Delphi XE 6 FMX TreeListVew text margin.left causes an runtime error

Question

I need to move TreeViewItem.Text on left. My code causes runtime error.

constructor TVppTreeViewItem.Create(AOwner: TComponent);
 var
 c:TTextControl;
begin
  inherited;
  self.Text:='test';
  self.TextObject.Align:=TAlignLayout.Left;
  self.TextObject.Margins.Left:=50;
end;

How do I code it correctly?

Answer 1

At creation time TextObject field of TTreeItem (and your TVppTreeItem) is nil and accessing it results in AV error. You should move code that modifies TextObject to ApplyStyle method where TextObject will be initialized from Style. Since it is not guaranteed that TextObject will be valid even after applying style, you should check it for nil before you attempt to do anything with it.

  TVppTreeViewItem = class(TTreeViewItem)
  protected
    procedure ApplyStyle; override;
  public
    constructor Create(AOwner: TComponent); override;
  end;

constructor TVppTreeViewItem.Create(AOwner: TComponent);
begin
  inherited;
  self.Text := 'test';
end;

procedure TVppTreeViewItem.ApplyStyle;
begin
  inherited;
  if Assigned(TextObject) then
    begin
      TextObject.Align := TAlignLayout.Left;
      TextObject.Margins.Left := 50;
    end;
end;