delphi – 在运行时删除和替换可视组件

function ReplaceControlEx(AControl: TControl; const AControlClass: TControlClass; const ANewName: string; const IsFreed : Boolean = True): TControl;
begin
  if AControl = nil then
  begin
    Result := nil;
    Exit;
  end;
  Result := AControlClass.Create(AControl.Owner);
  CloneProperties(AControl,Result);// copy all properties to new control
  // Result.Left := AControl.Left;   // or copy some properties manually...
  // Result.Top := AControl.Top;
  Result.Name := ANewName;
  Result.Parent := AControl.Parent; // needed for the InsertControl & RemoveControl magic
  if IsFreed then
    FreeAndNil(AControl);
end;

function ReplaceControl(AControl: TControl; const ANewName: string; const IsFreed : Boolean = True): TControl;
begin
  if AControl = nil then
    Result := nil
  else
    Result := ReplaceControlEx(AControl,TControlClass(AControl.ClassType),ANewName,IsFreed);
end;

使用此例程将属性传递给新控件

procedure CloneProperties(const Source: TControl; const Dest: TControl);
var
  ms: TMemoryStream;
  OldName: string;
begin
  OldName := Source.Name;
  Source.Name := ''; // needed to avoid Name collision
  try
    ms := TMemoryStream.Create;
    try
      ms.WriteComponent(Source);
      ms.Position := 0;
      ms.ReadComponent(Dest);
    finally
      ms.Free;
    end;
  finally
    Source.Name := OldName;
  end;
end;

使用它像：

procedure TFrame1.AfterConstruction;
var
  I: Integer;
  NewEdit: TMyEdit;
begin
  inherited;
  NewEdit := ReplaceControlEx(Edit1,TMyEdit,'Edit2') as TMyEdit;
  if Assigned(NewEdit) then
  begin
    NewEdit.Text := 'My Brand New Edit';
    NewEdit.Author := 'Myself';
  end;
  for I:=0 to ControlCount-1 do
  begin
    ShowMessage(Controls[I].Name);
  end;
end;

注意：如果您在框架的AfterConstruction中执行此操作,请注意托管表单构造尚未完成.释放控件可能会导致很多问题,因为你搞乱了Form控件的内务管理.如果您尝试阅读ShowMessage中显示的新编辑标题,请查看您获得的内容…在那种情况下,你会想要使用… ReplaceControl(Edit1,’Edit2′,False)然后做一个… FreeAndNil(EDIT1)后来.