变形点在一架飞机上(Deform points in a plane)

 在创建时， TTreeItem （和您的TVppTreeItem ）的TextObject字段nil ，访问它会导致AV错误。 您应该将修改TextObject代码移动到ApplyStyle方法，其中TextObject将从Style初始化。 由于无法保证TextObject即使在应用样式后仍然有效，因此在尝试对其执行任何操作之前，应将其检查为nil 。 
 
  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;

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;