Can I use TThread in android app in the same way like for windows app?
lazarus / 43-Android

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Atak_Snajpera · 2021-11-25 17:29

I have added cthreads to lpr file then I try creating and running
thread the same how I do on windows.

Simple example:

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 type 
TWorkerThread = class(TThread)  private    { Private declarations }  
x:integer;    procedure UpdateValue;  protected    procedure Execute;
override;  end;    
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
TForm1.ButtonClick(Sender: TObject);begin     
 WorkerThread:=TWorkerThread.Create(true);   
 WorkerThread.FreeOnTerminate:=false;   
 WorkerThread.Priority:=tpNormal;     WorkerThread.Start; end;       
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
TWorkerThread.Execute;begin   x:=0;       repeat         Inc(x);     
  Synchronize(UpdateValue);         sleep(1000);   until
Terminated=true; end;  
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
TWorkerThread.UpdateValue;begin   form1.jTextView.text:=IntToStr(x); 
end;
When I press button in android emulator nothing happens!

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engkin · 2021-11-26 04:32

TThread works on Android.

Synchronize needs CheckSynchronize to be called inside the main loop
of the app. This is by default on Windows for GUI applications. Not on
terminal or Android apps. You can add it there.

Test TThread without Synchronize.

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Atak_Snajpera · 2021-11-26 19:06

Where should I put CheckSynchronize exactly?

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MarkMLl · 2021-11-26 19:20

Seconded. @engkin, could we have a concise example please?

MarkMLl

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engkin · 2021-11-27 00:27

I'll provide an example as soon as get a chance.

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engkin · 2021-11-27 08:45

While other possibilities are there, I'll assume LAMW is being used
here since the original post mentioned jTextView. If you followed my
first reply, you'll see the thread is working but can not call
Synchronize.

To prove that Synchronize works, simply add a jTimer to your main form
and have it call CheckSynchronize(). If you are satisfied with this
timer, good for you.

A call to Synchronize uses WakeMainThread. Which makes finding a way
to call CheckSynchronize on the main thread simple. Android provides
RunOnUiThread. Unfortunately the implementation in LAMW is not
correct. It uses PJNIEnv of the main thread instead of the calling
thread. A thread var can be filled by each thread. Along these lines:
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 threadvar 
env:PJNIEnv;//<--- has to be a threadvar procedure
TWorkerThread.Execute;begin 
gVM^.AttachCurrentThread(gVM,@env,nil);//<--- needed for every thread 
WakeMainThread:=LetsWakeMainThread;//<--- needed once  x:=0;  repeat 
 inc(x);    Synchronize(UpdateValue);    Sleep(1000);  until
Terminated;  gVM^.DetachCurrentThread(gVM);//<--- when you are done
with the thread (Free/Destroy)end;
LetsWakeMainThread is:
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
TWorkerThread.LetsWakeMainThread(Sender:TObject);begin 
//MainForm.RunOnUiThread(Integer(Self));//<--- Wrong env variable, not
for this thread 
TAndroidModule1(MainForm).RunOnUiThread_corrected(env,0);end;
RunOnUiThread_corrected  is:
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.RunOnUiThread_corrected(correct_env:PJNIEnv;_tag:
integer);begin  //in designing component state: set value here...  if
Initialized then     jni_proc_i(correct_env, jSelf, 'RunOnUiThread',
_tag);end;
And the most important part is to add CheckSynchronize() to the
OnRunOnUiThread event of the main form:
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 T
AndroidModule1.AndroidModule1RunOnUiThread(Sender:TObject;tag:integer)
;begin  CheckSynchronize();end;

Full code of the thread:
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 unit
uThreadTest; {$mode delphi} interface uses  Classes, SysUtils, 
AndroidWidget,And_jni; type   { TWorkerThread }  
TWorkerThread=class(TThread)  private    procedure UpdateValue; 
protected    procedure Execute; override;  public    MainForm:jForm; 
 x:integer;    OnUpdate:Procedure of object;     procedure
LetsWakeMainThread(Sender: TObject);  end; implementationuses 
unit1; { TWorkerThread } procedure TWorkerThread.UpdateValue;begin  if
Assigned(OnUpdate) then    OnUpdate;end; threadvar  env:PJNIEnv;//<---
has to be a threadvar procedure TWorkerThread.Execute;begin 
gVM^.AttachCurrentThread(gVM,@env,nil);//<--- needed for every thread 
WakeMainThread:=LetsWakeMainThread;//<--- needed once  x:=0;  repeat 
 inc(x);    Synchronize(UpdateValue);    Sleep(1000);  until
Terminated;  gVM^.DetachCurrentThread(gVM);//<--- when you are done
with the thread (Free/Destroy)end; procedure
TWorkerThread.LetsWakeMainThread(Sender:TObject);begin 
//MainForm.RunOnUiThread(Integer(Self));//<--- Wrong env variable, not
for this thread 
TAndroidModule1(MainForm).RunOnUiThread_corrected(env,0);end; end.
Main form relevant 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.LetsUpdate;begin 
jTextView1.Text:=WorkerThread.x.ToString;end; procedure
TAndroidModule1.RunOnUiThread_corrected(correct_env:PJNIEnv;_tag:
integer);begin  if Initialized then     jni_proc_i(correct_env, jSelf,
'RunOnUiThread', _tag);end; procedure
TAndroidModule1.StartBtnClick(Sender:TObject);begin  if
WorkerThread=nil then  begin   
WorkerThread:=TWorkerThread.Create(True);   
WorkerThread.MainForm:=Self;    WorkerThread.OnUpdate:=LetsUpdate;   
WorkerThread.Start;  end;end; procedure
TAndroidModule1.StopBtnClick(Sender:TObject);begin 
WorkerThread.Terminate;end;

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MarkMLl · 2021-11-27 09:04

Thanks very much for that, it gives me a good incentive to look at
LAMW and possibly to investigate threads on Termux.

MarkMLl

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jmpessoa · 2021-11-27 15:14

@engkin

Nice!

Can you, please, put your LAMW project in some "open drive"  (or here,
if possible)


So we can add it to LAMW "demos"!

Thank you!

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engkin · 2021-11-27 20:36

Quote from: jmpessoa on November 27, 2021, 04:14:33 pmCan you, please,
put your LAMW project in some "open drive"  (or here, if possible)

Done!

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jmpessoa · 2021-11-28 05:55

Done!

Thank you!

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Atak_Snajpera · 2022-09-01 23:06

"Unfortunately the implementation in LAMW is not correct. It uses
PJNIEnv of the main thread instead of the calling thread. "

Has this been already fixed in latest version of lamw?