subthread(handling busy operation) notify mainthread to update UI-优快云博客

本文链接：https://blog.youkuaiyun.com/EricYeung/article/details/1623786

本文介绍了一个使用Delphi实现的线程与主窗口通信的案例，通过TMyThread子类化线程并利用CallPostMessage发送消息，使主线程能够更新UI状态，展示了一个简单的进度条和百分比显示的实现过程。

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Call PostMessage inside TMyThread.Execute to tell Main Form to update UI

unit MyConsts;

interface

uses Messages;

const
WM_UPDATE_STATUS = WM_USER + 1;

implementation

end.

///////////////////////////////////////////////////////////////////////

unit Unit1;

interface

uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, StdCtrls, ComCtrls, MyConsts;

type
TForm1 = class(TForm)
    btnSpawn: TButton;
    pgsBar: TProgressBar;
    lblPC: TLabel;
    procedure btnSpawnClick(Sender: TObject);
private
    { Private declarations }
protected
procedure OnUpdateStatus(var Msg: TMessage); message WM_UPDATE_STATUS;
public
    { Public declarations }
end;

var
Form1: TForm1;

implementation

uses Unit2;

{$R *.dfm}

procedure TForm1.btnSpawnClick(Sender: TObject);
var
AThread: TMyThread;
begin
AThread := TMyThread.CreateNew(100000, Handle);
AThread.Resume;
end;

procedure TForm1.OnUpdateStatus(var Msg: TMessage);
begin
pgsBar.Position := Msg.WParam;
lblPC.Caption := Format('%d%s', [Msg.WParam, '%']);
end;

end.

///////////////////////////////////////////////////////////////////////

unit Unit2;

interface

uses
Classes, Windows, Messages;

type
TMyThread = class(TThread)
private
    { Private declarations }
    FHandle: THandle;
    FCounter: Integer;
protected
    procedure Execute; override;

public
constructor CreateNew(Counter: Integer; AHandle: THandle);
end;

implementation

uses MyConsts;

constructor TMyThread.CreateNew(Counter: Integer; AHandle: THandle);
begin
inherited Create(true);
FCounter := Counter;
FHandle := AHandle;

FreeOnTerminate := true;
end;

procedure TMyThread.Execute;
var
i, r: Integer;
begin
for i := 1 to 100 do
begin
PostMessage(FHandle, WM_UPDATE_STATUS, i, 0);
Sleep(100);
end;
end;

end.