Delphi线程简介和它的create方法

TThread在Classes单元里的声明如下

type
    TThread = class
    private
        FHandle: THandle;
        FThreadID: THandle;
        FTerminated: Boolean;
        FSuspended: Boolean;
        FFreeOnTerminate: Boolean;
        FFinished: Boolean;
        FReturnValue: Integer;
        FOnterminate: TNotifyEvent;
        FMethod: TThreadMethod;
        FSynchronizeException: TObject;
        procedure CallOnTerminate;
        function GetPriority: TThreadPriority;
        procedure SetPriority(Value: TThreadPriority);
        procedure SetSuspended(value: Boolean);
    protected
        procedure DoTerminate; virtual;
        procedure Execute; virtual; abstract;
        procedure Synchronize(Method: TThreadMethod);
        property ReturnValue: Integer read FReturnValue write FReturnValue;
        property Terminated: Boolean read FTerminated;
    public
        constructor Create(CreateSuspended: Boolean);
        destructor Destroy; override;
        procedure Resume;
        procedure Terminate;
        function WaitFor: Integer;
        property FreeOnTerminate: Boolean read FFreeOnTerminate write FFreeOnTerminate;
        property Handle: THandle read FHandle;
        property Priority: TThreadPriority read GetPriority write SetPriority;
        property Suspended: Boolean read FSuspended write Suspended;
        property ThreadID: THandle read FThreadID;
        property OnTerminate: TNotifyEvent read FOnTerminate write FOnTerminate;
    end;

　　当TThread的Create()被调用的时候，需要传递一个布尔型的参数CreateSuspended。如果把这个参数设为False，那么当调用Create()之后，Execute()会被自动调用，也就是自动地执行线程代码。如果该参数设为True，则需要运行TThread的Resume()来唤醒线程。

　　一般情况下，当你调用Create()后，还会有一些其他的属性要求设置。所以，应当把CreateSuspended参数设置为True，因为在TThread已经执行的情况下设置TThread的属性可能引起麻烦。

　　在讲的深一点，在构造函数Create()中隐含调用一个RTL例程BeginThread()，而它又调用了一个API函数CreateThread()来创建一个线程对象的实例。CreateSuspended参数表明是否传递CREATE_SUSPENDED标志给CreateThread()。