德尔菲颜料盒没有关键事件

Question

我看到我的版本的德尔菲，没有关键的活动(OnKeyDown,OnKeyUp,OnKeyPress)事件对TPaintBox.我想到处理这样的事情。有别人的颜料盒与这些活动？

Answer 1

像TLama说，你会需要继承TCustomControl.但你会需要一些额外的代码发布的所有键盘的事件。你可以选择最容易的方法和继承TPanel由于TPanel已经暴露了一个帆布和数量的键盘的事件。

但这里的一些代码，以显示如何创建和注册一个新的控制，已发布的属性TCustomControl，并引入了一个新的OnPaint事件：

如果创建一个新的软件包，加入这一单元，并安装了，你会有一个新的TGTPaintBox控制，可以有焦点(虽然你看不见它)。它可以检索的键盘输入。

unit uBigPaintbox;

interface

uses Windows, Classes, Messages, Controls;

type
  TGTPaintBox = class(TCustomControl)
  private
    FOnPaint: TNotifyEvent;
  protected
    // Three methods below are for transparent background. This may not work that great,
    // and if you don't care about it, you can remove them.
    procedure WMEraseBkGnd(var Msg: TWMEraseBkGnd); message WM_ERASEBKGND;
    procedure CreateParams(var Params: TCreateParams); override;
    procedure SetParent(AParent: TWinControl); override;
  protected
    procedure Paint; override;
    procedure MouseDown(Button: TMouseButton; Shift: TShiftState; X, Y: Integer); override;
  public
    property Canvas;
  published
    // Introduce OnPaint event
    property OnPaint: TNotifyEvent read FOnPaint write FOnPaint;
    // Publish keyboard and mouse events.
    property OnKeyPress;
    property OnKeyDown;
    property OnKeyUp;
    property OnClick;
    property OnDblClick;
    property OnMouseUp;
    property OnMouseDown;
    property OnMouseMove;
    // And some other behavioral property that relate to keyboard input.
    property TabOrder;
    property TabStop;
  end;

procedure Register;

implementation

procedure Register;
begin
  RegisterComponents('GolezTrol', [TGTPaintBox]);
end;

{ TGTPaintBox }

procedure TGTPaintBox.CreateParams(var Params: TCreateParams);
begin
  inherited CreateParams(Params);
  Params.ExStyle := Params.ExStyle or WS_EX_TRANSPARENT;
end;

procedure TGTPaintBox.MouseDown(Button: TMouseButton; Shift: TShiftState; X,
  Y: Integer);
begin
  inherited;

  // Focus the control when it is clicked.
  if not (csDesigning in ComponentState) and CanFocus then
    SetFocus;
end;

procedure TGTPaintBox.Paint;
begin
  inherited;
  // Call paint even if it is assigned.
  if Assigned(FOnPaint) then
    FOnPaint(Self);
end;

procedure TGTPaintBox.SetParent(AParent: TWinControl);
var
  NewStyle: Integer;
begin
  inherited;
  if AParent = nil then
    Exit;

  // Make sure the parent is updated too behind the control.
  NewStyle := GetWindowLong(AParent.Handle, GWL_STYLE) and not WS_CLIPCHILDREN;
  SetWindowLong(AParent.Handle, GWL_STYLE, NewStyle);
end;

procedure TGTPaintBox.WMEraseBkGnd(var Msg: TWMEraseBkGnd);
begin
  SetBkMode(Msg.DC, TRANSPARENT);
  Msg.Result := 1;
end;

end.

我已经增加了一些功能，在试图使的控制的透明，因为一个颜料盒。一个缺点是，你需要重新绘制的父母清除先前绘制的内容。在演示中的应用程序，这是很容易。我只是无效的形式，而不是控制。:p
如果你不需要它，你可以除去 WMEraseBkGnd, CreateParams 和 SetParent 从控制。

小演示：把标签上的一种形式。把TGTPaintBox在它上面，并使它成为一个比较大。然后添加一个计时器，也许一些其他的控制。

确保你表位置的财产GTPaintBox到 True.

然后，执行以下活动；

// To repaint the lot.
procedure TForm1.Timer1Timer(Sender: TObject);
begin
  Invalidate;
end;

// Capture key input and save the last entered letter in the tag.
procedure TForm1.GTPaintBox1KeyPress(Sender: TObject; var Key: Char);
begin
  if Key in ['a'..'z'] then
    TGTPaintBox(Sender).Tag := Integer(Key);
end;

// Paint the control (this is called every second, when the timer invalidates the form
procedure TForm1.GTPaintBox1Paint(Sender: TObject);
var
  PaintBox: TGTPaintBox;
begin
  PaintBox := TGTPaintBox(Sender);

  // Draw a focus rect too. If you want the control to do this, you would normally
  // implement it in the control itself, and make sure it invalides as soon as it 
  // receives or loses focus.
  if PaintBox.Focused then
    PaintBox.Canvas.DrawFocusRect(PaintBox.Canvas.ClipRect);

  // It just draws the character that we forced into the Tag in the KeyPress event.
  PaintBox.Canvas.TextOut(Random(200), Random(200), Char(PaintBox.Tag));
end;

Answer 2

您还可以创建一个带有颜料盒的框架（与alClient对齐），然后根据需要重新使用该框架。TFrame是一个窗口控件，因此具有所有键盘事件。它们没有发布，但是您可以在代码中分配它们。