OSX优胜美地和XE7 Firemonkey

Question

can anybody tell me how to make a TTrackBar object read only in C++Builder (or Delphi) XE7 in an OSX firemonkey application? I tried the "Locked" property but it seems not working.

Cheers

dodo

Answer 1

Set the Enabled property to False . Locked locks the position of the trackbar in the designer so that you cannot accidentally move it.

Answer 2

Here's another answer because of your additional requirements. There is no "readonly" property that will keep the TrackBar enabled.

You could just use the TrackBar.OnChange event and just reset the value if the user tries to change it:

procedure TForm1.TrackBar1Change(Sender: TObject);
begin
  TrackBar1.Value := 50;
end;

A more advanced approach is using an observer in order to get a true readonly TrackBar.

TReadOnlyTrackObserver = class(TInterfacedObject, IEditLinkObserver, IObserver, ISingleCastObserver)
public
  procedure Removed;
  function GetActive: Boolean;
  procedure SetActive(Value: Boolean);
  function GetOnObserverToggle: TObserverToggleEvent;
  procedure SetOnObserverToggle(AEvent: TObserverToggleEvent);

  procedure Update;
  function Edit: Boolean;
  procedure Reset;
  procedure Modified;
  function IsModified: Boolean;
  function IsValidChar(AKey: Char): Boolean;
  function IsRequired: Boolean;
  function GetIsReadOnly: Boolean;
  procedure SetIsReadOnly(Value: Boolean);
  property IsReadOnly: Boolean read GetIsReadOnly write SetIsReadOnly;
  function GetIsEditing: Boolean;
  property IsEditing: Boolean read GetIsEditing;
  procedure BeginUpdate;
  procedure EndUpdate;
  function GetUpdating: Boolean;
  property Updating: Boolean read GetUpdating;
end;

function TReadOnlyTrackObserver.GetActive: Boolean;
begin
  Result := True;
end;

function TReadOnlyTrackObserver.GetIsReadOnly: Boolean;
begin
  Result := True;
end;

// todo: implement the other required functions of TReadOnlyTrackObserver 

var
  MyObserver: IEditLinkObserver;

  MyObserver := TReadOnlyTrackObserver.Create;
  TrackBar1.Observers.AddObserver(TObserverMapping.EditLinkID, MyObserver);