RAD Studio VCL Reference
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Provides default handling of exceptions for the application.
procedure HandleException(Sender: TObject);
__fastcall HandleException(TObject * Sender);
If an exception passes through all the try blocks in the application code, the application automatically calls HandleException, which displays a dialog box indicating an error occurred. Unless the exception object is EAbort, HandleException calls the OnException event handler, if one exists. Otherwise, it calls ShowException to display a message dialog box indicating an error occurred.
To assign other exception handling code for the application, use the OnException event handler.
Delphi Examples:
{ The following code is from the implementation of TTimer. It shows how the timer component’s constructor creates a hidden window to respond to Timer messages and how the destructor frees that window. } { TTimer implements a WndProc method that becomes the window procedure for the hidden window. } procedure MyTTimer.WndProc(var Msg: TMessage); begin with Msg do if Msg = WM_TIMER then { check for timer messages } try Timer; { this calls the OnTimer event handler } except Application.HandleException(Self); end else { Any other messages are passed to DefWindowProc, which tells Windows to handle the message. Note that the first parameter, FWindowHandle, is the handle of the window receiving this message. It is obtained from the call to AllocateHWnd in the constructor. } Result := DefWindowProc(FWindowHandle, Msg, wParam, lParam); end; { The TTimer constructor uses AllocateHWnd to create the window and save its handle. } constructor MyTTimer.Create(AOwner: TComponent); begin inherited Create(AOwner); FEnabled := True; FInterval := 1000; FWindowHandle := AllocateHWnd(WndProc); end; { The TTimer destructor calls DeallocateHWnd to free the hidden window. } destructor MyTTimer.Destroy; begin FEnabled := False; // UpdateTimer; done by TTimer Destroy DeallocateHWnd(FWindowHandle); inherited Destroy; end;
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