本程序演示如何通过程序来清空回收站。
向窗体上添加一个TButton组件，它用于激活清空回收站的操作。设计完成的主界面如图1所示。
 图1 主界面 |
首先在程序的implementation段中定义3个常数和一个类型声明，代码如下：
const
SHERB_NOCONFIRMATION = $00000001 ;
SHERB_NOPROGRESSUI = $00000002 ;
SHERB_NOSOUND = $00000004 ;
type
TSHEmptyRecycleBin=function(Wnd:HWND;LPCTSTR:PChar;DWORD:Word):Integer;stdcall; |
程序运行初期，程序首先会通过LoadLibrary函数加载动态链接库Shell32.dll，并且把加载后的操作句柄存储在LibHandle中。然后通过@SHEmptyRecycleBin:=GetProcAddress (LibHandle, 'SHEmptyRecycleBinA')语句读取SHEmptyRecycleBinA函数的地址，如果以上语句能够正确执行(也就是@SHEmptyRecycleBin不等于nil)，那么就调用SHEmptyRecycleBin完成清空回收站的操作。最后释放动态链接库。响应代码如下：
procedure TForm1.Button1Click(Sender: TObject);
var
SHEmptyRecycleBin:TSHEmptyRecycleBin;
LibHandle:THandle;
begin
LibHandle := LoadLibrary(PChar('Shell32.dll')) ;
if LibHandle <> 0 then
begin
@SHEmptyRecycleBin := GetProcAddress(LibHandle, 'SHEmptyRecycleBinA');
end
else
begin
MessageDlg('Failed to load Shell32.dll.', mtError, [mbOK], 0);
Exit ;
end ;
if @SHEmptyRecycleBin <> nil then
begin
SHEmptyRecycleBin(Application.Handle,'',SHERB_NOCONFIRMATION or SHERB_NOPROGRESSUI or SHERB_NOSOUND) ;
end;
FreeLibrary(LibHandle);
@SHEmptyRecycleBin := nil ;
end; |
程序代码如下：
unit Unit1;
interface
uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, StdCtrls;
type
TForm1 = class(TForm)
Button1: TButton;
procedure Button1Click(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
end;
var
Form1: TForm1;
implementation
const
SHERB_NOCONFIRMATION = $00000001 ;
SHERB_NOPROGRESSUI = $00000002 ;
SHERB_NOSOUND = $00000004 ;
type
TSHEmptyRecycleBin=function(Wnd:HWND;LPCTSTR:PChar;DWORD:Word):Integer;stdcall;
{$R *.dfm}
procedure TForm1.Button1Click(Sender: TObject);
var
SHEmptyRecycleBin:TSHEmptyRecycleBin;
LibHandle:THandle;
begin
LibHandle := LoadLibrary(PChar('Shell32.dll')) ;
if LibHandle <> 0 then
begin
@SHEmptyRecycleBin := GetProcAddress(LibHandle, 'SHEmptyRecycleBinA');
end
else
begin
MessageDlg('Failed to load Shell32.dll.', mtError, [mbOK], 0);
Exit ;
end ;
if @SHEmptyRecycleBin <> nil then
begin
SHEmptyRecycleBin(Application.Handle,'',SHERB_NOCONFIRMATION or SHERB_NOPROGRESSUI or SHERB_NOSOUND) ;
end;
FreeLibrary(LibHandle);
@SHEmptyRecycleBin := nil ;
end;
end. |
保存文件，然后按F9键运行程序，程序运行的初始画面如图2所示。
 图2 程序运行的初始画面 |
单击“清空回收站”按钮就会将操作系统回收站中的文件彻底删除。
本程序同时也演示了如何调用一个.dll文件中的函数。
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