constructor Create(AOwner: TComponent); override;
AOwner is the component that is responsible for freeing the Object instance. It becomes the value of the Owner property.
Create参数的不同主要是在对象的释放时候,nil的话要手工释放,Self是在指定对象释放的时候自动释放,Application是在应用程序退出的时候自动释放。