How to handling uncaught exception easier in LAMW like in LCL?
lazarus / 43-Android

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AFFRIZA 亜風実 · 2019-08-29 03:37

Currently, I've modified Laz_And_Controls jAsyncTask to become like
bellow, because I'm too lazy to make try..except on every task. Not
just that, I add "keepInBackground := False", because adding that into
every task doesn't look makes sense to me.
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i  procedure
jAsyncTask.GenEvent_OnAsyncEventDoInBackground(Obj: TObject; progress:
integer; out keepInBackground: boolean);begin  keepInBackground:=
True;  fExceptStr := '';  try    if Assigned(FOnDoInBackground) then 
   FOnDoInBackground(Obj,progress,keepInBackground);   
keepInBackground := False;  except    on e: exception do    begin    
keepInBackground := False;      fExceptStr := e.Message;    end; 
end;end;  procedure jAsyncTask.GenEvent_OnAsyncEventPostExecute(Obj:
TObject; progress: Integer);begin  if fExceptStr <> '' then   
gApp.ShowMessage('ASyncTask Exception Error', fExceptStr, 'OK');  if
Assigned(FOnPostExecute) then FOnPostExecute(Obj,progress);end; 
But still, the kinda unsatisfying result happens, it doesn't handle
nil variable. It's okay for now because it handles most exceptions
except the Access Violation.

I was trying to look to any LAMW sources because there's no loop in
the jApp (everything handled by events) so jApp.OnException is
impossible to use.

I've tried in this thread to modify the App.java template, but I have
no idea because I don't speak Java. Maybe someone can tell me how to
use this?

Does anyone have an idea?

Thank you.

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Thaddy · 2019-08-29 07:48

You can use this: https://www.freepascal.org/docs-
html/rtl/system/errorproc.html
Be careful if you use sysutils, this needs to be declared *after*
sysutils and you need to call the sysutils version for everything you
do not handle yourself.(Need to save the sysutils version's address in
that case.)

Note that on Android, you need the Java exception handling too, to
Freepascal it is an external exception. That is easy to do, but not as
easy as try/except.

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AFFRIZA 亜風実 · 2019-08-29 10:11

I do not really understand how to use that.
Quotethis needs to be declared *after* sysutilsWhat does that mean, is
that can be used in library? Can I get the sample usage?

Like this one maybe?
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i library
controls;  //[by LAMW: Lazarus Android Module Wizard: 22/08/2019
13:12:35]  {$mode delphi}  uses  {$IFDEF UNIX}  cthreads,  {$ENDIF} 
Classes, SysUtils, And_jni, And_jni_Bridge, AndroidWidget,
Laz_And_Controls,  Laz_And_Controls_Events, control_main;  {%region
/fold 'LAMW generated code'}  procedure OnError(ErrNo: LongInt;
Address: CodePointer; Frame: Pointer);begin  gApp.ShowMessage('An
Error Occured!', 'Exception error at address: '+   
sysBackTraceStr(Address), 'OK');end; begin  // I'm not quite sure
about this  ErrorProc := OnError;   gApp := jApp.Create(nil); 
gApp.Title := 'LAMW JNI Android Bridges Library';  gjAppName :=
'id.estoh.tumbas.stockwriter';  gjClassName :=
'id/estoh/tumbas/stockwriter/Controls';  gApp.AppName := gjAppName; 
gApp.ClassName := gjClassName;  gApp.Initialize; 
gApp.CreateForm(TControlMain, ControlMain);end.           
Btw, I'm just lost my mind maybe. So, I transformed all LAMW events
like this 
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i Procedure
Java_Event_pOnClick(env: PJNIEnv; this: jobject; Obj: TObject; Value:
integer);begin   //----update global "gApp": to whom it may
concern------  gApp.Jni.jEnv:= env;  gApp.Jni.jThis:= this; 
//------------------------------------------------------  // here we
go  try    if not (Assigned(Obj)) then Exit;    if Obj is jForm then 
 begin      jForm(Obj).UpdateJNI(gApp);     
jForm(Obj).GenEvent_OnClick(Obj);      Exit;    end;    // and etc.  
except    on e: exception do    begin      gApp.ShowMessage('Exception
Error!', e.Message, 'OK');    end;  end;end;

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commanderz · 2021-10-09 14:55

Very useful information, helped me get rid of the errors that the
"raise" method generated in the Indy library.
Thanks to author!

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jmpessoa · 2021-10-09 17:15

QuoteSo, I transformed all LAMW events like this..

Good!

I will try apply your solution to LAMW code!

Thank you!

SIDE NOTE:

QuoteRef.
https://forum.lazarus.freepascal.org/index.php/topic,56590.0.html


By engkin

In general, exceptions inside Java code can be tested with
ExceptionOccurred,
and should be cleared with ExceptionClear.


procedure TAndroidModule1.jButton1Click(Sender:TObject);
{$push}{$WriteableConst+}
const
  eIdx:integer=0;{$pop}
var
  e:array[0..2] of String=('3*(2+2)','2/0','2/4+');
  r:string;
begin
  jExpression1.SetFormula(e[eIdx],[]);
  r:=jExpression1.Evaluate.ToString;
  if gApp.Jni.jEnv^.ExceptionOccurred(gApp.Jni.jEnv)<>nil then
  begin
    gApp.Jni.jEnv^.ExceptionClear(gApp.Jni.jEnv);//<--- if you don't
clear it, your app will be killed
    r:='ERROR';
  end;

  ShowMessage(e[eIdx]+' = '+r);
  inc(eIdx); if eIdx>High(e) then eIdx:=0;
end;