Question

请教：delphi中application．messagebox和messagebox有什么区别？

我刚学delphi，很多不懂，请教老师们 请教：delphi中application．messagebox和messagebox有什么区别？ 为什么messagebox（’测试’，’测试’，mb_ok);编译不能通过？ 而application．messagebox（’测试’，’测试’，mb_ok)可以， messagebox（0，’测试’，’测试’，mb_ok)也可以？

Answer 1

Application是Form单元的一个全局对象 具体实现是 ---------------------- function TApplication.MessageBox(const Text, Caption: PChar; Flags: Longint): Integer; var ActiveWindow: HWnd; WindowList: Pointer; MBMonitor, AppMonitor: HMonitor; MonInfo: TMonitorInfo; Rect: TRect; FocusState: TFocusState; begin ActiveWindow := GetActiveWindow; MBMonitor := MonitorFromWindow(ActiveWindow, MONITOR_DEFAULTTONEAREST); AppMonitor := MonitorFromWindow(Handle, MONITOR_DEFAULTTONEAREST); if MBMonitor <> AppMonitor then begin MonInfo.cbSize := Sizeof(TMonitorInfo); GetMonitorInfo(MBMonitor, @MonInfo); GetWindowRect(Handle, Rect); SetWindowPos(Handle, 0, MonInfo.rcMonitor.Left + ((MonInfo.rcMonitor.Right - MonInfo.rcMonitor.Left) div 2), MonInfo.rcMonitor.Top + ((MonInfo.rcMonitor.Bottom - MonInfo.rcMonitor.Top) div 2), 0, 0, SWP_NOACTIVATE or SWP_NOREDRAW or SWP_NOSIZE or SWP_NOZORDER); end; WindowList := DisableTaskWindows(0); FocusState := SaveFocusState; if UseRightToLeftReading then Flags := Flags or MB_RTLREADING; try Result := Windows.MessageBox(Handle, Text, Caption, Flags); finally if MBMonitor <> AppMonitor then SetWindowPos(Handle, 0, Rect.Left + ((Rect.Right - Rect.Left) div 2), Rect.Top + ((Rect.Bottom - Rect.Top) div 2), 0, 0, SWP_NOACTIVATE or SWP_NOREDRAW or SWP_NOSIZE or SWP_NOZORDER); EnableTaskWindows(WindowList); SetActiveWindow(ActiveWindow); RestoreFocusState(FocusState); end; end; --------------------------------- MessageBox是Windows单元的函数 可以看到Application.MessageBox调用了Windows.MessageBox 编译时要包含相应的单元 比如用到Application.Messagebox就包含Form 用到MessageBox要包含WIndows 有什么问题可以研究一下 borland\delphi\source\vcl中的源码 会学到不少东西

Answer 2

Application是Form单元的一个全局对象 具体实现是 ---------------------- function TApplication.MessageBox(const Text, Caption: PChar; Flags: Longint): Integer; var ActiveWindow: HWnd; WindowList: Pointer; MBMonitor, AppMonitor: HMonitor; MonInfo: TMonitorInfo; Rect: TRect; FocusState: TFocusState; begin ActiveWindow := GetActiveWindow; MBMonitor := MonitorFromWindow(ActiveWindow, MONITOR_DEFAULTTONEAREST); AppMonitor := MonitorFromWindow(Handle, MONITOR_DEFAULTTONEAREST); if MBMonitor <> AppMonitor then begin MonInfo.cbSize := Sizeof(TMonitorInfo); GetMonitorInfo(MBMonitor, @MonInfo); GetWindowRect(Handle, Rect); SetWindowPos(Handle, 0, MonInfo.rcMonitor.Left + ((MonInfo.rcMonitor.Right - MonInfo.rcMonitor.Left) div 2), MonInfo.rcMonitor.Top + ((MonInfo.rcMonitor.Bottom - MonInfo.rcMonitor.Top) div 2), 0, 0, SWP_NOACTIVATE or SWP_NOREDRAW or SWP_NOSIZE or SWP_NOZORDER); end; WindowList := DisableTaskWindows(0); FocusState := SaveFocusState; if UseRightToLeftReading then Flags := Flags or MB_RTLREADING; try Result := Windows.MessageBox(Handle, Text, Caption, Flags); finally if MBMonitor <> AppMonitor then SetWindowPos(Handle, 0, Rect.Left + ((Rect.Right - Rect.Left) div 2), Rect.Top + ((Rect.Bottom - Rect.Top) div 2), 0, 0, SWP_NOACTIVATE or SWP_NOREDRAW or SWP_NOSIZE or SWP_NOZORDER); EnableTaskWindows(WindowList); SetActiveWindow(ActiveWindow); RestoreFocusState(FocusState); end; end; --------------------------------- MessageBox是Windows单元的函数 可以看到Application.MessageBox调用了Windows.MessageBox 编译时要包含相应的单元 比如用到Application.Messagebox就包含Form 用到MessageBox要包含WIndows 有什么问题可以研究一下 borland\delphi\source\vcl中的源码 会学到不少东西 查看原帖>>