我开发了以下AnimateRects()方法在Windows桌面上绘制动画矩形。我用它来动画显示模态形式,使它看起来像是从网格单元“增长”。
在表单显示之前,我使用bExpand参数= True调用该方法一次。然后,当用户关闭表单时,我再次调用它,但使用bExpand = False,以显示表单“折叠”到网格单元格中。
问题在于bExpand = False情况......在循环的第一次迭代中,第一次调用Rectangle(r)按预期绘制矩形,但就像<从未调用过强>第二对Rectangle(r)的调用 - 第一个矩形永远不会被异或。因此,在绘制了“折叠”矩形序列之后,我最终将第一个矩形保留为屏幕上的工件。
任何想法我做错了什么?
const
MSECS_PER_DAY = 24.0 * 60.0 * 60.0 * 1000;
procedure DelayMSecs(msecs: Word);
var
Later: TDateTime;
begin
Later := Now + (msecs / MSECS_PER_DAY);
while Now < Later do begin
Application.ProcessMessages;
sleep(0); //give up remainder of our time slice
end;
end;
procedure T_fmExplore.AnimateRects(ASourceRect, ADestRect: TRect; bExpand:
boolean; bAdjustSourceForFrame: boolean = True);
const
MINSTEPS = 10;
MAXSTEPS = 30;
MAXDELAY = 180; //150 - 200 is about right
MINDELAY = 1;
var
iSteps: integer;
DeltaHt: Integer; //Rect size chg for each redraw of animation window
DeltaWidth: Integer;
DeltaTop : integer; //Origin change for each redraw
DeltaLeft : integer;
NewWidth, NewHt: Integer;
iTemp: Integer;
iDelay: integer;
r : Trect;
ScreenCanvas: TCanvas;
begin
r := ASourceRect;
with r do begin
NewWidth := ADestRect.Right - ADestRect.Left; //Target rect's Width
NewHt := ADestRect.Bottom - ADestRect.Top; //Target rect's Height
//Temporarily, Deltas hold the total chg in Width & Height
DeltaWidth := NewWidth - (Right - Left); //NewWidth - old width
DeltaHt := NewHt - (Bottom - Top);
//With a static number of iSteps, animation was too jerky for large windows.
//So we adjust the number of iSteps & Delay relative to the window area.
iSteps := Max( DeltaWidth * DeltaHt div 6500, MINSTEPS ); //eg. 10 iSteps for 250x250 deltas (62500 pixels)
iSteps := Min( iSteps, MAXSTEPS );
//Now convert Deltas to the delta in window rect size
DeltaWidth := DeltaWidth div iSteps;
DeltaHt := DeltaHt div iSteps;
DeltaTop := (ADestRect.Top - ASourceRect.Top) div iSteps;
DeltaLeft := (ADestRect.Left - ASourceRect.Left) div iSteps;
iDelay := Max( MAXDELAY div iSteps, MINDELAY );
ScreenCanvas := TCanvas.Create;
try
ScreenCanvas.Handle := GetDC( 0 ); //Desktop
try
with ScreenCanvas do begin
Pen.Color := clWhite;
Pen.Mode := pmXOR;
Pen.Style := psSolid;
Pen.Width := GetSystemMetrics(SM_CXFRAME);
Brush.Style := bsClear;
if bAdjustSourceForFrame then
InflateRect(ASourceRect, -Pen.Width, -Pen.Width);
repeat
iTemp := (Bottom - Top) + DeltaHt; //Height
if (bExpand and (iTemp > NewHt)) or (not bExpand and (iTemp < NewHt)) then begin
Top := ADestRect.Top;
Bottom := Top + NewHt;
end else begin
Top := Top + DeltaTop; //Assign Top first...Bottom is calc'd from it
Bottom := Top + iTemp;
end;
iTemp := (Right - Left) + DeltaWidth; //Width
if (bExpand and (iTemp > NewWidth)) or (not bExpand and (iTemp < NewWidth)) then begin
Left := Left + DeltaLeft;
Right := Left + NewWidth;
end else begin
Left := Left + DeltaLeft; //Assign Left first...Right is calc'd from it
Right := Left + iTemp;
end;
ScreenCanvas.Rectangle(r);
SysStuff.DelayMSecs( iDelay );
ScreenCanvas.Rectangle(r); //pmXOR pen ...erase ourself
until (Right - Left = NewWidth) and (Bottom - Top = NewHt);
end;
finally
ReleaseDC( 0, ScreenCanvas.Handle );
ScreenCanvas.Handle := 0;
end;
finally
ScreenCanvas.Free;
end;
end;
end;
答案 0 :(得分:1)
最有可能的问题是,当模态形式仍然可见时,您开始绘制矩形。在某一点上,表单从屏幕上消失,上面有一个矩形,当你绘制相同的矩形以擦除前一个时,它现在在屏幕上。请注意,在表单上调用“Free”,“Hide”等不会立即隐藏它。
(编辑:这需要一些解释:表单将在代码的下一行运行之前隐藏,但无法保证未覆盖的窗口何时更新其无效区域)。
在关闭模式表单之后和调用Sleep
之前,或者调用AnimateRects
之前,解决方案将是Application.ProcessMessages
一段时间。如果模态形式不完全在您自己的应用程序的窗口上,后者可能没有多大帮助。如果模态形式在一个同时不断进行绘制的应用程序上,那么前者可能不会有太大帮助。像任务经理f.i ...
编辑虽然我可能对此感到不满,但这个问题正是LockWindowUpdate
存在的原因。当你想到它时,你会发现当你移动它时,当你显示一个窗口的拖动轮廓时(当禁用“拖动时显示窗口内容”),你正在做的事情与shell的作用没有什么不同。