Delphi 两个不同的对象使用一个内存区域？

我需要能够在我简单的delphi绘画中进行撤销和重做操作。所以我决定制作一些容器来保存历史记录（不是完整的历史记录，只有以前的一些位图文件）

在我的程序中，我就是这样使用它的

在历史中保存：

procedure TMainForm.FormCreate(Sender: TObject);
begin
 {...}
  picHistory:=myHistory.Create(10);   //FOR UNDO
  tempHistory:=myHistory.Create(10); //FOR REDO
end;

    //if mouse is up - that mean we finish to draw something on canvas, so we gonna save what we drew

    procedure TMainForm.imgMainMouseUp(Sender: TObject; Button: TMouseButton;
      Shift: TShiftState; X, Y: Integer);
    var bmp:TBitmap;
    begin
      mouseIsDown:=false;
      bmp:=TBitmap.Create;
      try
        bmp.Assign(imgMain.Picture.Bitmap);
        picHistory.Push(bmp);
      finally
        bmp.Free;
      end;

    end;

以及撤销和重做

    procedure TMainForm.btnUndoClick(Sender: TObject);
    var redBmp:TBitmap;

    begin
      if(not picHistory.isEmpty) then begin //if we draw something before
        //prepare to save what've done into history for redo
        redBmp:=TBitmap.Create;
        redBmp.Assign(picHistory.getLast);
       //showing what were done with image before on screen
        MainForm.imgMain.Canvas.Draw(0,0, picHistory.Pop);
        //but in case we want to be able get back our last changes we save it into redo history 
        tempHistory.Push(redBmp);
        redBmp.Free;
      end;

    end;

  {...}

    procedure TMainForm.btnRedoClick(Sender: TObject);

    begin
    //if there were something into history for redo then show int on canvas
      if(not tempHistory.isEmpty) then
        MainForm.imgMain.Canvas.Draw(0,0, tempHistory.Pop);
    end;

但是有很多事情发生了——我推动的

Undo

没有任何变化。当我按下“重做”，它的工作原理就像“撤消”

顺便说一下，当我以不同的长度声明重做和撤消的历史时

procedure TMainForm.FormCreate(Sender: TObject);
begin
 {...}
  picHistory:=myHistory.Create(6);   //FOR UNDO
  tempHistory:=myHistory.Create(12); //FOR REDO
end;

---

然后一步一步地看看

picHistory

中发生了什么，看起来它的数组长度不是6，而是12！所以我认为这两个对象使用同一个数组！为什么会发生这种情况以及如何纠正这种情况？

myHistory类的两个实例共享相同的全局数据。必须将数据声明移动到类中，使其成为每个实例的数据，而不是全局数据

试试这个：

type
myHistory = class
  private
    historyQueueArray: array of TBitmap;  //Now they are class members instead of global
    historyIndex, hSize:Integer;
  public
    constructor Create(Size:Integer);
    procedure Push(Bmp:TBitmap);
    function Pop():TBitmap;
    procedure Clean();
    procedure Offset();
    function isEmpty():boolean;
    function isFull():boolean;
    function getLast():TBitmap;
  protected
  end;

---

谢谢，先生！我甚至没有意识到这一点，当我急着做某事的时候，我比以往更加愚蠢：c

type
myHistory = class
  private
    historyQueueArray: array of TBitmap;  //Now they are class members instead of global
    historyIndex, hSize:Integer;
  public
    constructor Create(Size:Integer);
    procedure Push(Bmp:TBitmap);
    function Pop():TBitmap;
    procedure Clean();
    procedure Offset();
    function isEmpty():boolean;
    function isFull():boolean;
    function getLast():TBitmap;
  protected
  end;