Question

我创建了一个基于TPaintBox的组件TGridPaintBox。它基本上是一个添加了“网格功能”的绘图箱。它不是数据网格。更像是棋盘组件。

在对象资源管理器中，我可以设置某些属性。最重要的是，我可以设置网格尺寸（横跨/向下有多少个单元格），还可以设置与绘图相关的选项。细胞是否应该是正方形，奇数/偶数细胞的颜色等。

我的第一个版本的组件直接在类上有属性，当我更改属性时，立即更新了设计时图。随着组件的增长，我想更好地组织我的属性，并介绍了一些“选项属性”，如绘图选项，行为选项等。在介绍之后，设计时绘图不再像以前那样更新。更改属性后，我必须单击组件才能更新。谁能告诉我为什么会这样呢？

这是代码的精简版本。我希望它能解释这种行为：

（PS：这是我的第一个组件，即使我自1997年以来一直使用Delphi，所以如果有人能像我做的那样发现任何愚蠢的东西，请随时告诉我）

unit GridPaintBox;

interface

type
  TGridDrawOption = (gdoSquareCells,gdoCenterCells,gdoDrawCellEdges,gdoDrawFocus);
  TGridDrawOptions = set of TGridDrawOption;

  TGridOptions = class(TPersistent)
  private
    FCellsX : integer;
    FCellsY : integer;
    FDrawOptions : TGridDrawOptions;
  public
    constructor Create(aGridPaintBox : TGridPaintBox);
    procedure Assign(Source : TPersistent); override;
  published
    property CellsX : integer read FCellsX write FCellsX;
    property CellsY : integer read FCellsY write FCellsY;
    property DrawOptions : TGridDrawOptions read FDrawOptions write FDrawOptions;
  end;

  TGridPaintBox = class(TPaintBox)
  private
    FGridOptions : TGridOptions;
    FFocusedX,
    FFocusedY : integer;
    FOnFocusChanged: TNotifyEvent; 
    procedure CalculateSizeAndPosition; 
    procedure DrawCell(X,Y : integer);
    procedure DrawCells;
    procedure SetGridOptions(const Value: TGridOptions);
  protected
    procedure MouseDown(Button: TMouseButton; Shift: TShiftState; X, Y: Integer); override;
  public
    constructor Create(aOwner : TComponent); override;
    destructor Destroy; override;
    procedure Paint; override;
    procedure SetFocus(X,Y : integer);
  published
    property OnFocusChanged : TNotifyEvent read FOnFocusChanged write FOnFocusChanged;
    property Options : TGridOptions read FGridOptions write SetGridOptions;
  end;

procedure Register;

implementation

procedure Register;
begin
  RegisterComponents('Samples', [TGridPaintBox]);
end;

procedure TGridPaintBox.CalculateSizeAndPosition;
begin
  <...>
end;

constructor TGridPaintBox.Create(aOwner: TComponent);
begin
  inherited;
  FGridOptions := TGridOptions.Create(self);
end;

procedure TGridPaintBox.DrawCell(X, Y: integer);
begin
  <...>
end;

procedure TGridPaintBox.DrawCells;
var
  X,Y : integer;
begin
  CalculateSizeAndPosition;

  for Y := 0 to FGridOptions.CellsY-1 do
    for X := 0 to FGridOptions.CellsX-1 do
      DrawCell(X,Y);
end;

procedure TGridPaintBox.Paint;
begin
  Canvas.Font := Font;
  Canvas.Brush.Color := Color;
  Canvas.Brush.Style := bsSolid;
  Canvas.FillRect(Rect(0,0,Width,Height));
  DrawCells;
  if Assigned(OnPaint) then
    OnPaint(Self); 
end;

procedure TGridPaintBox.SetGridOptions(const Value: TGridOptions);
begin
  FGridOptions.Assign(Value);
  invalidate;
end;

procedure TGridPaintBox.MouseDown(Button: TMouseButton; Shift: TShiftState; X, Y: Integer);
begin
  SetFocus(PixelToCellX(X),PixelToCellY(Y));
  inherited;
end;

procedure TGridPaintBox.SetFocus(X, Y: integer);
begin
  if (FocusedX=X) and (FocusedY=Y) then 
    exit;

  FFocusedX := X;
  FFocusedY := Y;

  if assigned(OnFocusChanged) then
    OnFocusChanged(self);

  invalidate;
end;

constructor TGridOptions.Create(aGridPaintBox : TGridPaintBox);
begin
  FCellsX := 20;
  FCellsY := 8;
  FDrawOptions := [gdoSquareCells,gdoCenterCells,gdoDrawCellEdges];
end;

procedure TGridOptions.Assign(Source : TPersistent);
begin
  if Source is TGridOptions then
  begin
    FCellsX := TGridOptions(Source).CellsX;
    FCellsY := TGridOptions(Source).CellsY;
    FDrawOptions := TGridOptions(Source).DrawOptions;
  end
  else
    inherited;
end;

end.

Answer 1

之所以发生这种情况，是因为您没有设置选项集的setter，这会使您所属的控件失效。表单设计器中的单击调用控件使其无效，但您应该在自己的选项设置器中自行处理。所以我会存储选项所有者以便更好地访问直接所有者类实例，并在选项setter中强制该所有者，控件重绘：

type
  TGridPaintBox = class;
  TGridDrawOption = (gdoSquareCells, gdoCenterCells, gdoDrawCellEdges, gdoDrawFocus);
  TGridDrawOptions = set of TGridDrawOption;
  TGridOptions = class(TPersistent)
  private
    FOwner: TGridPaintBox;
    FCellsX: Integer;
    FCellsY: Integer;
    FDrawOptions: TGridDrawOptions;
    procedure SetCellsX(AValue: Integer);
    procedure SetCellsY(AValue: Integer);
    procedure SetDrawOptions(const AValue: TGridDrawOptions);
  public
    constructor Create(AOwner: TGridPaintBox);
    procedure Assign(ASource: TPersistent); override;
  published
    property CellsX: Integer read FCellsX write SetCellsX;
    property CellsY: Integer read FCellsY write SetCellsY;
    property DrawOptions: TGridDrawOptions read FDrawOptions write SetDrawOptions;
  end;

implementation

constructor TGridOptions.Create(AOwner: TGridPaintBox);
begin
  FOwner := AOwner;
  FCellsX := 20;
  FCellsY := 8;
  FDrawOptions := [gdoSquareCells, gdoCenterCells, gdoDrawCellEdges];
end;

procedure TGridOptions.SetCellsX(AValue: Integer);
begin
  if FCellsX <> AValue then
  begin
    FCellsX := AValue;
    FOwner.Invalidate;
  end;
end;

procedure TGridOptions.SetCellsY(AValue: Integer);
begin
  if FCellsY <> AValue then
  begin
    FCellsY := AValue;
    FOwner.Invalidate;
  end;
end;

procedure TGridOptions.SetDrawOptions(const AValue: TGridDrawOptions);
begin
  if FDrawOptions <> AValue then
  begin
    FDrawOptions := AValue;
    FOwner.Invalidate;
  end;
end;

进一步说明：

如果您没有明确需要绘制“已发布的属性和事件，例如Color，Font或OnPaint事件，请从TGraphicControl派生您的控件而不是来自TPaintBox。您可以选择自己发布的属性和事件。

当我更改属性时，为什么我的自定义组件不会更新？

1 个答案: