delphi - T图像未显示

Question

当将此组件拖放到表单上时，TImage 不会显示 map 图像(六边形)，直到我在表单上拖动该组件，然后它将显示它，直到我停止在表单上拖动它。 (这都是在设计模式下进行的)。怎么让它一直显示？不是只是拖动它时。

   type
      THexMap = Class(TScrollingWinControl)

构造函数

Constructor THexMap.Create(AOwner: Tcomponent);
begin
  inherited Create(AOwner);

  Width  := DEFAULT_MAP_WIDTH;
  Height := DEFAULT_MAP_HEIGHT;

  FCanvas := timage.Create(self);
  tempMap := timage.Create(self);

   fcanvas.Parent := self;
   tempmap.Parent := self;

  fCanvas.Width := DEFAULT_MAP_WIDTH;
  fCAnvas.Height := DEFAULT_MAP_WIDTH;


  { Set intial property values for component }

  //create map
  MakeSolidMap;

end;

制作实体 map

Procedure THexMap.MakeSolidMap;
var
p0 : TPoint;
looprow,Loopcol : integer;
begin
      TempMap.width := ((HexColumns-1) * round((1.5 * HexRadius))) + (2 * hexRadius);
      TempMap.height := ((HexRows) * (2 * rise)) + rise;

      With TempMap.Canvas do
      begin
        {set Background color}
        brush.Color := BackColor;
        fillrect(rect(0,0,TempMap.Width,TempMap.Height));

        {draw Hex's left to right / top to bottom}
        for looprow  := 1 to HexRows do
          begin
            for loopcol := 1 to HexColumns do
              begin
                {compute center coords}
                p0 := ConvertCoords(Point(LoopCol,LoopRow),ptROWCOL);

                {draw the hex}
                DrawSolidHex(Tempmap,bsSolid,hexColor,psSolid,LineColor,P0.X,p0.Y,hexRadius,hex3d);

            end;
          end;
      end;
end;

绘制SolidHex

 procedure THexMap.DrawSolidHex(Target: timage;
                                FillStyle: TBrushStyle;
                                FillColor: TColor;
                                LineStyle: TPenStyle;
                                LineColor: TColor;
                                x: Integer;
                                y: Integer;
                                Radius: Integer;
                                button: Boolean);
var
  p0,p1,p2,p3,p4,p5,p6:TPoint;
begin
   p0 := Point(x,y);

   {compute each point based on hex center}
   p1.X := p0.X - round(Radius /2);
   p1.Y := p0.Y - rise;
   p2.X := p0.X + round(Radius/2);
   p2.Y := p1.Y;
   p3.X := p0.X + Radius;
   p3.Y := p0.Y;
   p4.X := p2.X;
   p4.Y := p0.Y + rise;
   p5.X := p1.X;
   p5.Y := p4.Y;
   p6.X := p0.X - Radius;
   p6.Y := p0.Y;

   {set color / style of lines}
   target.canvas.Pen.Color := LineColor;
   target.canvas.Pen.Style := LineStyle;

   {set color / style of hex}
   target.canvas.Brush.Color := FillColor;
   Target.canvas.Brush.Style := FillStyle;

   {draw the hex}
   target.canvas.Polygon([p1,p2,p3,p4,p5,p6]);

   {if desired, draw the boarder for the hex}
   if button = true then
   begin
     with target.canvas do
     begin
       pen.Mode :=pmCopy;
       pen.Color :=clWhite;
       moveto(p5.X+1,p5.Y-1);
       lineto(p6.X+1,p6.Y);
       lineto(p1.X+1,p1.Y+1);
       lineto(p2.X-1,p2.Y+1);
       pen.Color :=clBlack;
       lineto(p3.X-1,p3.Y);
       lineto(p4.X-1,p4.Y-1);
       lineto(p5.X+1,p5.Y-1);
     end;
   end;
   invalidate;
end;

WndProc

procedure THexMap.WndProc(var Message: TMessage);
const
  DISCARD_CURRENT_ORIGIN = nil;
var
  R : TRect;
  PS : PAINTSTRUCT;
begin
  if Message.Msg = WM_PAINT then
  begin
    if GetUpdateRect( Handle, nil, false ) then
    begin
      BeginPaint( Handle, PS );
      try
        R := PS.rcPaint;
        bitblt(fCanvas.Canvas.Handle, R.Left, R.Top, R.Width, R.Height, TempMap.Canvas.Handle, R.Left+FOffset.X, R.Top+FOffset.Y, SRCCOPY);
      finally
        EndPaint( Handle, PS );
      end;
    end
    else
      inherited;
  end
  else
    inherited;
end;

Answer 1

没有显示任何内容，因为您已通过传递 WM_PAINT 接管了控件的绘制。在处理 WM_PAINT 时，您不会向 BeginPaint 返回的设备上下文绘制任何内容。您不会调用继承的处理程序，该处理程序将调用Paint，然后绘制子项。因此，您无法控制任何内容。

在我看来，您需要决定是使用视觉控件并让 VCL 绘制它们，还是自己绘制控件。您目前正在尝试两者兼而有之，但两者都没有实现!

我无法建议修复，因为我真的不知道你在做什么。我不明白为什么你有视觉控件并覆盖绘画消息处理程序。要继续前进，您需要选择一种方法或另一种方法。