delphi 多线程之System.TMonitor (续一)

2017-09-03 10:10:13来源:cnblogs.com作者:jjw人点击

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unit Unit1;interfaceuses  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,  Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls;type  TForm1 = class(TForm)    CheckBox1: TCheckBox;    CheckBox2: TCheckBox;    Button1: TButton;    Button2: TButton;    Memo1: TMemo;    procedure FormCreate(Sender: TObject);    procedure Button1Click(Sender: TObject);    procedure Button2Click(Sender: TObject);  private    { Private declarations }  public    { Public declarations }  end;var  Form1: TForm1;implementation{$R *.dfm}procedure Log(Msg: string);begin  TThread.Synchronize(nil, procedure    begin      Form1.Memo1.Lines.Add(Msg);    end);end;procedure TForm1.Button1Click(Sender: TObject);begin  if System.MonitorTryEnter(Self) then  //如果为 True  begin    Color := clRed;    System.MonitorExit(Self);    //也必须退出,否则 System.MonitorPulse(Self); 失效。  end;end;procedure TForm1.Button2Click(Sender: TObject);begin  System.MonitorPulse(Self);end;procedure TForm1.FormCreate(Sender: TObject);begin  TThread.CreateAnonymousThread(procedure    begin      while True do      begin        if Form1.CheckBox2.Checked then          Exit;        System.MonitorEnter(Form1);  //必须        Log('Thread1 Enter');        System.MonitorWait(Form1, INFINITE);        Log('Thread1 WaitFor');        System.MonitorExit(Form1);   //必须        Log('Thread1 Exit');        Log(DateTimeToStr(Now));        TThread.Sleep(100);      end;      Log('Thread Exit');    end).Start;end;end.

注意事项:
  if System.MonitorTryEnter(Self) then  //如果为 True
  begin
    Color := clRed;
    System.MonitorExit(Self);    //也必须退出(释放),否则 System.MonitorPulse(Self); 失效。
  end;
System.MonitorTryEnter 与 System.MonitorEnter 的区别在于是否会 block 当前调用 System.MonitorEnter 或 System.MonitorTryEnter 的线程。

System.MonitorEnter 会 block 调用线程
System.MonitorTryEnter 不会 block 调用线程。

此外
        System.MonitorEnter(Form1);          System.MonitorWait(Form1, INFINITE);  //执行后, Button1的onclick事件中,System.MonitorTryEnter(Self) 总会返回 True 
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