我一直在升级或从XP OS迁移我们的软件，以便能够在Windows 7下编译和运行。我们的软件开始显示我们在Windows XP下没有注意到的问题。目前，我正在处理用户定义的控件在TForm上闪烁。 它似乎偶尔会闪烁，但并不总是闪烁，但当它闪烁时它非常明显。我已经为TForm和TTrendChart类设置了DoubleBuffered，但它没有帮助。
这是TCustomPanel的用户定义控件。它应该在TForm上显示实时趋势图。
TTrendChart = class(TCustomPanel)
private
fCount:integer;
fColors:array[0..7] of TColor;
fNames:array[0..7] of string;
fMinText:string16;
fMaxText:string16;
fShowNames:Boolean;
fMaxTextWidth:integer;
data:TList;
Indexer:integer;
chartRect:TRect;
fWidth:integer;
fHeight:integer;
firstTime:Boolean;
function GetColors(Index:integer):TColor;
procedure SetColors(Index:integer; const value :TColor);
function GetNames(Index:integer):string;
procedure SetNames(Index:integer; const value: string);
procedure SetCount(const value : integer);
procedure rShowNames(const value : Boolean);
procedure SetMaxText(const value:string16);
procedure SetMinText(const value:string16);
procedure RecalcChartRect;
protected
procedure Resize; override;
procedure Paint; override;
public
constructor Create(AOwner : TComponent); override;
destructor Destroy; override;
procedure PlotPoints(p1,p2,p3,p4,p5,p6,p7,p8:real);
procedure ClearChart;
procedure Print;
property TrendColors[Index:integer]: TColor read GetColors write SetColors;
property TrendNames[index:integer]: string read GetNames write SetNames;
published
property TrendCount: Integer read fCount write SetCount default 8;
property ShowNames: Boolean read fShowNames write rShowNames default true;
property MaxText:string16 read fMaxText write SetMaxText;
property MinText:string16 read fMinText write SetMinText;
property Align;
property Alignment;
property BevelInner;
property BevelOuter;
property BevelWidth;
property DragCursor;
property DragMode;
property Enabled;
property Caption;
property Color;
property Ctl3D;
property Font;
property Locked;
property ParentColor;
property ParentCtl3D;
property ParentFont;
property ParentShowHint;
property PopupMenu;
property ShowHint;
property TabOrder;
property TabStop;
property Visible;
property OnClick;
property OnDblClick;
property OnDragDrop;
property OnDragOver;
property OnEndDrag;
property OnEnter;
property OnExit;
property OnMouseDown;
property OnMouseUp;
property OnMouseMove;
property OnResize;
end;
它是如何创建的：
constructor TTrendChart.Create(AOwner:TComponent);
var
i:integer;
tp:TTrendPoints;
begin
inherited Create(AOwner);
Parent := TWinControl(AOwner);
fCount := 8;
fShowNames := true;
Caption := '';
fMaxText := '100';
fMinText := '0';
fMaxTextWidth := Canvas.TextWidth('Bar 0');
firstTime := true;
BevelInner := bvLowered;
data := TList.Create;
Indexer := 0;
RecalcChartRect;
DoubleBuffered:=true;
for i := 0 to 10 do
begin
tp := TTrendPoints.Create(0.0 + 0.1 * fWidth,0.0,0.0,0.0,0.0,0.0,0.0,0.0);
data.Add(tp);
end;
for i := 0 to 7 do
begin
case i of
0: fColors[i] := clMaroon;
1: fColors[i] := clGreen;
2: fColors[i] := clOlive;
3: fColors[i] := clNavy;
4: fColors[i] := clPurple;
5: fColors[i] := clFuchsia;
6: fColors[i] := clLime;
7: fColors[i] := clBlue;
end;
fNames[i] := Format('Line %d',[i]);
end;
end;
以下是在表格上绘制的方式：
procedure TTrendChart.Paint;
var
oldColor:TColor;
dataPt:TTrendPoints;
i,j:integer;
curx:integer;
count,step:integer;
r:TRect;
begin
inherited Paint;
oldcolor := Canvas.Pen.Color;
Canvas.Brush.Color:=clWhite;
r.Left:=chartRect.Left-25;
r.Right:=chartRect.Right+11;
r.Top:=chartRect.Top-11;
r.Bottom:=chartRect.Bottom+22;
Canvas.FillRect(r);
if FirstTime then
begin
count := Indexer - 1;
end
else
count := data.Count - 2;
{ Draw minute lines }
Canvas.Pen.Color := clBtnShadow;
i := chartRect.left + 60;
while i < chartRect.Right do
begin
Canvas.Moveto(i, chartRect.top);
Canvas.LineTo(i, chartRect.bottom);
i := i + 60;
end;
{ Draw value lines }
step := (chartRect.bottom - chartRect.top) div 5;
if step > 0 then
begin
i := chartRect.bottom - step;
while i > (chartRect.top + step - 1) do
begin
Canvas.Moveto(chartRect.left,i);
Canvas.LineTo(chartRect.right,i);
i := i - step;
end;
end;
{ Draw Pens }
for j := 0 to fCount - 1 do
begin
Canvas.Pen.Color := fColors[j];
dataPt := TTrendPoints(data.Items[0]);
Canvas.MoveTo(chartRect.left,PinValue(round(chartRect.bottom - (fHeight * dataPt.pnts[j] / 100.0)),
chartRect.top,chartRect.bottom));
for i := 1 to count do
begin
dataPt := TTrendPoints(data.Items[i]);
if i <> Indexer then
begin
Canvas.LineTo(chartRect.left+i,PinValue(round(chartRect.bottom - (fHeight * dataPt.pnts[j] / 100.0)),
chartRect.top,chartRect.bottom));
end
else
begin
Canvas.MoveTo(chartRect.left+i,PinValue(round(chartRect.bottom - (fHeight * dataPt.pnts[j] / 100.0)),
chartRect.top,chartRect.bottom));
end;
end;
end;
r := chartRect;
InflateRect(r,1,1);
Canvas.Pen.Color := clBtnShadow;
Canvas.moveto(r.left,r.top);
Canvas.lineto(r.right,r.top);
Canvas.lineto(r.right,r.bottom);
Canvas.lineto(r.left,r.bottom);
Canvas.lineto(r.left,r.top);
{ draw index line }
// Canvas.Pen.Color := clWhite;
Canvas.Pen.Color := clBlack;
Canvas.MoveTo(chartRect.Left + Indexer,chartRect.top);
Canvas.LineTo(chartRect.left + Indexer, chartRect.bottom+1);
Canvas.Pen.Color := oldcolor;
Canvas.Font.COlor := clBlack;
Canvas.TextOut(chartRect.left-Canvas.TextWidth(string(fMinText))-2,chartRect.Bottom-8,string(fMinText));
Canvas.TextOut(chartRect.left-Canvas.TextWIdth(string(fMaxText))-2,chartRect.top-8,string(fMaxText));
if fShowNames then
begin
curx := 32;
for i := 0 to fCount - 1 do
begin
Canvas.Font.Color := fColors[i];
Canvas.TextOut(curx,chartRect.bottom+4,fNames[i]);
curx := curx + fMaxTextWidth + 16;
end;
end;
end;
以下是如何使用它：
TrendChart := TTrendChart.Create(form);
任何帮助将不胜感激。谢谢。
答案 0 :(得分：6)
我相信你有这种闪烁，因为你没有画到屏幕外的位图。如果你先在位图中绘制所有内容然后最后一步显示你的位图，那么你的闪烁就会消失。
您需要创建一个私有位图：
TTrendChart = class(TCustomPanel)
private
...
fBitmap: TBitmap;
...
end;
在构造函数中写：
constructor TTrendChart.Create(AOwner:TComponent);
begin
...
fBitmap := TBitmap.Create;
// and also make the ControlStyle opaque
ControlStyle := ControlStyle + [csOpaque];
...
end;
也不要忘记析构函数：
destructor TTrendChart.Destroy;
begin
...
fBitmap.Free;
inherited;
end;
最后在paint方法中，在找到Canvas的任何地方，将其替换为fBitmap.Canvas：
procedure TTrendChart.Paint;
...
begin
inherited Paint;
...
// here replace all ocurrences of Canvas with bBitmap.Canvas
...
// finally copy the fBitmap cache to the component Canvas
Canvas.CopyRect(Rect(0, 0, Width, Height), fBitmap.Canvas, Rect(0, 0, Width, Height));
end;
答案 1 :(得分：3)
您的控件似乎没有使用键盘输入。您也不希望在此图表上添加其他控件。如果你也可以不使用OnEnter和OnExit事件，那么继承更轻量级的TGraphicControl是完全安全的。
如果使用自定义绘图填充控件的整个边界矩形，则不必在覆盖的Paint例程中调用继承的Paint。
如果您想要键盘焦点的可能性，那么您当然应该像Andreas Rejbrand所提到的那样继承TCustomControl。
如果您希望控件（部分）看起来像Panel，请将其保留为TCustomPanel。但在这种情况下，也许ParentBackground属性部分是闪烁的原因，在继承的Paint中处理。将其设置为False。
作为一般提示：在绘制画布之前消除背景刷新：
type
TTrendChart = class(TCustomPanel)
private
procedure WMEraseBkgnd(var Message: TWMEraseBkgnd); message WM_ERASEBKGND;
...
procedure TTrendChart.WMEraseBkgnd(var Message: TWMEraseBkgnd);
begin
{ Eat inherited }
Message.Result := 1; // Erasing background is "handled"
end;