Thread issue, App closes immediately
lazarus / 43-Android

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dimonershov · 2023-02-22 12:19

Hi all! I need help.

I use laz4android. This is my first app with a Thread. My application
closes immediately!

Source code:

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 {hint:
Pascal files location: ...\Potok\jni }unit unit1; {$mode
delphi} interface uses  {$IFDEF UNIX}{$IFDEF UseCThreads}  cthreads, 
{$ENDIF}{$ENDIF}  Classes, SysUtils, AndroidWidget, Laz_And_Controls; 
type   { TAndroidModule1 }   TAndroidModule1 = class(jForm)   
Button1: jButton;    TextView1: jTextView;    procedure
Button1Click(Sender: TObject);  private    {private declarations} 
public    {public declarations}  end;  type   { ShdkThread
}  ShdkThread=class(TThread)  private   stroka: string;   procedure
Show;  protected   procedure Execute; override; end; var 
AndroidModule1: TAndroidModule1;  potok: ShdkThread; implementation 
{$R *.lfm} { ShdkThread } procedure ShdkThread.Show;begin stroka:='Rab
otaet'; AndroidModule1.TextView1.Text:=stroka;end; procedure
ShdkThread.Execute;begin Synchronize(Show);end; { TAndroidModule1
} procedure TAndroidModule1.Button1Click(Sender: TObject);begin 
potok:=ShdkThread.Create(true);  potok.FreeOnTerminate:=true; 
potok.stroka:='123';  potok.Priority:=tpLower;  potok.Resume;end;end. 
Why does the app close when the button is clicked?

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KodeZwerg · 2023-02-22 12:27

Welcome to forum!
Please use the [ # ] button and put your code within the [ code ] my
code [ / code ] tag. Thank you.

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tetrastes · 2023-02-22 13:13

Did you define UseCThreads somewhere?

Usually it looks like
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 {$define
UseCThreads} uses  {$IFDEF UNIX}{$IFDEF UseCThreads}  cthreads, 
{$ENDIF}{$ENDIF}...
or simply
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i uses 
{$IFDEF UNIX}  cthreads,  {$ENDIF}...
But AFAIK this must be in .lpr, at least for "normal" unixes.

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Peter H · 2023-02-22 16:20

An uneducated guess:

Should it not read: Synchronize(@Show);

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Thaddy · 2023-02-22 16:39

That is a good guess, but there is more because 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
ShdkThread.Execute;begin Synchronize(Show);end;means he is misusing a
thread and actually executes something what looks like a thread
without using the benefits of a thread: It simply executes in
consecutve order. (a.k.a. a Threat!   )
Bad code.
The output/result of a thread can be synchronized if needed, but plz
not the whole thread....That is completely missing the point.

I know thread programming is difficult, but that is because it is,
well, difficult.

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dimonershov · 2023-02-22 19:39

Thank you!

In control.lpr it worked! Application doesn't crash

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 ...uses 
{$IFDEF UNIX}  cthreads,  {$ENDIF}... 
But  my thread doesn't work! Help me? I press the button, nothing
happens. The main form has only text and a button.

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 {hint:
Pascal files location: ...\Potok\jni }unit unit1; {$mode
delphi} interface uses Classes, SysUtils, AndroidWidget,
Laz_And_Controls; type   { ShdkThread }  ShdkThread=class(TThread) 
private   stroka: string;   stop: boolean;   ii: integer;   procedure
Show;  protected   procedure Execute; override;  public    constructor
Create(CreateSuspended: boolean);end;  type   { TAndroidModule1 }  
TAndroidModule1 = class(jForm)    Button1: jButton;    TextView1:
jTextView;    procedure Button1Click(Sender: TObject);  private   
{private declarations}  public    {public declarations}  end;  var 
AndroidModule1: TAndroidModule1;  potok: ShdkThread; implementation 
{$R *.lfm} { TAndroidModule1 } procedure
TAndroidModule1.Button1Click(Sender: TObject);begin potok:=ShdkThread.
Create(true); potok.FreeOnTerminate:=true; potok.Priority:=tpNormal; p
otok.Resume; //potok.Start;end;  { ShdkThread } procedure ShdkThread.S
how;begin AndroidModule1.TextView1.Text:=stroka;end; procedure
ShdkThread.Execute;var  newStatus : string;begin stroka:='TMyThread
Starting ...'; Synchronize(Show); stroka:='TMyThread Running
...'; while (not Terminated) and (true {any condition required}) do
begin     //here goes the code of the main thread loop   
newStatus:='TMyThread Time: '+FormatDateTime('YYYY-MM-DD
HH:NN:SS',Now);     if NewStatus <> stroka then begin     
stroka:=newStatus;      Synchronize(Show);    end;    sleep(50); //
alternatively the thread may wait for an event. E.g., external I/O 
end; end; constructor ShdkThread.Create(CreateSuspended:
boolean);begin  FreeOnTerminate:=True;  inherited
Create(CreateSuspended);end;end.

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tetrastes · 2023-02-22 19:50

Quote from: Peter H on February 22, 2023, 05:20:30 pmAn uneducated
guess:

Should it not read: Synchronize(@Show);

Not in {$mode delphi}

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tetrastes · 2023-02-22 20:26

Quote from: dimonershov on February 22, 2023, 08:39:12 pmBut  my
thread doesn't work! Help me? I press the button, nothing happens. The
main form has only text and a button.

I cannot say why it doesn't work at android. At windows it works. But
change your code
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
TAndroidModule1.Button1Click(Sender: TObject);begin if not
Assigned(potok) then begin   potok:=ShdkThread.Create(true); 
 potok.FreeOnTerminate:=true;   potok.Priority:=tpNormal; 
 potok.Resume;   //potok.Start; end;end;
and add smth 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
TAndroidModule1.FormClose(Sender: TObject; var CloseAction:
TCloseAction);begin if Assigned(potok) then begin    potok.Terminate; 
  potok.WaitFor; end;end;
to avoid access violations.

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WayneSherman · 2023-02-23 03:41

Quote from: dimonershov on February 22, 2023, 08:39:12 pmBut  my
thread doesn't work! Help me? I press the button, nothing happens. The
main form has only text and a button.

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
...Synchronize(Show);...
The last time I tried (in 2018), TThread.Synchronize did not work
correctly using LAMW.  To work around the issue I used a timer to
periodically check the status of thread operations.  Reference these
discussions:

https://forum.lazarus.freepascal.org/index.php/topic,41523
https://forum.lazarus.freepascal.org/index.php/topic,57311

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dimonershov · 2023-02-23 18:27

Thanks everyone! I'll upload the source code tomorrow.

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dimonershov · 2023-02-24 20:01

Worked app is attached. For my small task i used jtimer and
CheckSynchronize() function. Very nice! I will write more.