说明：  delphi 窗体释放 关于窗体的释放:Close（）方法是将窗体隐藏，即form.hide 释放窗体或是控件的标准用法是Form.Free，其实Free方法只是调用了Destroy（）方法，在窗体不为nil时进行资源的释放，但并不将窗体实例置为nil，只有窗体实例没有创始化之前值才为nil,否则你要显示的将窗体实例置为nil.
(delphi release form releasing on the form: Close () method is to hide the form that form.hide release form or control standard usage is Form.Free, in fact, just call the Free method Destroy () method, When the form is nil without the release of resources, but does not set to an instance of the form nil, only the form instance is not only the founder of the prior value to nil, or you want to display examples of the form is set to nil.)