模式窗体与非模式窗体
非模式窗体从创建到销毁都需要代码来维护,防止内存未安全释放。
模式窗体就比较省心一些,只需要在代码段的try…finally中创建并维护即可。
下面用例子来说明一下两类窗体如何调用:
主窗体程序:
unit Main; interface uses Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms, Dialogs, StdCtrls,ModalForm,ModalessForm; type TForm8 = class(TForm) Button1: TButton; Button2: TButton; procedure Button2Click(Sender: TObject); procedure Button1Click(Sender: TObject); private { Private declarations } public { Public declarations } end; var Form8: TForm8; implementation {$R *.dfm} procedure TForm8.Button1Click(Sender: TObject); begin try Form9:=TForm9.Create(Application); Form9.ShowModal; finally Form9.Free; //窗体的清理放在同一代码段的try...finaally中,而不是在ModalForm中的Destroy方法里。 Form9:=nil; end; end; procedure TForm8.Button2Click(Sender: TObject); begin if not Assigned(Form10) then //防止出现多个窗体实例 Form10:=TForm10.Create(Application); //窗体的创建方式 Form10.Show; end; end.
模式窗体:
unit ModalForm; interface uses Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms, Dialogs; type TForm9 = class(TForm) private { Private declarations } public { Public declarations } end; var Form9: TForm9; implementation {$R *.dfm} end.
非模式窗体:
unit ModalessForm; interface uses Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms, Dialogs; type TForm10 = class(TForm) procedure FormClose(Sender: TObject; var Action: TCloseAction); procedure FormDestroy(Sender: TObject); private { Private declarations } public { Public declarations } end; var Form10: TForm10; implementation {$R *.dfm} procedure TForm10.FormClose(Sender: TObject; var Action: TCloseAction); begin Action:=caFree; end; procedure TForm10.FormDestroy(Sender: TObject); begin Form10:=nil; //这里是Form10设为nil而不是TForm10,否则将无法再次创建窗体。 end; end.
posted on 2010-10-30 11:53 Delphi7456 阅读(4870) 评论(0) 编辑 收藏 举报