Delphi - Indy TIdThreadComponent threads study

 

Indy IdThreadComponent thread study

 

A few days ago in the development of real-time data analysis function module, they found a huge amount of analytical data, especially time-consuming procedures run up a screen suspended animation.

In order to optimize the user experience, using the Indy comes IdThreadComponent control, the perfect solution to this problem.

Below follows IdThreadComponent record on some of the key properties and methods:

 

1: IdThreadComponent property

Here the main record about Active, Priority and StopMode property.

Active: Default False, when you need to make IdThreadComponent controls to take effect, set to True;

Priority: In order to avoid conflict between threads, select Normal, the system comes with assigning a priority;

StopMode: Here is divided into two kinds Terminate and Suspend, Terminate is forcibly terminated, Suspend to slow down and wait for termination.

 

2：IdThreadComponent方法

TIdThreadComponent use the Observer pattern, where all events are callbacks.

Generally more time-consuming operation is performed on OnRun in.

Event execution order is as follows:

On Before Execute；

On Before Run；

On Run; 

On Stopped;

On After Run;

On After Execute;

 

3: is illustrated by the following Demo

You need to explain:

In the thread can not directly control on the user interface, because sometimes control is destroyed and the thread is still running, then direct action AV throw an exception, so TIdThreadComponent callback event, if there is use to control, you must first It does judge whether the control is empty.

Interface is as follows:

code show as below:

  1 unit uMain;
  2 
  3 interface
  4 
  5 uses
  6   Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  7   Dialogs, RzButton, StdCtrls, RzEdit, IdBaseComponent, IdThreadComponent;
  8 
  9 type
 10   TMainFrm = class(TForm)
 11     IDTrd: TIdThreadComponent;
 12     mmMsg: TRzMemo;
 13     btnStart: TRzBitBtn;
 14     btnStop: TRzBitBtn;
 15     btnTerminal: TRzBitBtn;
 16     procedure btnStartClick(Sender: TObject);
17      procedure IDTrdRun (Sender: TIdCustomThreadComponent);
18      procedure IDTrdBeforeExecute (Sender: TIdCustomThreadComponent);
19      procedure IDTrdAfterExecute (Sender: TIdCustomThreadComponent);
20      procedure btnStopClick (Sender: TObject);
21      procedure btnTerminalClick (Sender: TObject);
22      procedure IDTrdAfterRun (Sender: TIdCustomThreadComponent);
23      procedure IDTrdBeforeRun (Sender: TIdCustomThreadComponent);
24      procedure IDTrdStopped (Sender: TIdCustomThreadComponent);
25    private 
26      { Private declarations }
 27   public
 28     { Public declarations }
 29   end;
 30 
 31 var
 32   MainFrm: TMainFrm;
 33 
 34 implementation
 35 
 36 {$R *.dfm}
 37 
 38 procedure TMainFrm.btnStartClick(Sender: TObject);
 39 begin
 40   IDTrd.Active := True;
 41 end;
 42 
 43 procedure TMainFrm.IDTrdRun(Sender: TIdCustomThreadComponent);
 44 var
45    the I: Integer;
 46 is  the begin 
47    for the I: = . 1  to  100  do 
48    the begin 
49      mmMsg.Lines.Add (the IntToStr (the I)); // analog consuming operations 
50    End ;
 51 is    // not operate directly in the thread interface controls, and sometimes control is destroyed and the thread is still running, 
52    // this time will be reported abnormal AV, 
53    // so have to use controls, must be added to determine whether the control is empty callback event in TIdThreadComponent 
54  End ;
 55  
56 is  Procedure TMainFrm.IDTrdBeforeExecute (Sender: TIdCustomThreadComponent);
 57 is  the begin 
58    IF Assigned(mmMsg) then
 59   begin
 60     mmMsg.Lines.Add('Before Execute');
 61   end;
 62 end;
 63 
 64 procedure TMainFrm.IDTrdAfterExecute(Sender: TIdCustomThreadComponent);
 65 begin
 66   if Assigned(mmMsg) then
 67   begin
 68     mmMsg.Lines.Add('After Execute');
 69   end;
 70 end;
 71 
 72 procedure TMainFrm.btnStopClick(Sender: TObject);
 73 begin
 74   IDTrd.Stop;
 75 end;
 76 
 77 procedure TMainFrm.btnTerminalClick(Sender: TObject);
 78 begin
 79   IDTrd.Terminate;
 80 end;
 81 
 82 procedure TMainFrm.IDTrdAfterRun(Sender: TIdCustomThreadComponent);
 83 begin
 84   if Assigned(mmMsg) then
 85   begin
 86     mmMsg.Lines.Add('After Run');
 87   end;
 88 end;
 89 
 90 procedure TMainFrm.IDTrdBeforeRun(Sender: TIdCustomThreadComponent);
 91 begin
 92   if Assigned(mmMsg) then
 93   begin
 94     mmMsg.Lines.Add('Before Run');
 95   end;
 96 end;
 97 
 98 procedure TMainFrm.IDTrdStopped(Sender: TIdCustomThreadComponent);
 99 begin
100   if Assigned(mmMsg) then
101   begin
102     mmMsg.Lines.Add('On Stopped');
103   end;
104 end;
105 
106 end.