想写一个提示窗口(放在dll中), 由主程序调用后显示出来, 但主程序执行查询之类的操作,提示窗就死掉了, 只有查询完成了才能恢复.
请问: 如何做能让提示窗在主程序运行时不受影响的显示?谢谢.
请问: 如何做能让提示窗在主程序运行时不受影响的显示?谢谢.
解决方案 »
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另外,如果线程执行的时间很长,在一定时间后,
用Application.ProcessMessages响应一下消息队列,
不然提示窗刷新的消息收不到,程序就像死了一样
Priority := tpLowest
在适当的地方应用application.ProcessMessages;
begin
Screen.Cursor:=crHourGlass;
Application.CreateForm(TFrmTest, FrmTest);
FrmTest.Show;
self.Terminate;
FrmMain.WindowState:=wsMaximized;
FrmMain.Caption:='.....';
Screen.Cursor:=crDefault;
end;procedure TInitThread.Execute;
begin
FreeOnTermiNate:=True;
Synchronize(CreateForm);
end;
你的方法虽然可以在线程中建立窗口,但窗口在查询结束后才出现....仍然是串行运行的, 我的目的是同时运行...难道只能写线程查询,无法写线程的提示窗口?
最起码要实现取消息以及派发消息的消息循环吧
PeekMesssage
DispatchMessage
不然难到使用主线程的消息派发循环?
2.写一个线程接受传入TProc参数
3.execute方法
showform;
proc;
freeform;
terminate;
3.主代码
threada.Create(theProc);
{
Question: I am trying query to display records in a dbgrid.however, due to size
of tables and joins takes a while for the query to Execute.is
there any way to Show a prorgess bar with a timer that increments
position but continues to work while the query is being executed.BTW,
using access so BDE is not used. Answer:
A progress bar would not be an ideal choice since you cannot determine up
front how long the query will take, so you do not know the range the progress
bar has to cover.A simple kind of animation that tells the user basically
only that the application is not hung would be more appropriate.One could do
such a thing in a secondary thread but it would have to be done using the
plain Windows API and * no * Synchronize calls (since the main thread is
blocked in the BDE call).Here is an example: unit anithread;
}interfaceuses
Classes, Windows, Controls, Graphics;type
TAnimationThread = class(TThread)
private
{ Private declarations }
FWnd: HWND;
FPaintRect: TRect;
FbkColor, FfgColor: TColor;
FInterval: integer;
protected
procedure Execute; override;
public
constructor Create(paintsurface : TWinControl; {Control to paint on }
paintrect : TRect; {area for animation bar }
bkColor, barcolor : TColor; {colors to use }
interval : integer); {wait in msecs between
paints}
end;implementationconstructor TAnimationThread.Create(paintsurface : TWinControl;
paintrect : TRect; bkColor, barcolor : TColor; interval : integer);
begin
inherited Create(True);
FWnd := paintsurface.Handle;
FPaintRect := paintrect;
FbkColor := bkColor;
FfgColor := barColor;
FInterval := interval;
FreeOnterminate := True;
Resume;
end; { TAnimationThread.Create }procedure TAnimationThread.Execute;
var
image : TBitmap;
DC : HDC;
left, right : integer;
increment : integer;
imagerect : TRect;
state : (incRight, incLeft, decLeft, decRight);
begin
Image := TBitmap.Create;
try
with Image do
begin
Width := FPaintRect.Right - FPaintRect.Left;
Height := FPaintRect.Bottom - FPaintRect.Top;
imagerect := Rect(0, 0, Width, Height);
end; { with }
left := 0;
right := 0;
increment := imagerect.right div 50;
state := Low(State);
while not Terminated do
begin
with Image.Canvas do
begin
Brush.Color := FbkColor;
FillRect(imagerect);
case state of
incRight:
begin
Inc(right, increment);
if right > imagerect.right then
begin
right := imagerect.right;
Inc(state);
end; { if }
end; { Case incRight }
incLeft:
begin
Inc(left, increment);
if left >= right then
begin
left := right;
Inc(state);
end; { if }
end; { Case incLeft }
decLeft:
begin
Dec(left, increment);
if left <= 0 then
begin
left := 0;
Inc(state);
end; { if }
end; { Case decLeft }
decRight:
begin
Dec(right, increment);
if right <= 0 then
begin
right := 0;
state := incRight;
end; { if }
end; { Case decLeft }
end; { Case }
Brush.Color := FfgColor;
FillRect(Rect(left, imagerect.top, right, imagerect.bottom));
end; { with }
DC := GetDC(FWnd);
if DC <> 0 then
try
BitBlt(DC,
FPaintRect.Left,
FPaintRect.Top,
imagerect.right,
imagerect.bottom,
Image.Canvas.handle,
0, 0,
SRCCOPY);
finally
ReleaseDC(FWnd, DC);
end;
Sleep(FInterval);
end; { While }
finally
Image.Free;
end;
InvalidateRect(FWnd, nil, True);
end; { TAnimationThread.Execute }end.{Usage:
Place a TPanel on a form, size it as appropriate.Create an instance of the
TanimationThread call like this: procedure TForm1.Button1Click(Sender : TObject);
}
var
ani : TAnimationThread;
r : TRect;
begin
r := panel1.clientrect;
InflateRect(r, - panel1.bevelwidth, - panel1.bevelwidth);
ani := TanimationThread.Create(panel1, r, panel1.color, clBlue, 25);
Button1.Enabled := False;
Application.ProcessMessages;
Sleep(30000); // replace with query.Open or such
Button1.Enabled := True;
ani.Terminate;
ShowMessage('Done');
end;