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