1

I have trouble keeping a TListbox in sync with a TList. Each time an item is added to a generic TList, OnNotify is called and the callback calls just one procedure: create_gradients. Its code is below:

  procedure TColor_Dialog.create_gradients;
  var Editor: TGradient_Editor;
      eGradient: Int32;
      y: single;
      s: string;
  begin
     List_Names.Clear;
     List_Gradients.Clear;

     for eGradient := 0 to FColor_Editor.nGradients - 1 do
     begin
        List_Names.Items.Add (FColor_Editor [eGradient].Check_Rainbow.Text);
     end; // for

     List_Gradients.BeginUpdate;
     try
        for eGradient := 0 to FColor_Editor.nGradients - 1 do
        begin
           Editor := FColor_Editor [eGradient];
           y := (eGradient + 1) * Editor.Height;
           Editor.Position.Y := y;
           s := Editor.Check_Rainbow.Text;
           List_Gradients.AddObject (Editor);
        end; // for
     finally
        List_Gradients.EndUpdate;
     end; // try..finally
  end; // create_gradients //

As you see it simply enumerates all items in the list. Each item in the list is a TGradient_Editor which in turn has TFrame as a parent. On the parent are some FMX controls as combolorboxes, an image and a checkbox (Check_Rainbow). Check_Rainbow.Text is used for identification purposes. When the gradient editor is created, it creates a unique name from frame_%s where %s is a sequence number that is incremented each time a gradient editor is created. Owner and Parent are both List_Gradients.

enter image description here

From the image above you can see what happens. the listbox on the right is added for checking and just shows the text's, which is the correct sequence by the way. When I use the debugger to follow the addition of the gradient editors to List_Gradient they are processed in the same order. But the order of the gradient editors is wrong. I have to mention that the aligment of the gradient editors is alTop. I added even some code to ensure that the editor is Positioned at the very bottom of the List_Gradients.

I appear not to understand something. I cannot imagine that sequential adding to a TListBox cannot result in the correct order. What am I doing wrong?

4

2 回答 2

3

试试这个：

procedure TColor_Dialog.create_gradients;
var
  Editor: TGradient_Editor;
  eGradient: Int32;
  y: single;
begin
  List_Names.Clear;
  List_Gradients.Clear;

  for eGradient := 0 to FColor_Editor.nGradients - 1 do
  begin
    List_Names.Items.Add (FColor_Editor[eGradient].Check_Rainbow.Text);
  end;

  List_Gradients.BeginUpdate;
  try
    y := 0.0; // or whatever value you want to start at...
    for eGradient := 0 to FColor_Editor.nGradients - 1 do
    begin
      Editor := FColor_Editor[eGradient];
      Editor.Position.Y := y;
      List_Gradients.AddObject(Editor);
      y := y + Editor.Height;
    end;
  finally
    List_Gradients.EndUpdate;
  end;
end;
于 2013-11-13T20:31:05.197 回答
3

根据要求，我将答案移至本节。正确的代码是：

  procedure TColor_Dialog.create_gradients;
  var Editor: TGradient_Editor;
      eGradient: Int32;
      y: single;
  begin
     List_Gradients.BeginUpdate;
     try
        List_Gradients.Clear;
        y := 0;
        for eGradient := 0 to FColor_Editor.nGradients - 1 do
        begin
           Editor := FColor_Editor [eGradient];
           Editor.Position.X := 0;
           Editor.Position.Y := y;
           Editor.Width := List_Gradients.Width;
           List_Gradients.AddObject (Editor);
           y := y + Editor.Height;
        end; // for
     finally
        List_Gradients.EndUpdate;
     end; // try..finally
  end; // create_gradients //

并且不再使用任何对齐方式。将对象添加到 aTListBox是 FMX 的一个非常好的特性。但是，请做好准备，有时事情的工作方式与您的预期不同。一方面：对象的定位方式与字符串不同。

于 2013-11-15T10:26:06.517 回答