在onresize里面写form1.postion：=poScreenCenter;报错？
在onresize里面写form1.postion：=poScreenCenter;报错？
出现 'can't change visible in OnShow and Onhide ‘错误！
写在Oncreate里面肯定是可以的，但为什么写onresize里面不行？
form1.width和form1.heght都可以控制，form1.postion：=poScreenCenter;却报错？


[解决办法]

Delphi(Pascal) code

procedure TCustomForm.SetWindowToMonitor;var  AppMon, WinMon: HMONITOR;  I, J: Integer;  ALeft, ATop: Integer;  LRect: TRect;begin    if (FDefaultMonitor <> dmDesktop) and (Application.MainForm <> nil) then    begin      AppMon := 0;      if FDefaultMonitor = dmMainForm then        AppMon := Application.MainForm.Monitor.Handle      else if (FDefaultMonitor = dmActiveForm) and (Screen.ActiveCustomForm <> nil) then        AppMon := Screen.ActiveCustomForm.Monitor.Handle      else if FDefaultMonitor = dmPrimary then        AppMon := Screen.PrimaryMonitor.Handle;      WinMon := Monitor.Handle;      for I := 0 to Screen.MonitorCount - 1 do        if (Screen.Monitors[I].Handle = AppMon) then          if (AppMon <> WinMon) then          begin            for J := 0 to Screen.MonitorCount - 1 do            begin              if (Screen.Monitors[J].Handle = WinMon) then              begin                if FPosition = poScreenCenter then                begin                  LRect := Screen.Monitors[I].WorkareaRect;                  SetBounds(LRect.Left + ((RectWidth(LRect) - Width) div 2),                    LRect.Top + ((RectHeight(LRect) - Height) div 2), Width, Height);                end                else                if FPosition = poMainFormCenter then                begin                  SetBounds(Screen.Monitors[I].Left + ((Screen.Monitors[I].Width - Width) div 2),                    Screen.Monitors[I].Top + ((Screen.Monitors[I].Height - Height) div 2),                     Width, Height)                end                else                begin                  ALeft := Screen.Monitors[I].Left + Left - Screen.Monitors[J].Left;                  if ALeft + Width > Screen.Monitors[I].Left + Screen.Monitors[I].Width then                    ALeft := Screen.Monitors[I].Left + Screen.Monitors[I].Width - Width;                  ATop := Screen.Monitors[I].Top + Top - Screen.Monitors[J].Top;                  if ATop + Height > Screen.Monitors[I].Top + Screen.Monitors[I].Height then                    ATop := Screen.Monitors[I].Top + Screen.Monitors[I].Height - Height;                  SetBounds(ALeft, ATop, Width, Height);                end;              end;            end;          end          else          begin            if FPosition = poScreenCenter then            begin              LRect := Screen.Monitors[I].WorkareaRect;              SetBounds(LRect.Left + ((RectWidth(LRect) - Width) div 2),                LRect.Top + ((RectHeight(LRect) - Height) div 2), Width, Height);            end;          end;    end;end;
[解决办法]
procedure TCustomForm.SetWindowToMonitor;
...
if FPosition = poScreenCenter then SetBounds(...)

因为 form1.postion:=poScreenCenter 会改变 form1 的尺寸和位置，在 onResize 中
执行到 form1.postion:=poScreenCenter 时会重新激活 onResize 事件，造成死循环。