemClickEvent;
    ...
  public
    ...
    property OnItemClick: TItemClickEvent read FOnItemClick write FOnItemClick;
  end;

The following works fine for me in D12.2:

uses
  ..., FMX.ListBox;

procedure TForm1.Button1Click(Sender: TObject);
var
  OnClickHandler: TCustomListBox.TItemClickEvent;
begin
  OnClickHandler := ListBox1.OnItemClick;
  ListBox1.OnItemClick := nil;
  // ...
  ListBox1.OnItemClick := OnClickHandler;
end;

You could also use an inline variable and let the compiler deduce the type:

uses
  ..., FMX.ListBox;

procedure TForm1.Button1Click(Sender: TObject);
begin
  var OnClickHandler := ListBox1.OnItemClick;
  ListBox1.OnItemClick := nil;
  // ...
  ListBox1.OnItemClick := OnClickHandler;
end;

 

Edited 6 hours ago by Remy Lebeau

[Fudley 1]

Thanks Dave, Remy!

Here's my reproducible (at least for me) example:
 

unit testlistboxerror1;

interface

uses
  System.SysUtils, System.Types, System.UITypes, System.Classes, System.Variants,
  FMX.Types, FMX.Controls, FMX.Forms, FMX.Graphics, FMX.Dialogs,
  FMX.Controls.Presentation, FMX.StdCtrls, FMX.Layouts, FMX.ListBox;
type
  TForm1 = class(TForm)
    Button1: TButton;
    ListBox1: TListBox;
     procedure Button1Tap(Sender: TObject; const Point: TPointF);
     procedure NoEventSetListBoxIndex   (aListBox : TCustomListBox;  aValue : integer);
  private
  public
  end;
var
  Form1: TForm1;

implementation

{$R *.fmx}

procedure TForm1.NoEventSetListBoxIndex   (aListBox : TCustomListBox;  aValue : integer);
var
  eItemClickEvent: TItemClickEvent ;  
  // also tried TCustomListBox.TItemClickEvent, same
  {<--[DCC Error] testlistboxerror1.pas(31): E2003
    Undeclared identifier: 'TItemClickEvent ' }          
  eGestureEvent  : TGestureEvent;
  eTapEvent      : TTapEvent;
begin
  eItemClickEvent        := aListBox.OnClick ;
  eGestureEvent        := aListBox.OnGesture;
  eTapEvent            := aListBox.OnTap;
  aListBox.OnClick        := nil;
  aListBox.OnGesture    := nil;
  aListBox.OnTap        := nil;
  aListBox.Itemindex     := aValue;
  aListBox.OnClick        := eItemClickEvent ;
  aListBox.OnGesture    := eGestureEvent;
  aListBox.OnTap        := eTapEvent;
end;    

procedure TForm1.Button1Tap(Sender: TObject; const Point: TPointF);
begin
 NoEventSetListBoxIndex(ListBox1,  5);
end;

end.

 

[Fudley 1]

Dave - the inline method worked great thanks!

[Lajos Juhász 286]

For me it is working:

 

var
  eItemClickEvent: TCustomListBox.TItemClickEvent;
 

and fails at:

 

eItemClickEvent        := aListBox.OnClick ;

since the OnClick and OnItemClick has different signatures.

 

For OnClick it should be:

 

var 

eOnClickEvent : TNotifyEvent;

 

eOnClickEvent:=aListBox.OnClick;